Ion Beam Source Construction and Applications
Presented by
Samah Ibrahim Radwan Torab Assistant lecturer in Accelerators and Ion Sources Department Basic Nuclear Science Division Nuclear Research Center Atomic Energy Authority
A Thesis Submitted To
Faculty of Science
Prof./ Lotif Zaki Ismail Prof./ Adel Gomah Helal Prof. Emeritus in Physics Dept. Prof. Emeritus in Accelerators and Faculty of Science Ion Sources Dept., Basic Nuclear Cairo University Science Division, Nuclear Research Center, Atomic Energy Authority
Prof./ Hesham El-Khabeary Dr./Galila Mehena Head of Accelerators and Ion Assistant Prof. in Physics Dept. Sources Dept., Basic Nuclear Faculty of Science Science Division, Nuclear Research Cairo University Center, Atomic Energy Authority
In Partial Fulfillment of the Requirements for The Degree of Doctor of Science (PLASMA PHYSICS) Physics Department Faculty of Science Cairo University (2011)
ﺑﺴﻢ ﺍﷲ ﺍﻟﺮﺣﻤﻦ ﺍﻟﺮﺣﻴﻢ
( ﻭﻗﻞ ﺭﺏ ﺯﺩﻧﻲ ﻋﻠﻤﺎ )
ﺻﺪق اﷲ اﻟﻌﻈﻴﻢ (ﺳﻮرة ﻃﻪ : ١١٤ﺁﻳﻪ )
APROVAL SHEET FOR SUMISSION
Thesis Title: Ion Beam Source Construction and Applications. Name of candidate: Samah Ibrahim Radwan Torab. This thesis has been approved for submission by the supervisors:
1- Prof./ Lotif Zaki Ismail Signature:
2- Prof./ Adel Gomah Helal Signature:
3- Prof./ Hesham El-Khabeary Signature:
4- Dr / Galila Mehena
Signature:
Prof./ Omar Mahmoud Osman
Chairman of Physics Department Faculty of Science - Cairo University
ACKNOWLEDGEMENT
First, praise to my God, most gracious and most merciful for his ever- present help and guidance. I also want to express my deep thanks to my mother, father, and brothers for their patience, encouragement, and support during this study. Much appreciation is due to Prof./ Lotif Zaki Ismail, Prof. Emeritus in Physics Department, Faculty of Science, Cairo University. I wish to express my gratitude to him for his kind supervision and valuable revision.
I am deeply indebted to Prof./ Adel Gomah Helal, Prof. Emeritus in Accelerators and Ion Sources Dept., Basic Nuclear Science Division, Nuclear Research Center, Atomic Energy Authority, for proposing the topic of this work, great assistance, useful discussions, and all efforts spent by him during the different stages of this work. Without his assistance, my thesis can not appear. He kindly offered me all facilities with great help in close supervision, revision, and valuable advices and continuous encouragement during the study.
I would like to express my deep gratitude and sincere appreciation to Prof./ Hesham El-Khabeary, Head of Accelerators and Ion Sources Department, Basic Nuclear Science Division, Nuclear Research Center, Atomic Energy Authority, Egypt for his supervising, interest, continuous assistance, guidance, great concern and constructive suggestions during all the stages of this thesis. Much thanks to Assistant Prof. /Galila Mehena, Physics Dept., Faculty of Science, Cairo University, for her supervision and help to me.I wish express my great deep thanks to Prof./ Mohamed Mostafa Abdel Baky and Prof./ Osama Ahamed Mostafa, Prof. Emeritus in my Dept., for helping me during this study. Also, much great thanks to Prof./ Samir Nouh, Physics department, Ain Shams University for providing the samples and his sincere supervision, and valuable revision. I like to thank Mr. / Adel Mohamed Fathi, the director of Nitrogen production laboratory, Accelerators and Ion Sources Department, for his cooperation and supplying the experimental facilities during this work. I like to thank everyone who gives me a hand throughout this study.
Ion Beam Source Construction and Applications
Presented by
Samah Ibrahim Radwan Torab Assistant lecturer in Accelerators and Ion Sources Department Basic Nuclear Science Division Nuclear Research Center Atomic Energy Authority
A Thesis Submitted To
Faculty of Science
In Partial Fulfillment of the Requirements for The Degree of Doctor of Science (PLASMA PHYSICS) Physics Department Faculty of Science Cairo University
(2011) ABSTRACT
The aim of this thesis is to improve the performance of a new shape cold cathode Penning ion source to be suitable for some applications.
In this work, many trials have been made to reach the optimum dimensions of the new shape of cold Molybdenum cathode Penning ion source with radial extraction. The high output ion beam can be extracted in a direction transverse to the discharge region.
The new shape cold cathode Penning ion source consists of Copper cylindrical hollow anode of 40 mm length, 12 mm diameter and has two similar cone ends of 15 mm length, 22 mm upper cone diameter and 12 mm bottom cone diameter. The two movable Molybdenum cathodes are fixed in Perspex insulator and placed symmetrically at two ends of the anode. The Copper emission disc of 2 mm thickness and has central aperture of different diameters is placed at the middle of the anode for ion beam exit. The inner surface of the emission disc is isolated from the anode by Perspex insulator except an area of diameter 5 mm to confine the electrical discharge in this area. A movable Faraday cup is placed at different distances from the emission electrode aperture and used to collect the output ion beam from the ion source.
The working gases are admitted to the ion source through a hole in the anode via a needle valve which placed between the gas cylinder and the ion source.
The optimum anode- cathode distance, the uncovered area diameter of the emission disc, the central aperture diameter of the emission electrode, the distance between emission electrode and Faraday cup have been determined using Argon gas. The optimum distances of the ion source were found to be equal to 6 mm, 5 mm, 2.5 mm, and 3 cm respectively where stable discharge current and maximum output ion beam current at low discharge current can be obtained.
The discharge characteristics, ion beam characteristics, and the efficiency of the ion source have been measured at different operating conditions and different gas pressures using Argon gas. The ion source characteristics are measured at the optimum operating conditions using Argon and Nitrogen gases. The effect of negative voltage applied to Faraday cup on the output ion beam current is determined.
The effect of permanent magnet on the discharge characteristics of the ion source has been determined. An axial Samarium- Cobalt permanent magnet of intensity, B, is used. The optimum permanent magnet - anode distance is equal to 1.5 cm which obtain from many trials.
The energy of the heavy charged particles in this plasma of the ion source is measured using energy analyzer system. The retarding of ions can be determined by applying positive voltage on the retarding grid and from the experimental results, the energy distribution can be obtained.
The efficiency of ion source can be determined using Nitrogen and Argon gases. The perveance of the ion source can be calculated from the experimental data of Argon and Nitrogen gases. The operating time of this ion source can be determined during the exposure of Argon gas on Molybdenum specimen. Also, the comparison between the experimental and theoretical data was made.
Finally, the output ion beam current from the ion source is used in some applications, especially for PM-355 polymer specimens. When the exposure time of the ion beam increases, the absorbance increases and the cross linking occurs. CONTENTS
Page no. FIGURES CAPTION……………………..……………..………... i NOMENCLATURE………………………………..……….....…xii ABSTRACT
CHAPTER [1]: Historical Review on Ion Sources
1.1- Introduction…………………………………….………….…... 1 1.2- Classification of ion sources……………………….………..… 3 1.2.1- Electron bombardment ion sources………………….……….4 1.2.2- Magnetron ion sources………………….……….…….….….5 1.2.3- Freeman ion sources……………………...……..…………... 6 1.2.4- RF ion sources……………………………….…………….…8 1.2.5- Vacuum arc ion sources………………..…………………....10 1.2.6- Large area ion sources…………………………….………...11 1.2.7- Surface and thermal ionization ion sources…………….…...12 1.2.7.1- Surface ionization ion sources…………………………..12 1.2.7.2- Thermo ionization ion sources………………………….14 1.2.8- Negative ion sources………………………….….……...….15 1.2.9- Penning ion sources…………………...……………….……16 1.2.10- Radial cold cathode ion sources………………..…….……19
CHAPTER [2]: Ion Beam Characteristics
2.1- Ion beam formation………………….………………....……..21 2.1.1- Extraction from fixed emitters………………….………...22
I 2.1.2- Extraction from plasma emitters…………….….……...... 22 2.2- Extraction of ions from plasma………………...... 25 2.2.1- Design of the ion extraction system…………………...… 26 2.2.2- Classical extraction system……………………….….….. 26 2.2.3- Different shapes of extraction system…………..….……..30 2.3- PIG ionization………………………………….….….…...…..33 2.4- Effect of static magnetic fields on gas discharges……..……..34 2.5- Cold cathode arc- discharge ion sources with oscillating electrons in magnetic field………………….….…...... 36 2.5.1- Cold cathode Penning ion sources with axial ion extraction ………..…………………………………………..…….....37 2.5.2- Cold cathode Penning ion sources with transversal ion extraction ………………………………………………...38 2.6- Paschen's law…………………………….………………….. 39 2.7- Particle analyzers………………………………………….…..42 2.7.1- Energy analyzers………………………………....….…....43 2.7.2- Mass analyzers…………………………………..…….….44
CHAPTER [3]: Design and Construction of Ion Source and Measuring Techniques
3.1- Design and construction of ion source………………….….…47 3.1.2- Design of a cold cathode Penning ion source…..………...47 3.1.2- Electrical circuit of the ion source…….…………………..48 3.2- Vacuum system characteristics……………………………... .49 3.2.1- Rotary pump……………………….……………………...50 3.2.2- Diffusion pump…………………………………………....50
II 3.2.3- Liquid Nitrogen trap……………...………….…………...50 3.2.4- Vacuum chamber…………………………………..……..52 3.2.5- Gas handling of the system……………………………….52 3.2.6- Operating of the system………………….………...... 52
CHAPTER [4]: Experimental Results of a Cold Molybdenum
Cathode Penning Ion Source
4.1- Determination of the optimum anode- cathode distance……...55 4.1.1- Input characteristics…………………………..…………..56 4.1.2- Output ion beam characteristics…………………………..58 4.1.3- The optimum gap distance between the anode and cathode ………….…………………………………………………63 4.2- Determination of the optimum diameter of uncovered area of emission disc...... ………………….…66 4.2.1- Input characteristics……………..………………….…….66 4.2.2- Output ion beam characteristics…………….…………….69 4.2.3- The optimum diameter of uncovered area of the emission disc………………………………………………….……..75 4.3- Determination of the optimum diameter of emission disc aperture…………………………..…………………………....78 4.3.1- Input characteristics…………..………………………..….78 4.3.2- Output ion beam characteristics……………..…….…..….81 4.3.3- The optimum diameter of the emission disc………………86 4.4- Determination of the optimum emission disc- Faraday cup distance………………………………………………….….…87 4.4.1- Input characteristics…………………………..…………...87 III 4.4.2- Output ion beam characteristics……………….……..…...90 4.4.3- The optimum distance between the emission disc- Faraday cup…………………………………………………..……..95 4.5- Determination of the optimum strength of permanent magnetic field……………………………………………………………98 4.5.1- Input characteristics…………….……………………..….98 4.5.2- Output ion beam characteristics………...……………….102 4.5.3- The optimum strength of permanent magnetic field……106 4.5.4- Comparison between output ion beam current value with and without magnet...... 107 4.6- The optimum parameters of PIG ion source using Nitrogen gas……………………………………………………...... …109 4.6.1- Input characteristics………….…………..………………109 4.6.2- Output ion beam characteristics………………………....110 4.7- The cold cathode Penning ion source cha r a c t e r i s t i c s u s i n g Nitrogen and Argon gases…..…………...…….…………...112 4.7.1- Input characteristics…………..………………….………112 4.7.2- Output ion beam characteristics…………..…….……… 113 4.8- Effect of negative voltage on Faraday cup…………..……....115 4.9- Effect of energy analyzer on extracted ion beam current……117 4.9.1- Ion retarding………...………………………………..….118 4.9.2- Energy distribution……………………..……….……… 119 4.10- Paschen curve………………………..………………….….121 4.10.1- Without applying magnetic field…………………….... 122 4.10.2- With applying magnetic field…………………………. 123
IV 4.10.3- Without and with applying magnetic field…………….124 4.11- Efficiency of ion source………………………………..….125 4.12- Perveance………………………………………………….126 4.13- Operating time of this ion source………………………….127
4.14- Comparison between theoretical and experimental results..128
CHAPTER [5]: Ion Beam Applications 5.1- Introduction……………………….….…………………..…129 5.2- Polymers……………..……………………………………...130 5.2.1- Brief history of polymers……………….…….…………130 5.2.2- PM – 355 polymer..….………………………..………...130
CHAPTER [6]: Conclusion and Discussion Conclusion……………………….………………………………133 REFERENCES…………………………………………………137 ARABIC SUMMARY
V FIGURES CAPTION
C H A P T E R [ 1 ] Page no.
Figure (1) Electron Bombardment Ion Source 5
Figure (2) Magnetron ion source 6
Figure (3) Freeman ion source 7
Figure (4) Inductively coupled RF ion source 9
Figure (5) Vacuum arc ion source 11
Figure (6) Large area multicusp ion source 12
Figure (7) Surface ionization ion source 13
Figure (8) Penning ion source with cold cathodes 16
Figure (9) Penning ion source with filament cathodes 17
Figure (10) Radial cold cathode ion source 19
CHAPTER [2] Page no.
Figure (1) Schematic diagram of ion beam formation 28 Schematic diagram of ion beam formation for high Figure (2) 30 intensity plasma Keller's version of a low intensity ion source with cold Figure (3) 37 cathode, oscillating electrons and axial ion extraction Heiniche – Bethge – Bauman's low intensity ion source Figure (4) with cold cathode, oscillating electrons and transversal ion 38 extraction Cold cathode Penning ion source and simple energy Figure (5) 44 analyzer electrical circuit
i CHAPTER [3] Page no. Construction of a cold Molybdenum Cathode Figure (1) 48 Penning ion source Electrical circuit of a cold Molybdenum cathode Figure (2) 49 Penning ion source Figure (3) Schematic diagram of the experimental arrangement 51
CHAPTER [4] Page no. Figure (1) Dimensions of cold cathode Penning ion source 55
Discharge current versus discharge voltage at dA-C = Figure (2) 5 mm, Dem. = 1.5 mm and dem. – F.C = 3 cm using 56 Argon gas
Discharge current versus discharge voltage at dA-C = 6 Figure (3) mm, Dem. = 1.5 mm and dem. – F.C = 3 cm using 57 Argon gas
Discharge current versus discharge voltage at dA-C = Figure (4) 7 mm, Dem. = 1.5 mm and dem. – F.C = 3 cm using 57 Argon gas
Discharge current versus discharge voltage at dA-C = Figure (5) 8 mm, Dem. = 1.5 mm and dem. – F.C = 3 cm using 58 Argon gas Output ion beam current versus discharge voltage at Figure (6) dA-C = 5 mm, Dem.= 1.5 mm and dem. – F.C = 3 cm using 59 Argon gas Output ion beam current versus discharge voltage at Figure (7) dA-C = 6 mm, Dem.= 1.5 mm and dem. – F.C = 3 cm using 59 Argon gas Output ion beam current versus discharge voltage at Figure (8) dA-C = 7 mm, Dem.= 1.5 mm and dem. – F.C = 3 cm using 60 Argon gas Output ion beam current versus discharge voltage at Figure (9) dA-C = 8 mm, Dem.= 1.5 mm and dem. – F.C = 3 cm using 60 Argon gas Output ion beam current versus discharge current at Figure (10) dA-C = 5 mm, Dem.= 1.5 mm and dem. – F.C = 3 cm using 61 Argon gas
ii Output ion beam current versus discharge current at Figure (11) dA-C = 6 mm, Dem.= 1.5 mm and dem. – F.C = 3 cm using 62 Argon gas Output ion beam current versus discharge current at Figure (12) dA-C = 7 mm, Dem. = 1.5 mm and dem. – F.C = 3 cm using 62 Argon gas Output ion beam current versus discharge current at Figure (13) dA-C = 8 mm, Dem. = 1.5 mm and dem. – F.C = 3 cm using 63 Argon gas Output ion beam current versus the distance between anode and cathode at different pressures, D = 1.5 Figure (14) em. 64 mm , dem. – F.C = 3 cm, and Id = 1 mA using Argon gas Output ion beam current versus the distance between Figure (15) anode and cathode at different pressures, Dem. =1.5 64 mm, dem.–F.C = 3 cm, and Id = 2 mA using Argon gas Output ion beam current versus the distance between anode and cathode distance at p = 3 X 10 -4 mm Hg, Figure (16) 65 Dem. = 1.5 mm , dem. – F.C = 3 cm, and Id = 1 and 2 mA using Argon gas
Discharge current versus discharge voltage at dA-C = 6 mm, D = 3 mm, D = 1.5 mm , Figure (17) uncovered em. disc em. 67 dem. – F.C = 3 cm, and different pressures using Argon gas
Discharge current versus discharge voltage at dA-C = Figure (18) 6 mm, Duncovered em. disc = 4 mm, Dem. = 1.5 mm , dem. – 67 F.C = 3 cm, and different pressures using Argon gas
Discharge current versus discharge voltage at dA-C = Figure (19) 6 mm, Duncovered em. disc = 5 mm, Dem.= 1.5 mm , dem. – F.C 68 = 3 cm, and different pressures using Argon gas
Discharge current versus discharge voltage at dA-C = Figure (20) 6 mm, Duncovered em. disc= 6 mm, Dem. = 1.5 mm , dem. – F.C 68 = 3 cm, and different pressures using Argon gas
Discharge current versus discharge voltage at dA-C = Figure (21) 6 mm, Duncovered em. disc = 7 mm, Dem.= 1.5 mm , dem. – F.C 69 = 3 cm, and different pressures using Argon gas Output ion beam current versus discharge voltage at d = 6 mm, D = 3 mm, D = 1.5 mm , Figure (22) A-C uncovered em. disc em. 70 dem. – F.C = 3 cm, and different pressures using Argon gas Figure (23) Output ion beam current versus discharge voltage at 70
iii dA-C = 6 mm, Duncovered em. disc = 4 mm, Dem. = 1.5 mm , dem. – F.C = 3 cm, and different pressures using Argon gas Output ion beam current versus discharge voltage at d = 6 mm, D = 5 mm, D = 1.5 mm , Figure (24) A-C uncovered em. disc em. 71 dem. – F.C = 3 cm, and different pressures using Argon gas Output ion beam current versus discharge voltage at d = 6 mm, D = 6 mm, D = 1.5 mm , Figure (25) A-C uncovered em. disc em. 71 dem. – F.C = 3 cm, and different pressures using Argon gas Output ion beam current versus discharge voltage at d = 6 mm, D = 7 mm, D = 1.5 mm , Figure (26) A-C uncovered em. disc em. 72 dem. – F.C= 3 cm, and different pressures using Argon gas Output ion beam current versus discharge current at d = 6 mm, D = 3 mm, D = 1.5 mm , Figure (27) A-C uncovered em. disc em. 73 dem. – F.C= 3 cm, and different pressures using Argon gas Output ion beam current versus discharge current at d = 6 mm, D = 4 mm, D = 1.5 mm , Figure (28) A-C uncovered em. disc em. 73 dem. – F.C= 3 cm, and different pressures using Argon gas Output ion beam current versus discharge current at d = 6 mm, D = 5 mm, D = 1.5 mm , Figure (29) A-C uncovered em. disc em. 74 dem. – F.C= 3 cm, and different pressures using Argon gas Output ion beam current versus discharge current at d = 6 mm, D = 6 mm, D = 1.5 mm , Figure (30) A-C uncovered em. disc em. 74 dem. – F.C= 3 cm, and different pressures using Argon gas Output ion beam current versus discharge current at d = 6 mm, D = 7 mm, D = 1.5 mm , Figure (31) A-C uncovered em. disc em. 75 dem. – F.C= 3 cm, and different pressures using Argon gas Output ion beam current versus uncovered area diameter of emission disc, D (mm), at Figure (32) uncovered em. disc 76 dA-C = 6 mm, Dem. = 1.5 mm , dem. – F.C = 3 cm, and Id = 1 mA , and different pressures using Argon gas Output ion beam current versus uncovered area Figure (33) diameter of emission disc, Duncovered em. disc (mm), at
iv dA-C = 6 mm, Dem. = 1.5 mm , dem. – F.C = 3 cm, and Id 76 = 2 mA , and different pressures using Argon gas
Output ion beam current versus uncovered area diameter of emission disc, D (mm), at Figure (34) uncovered em. disc 77 dA-C = 6 mm, Dem. = 1.5 mm , dem. – F.C = 3 cm, and Id =1 and 2 mA , and different pressures using Argon gas
Discharge current versus discharge voltage at dA-C = Figure (35) 6 mm, Duncovered em. disc = 5 mm, Dem.= 1.5 mm , dem. – F.C 79 = 3 cm, and different pressures using Argon gas
Discharge current versus discharge voltage at dA-C = 6 Figure (36) mm, Duncovered em. disc = 5 mm, Dem. = 2 mm , dem. – F.C 79 = 3 cm, and different pressures using Argon gas
Discharge current versus discharge voltage at dA-C = 6 Figure (37) mm, Duncovered em. disc = 5 mm, Dem. = 2.5 mm , dem. – F.C 80 = 3 cm, and different pressures using Argon gas
Discharge current versus discharge voltage at dA-C = 6 Figure (38) mm, Duncovered em. disc = 5 mm, Dem. = 3 mm , dem. – F.C = 80 3 cm, and different pressures using Argon gas Output ion beam current versus discharge voltage at d = 6 mm, D = 5 mm, D = 1.5 mm , Figure (39) A-C uncovered em. disc em. 81 dem. – F.C = 3 cm, and different pressures using Argon gas Output ion beam current versus discharge voltage at d = 6 mm, D = 5 mm, D = 2 mm , Figure (40) A-C uncovered em. disc em. 82 dem. – F.C = 3 cm, and different pressures using Argon gas Output ion beam current versus discharge voltage at d = 6 mm, D = 5 mm, D = 2.5 mm , Figure (41) A-C uncovered em. disc em. 82 dem. – F.C = 3 cm, and different pressures using Argon gas Output ion beam current versus discharge voltage at d = 6 mm, D = 5 mm, D = 3 mm , Figure (42) A-C uncovered em. disc em. 83 dem. – F.C = 3 cm, and different pressures using Argon gas Output ion beam current versus discharge current at d = 6 mm, D = 5 mm, D = 1.5 mm , Figure (43) A-C uncovered em. disc em. 84 dem. – F.C = 3 cm, and different pressures using Argon gas Output ion beam current versus discharge current at Figure (44) 84 dA-C = 6 mm, Duncovered em. disc= 5 mm, Dem. = 2 mm ,
v dem. – F.C = 3 cm, and different pressures using Argon gas Output ion beam current versus discharge current at d = 6 mm, D = 5 mm, D = 2.5 mm , Figure (45) A-C uncovered em. disc em. 85 dem. – F.C = 3 cm, and different pressures using Argon gas Output ion beam current versus discharge current at d = 6 mm, D = 5 mm, D = 3 mm , Figure (46) A-C uncovered em. disc em. 85 dem. – F.C = 3 cm, and different pressures using Argon gas Output ion beam current versus diameter of emission disc, D (mm), at d =6 mm, D = 5 Figure (47) em. A-C uncovered em. disc 86 mm , dem. – F.C = 3 cm, and Id = 1 mA , and different pressures using Argon gas
Discharge current versus discharge voltage at dA-C = 6 Figure (48) mm, Duncovered em. disc = 5 mm, Dem. = 2.5 mm , dem. – F.C 88 = 1 cm, and different pressures using Argon gas
Discharge current versus discharge voltage at dA-C = 6 Figure (49) mm, Duncovered em. disc = 5 mm, Dem. = 2.5 mm , dem. – F.C 88 = 2 cm, and different pressures using Argon gas
Discharge current versus discharge voltage at dA-C = 6 Figure (50) mm, Duncovered em. disc = 5 mm, Dem. = 2.5 mm , dem. – F.C 89 = 3 cm, and different pressures using Argon gas
Discharge current versus discharge voltage at dA-C = 6 Figure (51) mm, Duncovered em. disc = 5 mm, Dem. = 2.5 mm , dem. – F.C 89 = 4 cm, and different pressures using Argon gas Output ion beam current versus discharge voltage at d = 6 mm, D = 5 mm, D = 2.5 mm Figure (52) A-C uncovered em. disc em. 90 , dem. – F.C = 1 cm, and different pressures using Argon gas Output ion beam current versus discharge voltage at d = 6 mm, D = 5 mm, D = 2.5 mm , Figure (53) A-C uncovered em. disc em. 91 dem. – F.C = 2 cm, and different pressures using Argon gas Output ion beam current versus discharge voltage at d = 6 mm, D = 5 mm, D = 2.5 mm Figure (54) A-C uncovered em. disc em. 91 , dem. – F.C = 3 cm, and different pressures using Argon gas Output ion beam current versus discharge voltage at Figure (55) dA-C = 6 mm, Duncovered em. disc = 5 mm, Dem.= 2.5 mm , 92 dem. – F.C = 4 cm, and different pressures using Argon
vi gas Output ion beam current versus discharge current at d = 6 mm, D = 5 mm, D = 2.5 mm , Figure (56) A-C uncovered em. disc em. 93 dem. – F.C = 1 cm, and different pressures using Argon gas Output ion beam current versus discharge current at d = 6 mm, D = 5 mm, D = 2.5 mm , Figure (57) A-C uncovered em. disc em. 93 dem. – F.C = 2 cm, and different pressures using Argon gas Output ion beam current versus discharge current at d = 6 mm, D = 5 mm, D = 2.5 mm , Figure (58) A-C uncovered em. disc em. 94 dem. – F.C = 3 cm, and different pressures using Argon gas Output ion beam current versus discharge current at d = 6 mm, D = 5 mm, D = 2.5 mm , Figure (59) A-C uncovered em. disc em. 94 dem. – F.C = 4 cm, and different pressures using Argon gas Output ion beam current versus distance between emission disc and Faraday cup at d = 6 mm, Figure (60) A-C 95 Duncovered em. disc = 5 mm, Dem. = 2.5 mm, Id = 0.5 mA , and different pressures using Argon gas Output ion beam current versus distance between emission disc and Faraday cup at d = 6 mm, Figure (61) A-C 96 Duncovered em. disc = 5 mm, Dem. = 2.5 mm, Id = 1 mA , and different pressures using Argon gas Output ion beam current versus distance between emission disc and Faraday cup at d = 6 mm, Figure (62) A-C 97 Duncovered em. disc = 5 mm, Dem. = 2.5 mm, Id = 0.5 and 1 mA , and P= 5 X 10-4 mm Hg using Argon gas The effect of Argon ion beam on Copper Faraday cup Figure (63) 97 exposed for one hour without magnetic field
Discharge current versus discharge voltage at dA-C = 6 mm, D = 5 mm, D = 2.5 mm , d Figure (64) uncovered em. disc em. em. – F.C 99 = 3 cm, B = 50 G, and different pressures using Argon gas
Discharge current versus discharge voltage at dA-C = 6 mm, D = 5 mm, D = 2.5 mm , d Figure (65) uncovered em. disc em. em. – F.C 99 = 3 cm, B = 100 G, and different pressures using Argon gas Discharge current versus discharge voltage at d = 6 Figure (66) A-C 100 mm, Duncovered em. disc = 5 mm, Dem. = 2.5 mm , dem. – F.C
vii = 3 cm, B = 200 G, and different pressures using Argon gas
Discharge current versus discharge voltage at dA-C = 6 mm, D = 5 mm, D = 2.5 mm , Figure (67) uncovered em. disc em. 100 dem. – F.C = 3 cm, B = 230 G, and different pressures using Argon gas
Discharge current versus discharge voltage at dA-C = 6 mm, D = 5 mm, D = 2.5 mm , Figure (68) uncovered em. disc em. 101 dem. – F.C = 3 cm, B = 300 G, and different pressures using Argon gas
Discharge current versus discharge voltage at dA-C = 6 mm, D = 5 mm, D = 2.5 mm , Figure (69) uncovered em. disc em. 101 dem. – F.C = 3 cm, B = 330 G, and different pressures using Argon gas
Discharge current versus discharge voltage at dA-C = 6 mm, D = 5 mm, D = 2.5 mm , Figure (70) uncovered em. disc em. 102 dem. – F.C = 3 cm, B = 400 G, and different pressures using Argon gas Output ion beam current versus discharge current at d = 6 mm, D = 5 mm, D = 2.5 mm , Figure (71) A-C uncovered em. disc em. 103 dem. – F.C = 3 cm, B = 50 G, and different pressures using Argon gas Output ion beam current versus discharge current at d = 6 mm, D = 5 mm, D = 2.5 mm , Figure (72) A-C uncovered em. disc em. 103 dem. – F.C = 3 cm, B = 100 G, and different pressures using Argon gas Output ion beam current versus discharge current at d = 6 mm, D = 5 mm, D = 2.5 mm , Figure (73) A-C uncovered em. disc em. 104 dem. – F.C = 3 cm, B = 200 G, and different pressures using Argon gas Output ion beam current versus discharge current at d = 6 mm, D = 5 mm, D = 2.5 mm , Figure (74) A-C uncovered em. disc em. 104 dem. – F.C = 3 cm, B = 230 G, and different pressures using Argon gas Output ion beam current versus discharge current at d = 6 mm, D = 5 mm, D = 2.5 mm , Figure (75) A-C uncovered em. disc em. 105 dem. – F.C = 3 cm, B = 300 G, and different pressures using Argon gas Output ion beam current versus discharge current at Figure (76) dA-C = 6 mm, Duncovered em. disc= 5 mm, Dem.= 2.5 mm , 105 dem. – F.C = 3 cm, B = 330 G, and different pressures
viii using Argon gas
Output ion beam current versus discharge current at d = 6 mm, D = 5 mm, D = 2.5 mm , Figure (77) A-C uncovered em. disc em. 106 dem. – F.C = 3 cm, B = 400 G, and different pressures using Argon gas
Output ion beam current versus magnetic field strength at d = 6 mm, D = 5 mm, Figure (78) A-C uncovered em. disc 107 Dem. = 2.5 mm , dem. – F.C = 3 cm, and different pressures using Argon gas Output ion beam current versus discharge current at Figure (79) optimum operating conditions and P= 6 X10-4 mmHg 108 with B= 300 G and without magnet using Argon gas. The effect of Argon ion beam on Copper Faraday cup Figure (80) for one hour with magnetic field of strength B= 300 108 Gauss
Discharge current versus discharge voltage at dA-C = 6 mm, D = 5 mm, D = 2.5 mm , d Figure (81) uncovered em. disc em. em. – F.C 109 = 3 cm, B = 300 G, and different pressures using Nitrogen gas Output ion beam current versus discharge voltage at d = 6 mm, D = 5 mm, D = 2.5 mm Figure (82) A-C uncovered em. disc em. 110 , dem. – F.C = 3 cm, B = 300 G, and different pressures using Nitrogen gas Output ion beam current versus discharge current at d = 6 mm, D = 5 mm, D = 2.5 mm , Figure (83) A-C uncovered em. disc em. 111 dem. – F.C = 3 cm, B = 300 G, and different pressures using Nitrogen gas
Discharge current versus discharge voltage at dA-C = 6 mm, D = 5 mm, D = 2.5 mm , Figure (84) uncovered em. disc em. 112 dem. – F.C = 3 cm, B = 300 G, and different pressures using Argon and Nitrogen gases Output ion beam current versus discharge voltage at d = 6 mm, D = 5 mm, D = 2.5 mm , Figure (85) A-C uncovered em. disc em. 113 dem. – F.C = 3 cm, B = 300 G, and different pressures using Argon and Nitrogen gases Output ion beam current versus discharge current at d = 6 mm, D = 5 mm, D = 2.5 mm , Figure (86) A-C uncovered em. disc em. 114 dem. – F.C = 3 cm, B = 300 G, and different pressures using Argon and Nitrogen gases Figure (87) Output ion beam current versus discharge current at 115
ix dA-C = 6 mm, Duncovered em. disc = 5 mm, Dem.= 2.5 mm , dem. – F.C = 3 cm, B = 300 G, and different negative voltages applied on Faraday cup using Argon gas Output ion beam current versus negative voltage applied on Faraday cup at d = 6 mm, D Figure (88) A-C uncovered em. disc 117 = 5 mm, Dem. = 2.5 mm , dem. – F.C = 3 cm, B = 300 G, and different discharge current using Argon gas Output ion beam current versus voltage applied on retarding grid at dA-C = 6 mm, Duncovered em. disc = 5 mm, Figure (89) Dem. = 2.5 mm , dem. – F.C = 3 cm, B= 300 G, and P = 9 119 X 10 -4 mm Hg using discharge voltages 2 and 3 KV Argon gas The effect of Argon ion beam on Copper Faraday cup Figure (90) at optimized parameters in case of retarding grid is 119 positive potential The energy distribution at the optimized parameters at Figure (91) pressure equals 9X10-4 mmHg, different discharge 121 voltage, and using Argon gas Pressure multiplied by gap distance versus discharge current at d = 6 mm, D = 2.5 mm, D Figure (92) A-C em. uncovered em. disc 122 = 5 mm, dem. – F.C = 3 cm, B = 0, and different discharge current using Argon gas Pressure multiplied by gap distance versus discharge current at d = 6 mm, D = 2.5 mm, D Figure (93) A-C em. uncovered em. disc 123 = 5 mm, dem. – F.C = 3 cm, B = 300 G, and different discharge current using Argon gas
Discharge voltage versus discharge current at dA-C= 6 mm, D = 2.5 mm, D = 5 mm, d Figure (94) em. uncovered em. disc em. – F.C 124 = 3 cm, P = 6 X 10-4 mm Hg, without and with applying magnetic field using Argon gas
Gas pressure versus ion source efficiency at dA-C= 6 mm, D = 2.5 mm, D = 5 mm, d Figure (95) em. uncovered em. disc em. – F.C 125 = 3 cm, Vd = 3.92 KV, with applying magnetic field using Nitrogen and Argon gases Perveance versus the discharge current at the Figure (96) optimized parameters of ion source, pressure equals 126 -4 7 X 10 mmHg, and using Argon and Nitrogen gases Output ion beam current versus the exposed time at the optimized parameters of the ion source, pressure Figure (97) 127 equals 7 X 10-4 mmHg, and using Argon gas bombarded with Molybdenum specimen
x Output ion beam current versus the discharge current at the optimized parameters of the ion source, pressure Figure (98) 128 equals 8 X 10-4 mmHg, and for experimental and theoretical results using Argon gas
CHAPTER [5] Pages no. Absorbance versus fluence at optimized ion source parameters and different wave lengths using Argon Figure (1) 131 ion beam bombarded with PM- 355 polymer specimen.
xi NOMENCLATURE
Ib Output ion beam current PIG Penning
Qo Influx of neutral atoms ni Ion density η Gas utilization factor Π Poissance p Ionization probability Pc Perveance Transmission through Time taken by neutral to traverse α τ electrode for the ions o the beam no Average neutral density A Emitting area Minimum theoretical divergence n Average ion density ω + o angle vo Neutral velocity a Half width of the slit (m) v+ Ion velocity d Gap width (m) Fraction of total ion current, Secondary electron emission β γ goes to the cathode i coefficient of cathode surface
Je Current density S1 Plasma surface v Electron velocity S2 Sheath
σ Ionization cross section S3 Extractor e Electron charge G Neutral gas molecule Gas phase excited state atom or M Ion mass G* i molecule me Electron mass M Target molecule U Cathode fall M+ Radical molecular cation
Ie Electron current De Diffusion coefficient
Φ Energy (eV) fH Larmor frequency ni Number of ions ν Number of electron oscillations no Number of atoms n Ion or electron density gi Statistical weights for ions Ac Collecting area go Statistical weights for atoms IC Collector current
φi Ionization potential of atom ФD Discriminator voltage
φg Work function of the surface dA-C Anode – cathode distance Emission electrode ion exit J Maximum current density D em. aperture diameter Emission electrode – Faraday cup ε Permitivity d o em.-F.C. distance
xii Permanent magnet – anode q Electric charge d A-mag. distance Extractor electrode – emission q* Charge state d em.- E electrode distance Central aperture diameter of m Atomic mass D E the extractor electrode u Mass ( atomic mass units) P Pressure of entering gas
φ Potential drop Vext Extracting voltage B Brightness F Energy distribution function Saturation value of ion current One-dimensional velocity J f(v ) s density z distribution function k Boltzman constant Id Discharge current
Te Electron temperature Vd Discharge voltage
B Magnetic field strength Ib Output ion beam current Voltage applied the retarding Negative voltage applied on V V ret grid ng Faraday cup Number of ions evaporated Number of atoms evaporated from n n i from the surface o the surface gi Statistical weights for ions go Statistical weights for atoms
φi Ionization potential of atom φg Work function of the surface Diameter of uncovered area of the emission D uncovered em. disc disc
xiii 1.1- Introduction
An ion source is defined as a device in which the gas ions are produced, focused Giannuzzi et al [1], accelerated and emitted as a narrow intense beam Molokovsky et al [2]. The ion source is the important element in an ion beam system. In all types of ion sources Wolf [3], the ions are produced by an electrical discharge Lieberman et al [4] through a gas or vapor of liquid or solid at low pressure. The ionization is produced by electron impact in gaseous discharge. The general requirements are a source of electrons, a small region of relatively high gas pressure (10-2 – 10-4 mmHg), an electric field to accelerate the electrons in order to produce intense gas discharge, plasma, with relatively high electrons and ions density and special mechanism for extracting a collimated parallel high current ion beam. The emerging ion beam from any ion source Brown [5] is divergent due to the aperture effect.
However, some emergent ions while going through the aperture hit its sides and are then lost causing the reduction of the ion source efficiency. The divergence in the ion beam is undesirable in many applications because it forces the user to place the specimen very close to the source. In particle accelerator Hellborg [6] applications, it is necessary to use an ion beam with low divergence angle. Nowadays, these apparatuses are necessary tools in scientific research, therapy, technical analyses and in a number of industrial fields. Also, they are used in surface cleaning and pretreatment for large area deposition, thin-film deposition, deposition of thick
1 Diamond-like carbon (DLC) films, and surface roughening of polymers for improved adhesion and/or biocompatibility [7]. Ion rays were first observed by Goldstein [8] while studying gas discharge at low gas pressure. Wien investigated the properties of the ion rays and concluded that the ion beam originated from the atoms of the gas in the discharge tube Wien [9]. Thomson [10, 11] had been succeeded in the isotopes structure of Ne20 and Ne22 ion beam by using long tube for time of flight mass characteristics. The aim of the development of ion sources utilizing gas discharge was the generation of high ion concentrations by the use of relatively low applied voltage. A potential source of this type seemed to be arc discharge with a high intensity current at low voltage.
Polymer science was born in the great industrial laboratories of the world of the need to make and understand new kinds of plastics, rubber, adhesives, fibers, and coatings. Only much later did polymer science come to academic life. Perhaps because of its origins, polymer science tends to be more interdisciplinary than most sciences, combining chemistry, chemical engineering, materials, and other fields as well Spetling [12].
In this work, a new shape of cold cathode Penning ion source is used. The electrical discharge parameters such as discharge voltage, discharge current, and output ion beam current were measured at different dimensions and different pressures using Argon gas. The effect of magnetic field on this ion source has been determined at different pressures using Argon gas. The different anode –
2 permanent magnet distances and magnetic field strengths are determined at different pressures using Argon gas. The effect of negative voltage applied to Faraday cup on the output ion beam current is measured at the optimum conditions of this ion source and different discharge current using Argon gas.
The simple energy analyzer consists of two grids is used. The effect of positive voltage applied to the retarding grid on the extracted ion beam current is determined at two variable values of discharge voltage and certain pressure using Argon gas.
The efficiency of the new shape of cold cathode Penning ion source is determined at constant discharge voltage equals 3.92 KV and optimum operating parameters using Nitrogen and Argon gases. The divergence angle of the ion beam exit from the emission disc is calculated. The effect of ion beam using the new shape of cold cathode Penning ion source on the optical properties of PM- 355 polymer is measured.
1.2- Classification of ion sources
An ion source can determine the characteristics of accelerated beams and is characterized by two fundamental functions: 1- The creation of intense plasma with high electron and ion densities. 2- The extraction from the plasma and focusing of the ion beam into an exit canal.
3 Ion sources can be classified into different categories depending on: 1- The produced amount of beam current; a low or a high ion beam. 2- The charge of beam particles; positive or negative, singly charged or multiply charged ions or even a neutral beam. 3- The method used to produce ion beams in an ion source.
1.2.1- Electron bombardment ion sources History Electron bombardment ion sources have been investigated by many people starting with Dempster in 1916 [13].
Working principle Electrons are emitted by a cathode, usually by thermionic emission, and accelerated to an anode. Some of these primary electrons have collisions with gas atoms and ionize them. Secondary electrons from these collisions can be accelerated toward the anode to energies depending on the potential distribution and the starting point of the electron. The ionizing electrons energy is uniform and the energy spread of the ions is small. This is called the forced electron beam induced arc discharge (FEBIAD) mode see figure (1). Ions can be extracted through the anode or through the cathode area. An additional small magnetic field confines the electrons inside the anode, lets them spiral along its lines, and increases the ionization efficiency of the ion source.
4
Fig. (1) FEBIAD ion source Kirchner et al [14].
Advantages
Low energy spread of the ions, easy and cheap design possible. Disadvantages Low ion current, filament problems with Oxygen and corrosive elements.
1.2.2- Magnetron ion sources History It was first presented by Van Voorhis et al [15].
Working principle The magnetron has a hollow anode, but the cathode is a straight wire parallel to the anode axis and the magnetic field which is 0.1 T or more see figure (2).
5
Fig. (2) Magnetron ion source.
The primary electrons have to spiral along the magnetic field lines, which gives them a good ionization efficiency. Its performance is similar to a hot cathode penning source.
Applications
Mass separator, ion implantation, accelerators, ion beam analysis, and optical spectroscopy.
1.2.3- Freeman ion sources
History
A similar ion source design to that of the magnetron was developed at Harwell by Freeman in 1963 [16]. Optimization of the Freeman ion source for high current was done by Aitken in the 1980s [17].
6 Working principle and description of the discharge
It differs from the magnetron that it uses just a low external magnetic field of about 100 Gauss shown in figure (3). The magnetic field is maintained parallel to the axis of the cathode. The lifetime of this source is limited by the lifetime of the filament cathode. To improve the cathode lifetime, changing the polarity of the filament after some time of operation or heating by a.c. The Freeman ion sources are especially designed to deliver ion beams from nongaseous materials.
Fig. (3) Freeman ion source.
Advantages
High beam quality, stable operation for all elements.
Disadvantage
Cathode lifetime limited for Oxygen and corrosive gases.
7 Applications
It is one of the most appropriate for use in ion implanters and isotope separation till now. It is capable of delivering stable and high ion beams current for a variety of elements, gases, liquids and solids. Also it can be used for research in physics, industrial applications, and technology of ion beam generation and extraction.
1.2.4- RF ion sources History
The first radio frequency (RF) source was built by Getting and the technology advanced by Thoneman et al and Moak et al. A review of RF ion source and their operating characteristics which produces ion-beam current more than 100 mA of axial extraction type was developed by Tallgren [18] at CERN.
Working principle and description of the discharge
In practice, an RF discharge is formed in a vacuum vessel filled with a gas at a pressure of about 10-3 to 10-2 torr. To establish a suitable discharge, a few hundred watts of RF power is required. The RF frequency can vary from a mega-hertz to tens of megahertz. A low-pressure gas can be excited by RF voltages using two ways:
(1) Capacitively coupled discharge in which a discharge between two parallel plates across which is applied an alternating potential.
8 (2) Inductively coupled discharge in which a discharge generated by an induction coil. Most RF ion sources are operated with the second type of discharge.
Figure (4) shows a schematic diagram of a Thonemann type inductively coupled RF ion source [19]. It consists of a quartz discharge chamber to reduce recombination at the inside surface of the vessel surrounded by the RF induction coil from the outside. There are four external variables that affect the character of the discharge and the resulting ion beam such as; the gas pressure in the chamber, the magnitude and coupling to the plasma of the RF field, the external magnetic field and the extraction voltage.
Fig. (4) Inductively coupled RF ion source.
Advantages
Its clean resulting from absence of metallic surfaces in the discharge, high proton percentages (up to 90%), operation at low pressure yields a higher efficiency with respect to gas consumption and simplicity of construction and maintenance.
9 Applications
Research: for cyclotrons or synchrotrons and in neutral beam injectors for fusion research.
Industry: for ion implantation, ion beam etching, ion beam lithography, material surface modification.
1.2.5- Vacuum arc ion sources History The first reliable metal vapor vacuum arc (MEVVA) ion source was developed at Berkeley by Brown in the early 1980s Brown et al [20], MacGill et al [21].
Working principle and description of the discharge
The metal vapor vacuum arc occurs between hot cathode spots and a cold anode in vacuum. The principal arrangement of the vacuum arc ion source electrodes and the electric circuitry see figure (5). After ignition by a high voltage spark the vacuum arc plasma is maintained between cathode spots and the anode. The arc plasma expands through a hole in the anode into an expansion area that is usually connected to the anode via a resistor. The expansion area is terminated by an extractor grid for ion beam extraction. The ion current yield during the lifetime of a cathode is nearly constant and varies little from one cathode to the next.
10
Fig. (5) Vacuum arc ion source.
1.2.6- Large area ion sources
History Large area, multiple aperture ion sources were first developed as ion thrusters for space exploration Brewer [22] and Kaufman [23].
Working principle and description of the discharge
In order to form large ion beams, a sizable ion source chamber is needed. To achieve long cathode lifetime, the big multicusp sources are normally equipped with large numbers of Tungsten filaments. Electrons are emitted from these filament cathodes thermally. They can ionize the background gas particles and form a discharge plasma. The loss rate for the energetic primary electrons on the chamber walls (the anode) are drastically reduced by installing rows of permanent magnets on the external surface of the chamber as shown in figure (6).
11
Fig. (6) Large area multicusp ion source.
The magnetic cusp- fields are localized near the chamber wall leaving the interior volume almost free of magnetic field. It has been demonstrated that if a magnetic filter field is present in the source Ehlers et al [24]. The primary electrons are prevented from reaching the extraction region.
1.2.7- surface and thermal ionization ion sources 1.2.7.1- Surface ionization ion sources History Ionization at hot surfaces was first investigated by Langmuir et al in 1923 [25].
Working principle Surface ionization ion sources consist of a high temperature ionizer made of high work function material such as Tungsten, Rhenium, Iridium, or Zeolite for positive ion production, or low work function material such as Platinium coated with C, Tungsten
12 with a Cs monolayer, or Lanthanum hexaboride for the generation of negative ions as shown in figure (7).
Fig. (7) Surface ionization ion source Daley [26].
An example of surface ionization ion sources is the source of Daley as shown in figure (7) keeps the reservoir with the liquid material separate from the porous Tungsten ionizer and, thus, only vapor can reach the ionizer, which is protected from clogging liquid. The ionizer can be made of porous material where the element to be ionized can diffuse through from the rear side ( see figure 7) or can be contained inside a W- sponge Heinz [27]. The ionizer can be coated with material containing the element to be ionized or vapor of the respective element is directed to the hot surface where it may be ionized and reflected, adsorbed at the surface, and re-evaporated as ion or atom or just reflected as atom.
Advantages Stable surface for ion extraction, suited for usually difficult elements such as halogens and alkalines, highly element selective.
13 Disadvantages Extensive heat dissipation to the environment only suited for low work function or high electron affinity elements.
1.2.7.2- Thermo ionization ion sources History This ion source was developed around 1970 by Johnson et al at LBL [28] and by Beyer et al at JINR [29].
Working principle Thermo ionization is the same as surface ionization but is used in connection with a hot cavity as ionizer. The ionization efficiency can be improved since the particles are trapped inside the cavity and undergo several collisions with the cavity walls before leaving the source. At low plasma densities in the source, the degree of the ionization in the volume exceeds by far the one at the surface, but stays below the theoretical limit given by using Saha equation:
(1.1)
Where ni and no are the number of ions or atoms evaporated from the surface, gi and go are the statistical weights for ions or atoms, φi is the ionization potential of the atom, and φg is the work function of the surface.
14 1.2.8- Negative ion sources History Negative ion sources have been developed according to requirements from their application fields such as accelerators, fusion research, and material science. Light negative ions, especially hydrogen negative ions, were required for high energy accelerators and fusion research. During the development of hydrogen negative ion sources, a new mechanism in hydrogen negative ion production, i.e., volume production, and then the development of hydrogen negative ion sources based on the volume production started. Heavy negative ions were required for tandem accelerators. Sputter type heavy negative ion sources were successfully developed and have recently been able to deliver sufficient negative ion currents for material science applications. Also, negative ions could be produced by means of charge transfer from a positive ion beam.
Mechanism of negative ion production
In an ordinary ion source plasma, an ionization cross section for negative ions by particle collision is several orders of magnitude lower than that for positive ions. An electron detachment of negative ions due to a collision with plasma electrons takes place because the absolute value of electron affinity is as low as about 1 eV. The percentage of the negative ions is quite low, and high current negative ion extraction from the plasma is considered extremely difficult.
15 1.2.9- Penning ion sources History
Penning ion sources were first used as internal sources in cyclotrons Livingston [30]. Later, they were adjusted to linear accelerators as ion sources for multiply charged ions Gavin [31], and Wolf [32]. Working principle and description of the discharge
Figures (8) and (9) show the Penning ion source which consists of a hollow anode cylinder with one cathode on each end. A strong axial magnetic field confines the electrons inside the anode and keeps them oscillating between the cathodes which gives a high ionization efficiency. The cathodes can be cold or hot as shown in figure (8), one filament and a cold anticathode as shown in figure (9).
Fig. (8) Penning ion source with cold cathodes.
16 Gas is fed to the discharge through the anode close to the cathode(s) to ease the ignition of the arc and to keep the neutral gas flow through the extraction slit in the anode low. PIG sources can be operated in d.c. or pulsed mode, depending on the operational mode of the accelerator and on the power level needed to generate a specific ion beam. The arc voltage of a PIG ion source can vary from a few hundred volts to several kilovolts and the arc current from some mill amperes to tens of amperes, depending on the cathode and on the gas pressure. The magnetic field is between 0.1 and 1 T and is usually homogeneous.
Fig.(9) Penning ion source with filament cathode.
The ion sources Rovey et al [33] on the basis of a gas discharge with oscillating electrons (Penning discharge) are widely used due to a low working pressure, high gas profitability, capabilities of ion beams formation with a large current magnitude. A Penning ion generator (PIG) works with cold or heated cathodes Brown [34] to establish a high voltage, low pressure plasma discharge Liberman et
17 al [4]. In a typical configuration, electrons oscillate between two cathode electrodes inside an anode ring. An axial magnetic field increases the path length of ionizing electrons, making plasma production more efficient. Ions can be extracted Abdelrahman et al [35] and Giannuzzi et al [1] from PIG ion sources either axially through one cathode in the direction parallel to the discharge axis or, more commonly, radially through a slit in the anode normal to the discharge axis direction. The axial extraction is preferably applied in low intense ion sources, while the radial extraction is chosen mostly for high intensity ion sources. The Penning (PIG) ion sources have been widely used in particle accelerators Hellborg [6], sputtering Baragiola [36] and Behrisch et al [37], ion implantation Nastasi et al [38], evaporation of surfaces, electromagnetic separation of isotopes, fusion applications Loeb [39], and other ion beam equipment.
Advantages
High currents of multiple charged ions (Xe+16), easy metal ion production by sputtering, internal source for cyclotrons.
Disadvantages
Noisy beam, medium beam quality changes during source operation time, short lifetime (filament) with highly heavy ions, expensive if separate ion source magnet is needed.
18 Applications
Internal ion source for cyclotrons, linear accelerators and can be used for high- energy ion implantation.
1.2.10- Radial cold cathode ion source
This ion source is designed and constructed in Accelerators and Ion Sources Department – Nuclear Research Centre – Egyptian Atomic Energy Authority and used in all experimental results for my master work [40]. A schematic diagram of the radial cold cathode ion source is shown in figure (10).
Fig. (10) Schematic diagram of a radial cold cathode ion source.
It consists of two Copper disc anodes are placed on both sides of the Copper disc cathode at the same distance. The two Copper disc anodes and the Copper disc cathode are immersed in an insulator cylinder of Perspex material. The collector (Faraday cup) is situated
19 at a distance of 5 cm from the ion exit aperture of the cathode. The working gas is admitted to the ion source through a hole in the Perspex cylinder.
The operating principle of this ion source is based on the ionization produced by primary electrons colliding with gas molecules and the balance of ions in the centre between the two anodes due to equal positive voltage applied to the two anodes. Therefore high ion beam current can be extracted radially in a direction transverse to the discharge region.
Applications:
(1) It has been used for improving the mechanical properties such as hardness and tensile strength of stainless steel specimen with thickness 0.5 mm using pure Nitrogen gas. It was concluded that the hardness and the tensile strength of stainless steel specimen are increased about 23.25 % after exposure to pure Nitrogen ions for 200 minutes.
(2) It is used to determine the rate of sputtering of ceramic and stainless steel specimens of thickness 0.5 mm using Nitrogen gas for 90 and 200 minutes. It was found that the rate of sputtering of these specimens reach about 0.05 and 0.11 cm/sec respectively.
20 2.1- Ion beam formation
The extracted current from a charged particle source is limited either by the emission capability or by space charge forces. The maximum current density J can be calculated by the Child- Langmuir [41, 42] equations (2.1), (2.2):
J(A/m2)= (2.1)
-12 * With permittivity εo = 8.854 X 10 F/m, electric charge q = q X 1.602 X 10-19 AS, q* is the charge state, atomic mass m= u X 10-24 g, u is the mass in atomic mass units, φ (V) is the potential drop across the gap d (m), in more practical units:
J (A/m2) = (2.2)
For beam transport, not only the extracted current, but also the beam quality is important. The beam quality is measured by the emittance, which describes the particle distribution δ in phase space δ. A measure of the density of the four dimensional phase space density is the brightness B of a beam and can be calculated by the relation:
(2.3)
21
The brightness is a measure of the current density per unit solid angle. When the beam is accelerated, the transverse phase space will shrink with the velocity.
The normalized emittance is therefore: * εn, x = εx . β (2.4) * εn, y = εy . β (2.5)
2.1.1- Extraction from fixed emitters The particle starting coordinates are given by the geometry of the emitter itself. The emittance of the beam is determined by the emitting area, its shape, and the temperature of the emitted particles. The longitudinal emittance is given by the temperature of the particles and the stability of the extraction voltage.
2.1.2- Extraction from plasma sources In plasma sources the ions are generated in a discharge chamber. From the point of generation they drift until a fraction of them reaches the extraction region. The saturation value of ion current density, js, which can be extracted from plasma, is given by Coupland et al [43] and Thompson [44]:
(2.6)
Where k = 8.616 X 10-5 eV/ K, which is the Boltzmann constant,
Te is the electron temperature, and ni is the ion density in the plasma. 22 The emittance of the extracted beam is given by the plasma parameter, existing magnetic fields, and aberrations in the extraction. There is only one potential for a given geometry and plasma conditions that will create a beam with desired properties. The Poissance Π Green [45] and Lejeune [46] has been defined as an electrical quantity:
Π = (2.7)
With I the extracted current, the perveance Pc has been defined as a geometric quantity Green [45] and Lejeune [46]:
Pc = (2.8)
Where A is the emitting area.
The minimum theoretical divergence angle ωo of the beam for planar extraction systems (slit) has been estimated as Thompson [44] and Green [45]:
(2.9)
Where a (m) is the half width of the slit and d (m) is the gap width. For round apertures with radius r a similar expression can be estimated:
(2.10)
23 According to these equations round apertures have smaller divergence angles; however, zero divergence can not be achieved because of: - Thermal energy spread in the plasma - Aberrations within the extractor For the cylindrically symmetric case the maximum current can be estimated and the assumption of a certain aspect ratio. A good aspect ratio is on the order of S ~ 0.5 Green [45].
I (mA) = 0.703 (2.11)
The voltage breakdown limit determines the necessary gap width. The empirically determined limit is:
d (mm) ≥ 1.41X10-2 .φ(KV)3/2 (2.12)
The emittance of the extracted beam can be estimated as:
εx, y ~ ωo . ropt (2.13)
If the emittance has a waist at that location, ωo is the maximum divergence angle. The expected emittance can be rewritten as:
-2 3/2 εx, y ≥ 0.7 X 10 . ωo . φ (KV) (2.14)
The upper limit of the brightness can be given as:
(2.15)
24 2.2- Extraction of ions from plasma
The extraction process basically consists of applying a high voltage between an ion reservoir and a perforated accelerated electrode. The trajectories of the accelerated ions, which immediately determine the maximum beam quality are influenced by several factors: The applied field strength, The shape of the emitting surface which may be solid ( field- and surface ionization sources) or flexiable (plasma sources), and The space charge density of the resulting beam itself. In the case of plasma sources, the emitting surface is termed by the "meniscus". Its detailed shape depends on the electrical field distribution due to the applied boundary conditions and the local densities of plasma ions, electrons and accelerated ions.
With plasma sources, the plasma meniscus acts as the boundary layer between the discharge plasma and the accelerated beam particles. The depth and position of this layer, with respect to the surrounding electrodes depends on the densities of plasma electrons and ions, their mobilities which can be expressed in terms of temperatures. From ion optical considerations one can deduce that the ion temperature for some sources might typically be around 0.2eV, whereas a typically electron energy would be a few electron volts Ehlers et al [47].
25 2.2.1- Design of the ion extraction system
In order to extract ions from the appropriate source, and to accelerate and collimate them for subsequent focusing into the desired being shape, an arrangement of carefully designed electrodes must be used. This electrode system must create the proper configuration of electric fields at the surface of the ion source and along the acceleration path. The surface which forms the source of ions can be either of fixed geometrical form. An optimum geometry for the extraction electrode is essential, with the following requirements: (a) It must give high convergent ion beam free of aberration with maximum number of ions. (b) It must prevent neutral particles from leaking to the high- vacuum chamber. If these two requirements are satisfied, the efficiency of the ion source is increased.
2.2.2- Classical extraction system
The plasma is an equipotential region with very weak electric field i.e. no electric field inside. If an electrode surface comes nearer to the plasma surface S1, figure (1-a), with potential less than that of the plasma surface, a positive ion sheath is formed and the whole potential difference between the plasma and this electrode is localized within the sheath, the wall of the discharge vessel or any electrode carrying a potential less than that of the plasma. As the
26 potential difference between the plasma and the electrode S2 Changes, the thickness of the sheath alters in such a way that the surface S1 remains in equilibrium, where S1 is an equipotential surface, vs1= vp, where vp is the plasma potential.
When a hole is drilled in S2 (the sheath) the plasma expands and gives a concave plasma boundary outside the discharge as shown in figure (1-b) Thonemann et al [19].This plasma boundary is the ion- emitting surface and ions can be extracted from it, or diffused out, by applying a negative potential to an electrode S3, (extractor), nearest to it, as shown in figure (1-c). The plasma boundary is considered as an elastic electrode, its shape and position is affected by the electric field, the extractor electrode, the shape of this electrode, and the discharge parameters.
To obtain a parallel ion beam from the plasma boundary surface an optimum potential is applied between the shield and the extraction electrode, see figure (1-c). At that potential difference the emitting surface of the plasma boundary is flat. After an intense beam has passed the extraction electrode, its space charge has to be compensated; otherwise servers below- up of the beam envelope would occur. In many cases some of the residual gas particles that are present within the beam line will be ionized by impinging beam ions, and this process can generate a sufficient number of compensating electrons.
27
S1 Plasma boundary (ion emitting surface), S2 Discharge vessel wall, S3 Extraction electrode.
Fig.(1) Schematic Diagram of ion beam formation AWAD [48].
But the electrons must be kept from being accelerated back into the source by the extraction field. When a high ion current is required, the aperture hole in the extraction electrode can be increased, also higher extraction voltages may be used to form a concave plasma boundary which results in producing a focused beam of higher intensity as shown in figure (2-a). However, increasing the area of the holes cannot be done indefinitely because of gas loading, and the use of high extraction voltages which may be accompanied by high voltage breakdown. 28 Therefore, the advantages of plasma diffusing outside the source through a small aperture, which restricts the gas flow from the source to the extraction region, can be used. This depends upon the plasma penetration through a small hole outside the source. This principle is well known and was first used in ion sources by Gabovich et al [49]. The plasma passes through a small aperture to the extraction region and leads to bigger plasma boundary which results in a larger ion current. The ions can be extracted from the expanded plasma by applying a negative potential electrode S3 as shown in figure (2-b). This electrode may be a cylinder or a grid Solpnshkov [50].This method has the advantage of producing ion beams with low divergent angle Collins et al [51]. Another way for ion extraction is shown in figure (2-c). It depends on fixing a grid in the hole of S2 electrode and using an extraction grid. This gives well- defined extraction geometry and the plasma boundary in this case will be defined according to the geometrical design Rose [52]. These two conditions are satisfied for an emissive conducting surface, operating in space- charge- limited conditions; S is an equipotential surface, with zero normal gradient. Gas discharge ion sources that provide beams of high intensity fall into two categories:
+ 8 + 10 -3 (1) The density ni is low or medium (10 < ni < 10 cm ). + 10 + 14 -3 (2) The density ni is very high (10 < ni < 10 cm ); the method of producing the plasma determines the category.
29
S1 Plasma boundary, S2 Discharge vessel wall, S3 Extraction electrode.
Fig. (2) Schematic Diagram of ion beam formation for high intensity plasma AWAD [48].
2.2.3- Different shapes of extraction system
a- Axial diode system
This simple extraction scheme can be applied if space charge compensation within the extracted ion beam is not important. Two electrodes determine the extraction system: an outlet electrode and a ground electrode. b- Axial Triode system
The extraction system consists of three electrodes: an outlet electrode, a screening electrode, and a ground electrode. The reasons for using a triode extraction system:
30 • Preserving the space charge compensation of the extracted ion beam (accel- decel system). • Having the possibility to change the extraction field strength without changing the beam strength Tinschert et al [53] and Spädtke et al [54].
c- Multigap Extraction Systems
Extraction systems with more electrodes such as tetrodes Whealton [55] or pentodes Keller et al [56] have been used for special purposes. Possible applications are special beam forming electrodes to improve the beam quality, post acceleration to higher voltages, or intermediate electrodes in H- extraction systems to separate the electrons from the negative ions.
d- Multiaperture Extraction System
If the emitting area is too small to deliver enough current, it can not be increased above a certain limit without reduction in beam quality. One possible solution to this problem is to increase the number of extraction holes. In practice, up to several thousand holes have been realized. The emitting area of the multiaperture system is in such a case. The highest achievable transparency can be estimated as ~ 60 %.
31 e- Mesh Extraction System
Advantages of mesh extraction systems are: • It provides a stable, well defined emitting surface. • Emission control capability True [57]. • High transparency.
The disadvantage is the limited lifetime of the mesh due to sputtering. A mesh in front of the extraction system can also be used to minimize the noise of the beam Arango et al [58] and Hiraoka et al [59]. f- Postacceleration
If the extraction voltage is not high enough for the desired beam energy, the post acceleration is necessary. This requires that the charged particle source, including all power supplies, be installed on a high voltage platform which the beam can be post accelerated. Mass and charge state can be done on the high voltage platform.
The post acceleration can be done with a multi- or a single- gap acceleration column. In both cases the focusing strength of the gap should be matched to the beam emittance, the rigidity of the beam, and the defocusing strength of the space charge. Multigap structures normally have low focusing power, best suited for lower ion currents. For higher beam
32 current, stronger focusing single- gap devices are used. A negative screening electrode can be used behind the acceleration system to preserve the space charge compensation of the accelerated beam.
g- Extraction in Transverse Magnetic Fields
When the magnetic field is perpendicular to the extraction system, charge separation takes place already in the extraction. An example of such a situation is the radial extraction from a Penning ion source.
2.3- PIG ionization
Penning ionization is a form of chemi-ionization, an ionization process involving reactions between neutral atoms and/or molecules Arango et al [58] and Hiraoka et al [59]. The process is named after the Dutch physicist Frans Michel Penning who first reported it in 1927 Penning [60].
Penning ionization refers to the interaction between a gas-phase excited-state atom or molecule G* and a target molecule M resulting in the formation of a radical molecular cation M+., an electron e−, and a neutral gas molecule G [61]:
(2.16)
Penning ionization occurs when the target molecule has an ionization potential lower than the internal energy of the excited-
33 state atom or molecule. Associative Penning ionization can also occur:
(2.17)
Surface Penning ionization refers to the interaction of the excited- state gas with a surface S, resulting in the release of an electron.
(2.18)
The positive charge symbol S + that would appear to be required for charge conservation is omitted, because S is a macroscopic surface and the loss of one electron has a negligible effect.
2.4- Effect of static magnetic field on gas discharges
The electron and ion currents leaving the plasma of the discharge are determined by diffusion. If the gas discharge is exposed to a static magnetic field, the diffusion of charged particles will change. If a d.c. gas discharge is exposed to a magnetic field with a direction parallel to that of the electric field, the charged particle currents will decrease towards the tube wall in the direction normal to the magnetic field. This decrease is caused partly by the change in the movement of electrons normal to the axis under the magnetic field action. As the magnetic field increases, smaller number of electrons is able to reach the tube wall as they move on a helical path with decreasing radius. The other cause of the decrease is understood
34 from the diffusion theory since in the equation describing the electron current reaching the wall by diffusion as:
Je = - De grad ne (2.19)
The diffusion coefficient De decrease in a magnetic field in the direction normal to that of the field according to the ratio:
2 DH ~ DH=0 / H (2.20)
2 2 2 As given by: DH = DH=0 / [ 1 + (x H / v x ) (2.21)
The value of the diffusion coefficient remains unchanged in the direction parallel to that of the magnetic field. Because of the greater mass of the ions, their motion is only slightly affected by the magnetic field. If the discharge is exposed on a magnetic field, two effects will assert themselves. One of these effects causes the positive column of the discharge to be deflected by the magnetic field towards one of the tube walls. The other effect is the decrease in the diffusion of charged particles in the direction normal to the magnetic field, which in this case coincides with the directions of the axes of the electric field and the discharge.
In the high frequency discharge with alternating electric field the charged particle current from the quasi- neutral plasma is determined by the diffusion process. The exposure of an alternating magnetic field induced high frequency discharge to a static magnetic field is also responsible for effects other than the resonance phenomenon. If
35 the value of the magnetic field continues to increase, it causes the power consumption and the plasma concentration to increase as well. This phenomenon can be explained by the mentioned decreasing diffusion in the direction normal to the magnetic field.
2.5- Cold cathode arc- discharge ion sources with oscillating electrons in magnetic field
In the ion sources with heated cathode, the cathode lifetime limits that of the ion source and the construction of the assembly is complicated by the use of heated cathode. Many investigations prefer cold cathode ion sources for the production of both low and high intensity ion beams. The latter have a longer lifetime, they are of simpler design and their power requirement is lower. These types are known as cold cathode, Penning type ion sources Nagy [62, 63].
The cathode lifetime, the anode voltage and the discharge stability must also be considered. The cathode lifetime is determined by the degree of cathode sputtering while the anode voltage and the stability of the discharge depend on the maintenance of the cathode surface properties. The ions are extracted from the cold cathode, Penning type ion sources either axially in the direction parallel to that of the discharge axis and of the magnetic field, or transversally in the direction normal to the axial direction. The axial extraction is applied in low intensity ion sources, while the transversal arrangement is chosen for high intensity ion sources. Low intensity beams can be extracted with a transversal and high intensity beams
36 with an axial arrangement. The contribution from atomic ions to the beams extracted from these types of ion source is rather small, not more than 10 to 50 per cent of the beam.
2.5.1- Cold cathode Penning type ion sources with axial ion extraction
One of the Penning type ion sources with axial ion extraction which produces low intensity beams utilizing a permanent magnet for the generation of the magnetic field as shown in figure (3) Nagy [64].
Fig. (3) Keller's version of a low intensity ion source with cold cathode, oscillating electrons and axial ion extraction.
The cathodes of the ion source are hollow to improve the stability of the discharge. Cathodes of this type are made of iron Keller [65] or magnesium Keller [66, 67]. In this source they are attached to the mild iron poles of the permanent magnet. The ions are extracted
37 from the discharge volume at the anticathode aperture. This ion source operates with iron cathodes in the anode voltage range Ua =
470 to 520 V and the discharge current is in the range Ia = 10 to 120 mA. The ion current obtainable from this source varies from 0.1 to 1 mA. The magnetic field applied to the discharge volume of this source is ~ 1000 gauss.
2.5.2- Cold cathode Penning type ion sources with transversal ion extraction
One of the Penning type ion sources with axial ion extraction which produces low intensity beams can be seen in figure (4).
Fig. (4) Heiniche – Bethge – Bauman's low intensity ion source with cold cathode, oscillating electrons and transversal ion extraction.
The source has 3 mm thick cathodes made of Tantalum and attached to the poles of the electromagnet. The cathodes are
38 electrically isolated from the magnetic poles. Their useful lifetime is about 12 hours. The outlet aperture is on the side wall of the cylindrical Molybdenum anode. The anode is attached to the electrode of the extracting system and it can be adjusted along with the latter. The magnetic field in the discharge volume varies between 0.5 and 1 k gauss. The maximum ion current obtainable from this source is ~ 100 µA. In the high intensity ion source the cold cathodes are exposed to intense ion bombardment. The temperature of the cathode surfaces can be raised by this bombardment which causes the electron emission to increase together with the intensity of the discharge. This effect can become more important if the heat conduction of the cathodes is poor. In this case, the voltage drop in the discharge decreases to a few hundred volts Mills et al [68].
2.6- Paschen's law
Friedrich Paschen developed a law in 1889 Paschen [69], which sets the breakdown voltage as a function of the product of the pressure (p) and the inter-electrode distance (d):
Vb = f (p× d) (2.22)
Townsend [70] presented a model for the gas breakdown process in 1915. From this model, it is possible to deduce mathematical formulae for the Paschen coefficients. Paschen’s law states that the breakdown potential, Vb, of a gas is a function of the pressure
39 multiplied by the distance between the electrodes. There will generally be a minimum value for Vb and that value is constant for a given electrode pair in a given gas. The Vb versus PD curve is found by applying a voltage across two electrodes in a vacuum chamber. The voltage is increased until current crosses the gap. The pressure is then adjusted and the process is repeated [71].
(2.23)
(2.24)
The first Townsend coefficient α is the probability to ionize a gas neutral by collision per unit length of path, i.e. it is the number of collision per unit length of path times the ionization probability per collision. Hence:
α = (1/ λe) X [ exp( - Ei / Ee ) ] (2.25)
With λe the electrons mean free path, Ei the ionization energy of the gas, Ee the electron energy colliding with the gas neutral. Equation (4) is more commonly known as (Cobine [72] p. 162): α = A P exp ( - BP / E) (2.26)
40 With Ee = e λe E . Assuming that the electric field is uniform before the gas breakdown ( E = Vb / d ) equation (2.22) can be transformed to:
Vbr = BPd / ( C + ln Pd ) (2.27)
With λe = KB T / σei P, one can deduce:
A = σei / K T (2.28)
and the Paschen coefficients:
B = σei Ei / e K T,
C = ln ( σei / α d K T ) (2.29)
2 Where σei is the electron impact ionization cross-section (in m ),
Ei is the ionization energy of the gas (in J), e is the elementary charge (in C), k is the Boltzmann constant, T is the temperature (in K). The ionization cross section of Argon by electron impact has been the topic of numerous investigations and give consistent results with a maximum value (regarding its dependency on the impacting electron energy) ranging from 2.7×10-20 m2 Lotz [73] to 3.8×10-20 m2 Jha et al [74]. We take the value given 3.5×10-20 m2, this leads to the calculated value for A is 8.5 Pa-1.m-1, which is in the range of the experimental values. Similarly, the calculated value of cold Molybdenum cathode Penning ion source for B is 82.84 V. Pa-1. m-1.
41 2.7- Particle analyzers
Ion-assisted plasma processing is an active field of research. The ion flux onto the substrate is as well as the ion energy distribution having been identified as significant parameters for dry etching or thin film deposition. External bias voltages are typically applied to the substrate to manipulate the ion energy distribution during processing Patterson et al. [75]. It has been shown that adequate biasing of the substrate can significantly support the etch selectivity in semiconductor processing Wang et al. [76], Silapunt et al. [77], Buzzi et al. [78], or the synthesis of certain crystalline phases in the deposition of hard coatings Yamada et al. [79] , and Audronis et al. [80]. Several experimental and theoretical methods have been developed and applied to determine the ion flux and the ion energy distribution at the substrate, such as the use of ion mass/energy analyzers Janes et al. [81], Abraham et al. [82], Woodworth et al. [83] or extensive modeling of plasma and sheath Kratzer et al. [84], Agarwal et al. [85].
More sophisticated analyzers can be used for the analysis of the atoms, molecules or their ions as well as the electrons in the discharge. Depending on the type of analyzer, we can obtain the energy distribution, the mass distribution or both. Particle energy analyzers are more versatile, and can be used to obtain more reliable measurements of the electron and ion energy distribution functions than we can obtain from probes, at the price of complexity and
42 a greater perturbation of the plasma. In large volume plasma, the analyzer can be placed within the plasma Oertl et al. [86], Stenzel et al. [87], but in most laboratory plasmas used for materials treatment, a more convenient arrangement is to place it behind an electrode, coupled to the plasma via a small hole. The most obvious example is to use the analyzer to measure the velocity or charge/mass distribution of the ions (or neutral particles) incident on
a substrate (for example the cathode of a discharge).
2.7.1- Energy analyzers
It is often important to measure the energy of the heavy charged particles in plasma. Although probes can provide useful and detailed information about the electron component, such measurements of the ions require the use of an energy analyzer, where the electron component can be removed by the application of suitable potentials. The energy distribution of the emergent ion beam was investigated by using a simple retarding field analyzer which is shown in figure (5). This energy analyzer was made from two Copper grids which were of 40% transmission. It consists of two grids called screen and retarding grids, in which the positive potential, VR, was applied to the retarding grid and the screen grid was at the earth potential. The purpose of the screening grid is to screen the Faraday cup from the high field produced by the retarding grid so that the secondary electrons from the Faraday cup are not accelerated towards the retarding grid.
43
Fig. (5) Cold cathode Penning ion source and simple energy analyzer electrical circuit.
2.7.2- Mass analyzer
In most plasma, there are several ion species present; even in relatively clean hydrogen plasma in fusion machines, there are always contaminants such as carbon which is sputtered from the walls and which enters the plasma. The measurement of these ions is important for correlation with the general level of contamination in the plasma. Although it is interesting to measure the energy distribution of these ions, it is crucial to measure their charge states and absolute concentrations (if possible). In plasmas for materials treatment, the multiple reactive species in the plasma are responsible for the phenomena which we want to promote: etching of a surface, surface deposition of a given material, or the production of new 44 species in plasma chemistry. When we want to measure the mass spectrum of charged particles, we need to use mass analyzers – devices which separate the ion current according to the mass of the ion.
There are several designs which have been used over the years, some with more universal applicability than others, and some with particular interest because of their compact nature. A convenient orientation is to place the analyzer in an evacuated chamber, behind the cathode of the discharge, connected via a small hole to the main discharge volume. In this case, a small fraction of the ions streaming toward the cathode surface will pass through the hole, and be analyzed. As in the case of the energy analyzers, this hole should be smaller than the sheath dimension (a few Debye lengths) in order to be able to exclude the plasma. Since the size of the hole will then scale with n-½, we find that the current will only depend on the electron temperature and the ion mass.
45
46 3.1- Design and construction of ion source
Many trials have been made on Penning ion source. Finally, the design and construction of the new shape Penning ion source with two cold Molybdenum cathodes is given as below with the following dimensions to suit the required parameters used in applications.
3.1.1- Design of the cold Molybdenum cathode Penning ion source
A schematic diagram of the cold Molybdenum cathode Penning ion source is shown in figure (1). It consists of Copper cylindrical hollow anode of 40 mm length, 12 mm diameter, and has two cone ends of 15 mm length, 22 mm upper diameter and 12 mm bottom diameter. The two movable Molybdenum cathodes are fixed in Perspex insulator and placed symmetrically at two ends of the anode. The Copper emission disc of 2 mm thickness and has central aperture of different diameters is placed at the middle of the anode for ion beam exit. The inner surface of the emission disc is isolated from the anode by Perspex insulator except an area of 5 mm diameter to confine the discharge in this area. Faraday cup is placed at different distances from the emission disc aperture and used to collect the output ion beam from the ion source. The Copper extractor electrode is placed at different distances from the emission electrode and used to extract the ions from the ion source.
47
Fig.(1): Construction of a cold Molybdenum cathode Penning ion source.
An axial Samarium - Cobalt permanent magnet is placed around the anode at different distances to increase the ionization efficiency. The working gas is admitted to the ion source through a hole of 1 mm diameter in the outer surface of the cylinder anode.
3.1.2- Electrical circuit of the ion source
The electrical circuit of the cold Molybdenum cathode Penning ion source is shown in figure (2). Digital stabilized power supply is used for measuring the gas discharge which is capable to produce an output d.c voltage which varies from 0 to 20 KV with d.c current varying from 0 to 25 mA. A limiting resistance of 100 KΩ, 10 watt is used to protect the power supply when the breakdown occurs.
48 A voltmeter (kilovolts) ranging from 0 to 20 KV was connected in parallel and ammeter (milliamperes) measuring from 0 to 10 mA was connected in series with the load to measure both the discharge voltage Vd and the discharge current Id of the working gas respectively.
Fig.(2): Electrical circuit of cold Molybdenum cathode Penning ion source.
The Faraday cup terminal was connected to the earth through ammeter (microamperes) from 0 to 1000 µA ranges to measure the output ion beam current Ib extracted from the ion source.
3.2- vacuum system characteristics
The experimental investigations have been carried out by using a high vacuum system of standard type. It consists of a stainless steel Mercury diffusion pump backed by rotary pump. A liquid Nitrogen
49 trap is fixed between the vacuum system and the ion source vacuum chamber. A differential solenoid – operated valve which is designed to close the vacuum manifold and to admit atmospheric air into the pump when it is stopped. Prepumping of the chamber is carried out using a vacuum manifold branch with a hand – operated valve. The components of the system used, is shown in the figure (3) which consists of:
3.2.1- rotary pump
It is Edwards type 1 Sc 450 B of speed 450 L/ minute. It is used for obtaining a pressure about 10-2 to 10-3 mmHg.
3.2.2- diffusion pump
It is speedivac Edwards with electrical heater type 6 M 3 A of speed 270 L/ sec. It is used to obtain high vacuum about 10-3- 10-7 mmHg. It must be operated continuously in series with the rotary pump. In a vacuum system, a chamber is connected directly to a diffusion pump, backed by a rotary pump.
3.2. 3- liquid Nitrogen trap
The liquid Nitrogen trap is fixed between the vacuum system and the ion source vacuum chamber.
50
Fig. (3) Schematic diagram of the experimental arrangement.
51 3.2. 4- Vacuum chamber
The ion source vacuum chamber is a stainless steel cylindrical tube of diameter 25 cm and 18 cm length. The chamber has a Perspex flange carrying the terminals of the electrical circuit which are feeding and measuring the parameters governing the characteristics of the ion source at one side. The electrodes are electrically connected to the other side of the flange.
A digital vacuum meter type 1005 Edwards with two gauge heads is used, where the vacuum gauge head (pirani) is used to measure the fore vacuum inside the connecting tubes and the ion source vacuum chamber. The vacuum gauge head (ionization lamp) is used to measure the high vacuum inside the ion source vacuum chamber.
3.2.5- Gas handling of the system
The gases (Argon and Nitrogen) used in the experimental investigations are admitted into the ion source from cylinder tanks via tubes through a rubber hose connected with a needle valve to control and adjust the rate of flow of the gas used. Gas is fed to these two ion sources usually through aperture in the anode.
3.2.6- Operating of the system
The ion source has been cleaned before connected to the vacuum system. The procedure of cleaning is done by polishing to remove irregular parts from the surfaces. Then washing all electrodes,
52 envelope and Faraday cup with Ethanol and distilled water to remove the contamination due to the eroded material of the discharge. The rotary pump is switched on and left running until the ultimate pressure of the pump is reached and then the valve between the rotary pump and ion source chamber is opened. Then the water cooled diffusion pump is connected to the ion source chamber after the pressure in the connecting tubes and ion source chamber reaches 10-2 mmHg. The trap between the diffusion pump and the ion source chamber is filled with liquid Nitrogen, this is necessary to avoid the Mercury vapor to contaminate the ion source chamber. The experiment starts after the pressure in the ion source chamber is about 10-6 mmHg.
The gas is admitted through the needle valve to flow in the ion source to reach the working pressure which depending upon the aim of the experiment ranges between 10-2 to 10-4 mmHg. Then the instrument is ready to be used for measuring the different parameters. For a fixed geometry of the ion source and gas pressure, the anode voltage is increased gradually to reach the glow discharge region. Glow discharge sets up between the two cathodes and anode. With the increase of the anode potential, the plasma boundary layer is extended to the cathode, where the glow discharge takes place between the anode and the cathode for a potential range between 0 to 8 KV.
53 The ion beam is extracted from the discharge region through the exit hole placed on the anode and collected by the Faraday cup. The discharge current, the discharge voltage and the output ion beam current for various chamber pressures were measured for different gases.
54 4- Experimental Results of a Cold Molybdenum cathode Penning Ion Source
The experimental results have been carried out using a cold Molybdenum cathode Penning Ion Source as shown in figure (1) which has the following dimensions:
Fig. (1) Dimensions of cold cathode Penning ion source.
4.1- Determination of the optimum anode – cathode distance
In this experiment, the distance between the anode and each cathode, dA-C, is varied with values equals 5, 6, 7, and 8 mm at Dem. equals 1.5 mm, Duncovered em. disc equals 5 mm, and dem.-F.C. is fixed at 3 cm. The optimum dA-C for stable discharge current and a maximum output ion beam current can be obtained.
55 4.1.1- Input characteristics
Figures (2), (3), (4) and (5) show the discharge voltage, Vd (KV), versus the discharge current, Id (mA), at different pressures using
Argon gas, Dem = 1.5 mm, dem.-F.C = 3 cm, and dA-C is varied with values equal to 5, 6, 7, and 8 mm. It is clear from the figures that the discharge current increases with increasing the discharge voltage and the discharge voltage starts at lower potential in case of high pressure (6 X10-4 mmHg) than that in case of low pressure (3 X 10-4 mmHg).
-4 2.5 1 P=3X10 mmHg dA-C = 5 mm Ar 2 P=4X10-4 mmHg -4 1 3 P=5X10 mmHg 4 3 2
) 4 P=6X10-4 mmHg A 2 (m d , I t
n 1.5 DUncovered emission disc= 5mm e r
r dem-F.C= 3cm
cu Dem= 1.5 mm e g 1 ar sch i D 0.5
0 00.511.522.533.5
Discharge voltage , V (KV) d
Fig.(2) Discharge current versus discharge voltage at dA-C = 5 mm, Dem. = 1.5 mm and dem. – F.C = 3 cm using Argon gas.
56 2.5 D = 5mm 1 P=3X10-4 mmHg dA-C = 6 mm Uncovered emission disc 2 P=4X10-4 mmHg dem-F.C= 3cm 3 P=6X10-4 mmHg Dem= 1.5 mm
2 ) mA (
d
, I 2 1.5 3
t 1 rren Ar
e cu 1 rg a h c s Di 0.5
0 1 1.5 2 2.5 3 3.5 4
Discharge voltage , Vd (KV)
Fig.(3) Discharge current versus discharge voltage at dA-C = 6 mm, Dem. = 1.5 mm and dem. – F.C = 3 cm using Argon gas.
2.5 dA-C = 7 mm 1 P=3X10-4 mmHg Ar 2 P=4X10-4 mmHg -4 3 P=5X10 mmHg 4 3 -4 2 2 4 P=6X10 mmHg ) A
(m DUncovered emission disc= 5mm d 1 , I 1.5 dem-F.C= 3cm t Dem= 1.5 mm rren cu e
g 1 r a sch i D
0.5
0 0 0.5 1 1.5 2 2.5 3 3.5 4
Discharge voltage , Vd (KV)
Fig.(4) Discharge current versus discharge voltage at dA-C = 7 mm, Dem. = 1.5 mm and dem. – F.C = 3 cm using Argon gas.
57 2.5 -4 1 P=3X10 mmHg dA-C = 8 mm Ar 2 P=4X10-4 mmHg -4 3 1 3 P=5X10 mmHg 4 2 -4 2 4 P=6X10 mmHg ) A DUncovered emission disc= 5mm
(m 1.5 d dem-F.C= 3cm , I Dem= 1.5 mm t
rren 1 cu e rg a h sc i 0.5 D
0 00.511.522.533.5
Discharge voltage , Vd (KV)
Fig.(5) Discharge current versus discharge voltage at dA-C = 8 mm, Dem. = 1.5 mm and dem. – F.C = 3 cm using Argon gas.
4.1.2- Output ion beam characteristics
Figures (6), (7), (8) and (9) show the output ion beam current, Ib
(µA), versus discharge voltage, Vd (KV), at different pressures, Dem
= 1.5 mm, dem.-F.C = 3 cm, and dA-C is varied with values equal to 5, 6, 7, and 8 mm using Argon gas. It is clear that these figures are similar in shape to the discharge voltage – discharge current curves. In order to increase the output ion beam current through the discharge; we must increase the number of electrons created by the ionization. The electric field and hence the voltage across the anode and the cathode must be large to increase the ionization rate by the electron impact.
58 70 1 P=3X10-4 mmHg Ar dA-C = 5 mm 2 P=4X10-4 mmHg 1 -4
) 60 3 P=5X10 mmHg A (µ b
, I 50 t
en DUncovered emission disc= 5mm r 2 r 40 dem-F.C= 3cm cu Dem= 1.5 mm eam
b 30 n o
i 3
t u
p 20 t u O 10
0 00.511.522.533.5
Discharge voltage , Vd (KV)
Fig.(6) Output ion beam current versus discharge voltage at dA-C = 5 mm, Dem. = 1.5 mm and dem. – F.C = 3 cm using Argon gas.
120 Ar 1 P=3X10-4 mmHg dA-C = 6 mm 1 2 P=4X10-4 mmHg -4 ) 100 3 P=5X10 mmHg A (µ b , I 80 t
n DUncovered emission disc= 5mm
e 2 r
r dem-F.C= 3cm u
c 60 Dem= 1.5 mm m a 3 on be
i 40
put t
Ou 20
0 0 0.5 1 1.5 2 2.5 3 3.5 4
Discharge voltage , Vd (KV)
Fig.(7) Output ion beam current versus discharge voltage at dA-C = 6 mm, Dem. = 1.5 mm and dem. – F.C = 3 cm using Argon gas.
59
80 -4 dA-C = 7 mm 1 P=3X10 mmHg Ar 1 2 P=4X10-4 mmHg 70 3 P=5X10-4 mmHg 2 ) A 60 (µ b , I
t 50 DUncovered emission disc= 5mm en
rr dem-F.C= 3cm 3
cu 40 Dem= 1.5 mm am e b
n 30 o i t u p t 20 u O
10
0 01234
Discharge voltage , Vd (KV)
Fig.(8) Output ion beam current versus discharge voltage at dA-C = 7 mm, Dem. = 1.5 mm and dem. – F.C = 3 cm using Argon gas.
70 Ar 1 P=3X10-4 mmHg dA-C = 8 mm 2 P=4X10-4 mmHg 60 3 P=5X10-4 mmHg 1 ) A (µ
b 50 , I t
en 40 DUncovered emission disc= 5mm rr dem-F.C= 3cm cu 2 30 Dem= 1.5 mm eam b n
o 3 i
t 20 u p t u O 10
0 00.511.522.533.5
Discharge voltage , Vd (KV)
Fig.(9) Output ion beam current versus discharge voltage at dA-C = 8 mm, Dem. = 1.5 mm and dem. – F.C = 3 cm using Argon gas.
60
Figures (10), (11), (12) and (13) show the output ion beam current, Ib (µA), versus discharge current, Id (mA), at different pressures, Dem = 1.5 mm, dem.-F.C. = 3 cm and dA-C is varied with values equal to 5, 6, 7, and 8 mm using Argon gas. It is clear from the figures that the output ion beam current increases with increasing -4 the discharge current and at P = 3 X 10 mmHg and dA-C = 6 mm, a maximum output ion beam current equals 106 µA can be obtained.
70 1 P=3X10-4 mmHg Ar dA-C = 5 mm 2 P=4X10-4 mmHg 3 P=5X10-4 mmHg 60 1 ) 4 P=6X10-4 mmHg A (µ
b 50 , I
t DUncovered emission disc= 5mm
en 40 r dem-F.C= 3cm 2 r Dem= 1.5 mm cu 30 eam b
n 3
o 20 i t u
p 4 t
u 10 O
0 00.511.522.5
Discharge current , Id (mA)
Fig.(10) Output ion beam current versus discharge current at dA-C = 5 mm, Dem. = 1.5 mm and dem. – F.C = 3 cm using Argon gas.
61 -4 120 1 P=3X10 mmHg dA-C = 6 mm Ar 2 P=4X10-4 mmHg 1 3 P=5X10-4 mmHg 100 4 P=6X10-4 mmHg ) A (µ
b DUncovered emission disc= 5mm 80 , I dem-F.C= 3cm t
n Dem= 1.5 mm 2 e r r
u 60 c
m a e 3 b 40
ion 4 ut p t 20 Ou
0 00.511.522.5
Discharge current , Id (mA)
Fig.(11) Output ion beam current versus discharge current at dA-C = 6 mm, Dem. = 1.5 mm and dem. – F.C = 3 cm using Argon gas.
-4 80 1 P=3X10 mmHg dA-C = 7 mm Ar -4 2 P=4X10 mmHg 1 3 P=5X10-4 mmHg 70 -4 4 P=6X10 mmHg 2
) 60
A DUncovered emission disc= 5mm
(µ dem-F.C= 3cm b
, I 50 Dem= 1.5 mm t n e r r 3 u
c 40
m a 30
ion be 4 t u p
t 20 u O
10
0 0 0.5 1 1.5 2 2.5
Discharge current , Id (mA)
Fig.(12) Output ion beam current versus discharge current at dA-C = 7 mm, Dem. = 1.5 mm and dem. – F.C = 3 cm using Argon gas.
62 70 1 P=3X10-4 mmHg dA-C = 8 mm Ar 2 P=4X10-4 mmHg 1 3 P=5X10-4 mmHg 60 4 P=6X10-4 mmHg ) A
(µ 50 DUncovered emission disc= 5 mm b
, I dem-F.C= 3cm t
n Dem= 1.5 mm e
r 40 r u c
m
a 2 30 be ion
ut 20 p t u 3 O 10 4
0 00.511.522.5
Discharge current , Id (mA)
Fig.(13) Output ion beam current versus discharge current at dA-C = 8 mm, Dem. = 1.5 mm and dem. – F.C = 3 cm using Argon gas.
4.1.3- The optimum gap distance between the anode and the cathode.
Figures (14) and (15) show the output ion beam current, Ib (µA), versus the anode – cathode distance, dA-C (mm), at Dem. = 1.5 mm, dem.-F.C = 3 cm, Id equal to 1 and 2 mA respectively ,and different pressures using Argon gas. It is obvious from the curves that at -4 P = 3 X 10 mmHg, Id = 1 mA and dA-C = 6 mm, a maximum output ion beam current equal to 61 µA can be obtained, but at Id = 2 mA, a maximum output ion beam current equal to 106 µA can be obtained. While before and after this distance the output ion beam current decreases.
63 -4 70 DUncovered emission disc= 5mm 1 P=3X10 mmHg -4 dem-F.C= 3cm 2 P=4X10 mmHg -4 Dem= 1.5 mm 3 P=5X10 mmHg 60 ) 4 P=6X10-4 mmHg A (µ b 50 , I
Ar Id = 1 mA t n
e 40 r r u
c 1
m 30 a n be o i 20 2 put t u 10 O 3 4 0 456789
Anode- cathode distance , dA-C ( mm)
Fig.(14) Output ion beam current versus anode – cathode distance at different pressures, Dem. = 1.5 mm , dem. – F.C = 3 cm, and Id = 1 mA using Argon gas.
1 P=3X10-4 mmHg 120 DUncovered emission disc= 5mm 2 P=4X10-4 mmHg dem-F.C= 3cm 3 P=5X10-4 mmHg Dem= 1.5 mm -4 ) 4 P=6X10 mmHg
A 100 µ (
b
, I Id = 2 mA
t 80 Ar en rr
cu 60 1 m a e b
n
o 40 i t
u 2 p t u
O 20 3
4 0 456789
, d ( mm) Anode - Cathode distance A-C
Fig.(15) Output ion beam current versus the anode – cathode distance at different pressures, Dem. = 1.5 mm , dem. – F.C = 3 cm, and Id = 2 mA using Argon gas.
64 Figures (16) shows the output ion beam current, Ib (µA), versus the anode – cathode distance, dA-C (mm), at Dem. = 1.5 mm, dem.-F.C = -4 3 cm, Id equal to 1 and 2 mA, and P= 3 X 10 mmHg using Argon gas. It is obvious from the curves that at Id = 2 mA, dA-C = 6 mm, a maximum output ion beam current equal to 106 µA can be obtained.
Also, at Id = 1 mA, dA-C = 6 mm, a maximum output ion beam current equal to 61 µA can be obtained. While before and after this distance, the output ion beam current decreases. The output ion beam is convergent at the optimum distance, while before and after this distance, the output ion beam is divergent.
Ar 120 DUncovered emission disc= 5mm
dem-F.C= 3cm Dem= 1.5 mm 1 I = 1 mA 100 d )
A 2 Id = 2 mA µ ( b 80 , I -4
t P = 3X10 mm Hg n e
r 2 r 60 u c m a 40 n be o
i 1
ut p
t 20 u O
0 456789
Anode - cathode distance , dA-C ( mm)
Fig.(16) Output ion beam current versus the anode – cathode distance at -4 p = 3 X 10 mm Hg, Dem. = 1.5 mm , dem. – F.C = 3 cm, and Id equals to 1 and 2 mA using Argon gas.
65 4.2- Determination of the optimum diameter of uncovered area of emission disc
In this experiment, the uncovered area diameter of emission disc,
Duncovered em. disc, is varied with values equals 3, 4, 5, 6, and 7 mm at dA-C equals 6 mm, Dem. equals 1.5 mm, and dem.-F.C. is fixed at 3 cm. The optimum uncovered area diameter of emission disc,
Duncovered em. disc for stable discharge current and a maximum output ion beam current can be obtained.
4.2.1- Input characteristics
Figures (17), (18), (19), (20), and (21) show the discharge current, Id (mA), versus the discharge voltage, Vd (KV), at different pressures Dem = 1.5 mm, dA-C = 6 mm, dem.-F.C = 3 cm, and
Duncovered em. disc is varied with values equal to 3, 4, 5, 6, and 7 mm using Argon gas. It is clear from the figures that the discharge current increases with increasing the discharge voltage and the discharge voltage starts at lower potential in case of high pressure (6 X 10-4 mmHg) than that in case of low pressure (3 X 10-4 mmHg).
66 2.5 1 P=3X10-4 mmHg Duncovered emission disc= 3 mm Ar 2 P=4X10-4 mmHg -4 3 P=5X10 mmHg 4 3 1 4 P=6X10-4 mmHg 2 2 ) A (m
d d A-C = 6 mm
, I 1.5 dem-F.C= 3 cm t
n Dem= 1.5 mm rre u c e
rg 1 a h c s i D
0.5
0 0 0.5 1 1.5 2 2.5 3 3.5 4
Discharge voltage , V (KV) d Fig.(17) Discharge current versus discharge voltage at dA-C= 6 mm, Duncovered em. disc = 3 mm, Dem. = 1.5 mm , dem. – F.C = 3 cm, and different pressures using Argon gas.
2.5 D = 4 mm 1 P=3X10-4 mmHg uncovered emission disc Ar 2 P=4X10-4 mmHg 3 P=5X10-4 mmHg 4 2 1 4 P=6X10-4 mmHg 3 2 ) A
(m 1.5 d A-C = 6 mm d
, I dem-F.C= 3 cm
t Dem= 1.5 mm en r r
cu 1 e g ar sch i D 0.5
0 012345
Discharge voltage , Vd (KV)
Fig.(18) Discharge current versus discharge voltage at dA-C = 6 mm, Duncovered em. disc = 4 mm, Dem. = 1.5 mm, dem. – F.C = 3 cm, and different pressures using Argon gas.
67 2.5 Duncovered emission disc= 5 mm 1 P=3X10-4 mmHg Ar 2 P=4X10-4 mmHg -4 2 1 3 P=5X10 mmHg 3 2 ) A (m d
, I 1.5 d A-C = 6 mm t
n dem-F.C= 3 cm rre Dem= 1.5 mm cu
e 1 arg sch i D 0.5
0 0 0.5 1 1.5 2 2.5 3 3.5 4
Discharge voltage , Vd (KV)
Fig.(19) Discharge current versus discharge voltage at dA-C = 6 mm, Duncovered em. disc = 5 mm, Dem. = 1.5 mm and dem. – F.C = 3 cm, and different pressures using Argon gas.
2.5 Duncovered emission disc= 6 mm 1 P=3X10-4 mmHg Ar 2 P=4X10-4 mmHg 3 P=5X10-4 mmHg 4 2 -4 3 2 4 P=6X10 mmHg )
A 1 (m d 1.5 , I d A-C = 6 mm t dem-F.C= 3 cm
rren Dem= 1.5 mm
e cu 1 rg a h sc Di 0.5
0 012345
Discharge voltage , Vd (KV)
Fig.(20) Discharge current versus discharge voltage at dA-C = 6 mm, Duncovered em. disc = 6 mm, Dem. = 1.5 mm and dem. – F.C = 3 cm, and different pressures using Argon gas.
68 2.5 -4 1 P=3X10 mmHg Duncovered emission disc= 7 mm Ar 2 P=4X10-4 mmHg 3 P=5X10-4 mmHg 4 3 2 -4 2 4 P=6X10 mmHg ) A
(m 1.5 d A-C= 6 mm d dem-F.C= 3 cm 1 , I Dem= 1.5 mm nt e r r
u 1 c e g r ha c s i
D 0.5
0 00.511.522.5
Discharge voltage , Vd (KV)
Fig.(21) Discharge current versus discharge voltage at dA-C = 6 mm, Duncovered em. disc = 7 mm, Dem. = 1.5 mm and dem. – F.C = 3 cm, and different pressures using Argon gas.
4.2.2- Output ion beam characteristics
Figures (22), (23), (24), (25), and (26) show the output ion beam current, Ib (µA), versus discharge voltage, Vd (KV) , at Dem = 1.5 mm, dA-C = 6 mm, dem.-F.C = 3 cm, Duncovered em. disc is varied with values equal to 3, 4, 5, 6, and 7 mm, and different pressures using Argon gas. It is clear that these figures are similar to the discharge current – discharge voltage curves. In order to increase the output ion beam current through the discharge; we must increase the number of electrons created by the ionization.
69 30 Ar 1 P=3X10-4 mmHg Duncovered emission disc= 3 mm -4 2 P=4X10 mmHg 1 3 P=5X10-4 mmHg 25 )
A 20
(µ d A-C = 6 mm 2 b
, I dem-F.C= 3 cm
t Dem= 1.5 mm en r r 15 3 cu eam b
n 10 o i t u p t u O 5
0 0 0.5 1 1.5 2 2.5 3 3.5 4
Discharge voltage , Vd (KV)
Fig.(22) Output ion beam current versus discharge voltage at dA-C =6 mm, Duncovered em. disc = 3 mm, Dem. = 1.5 mm, dem. – F.C = 3 cm, and different pressures using Argon gas.
60 Duncovered emission disc= 4 mm Ar 1 P=3X10-4 mmHg 2 P=4X10-4 mmHg 1 50 3 P=5X10-4 mmHg A) (µ
b 40
, I d A-C = 6 mm
t dem-F.C= 3 cm n e
r Dem= 1.5 mm r 2
u 30 c m
a 3 n be o
i 20
ut p t u O 10
0 012345
Discharge voltage , Vd (KV)
Fig.(23) Output ion beam current versus discharge voltage at dA-C =6 mm, Duncovered em. disc = 4 mm, Dem. = 1.5 mm, dem. – F.C = 3 cm, and different pressures using Argon gas. 70 120 Duncovered emission disc= 5 mm Ar 1 P=3X10-4 mmHg -4 2 P=4X10 mmHg 1 -4 100 3 P=5X10 mmHg ) A (µ b
, I 80 nt e
r d A-C = 6 mm 2 r
u dem-F.C= 3 cm c
m 60 Dem= 1.5 mm a 3 n be
io 40 put t Ou 20
0 0 0.5 1 1.5 2 2.5 3 3.5 4
Discharge voltage , Vd (KV)
Fig.(24) Output ion beam current versus discharge voltage at dA-C =6 mm, Duncovered em. disc = 5 mm, Dem. = 1.5 mm, dem. – F.C = 3 cm, and different pressures using Argon gas.
90 -4 1 P=3X10 mmHg Duncovered emission disc= 6 mm Ar 2 P=4X10-4 mmHg 80 3 P=5X10-4 mmHg 1
) 70 A (µ
b 60 2 , I t
n d A-C = 6 mm
e 50 r
r dem-F.C= 3 cm u
c Dem= 1.5 mm 3 m 40 a
30 on be i put
t 20 u O 10
0 012345 Discharge voltage , V (KV) d Fig.(25) Output ion beam current versus discharge voltage at dA-C =6 mm, Duncovered em. disc = 6 mm, Dem. = 1.5 mm, dem. – F.C = 3 cm, and different pressures using Argon gas.
71 16 Duncovered emission disc= 7 mm Ar 1 P=3X10-4 mmHg 1 14 2 P=4X10-4 mmHg
2 12 ) d A-C = 6 mm A
(µ dem-F.C= 3 cm b 10
, I Dem= 1.5 mm t n e r
r 8 u c m
a 6 be
ion 4 ut p t u
O 2
0 00.511.522.5
Discharge voltage , V (KV) d Fig.(26) Output ion beam current versus discharge voltage at dA-C =6 mm, Duncovered em. disc = 7 mm, Dem. = 1.5 mm, dem. – F.C = 3 cm, and different pressures using Argon gas.
Figures (27), (28), (29), (30), and (31) show the output ion beam current, Ib (µA), versus discharge current, Id (mA), at Dem =
1.5 mm, dem.-F.C. = 3 cm, dA-C = 6 mm, and Duncovered em. disc is varied with values equals 3, 4, 5, 6, and 7 mm, and different pressures using Argon gas. It is clear from the figures that the output ion beam current increases with increasing the discharge current and at -4 P = 3 X 10 mmHg and Duncovered em. disc= 5 mm, a maximum output ion beam current equals 106 µA can be obtained.
72 30 -4 1 P=3X10 mmHg Duncovered emission disc= 3 mm Ar 2 P=4X10-4 mmHg 1 3 P=5X10-4 mmHg 25 4 P=6X10-4 mmHg A) (µ
b 20 d A-C = 6 mm , I 2
t dem-F.C= 3 cm en
r Dem= 1.5 mm r
cu 15 3 eam b n
o 4 i
t 10 u p t u O
5
0 0 0.5 1 1.5 2 2.5 Discharge current , I (mA) d Fig.(27) Output ion beam current versus discharge current at dA-C = 6 mm, Dem. = 1.5 mm, Duncovered em. disc = 3 mm, dem. – F.C = 3 cm, and different pressures using Argon gas.
60 -4 1 P=3X10 mmHg Duncovered emission disc= 4 mm Ar 2 P=4X10-4 mmHg 3 P=5X10-4 mmHg 1 50 4 P=6X10-4 mmHg ) A (µ b
, I 40 d A-C = 6 mm
nt dem-F.C= 3 cm e r
r Dem= 1.5 mm u 30 2 c m a
e 3 20 on b
i 4 ut p
Out 10
0 00.511.522.5
Discharge current , Id (mA)
Fig.(28) Output ion beam current versus discharge current at dA-C = 6 mm, Dem. = 1.5 mm, Duncovered em. disc = 4 mm, dem. – F.C = 3 cm, and different pressures using Argon gas.
73 120 D = 5 mm 1 P=3X10-4 mmHg uncovered emission disc Ar 2 P=4X10-4 mmHg 1 3 P=5X10-4 mmHg 100 4 P=6X10-4 mmHg A)
(µ 80 b
, I d A-C= 6 mm dem-F.C= 3 cm 2 nt e r r 60 Dem= 1.5 mm u c m a 3 40 on be i 4 put t u 20 O
0 0 0.5 1 1.5 2 2.5
Discharge current , Id (mA)
Fig.(29) Output ion beam current versus discharge current at dA-C = 6 mm, Dem. = 1.5 mm, Duncovered em. disc = 5 mm, dem. – F.C = 3 cm, and different pressures using Argon gas.
90 Duncovered emission disc= 6 mm 1 P=3X10-4 mmHg Ar 2 P=4X10-4 mmHg 80 1 3 P=5X10-4 mmHg 4 P=6X10-4 mmHg 70 ) A (µ
b 60 2 , I d A-C = 6 mm t n
e 50 dem-F.C= 3 cm r r
u Dem= 1.5 mm c 40 m a e
30 3 ion b put
t 20 u 4 O 10
0 0 0.5 1 1.5 2 2.5
Discharge current , Id (mA)
Fig.(30) Output ion beam current versus discharge current at dA-C = 6 mm, Dem. = 1.5 mm, Duncovered em. disc = 6 mm, dem. – F.C = 3 cm, and different pressures using Argon gas.
74 16 -4 1 P=3X10 mmHg Duncovered emission disc= 7 mm Ar 2 P=4X10-4 mmHg 14 3 P=5X10-4 mmHg 1 4 P=6X10-4 mmHg 2 12
A) d A-C = 6 mm
(µ 10
b dem-F.C= 3 cm
, I Dem= 1.5 mm t 3
en 8 r r cu 6 eam b 4 n o i
t 4 u p t u
O 2
0 0 0.5 1 1.5 2 2.5
Discharge current , Id (mA)
Fig.(31) Output ion beam current versus discharge current at dA-C = 6 mm, Dem. = 1.5 mm, Duncovered em. disc = 7 mm, dem. – F.C = 3 cm, and different pressures using Argon gas.
4.2.3- The optimum diameter of uncovered area of emission disc
Figures (32) and (33) show the output ion beam current, Ib (µA), versus diameter of uncovered area of emission disc, Duncovered em. disc
(mm), at dA-C = 6 mm, Dem. = 1.5 mm, dem.-F.C = 3 cm, Id equal to 1 and 2 mA respectively ,and different pressures using Argon gas. It -4 is obvious from the curves that at P= 3 X 10 mmHg, Id = 1 mA, and
Duncovered em. disc = 5 mm, a maximum output ion beam current equal to -4 61 µA can be obtained. Also, at P = 3 X 10 mmHg, Id = 2 mA, and
Duncovered em. disc = 5 mm, a maximum output ion beam current equal to 106 µA can be obtained. While before and after this distance the output ion beam current decreases.
75 1 P=3X10-4 mmHg Ar 70 dA-C = 6 mm 2 P=4X10-4 mmHg dem-F.C= 3cm 3 P=5X10-4 mmHg 1 60 D = 1.5 mm 4 P=6X10-4 mmHg em ) A 50 (µ b , I
nt 40
e 2
r Id = 1 mA r u
c 30 m a 3
n be 20 o
4 put i t 10 u O 0 2345678
Uncovered area diameter of emission disc, Duncovered emission disc (mm)
Fig.(32) Output ion beam current versus uncovered area diameter of emission disc, Duncovered em. disc (mm), at dA-C = 6 mm, Dem. = 1.5 mm , dem. – F.C = 3 cm, and Id = 1 mA , and different pressures using Argon gas.
120 1 P=3X10-4 mmHg Ar dA-C = 6 mm 2 P=4X10-4 mmHg dem-F.C= 3cm -4 3 P=5X10 mmHg 1 100 Dem= 1.5 mm 4 P=6X10-4 mmHg ) A (µ b 80 , I
t n
e 2 r r 60 Id = 2 mA cu eam
b 40 n
o 3 i t u p
t 4
u 20 O
0 2345678
Uncovered area diameter of emission disc , Duncovered emission disc (mm)
Fig.(33) Output ion beam current versus uncovered area diameter of emission disc, Duncovered em. disc (mm), at dA-C = 6 mm, Dem. = 1.5 mm , dem. – F.C = 3 cm, and Id = 2 mA , and different pressures using Argon gas.
76 Figure (34) shows the output ion beam current, Ib (µA), versus diameter of uncovered area of emission disc, Duncovered em. disc (mm), at dA-C = 6 mm, Dem. = 1.5 mm, dem.-F.C = 3 cm, Id equal to 1 and 2 mA, and P= 3 X 10-4 mmHg using Argon gas. It is obvious from the curves that at Id = 2 mA , Duncovered em. disc = 5 mm, a maximum output ion beam current equal to 106 µA can be obtained. Also, at Id = 1 mA ,
Duncovered em. disc = 5 mm, a maximum output ion beam current equal to 61 µA can be obtained. While before and after this diameter, the output ion beam current decreases.
120 -4 dA-C = 6 mm P = 3X10 mmHg 2 dem-F.C= 3cm
100 Dem= 1.5 mm ) A
(µ 1 I = 1 mA b 80 d , I 2 Ib = 2 mA 1 Ar nt e r
r 60 u c
m a e 40 on b i put t 20 u O
0 2345678
Uncovered area diameter of emission disc, Duncovered emission disc (mm)
Fig.(34) Output ion beam current versus uncovered area diameter of emission disc, Duncovered em. disc (mm), at dA-C = 6 mm, Dem. = 1.5 mm , dem. – F.C = 3 cm, and Id equal to 1 and 2 mA , and different pressures using Argon gas.
77 4.3- Determination of the optimum diameter of emission disc aperture
In this experiment, the diameter of the emission disc aperture,
Dem., is varied with values equal to 1.5, 2, 2.5, and 3 mm at dA-C =
6 mm, Duncovered em. disc = 5 mm, and dem.-F.C. is fixed at 3 cm. The
optimum Dem. for stable discharge current and a maximum output ion beam current can be obtained.
4.3.1- Input characteristics
Figures (35), (36), (37), (38), and (39) show the discharge current, Id (mA), versus discharge voltage, Vd (KV), at Duncovered em. disc = 5 mm, dA-C = 6 mm, dem.-F.C = 3 cm, Dem. is varied with values equal to 1.5, 2, 2.5, and 3 mm, and different pressures using Argon gas. It is clear from the figures that the discharge current is increased by increasing the discharge voltage applied on the anode and the discharge voltage starts at lower potential in case of high pressure (6 X10-4 mmHg) than that in case of low pressure (3 X 10-4 mmHg).
78 2.5 Dem= 1.5 mm Ar 1 P=3X10-4 mmHg 2 P=4X10-4 mmHg 3 P=5X10-4 mmHg 3 2 1 2 ) A
(m 1.5 D = 5mm d Uncovered emission disc , I dem-F.C= 3cm t n dA-C = 6 mm rre 1 e cu rg a h c s i D 0.5
0 0 0.5 1 1.5 2 2.5 3 3.5 4
Discharge voltage , Vd (KV)
Fig.(35) Discharge current versus discharge voltage at dA-C = 6 mm, Duncovered em. disc = 5 mm, Dem. = 1.5 mm, dem. – F.C = 3 cm, and different pressures using Argon gas.
2.5 -4 1 P = 4 X10 mmHg Dem= 2 mm Ar 2 P = 5 X10-4 mmHg 3 P = 6 X10-4 mmHg 3 2 2
D = 5mm ) Uncovered emission disc A d = 3cm em-F.C 1 (m 1.5 d dA-C = 6 mm , I t en rr
cu 1 e g ar h c s Di 0.5
0 22.533.544.55
Discharge voltage , Vd (KV)
Fig.(36) Discharge current versus discharge voltage at dA-C = 6 mm, Duncovered em. disc = 5 mm, Dem. = 2 mm, dem. – F.C = 3 cm, and different pressures using Argon gas.
79 2.5 -4 Ar 1 P = 4 X10 mmHg Dem= 2.5 mm 2 P = 5 X10-4 mmHg -4 3 P = 6 X10 mmHg 2 3 2
DUncovered emission disc= 5mm ) A 1.5 dem-F.C= 3cm (m
d dA-C = 6 mm , I t n e
r 1 r 1 cu e g ar h c s i D 0.5
0 0246810
Discharge voltage , V (KV) d
Fig.(37) Discharge current versus discharge voltage at dA-C = 6 mm, Duncovered em. disc = 5 mm, Dem. = 2.5 mm, dem. – F.C = 3 cm, and different pressures using Argon gas.
300 -4 Ar 1 P = 5 X10 mmHg Dem= 3 mm -4 2 P = 6 X10 mmHg 2 1 250
) DUncovered emission disc= 5mm A 200 d = 3cm
(m em-F.C d
, I dA-C = 6 mm t 150 rren cu e arg 100 sch Di
50
0 0 0.5 1 1.5 2 2.5
Discharge voltage , Vd (KV)
Fig.(38) Discharge current versus discharge voltage at dA-C = 6 mm, Duncovered em. disc = 5 mm, Dem. = 3 mm, dem. – F.C = 3 cm, and different pressures using Argon gas.
80 4.3.2- Output ion beam characteristics
Figures (39), (40), (41), and (42) show the output ion beam current, Ib (µA), versus discharge voltage, Vd (KV) , at dA-C = 6 mm, dem.-F.C = 3 cm, Duncovered em. disc = 5 mm, and the diameter of emission disc aperture, Dem., is varied with values equals 1.5, 2, 2.5, and 3 mm, and different pressures using Argon gas. It is clear that these figures are similar in shape to the discharge current – discharge voltage curves. In order to increase the output ion beam current through the discharge; we must increase the number of electrons created by the ionization.
120 Ar 1 P=3X10-4 mmHg Dem= 1.5 mm -4 2 P=4X10 mmHg 1 3 P=5X10-4 mmHg 100 ) A
(µ 80 b
, I DUncovered emission disc= 5mm t
n dem-F.C= 3cm 2 e rr
u 60 dA-C = 6 mm c
m a
e 3 n b
o 40 i ut p t u O 20
0 00.511.522.533.54
Discharge voltage , V (KV) d Fig.(39) Output ion beam current versus discharge voltage at dA-C= 6 mm, Duncovered em. disc = 5 mm, Dem. = 1.5 mm, dem. – F.C = 3 cm, and different pressures using Argon gas.
81 200 Ar 1 P = 4 X10-4 mmHg Dem= 2 mm 1 180 -4 2 P = 5 X10 mmHg 2 3 P = 6 X10-4 mmHg 160 ) A (µ
b 140
, I DUncovered emission disc= 5mm t 3 120 dem-F.C= 3cm rren dA-C = 6 mm cu 100 eam b
n 80 o i
t u
p 60 t u O 40
20
0 2 2.5 3 3.5 4 4.5 5
Discharge voltage , Vd (KV)
Fig.(40) Output ion beam current versus discharge voltage at dA-C= 6 mm, Duncovered em. disc = 5 mm, Dem. = 2 mm, dem. – F.C = 3 cm, and different pressures using Argon gas. 500 Ar -4 Dem= 2.5 mm 1 P = 4 X10 mmHg 2 450 2 P = 5 X10-4 mmHg
400
) 350 A 1 (µ b D = 5mm , I 300 Uncovered emission disc
t dem-F.C= 3cm en r r 250 dA-C = 6 mm u c
eam 200 b n o i
t 150 u p t u
O 100
50
0 3456789
Discharge voltage, Vd (KV)
Fig.(41) Output ion beam current versus discharge voltage at dA-C= 6 mm, Duncovered em. disc = 5 mm, Dem. = 2.5 mm, dem. – F.C = 3 cm, and different pressures using Argon gas.
82 300 Ar -4 1 P = 5 X10 mmHg Dem= 3 mm 2 2 P = 6 X10-4 mmHg 250 ) A (µ b DUncovered emission disc= 5mm , I 200 dem-F.C= 3cm
nt d = 6 mm
e A-C r r u c 150 1 m a be n o
i 100 ut p t u O 50
0 2.5 3 3.5 4 4.5 5
Discharge voltage , Vd (KV)
Fig.(42) Output ion beam current versus discharge voltage at dA-C= 6 mm,
Duncovered em. disc = 5 mm, Dem. = 3 mm, dem. – F.C = 3 cm, and different pressures using Argon gas.
Figures (43), (44), (45), and (46) show the output ion beam
current, Ib (µA), versus discharge current, Id (mA), at Duncovered em. disc =
5 mm, dem.-F.C. = 3 cm, dA-C = 6 mm, and the diameter of emission
disc aperture, Dem., is varied with values equals 1.5, 2, 2.5, and 3 mm, and for different pressures using Argon gas. It is clear from the figures that the output ion beam current increases with increasing the discharge current and at P = 5 X 10-4 mmHg and
Dem.= 2.5 mm, a maximum output ion beam current equals 462 µA can be obtained.
83 120 Ar 1 P=3X10-4 mmHg Dem= 1.5 mm 2 P=4X10-4 mmHg 1 -4 100 3 P=5X10 mmHg 4 P=6X10-4 mmHg ) A (µ
b 80 DUncovered emission disc= 5mm , I dem-F.C= 3cm
nt 2 e r
r dA-C = 6 mm u 60 c
m a
be 3 40 ion put
t 4
Ou 20
0 00.511.522.5
Discharge current , Id (mA)
Fig.(43) Output ion beam current versus discharge current at dA-C= 6 mm, Dem.
= 1.5 mm, Duncovered em. disc = 5 mm, dem. – F.C = 3 cm, and different pressures using Argon gas.
200 1 P = 4 X10-4 mmHg Dem= 2 mm Ar -4 180 2 P = 5 X10 mmHg 1 3 P = 6 X10-4 mmHg 2 160
) 140 A DUncovered emission disc= 5mm (µ b dem-F.C= 3cm , I 120 3
t dA-C = 6 mm n e r r
u 100 c m a 80 on be
i 60 ut p t u
O 40
20
0 00.511.522.5
Discharge current , Id (mA)
Fig.(44) Output ion beam current versus discharge current at dA-C= 6 mm, Dem.
= 2 mm, Duncovered em. disc = 5 mm, dem. – F.C = 3 cm, and different pressures using Argon gas.
84 500 1 P = 4 X10-4 mmHg D = 2.5 mm Ar em 2 2 P = 5 X10-4 mmHg 450 3 P = 6 X10-4 mmHg 400 3 DUncovered emission disc= 5 mm )
A 350 dem-F.C= 3 cm
(µ 1 b dA-C = 6 mm , I 300 nt rre
u 250 c m a 200 be on
i 150 put t u
O 100
50
0 0 0.5 1 1.5 2 2.5
Discharge current , Id (mA)
Fig.(45) Output ion beam current versus discharge current at dA-C= 6 mm, Dem.
= 2.5 mm, Duncovered em. disc = 5 mm, dem. – F.C = 3 cm, and different pressures using Argon gas.
Ar 300 1 P = 5 X10-4 mmHg Dem= 3 mm 2 P = 6 X10-4 mmHg 2
1 250
DUncovered emission disc= 5 mm ) d = 3 cm
A em-F.C
(µ dA-C = 6 mm b 200 , I t en r r 150 cu eam b n 100 io
t u p t u O 50
0 00.511.522.5
Discharge current , I (mA) d Fig.(46) Output ion beam current versus discharge current at dA-C= 6 mm, Dem.
= 3 mm, Duncovered em. disc = 5 mm, dem. – F.C = 3 cm, and different pressures using Argon gas. 85 4.3.3- The optimum diameter of emission disc aperture
Figure (47) shows the diameter of emission disc aperture, Dem.
(mm), versus output ion beam current, Ib (µA), at dA-C = 6 mm,
Duncovered em. disc = 5 mm, dem.-F.C = 3 cm, Id = 1 mA, and different pressures using Argon gas. It is obvious from the curve that at -4 P= 3 X 10 mmHg and Dem. = 2.5 mm, a maximum output ion beam current equal to 312 µA can be obtained. While before and after this distance the output ion beam current decreases.
350 1 P = 4 X10-4 mmHg Dem= 2.5 mm Ar 2 P = 5 X10-4 mmHg 300 3 P = 6 X10-4 mmHg Id = 1 mA 1 250 )
DUncovered emission disc= 5mm (µA b dem-F.C= 3cm
, I 200
n dA-C = 6 mm e r r
u 2 c 150 am e n b
o 100
i 3 ut p t u 50 O
0 00.511.522.533.5
Diameter of emission disc aperture, Dem. (mm)
Fig.(47) Output ion beam current versus diameter of emission disc aperture, Dem. (mm), at dA-C = 6 mm, Duncovered em. disc = 5 mm , dem. – F.C = 3 cm, and Id = 1 mA , and different pressures using Argon gas.
86 4.4- Determination of the optimum emission disc- Faraday cup distance
In this experiment, the distance between the emission disc and
Faraday cup, dem.-F.C., is varied with values equals 1, 2, 3, and 4 mm
at Dem. = 2.5 mm, dA-C = 6 mm, and Duncovered em. disc = 5 mm. The
optimum dem.-F.C. for stable discharge current and a maximum output ion beam current can be obtained. 4.4.1- Input characteristics
Figures (48), (49), (50) and (51) show the discharge current, Id
(mA), versus the discharge voltage, Vd (KV), at Dem = 2.5 mm, dA-C
= 6 mm, Duncovered em. disc = 5 mm, and dem.-F.C. is varied with values equal to 1, 2, 3, and 4 mm for different pressures using Argon gas. It is clear from the figures that the discharge current is increased by increasing the discharge voltage applied on the anode and the discharge voltage starts at lower potential in case of high pressure (6 X10-4 mm Hg) than that in case of low pressure (4 X 10-4 mm Hg).
87 1.6 -4 Ar 1 P= 4X10 mmHg dem-F.C= 1cm 3 2 P= 5X10-4 mmHg 1.4 3 P= 6X10-4 mmHg
1.2 2
A) DUncovered emission disc= 5mm (m
d d = 6 mm 1 A-C 1 , I D = 2.5 mm
t em en
rr 0.8 cu e
arg 0.6 sch i D 0.4
0.2
0 22.533.5 44.555.56
Discharge voltage , Vd (KV)
[ Fig.(48) Discharge current versus discharge voltage at dA-C= 6 mm, Dem. = 2.5 mm, Duncovered em. disc = 5 mm, dem. – F.C = 1 cm, and different pressures using Argon gas.
1.6 1 P= 4X10-4 mmHg dem-F.C= 2 cm 3 Ar 2 P= 5X10-4 mmHg 1.4 -4 3 P= 6X10 mmHg 2
1.2 )
mA DUncovered emission disc= 5mm (
d
I 1 dA-C = 6 mm , 1
t Dem= 2.5 mm n e r
r 0.8 cu e
g 0.6 ar sch i 0.4 D
0.2
0 22.533.544.555.56
Discharge voltage , Vd (KV)
Fig.(49) Discharge current versus discharge voltage at dA-C= 6 mm, Dem. = 2.5 mm, Duncovered em. disc = 5 mm, dem. – F.C = 2 cm, and different pressures using Argon gas.
88 2.5 dem-F.C= 3 cm Ar 1 P= 4X10-4 mmHg 2 P= 5X10-4 mmHg 3 P= 6X10-4 mmHg 3 2 2
DUncovered emission disc= 5mm A) dA-C = 6 mm (m d 1.5
, I Dem= 2.5 mm t en r r 1 cu
e 1 g ar sch Di
0.5
0 0246810
Discharge voltage , Vd (KV)
Fig.(50) Discharge current versus discharge voltage at dA-C= 6 mm, Dem. = 2.5 mm, Duncovered em. disc = 5 mm, dem. – F.C = 3 cm, and different pressures using Argon gas.
1.4 -4 1 P= 4X10 mmHg dem-F.C= 4 cm Ar 2 P= 5X10-4 mmHg 2 -4 3 1.2 3 P= 6X10 mmHg
1 DUncovered emission disc= 5mm dA-C = 6 mm
) Dem= 2.5 mm A 0.8 (m d , I t en
r 0.6 r
u 1 e c g r
a 0.4 h sc i D 0.2
0 3 3.5 4 4.5 5 5.5 6 6.5
Discharge voltage , Vd (KV)
Fig.(51) Discharge current versus discharge voltage at dA-C= 6 mm, Dem. = 2.5 mm, Duncovered em. disc = 5 mm, dem. – F.C = 4 cm, and different pressures using Argon gas.
89 4.4.2- Output ion beam characteristics
Figures (52), (53), (54), and (55) show the output ion beam current, Ib (µA), versus discharge voltage, Vd (KV) , at dA-C = 6 mm,
Dem. = 2.5 mm, Duncovered em. disc= 5 mm, the distance between the emission disc and Faraday cup, dem. – F.C. , is varied with values equals 1, 2, 3, and 4 mm, and for different pressures using Argon gas. It is clear that these figures are similar in shape to the discharge voltage – discharge current curves. In order to increase the output ion beam current through the discharge; we must increase the number of electrons created by the ionization.
250 -4 dem-F.C= 1cm Ar 1 P= 4X10 mmHg 3 -4 2 P= 5X10 mmHg
) -4 3 P= 6X10 mmHg 1 µA
( 200
b
, I 2 t en
r DUncovered emission disc= 5mm r
u 150 dA-C = 6 mm c
m Dem= 2.5 mm ea b 100 on i
t u tp u
O 50
0 22.533.544.555.56
Discharge voltage , Vd (KV)
Fig.(52) Output ion beam current versus discharge voltage at dA-C= 6 mm, Dem. = 2.5 mm, Duncovered em. disc = 5 mm, dem. – F.C = 1 cm, and different pressures using Argon gas.
90 300 -4 Ar 1 P= 5X10 mmHg dem-F.C= 2 cm 2 1 2 P= 6X10-4 mmHg 250 ) A (µ b 200 D = 5mm , I Uncovered emission disc t
n dA-C = 6 mm e r r 150 D = 2.5 mm u em c
m a 100 be n o i ut
p 50 t Ou
0 22.533.544.555.56
Discharge voltage , Vd (KV)
Fig.(53) Output ion beam current versus discharge voltage at dA-C= 6 mm, Dem. = 2.5 mm, Duncovered em. disc = 5 mm, dem. – F.C = 2 cm, and different pressures using Argon gas.
500 d = 3 cm Ar 1 P= 4X10-4 mmHg em-F.C 2 450 2 P= 5X10-4 mmHg
400
) DUncovered emission disc= 5mm A 350
(µ d = 6 mm b A-C 1 , I D = 2.5 mm t 300 em rren 250 cu
eam 200 b n o i t 150 u p t u
O 100
50
0 3456789 Discharge voltage , Vd (KV)
Fig.(54) Output ion beam current versus discharge voltage at dA-C= 6 mm, Dem. = 2.5 mm, Duncovered em. disc = 5 mm, dem. – F.C = 3 cm, and different pressures using Argon gas.
91 300 -4 Ar 1 P= 4X10 mmHg dem-F.C= 4 cm -4 2 P= 5X10 mmHg 2 -4 250 3 P= 6X10 mmHg A) (µ
b 200 DUncovered emission disc= 5mm 3 , I dA-C = 6 mm
t Dem= 2.5 mm n e r
r 150 u 1 c m a 100 n be o i put t
u 50 O
0 33.5 44.5 55.5 66.5
Discharge voltage , Vd (KV)
Fig.(55) Output ion beam current versus discharge voltage at dA-C= 6 mm, Dem. = 2.5 mm, Duncovered em. disc = 5 mm, dem. – F.C = 4 cm, and different pressures using Argon gas.
Figures (56), (57), (58), and (59) show the output ion beam
current, Ib (µA), versus discharge current, Id (mA), at dA-C = 6 mm,
Dem. = 2.5 mm, Duncovered em. disc = 5 mm, the distance between the
emission disc and Faraday cup, dem. – F.C , is varied with values equals 1, 2, 3, and 4 mm, and for different pressures using Argon gas. It is clear from the figures that the output ion beam current increases with increasing the discharge current and at P = 5 X 10-4 mmHg
and dem. – F.C. = 3 cm, a maximum output ion beam current equals 462 µA can be obtained.
92 250 -4 3 1 P= 4X10 mmHg dem-F.C= 1cm Ar 2 P= 5X10-4 mmHg 3 P= 6X10-4 mmHg 1 200 2 )
A DUncovered emission disc= 5mm (µ b 150 dA-C = 6 mm , I Dem= 2.5 mm t en r r u
c 100 eam b
n o i t
u 50 p t u O
0 00.511.52
Discharge current , Id (mA)
Fig.(56) Output ion beam current versus discharge current at dA-C= 6 mm, Dem. = 2.5 mm, Duncovered em. disc = 5 mm, dem. – F.C = 1 cm, and different pressures using Argon gas.
300 -4 1 P= 4X10 mmHg dem-F.C= 2 cm Ar 2 P= 5X10-4 mmHg 2 -4 3 P= 6X10 mmHg 3 250 ) A (µ
b DUncovered emission disc= 5mm
, I 200 dA-C = 6 mm Dem= 2.5 mm nt e r r
u 1
c 150 m a
n be 100 o i ut p t u
O 50
0 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6
Discharge current , I (mA) d Fig.(57) Output ion beam current versus discharge current at dA-C= 6 mm, Dem. = 2.5 mm, Duncovered em. disc = 5 mm, dem. – F.C = 2 cm, and different pressures using Argon gas.
93 500 1 P= 4X10-4 mmHg dem-F.C= 3 cm Ar 2 P= 5X10-4 mmHg 2 450 3 P= 6X10-4 mmHg
400 3 DUncovered emission disc= 5mm
350 dA-C = 6 mm A) 1
(µ Dem= 2.5 mm b
, I 300 t n e r
r 250 cu
eam 200 b n o i
t 150 u p t u
O 100
50
0 0 0.5 1 1.5 2 2.5
Discharge current , I (mA) d Fig.(58) Output ion beam current versus discharge current at dA-C= 6 mm, Dem.
= 2.5 mm, Duncovered em. disc = 5 mm, dem. – F.C = 3 cm, and different pressures using Argon gas.
-4 300 1 P= 4X10 mmHg Ar -4 dem-F.C= 4 cm 2 P= 5X10 mmHg -4 3 P= 6X10 mmHg 2
250 ) DUncovered emission disc= 5 mm (µA
dA-C = 6 mm b I em , D = 2.5 mm 200 nt
e 3 r cur 150 1 beam n o i t 100 u p t u O
50
0 0 0.2 0.4 0.6 0.8 1 1.2 1.4
, I (mA) Discharge curre nt d Fig.(59) Output ion beam current versus discharge current at dA-C= 6 mm, Dem.
= 2.5 mm, Duncovered em. disc = 5 mm, dem. – F.C = 4 cm, and different pressures using Argon gas. 94 4.4.3- The optimum distance between emission disc- Faraday cup
Figures (60) and (61) show output ion beam current, Ib (µA), versus the distance between the emission disc and Faraday cup, dem. – F.C. , at dA-C = 6 mm, Duncovered em. disc = 5 mm, Dem. = 2.5 mm, Id equal to 0.5 and 1 mA, and for different pressures using Argon gas. It is -4 obvious from the curves that at P= 5 x 10 mmHg and dem. – F.C. = 3 cm, a maximum output ion beam current equal to 189, 462 µA respectively can be obtained. While before and after this distance the output ion beam current decreases.
1 P= 4X10-4 mmHg 160 I (mA) = 0.5 mA Ar 2 P= 5X10-4 mmHg d -4 140 3 P= 6X10 mmHg
A) 1 µ 120 ( b , I
t 100 n e r r 2 80 cu
eam 60 3 b n
o DUncovered emission disc= 5mm i
t
u 40 dA-C = 6 mm p t Dem= 2.5 mm Ou 20
0 012345
Distance between emission disc - Faraday cup , d em.- F.C. (cm)
Fig.(60) Output ion beam current versus the distance between the emission disc and Faraday cup, dem. – F.C. , at dA-C = 6 mm, Duncovered em. disc = 5 mm , Dem. = 2.5 mm, and Id = 0.5 mA , and different pressures using Argon gas.
95 -4 350 1 P= 4X10 mmHg Ar -4 2 P= 5X10 mmHg 1 3 P= 6X10-4 mmHg 300
DUncovered emission disc= 5mm ) 250 dA-C = 6 mm
µA Id (mA) = 1 mA
( Dem= 2.5 mm b
, I 200
t 2 en r r 150
cu 3 eam
b 100 n o i t u p
t 50 u O
0 012345
Distance between emission disc - Faraday cup , d em.- F.C. (cm)
Fig.(61) Output ion beam current versus the distance between the emission disc and Faraday cup, dem. – F.C. , at dA-C = 6 mm, Duncovered em. disc = 5 mm , Dem. = 2.5 mm, and Id = 1 mA , and different pressures using Argon gas.
Figures (62) shows output ion beam current, Ib (µA), versus the distance between the emission disc and Faraday cup, dem.– F.C. (cm), at dA-C = 6 mm, Duncovered em. disc = 5 mm, Dem. = 2.5 mm, Id equal to 0.5 and 1 mA, and for P= 5 X 10-4 mm Hg using Argon gas. It is obvious from the curves that at Id = 1 mA , dem.-F.C = 3 cm, a maximum output ion beam current equal to 189 µA can be obtained. Also, at Id = 0.5 mA , dem.-F.C = 3 cm, a maximum output ion beam current equal to 105 µA can be obtained. While before and after this distance, the output ion beam current decreases.
96 -4 Ar 200 1 Id (mA) = 0.5 mA P= 5 X10 mm Hg 2 Id (mA) = 1 mA 180 2
160 DUncovered emission disc= 5mm
dA-C = 6 mm A) 140 µ D = 2.5 mm ( em b 120 , I
t 100 en r r 1
cu 80
eam 60 b n o i
t 40 u p t
u 20 O
0 012345
Distance between emission disc - Faraday cup , d em.- F.C. (cm)
Fig.(62) Output ion beam current versus the distance between the emission disc and Faraday cup, dem. – F.C. , at dA-C = 6 mm, Duncovered em. disc = 5 mm , and Id equal to 0.5 and 1 mA , and for P = 5 X 10 -4 mm Hg using Argon gas.
Fig.(63) The effect of Argon ion beam on Copper Faraday cup for one hour without magnetic field.
97 4.5- Determination of the optimum strength of permanent magnetic field
In this experiment, the strength of permanent magnetic field, B is varied with values equals 50, 100, 200, 230, 300, 330, and 400
Gauss at Dem. = 2.5 mm, dA-C = 6 mm, dem.-F.C = 3 cm, and
Duncovered em. disc = 5 mm. The magnetic field is placed at 1.5 cm from the anode body. The optimum magnetic field strength for stable discharge current and a maximum output ion beam current can be obtained.
4.5.1- Input characteristics
Figures (64), (65), (66), (67), (68), (69), and (70) show the discharge current, Id (mA), versus the discharge voltage, Vd (KV), at
Dem = 2.5 mm, dA-C = 6 mm, Duncovered em. disc = 5 mm, and dem.-F.C.=
3 cm, B is varied with values equal to 50, 100, 200, 230, 300, 330, and 400 Gauss for different pressures using Argon gas. It is clear from the figures that the discharge current is increased by increasing the discharge voltage applied on the anode and the discharge voltage starts at lower potential in case of high pressure (9 X 10-4 mmHg) than that in case of low pressure (6 X 10-4 mmHg).
98 1 P= 5 X10-4 mmHg Ar 2 P= 6 X10-4 mmHg 4 2 2 5 3 3 P= 7 X10-4 mmHg 4 P= 8 X10-4 mmHg 5 P= 9 X10-4 mmHg 1 )
A 1.5 (m d , I t n rre 1 B = 50 G e cu rg a h c s i D
DUncovered emission disc = 5 mm 0.5 dA-C = 6 mm dem-F.C= 3 cm dmag .- A = 1.5 cm Dem= 2.5 mm
0 123456 Discharge voltage , V (KV) d Fig.(64) Discharge current versus discharge voltage at dA-C= 6 mm, Duncovered em. disc
= 5 mm, Dem. = 2.5 mm, dem. – F.C = 3 cm, B = 50 G, and different pressures using Argon gas.
2.5 1 P= 5X10-4 mmHg B = 100 G Ar 2 P= 6X10-4 mmHg -4 3 P= 7X10 mmHg 5 4 3 2 -4 2 4 P= 8X10 mmHg -4
) 5 P= 9X10 mmHg A (m d
, I 1
t 1.5 en r r DUncovered emission disc = 5 mm cu
e dA-C = 6 mm g
ar 1 dem-F.C= 3 cm
sch dmag .- A = 1.5 cm i
D Dem= 2.5 mm
0.5
0 0123456
Discharge voltage , Vd (KV)
Fig.(65) Discharge current versus discharge voltage at dA-C = 6 mm, Duncovered em. disc
= 5 mm, Dem. = 2.5 mm, dem. – F.C = 3 cm, B = 100 G, and different pressures using Argon gas. 99 1.4 -4 B = 200 G 1 P= 6X10 mmHg Ar 2 P= 7X10-4 mmHg 1.2 -4 3 P= 8X10 mmHg 3 )
A 1
(m DUncovered emission disc = 5 mm d
, I dA-C = 6 mm
t 0.8 dem-F.C= 3 cm en r
r dmag .- A = 1.5 cm
u 2
c Dem= 2.5 mm
e 0.6 g ar
sch 1 0.4 1 Di
0.2
0 11.522.53
Discharge voltage , Vd (KV)
Fig.(66) Discharge current versus discharge voltage at dA-C = 6 mm, Duncovered em. disc
= 5 mm, Dem. = 2.5 mm, dem. – F.C = 3 cm, B = 200 G, and different pressures using Argon gas
1.6 B = 230 G Ar 1 P= 6X10-4 mmHg 2 P= 7X10-4 mmHg 4 1.4 3 P= 8X10-4 mmHg 4 P= 9X10-4 mmHg 1.2 ) A 2 D = 5 mm (m 1 Uncovered emission disc 3 d
, I dA-C = 6 mm t d = 3 cm en em-F.C
r 0.8 r 1 dmag.- A= 1.5 cm e cu
g Dem= 2.5 mm r 0.6 a h sc
Di 0.4
0.2
0 1 1.5 2 2.5 3 3.5
Discharge voltage , Vd (KV)
Fig.(67) Discharge current versus discharge voltage at dA-C = 6 mm, Duncovered em. disc
= 5 mm, Dem. = 2.5 mm, dem. – F.C = 3 cm, B = 230 G, and different pressures using Argon gas 100 1.6 1 P= 6X10-4 mmHg B = 300 G Ar 2 P= 7X10-4 mmHg 2 1.4 3 P= 8X10-4 mmHg 4 4 P= 9X10-4 mmHg 1 1.2 3 )
A DUncovered emission disc = 5 mm (m
d 1 dA-C = 6 mm , I dem-F.C= 3 cm t d = 1.5 cm en 0.8 mag.- A r r Dem= 2.5 mm e cu g
r 0.6 a h sc
Di 0.4
0.2
0 22.533.5 44.555.56
Discharge voltage , Vd (KV)
Fig.(68) Discharge current versus discharge voltage at dA-C = 6 mm, Duncovered em. disc
= 5 mm, Dem. = 2.5 mm, dem. – F.C = 3 cm, B = 300 G, and different pressures using Argon gas
2.5 -4 1 P= 6X10 mmHg B = 330 G Ar 2 P= 7X10-4 mmHg 3 P= 8X10-4 mmHg 4 P= 9X10-4 mmHg 4 3 2 2
DUncovered emission disc = 5 mm )
A dA-C = 6 mm (m
d dem-F.C= 3 cm
, I 1.5 dmag.- A= 1.5 cm t n
e Dem= 2.5 mm r r 1 e cu g r a
h 1 sc i D
0.5
0 123456
Discharge voltage , Vd (KV)
Fig.(69) Discharge current versus discharge voltage at dA-C = 6 mm, Duncovered em. disc
= 5 mm, Dem. = 2.5 mm, dem. – F.C = 3 cm, B = 330 G, and different pressures using Argon gas 101 2 1 P= 6X10-4 mmHg B = 400 G Ar 2 P= 7X10-4 mmHg 4 1.8 3 P= 8X10-4 mmHg 4 P= 9X10-4 mmHg 3 1.6
) 2 A 1.4
(m DUncovered emission disc = 5 mm d
, I dA-C = 6 mm
t 1.2 dem-F.C= 3 cm en r r
u dmag.- A= 1.5 cm 1 e c Dem= 2.5 mm g r a h 0.8 sc i D
0.6 1
0.4
0.2
0 11.522.5 33.54
Discharge voltage , Vd (KV)
Fig.(70) Discharge current versus discharge voltage at dA-C = 6 mm, Duncovered em. disc
= 5 mm, Dem. = 2.5 mm, dem. – F.C = 3 cm, B = 400 G, and different pressures using Argon gas.
4.5.2- Output ion beam characteristics
Figures (71), (72), (73), (74), (75), (76), and (77) show output
ion beam current, Ib (µA), versus the discharge current, Id (mA), at
dA-C = 6 mm, Dem. = 2.5 mm, Duncovered em. disc = 5 mm, dem. – F.C. = 3 cm
, B is varied with values equals 50, 100, 200, 230, 300, 330, and 400 Gauss and for different pressures using Argon gas. It is clear from the figures that the output ion beam current increases with increasing the discharge current and at P = 6 X 10-4 mmHg and B = 300 G, a maximum output ion beam current equals 298 µA can be obtained.
102 250 1 P= 5 X10-4 mmHg B = 50 G Ar 2 P= 6 X10-4 mmHg 3 P= 7 X10-4 mmHg 12 4 P= 9 X10-4 mmHg 200 A) µ (
b DUncovered emission disc = 5 mm I , dA-C = 6 mm
nt 150 3 dem-F.C= 3 cm rre
u dmag.- A= 1.5 cm c
m Dem= 2.5 mm a
100 4 on be i
put t u O
50
0 0 0.5 1 1.5 2 2.5
Discharge current , Id (mA)
Fig.(71) Output ion beam current versus discharge current at dA-C=6 mm, Dem.
= 2.5 mm, Duncovered em. disc = 5 mm, dem. – F.C = 3 cm, B = 50 G, and different pressures using Argon gas.
400 1 P= 5X10-4 mmHg B = 100 G Ar 2 P= 6X10-4 mmHg -4 350 3 P= 7X10 mmHg 1 4 P= 9X10-4 mmHg
) 300 2 A DUncovered emission disc = 5 mm (µ b
, I 250 dA-C = 6 mm d =3 cm
nt em-F.C e r
r dmag.- A= 1.5 cm 3 u 200 c Dem= 2.5 mm m a e 150
on b 4 i put t
u 100 O
50
0 00.511.522.5
Discharge current , Id (mA)
Fig.(72) Output ion beam current versus discharge current at dA-C=6 mm, Dem.
= 2.5 mm, Duncovered em. disc = 5 mm, dem. – F.C = 3 cm, B= 100 G, and different pressures using Argon gas.
103 80 1 P= 6X10-4 mmHg B = 200 G Ar -4 4 2 P= 7X10 mmHg -4 3 70 3 P= 8X10 mmHg 4 P= 9X10-4 mmHg
60
A) A µ r b (
I 2 , 50 1 t en r
r DUncovered emission disc = 5 mm u 40 c dA-C = 6 mm dem-F.C= 3 cm eam
b dmag .- A = 1.5 cm
n 30
o Dem= 2.5 mm i t u tp
u 20 O
10
0 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6
Discharge current , I (mA) d Fig.(73) Output ion beam current versus discharge current at dA-C=6 mm, Dem. =
2.5 mm, Duncovered em. disc = 5 mm, dem. – F.C = 3 cm, B = 200 G, and different pressures using Argon gas.
80 1 P= 6X10-4 mmHg B = 230 G Ar -4 2 P= 7X10 mmHg 4 -4 70 3 P= 8X10 mmHg 1 2 4 P= 9X10-4 mmHg
) 60 A 3 (µ b
, I 50 nt e r r u
c 40 m a be
n 30 o DUncovered emission disc = 5 mm ut i
p dA-C = 6 mm t u 20 O dem-F.C= 3 cm
dmag.- A= 1.5 cm
10 Dem= 2.5 mm
0 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6
Discharge current , Id (mA)
Fig.(74) Output ion beam current versus discharge current at dA-C=6 mm, Dem.
= 2.5 mm, Duncovered em. disc = 5 mm, dem. – F.C = 3 cm, B = 230 G, and different pressures using Argon gas.
104 350 1 P= 6X10-4 mmHg B = 300 G Ar 2 P= 7X10-4 mmHg -4 1 300 3 P= 8X10 mmHg 4 P= 9X10-4 mmHg 2
250
A) DUncovered emission disc = 5 mm µ ( d = 6 mm b A-C I , 200 dem-F.C= 3 cm 3 d = 1.5 cm
nt mag.- A 4
rre Dem= 2.5 mm u c
150 m a
on be 100 i t u p t u
O 50
0 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6
Discharge current , I (mA) d Fig.(75) Output ion beam current versus discharge current at dA-C=6 mm, Dem. =
2.5 mm, Duncovered em. disc = 5 mm, dem. – F.C = 3 cm, B = 300 G, and different pressures using Argon gas.
300 1 P= 6X10-4 mmHg B = 330 G Ar 2 P= 7X10-4 mmHg 3 P= 8X10-4 mmHg 1 250 4 P= 9X10-4 mmHg 2 A) µ ( DUncovered emission disc = 5 mm b
I 200 , dA-C = 6 mm t
n 3
e dem-F.C= 3 cm r r u dmag.- A= 1.5 cm c 150 m D = 2.5 mm
a em be n o i
ut 100 p t u O
50
0 0 0.5 1 1.5 2 2.5 Discharge current , I (mA) d
Fig.(76) Output ion beam current versus discharge current at dA-C=6 mm, Dem. =
2.5 mm, Duncovered em. disc = 5 mm, dem. – F.C = 3 cm, B = 330 G, and different pressures using Argon gas.
105 150 -4 1 P= 7X10 mmHg B = 400 G Ar 2 P= 8X10-4 mmHg -4 130 3 P= 9X10 mmHg
1 )
A 110
(µ DUncovered emission disc = 5 mm b 2 , I dA-C = 6 mm 90
nt dem-F.C= 3 cm e
r 3 r
u dmag.- A= 1.5 cm c 70 D = 2.5 mm
m em a on be i
50 put t u O 30
10
0 0.5 1 1.5 2 -10
Discharge current , Id (mA)
Fig.(77) Output ion beam current versus discharge current at dA-C=6 mm, Dem. =
2.5 mm, Duncovered em. disc = 5 mm, dem. – F.C = 3 cm, B = 400 G, and different pressures using Argon gas.
4.5.3- The optimum strength of permanent magnetic field
Figure (78) shows output ion beam current, Ib (µA), versus the magnetic field strength, B (Gauss) , at dA-C = 6 mm, Duncovered em. disc =
5 mm, Dem. = 2.5 mm, dA-C = 6 mm, Id = 1 mA, and for different pressures using Argon gas. It is obvious from the curves that at P= 7 X 10-4 mmHg and B= 300 Gauss, a maximum output ion beam current equal to 190 µA can be obtained. While before and after this distance the output ion beam current decreases.
106 200 DUncovered emission disc = 5 mm Id = 1 mA Ar dA-C = 6 mm dem-F.C= 3 cm 180 dmag .- A = 1.5 cm Dem= 2.5 mm ) 160
µA -4 1 P= 7X10 mmHg b (
I -4 , 140 2 P= 8X10 mmHg -4
nt 3 P= 9X10 mmHg e r r
u 120 c m a 100 n be o i 80 1 put t u
O 2 60 3
40 0 50 100 150 200 250 300 350 400 450 Magnetic field strength, B (Gauss)
Fig.(78) Output ion beam current versus magnetic field strength at dA-C=6 mm,
Duncovered em. disc = 5 mm, Dem. = 2.5 mm, dem. – F.C = 3 cm, and different pressures using Argon gas.
4.5.4-Comparison between output ion beam current value with and without magnet
Figure (79) shows the relation between the output ion beam -4 current, Ib (µA), versus the discharge current, Id (mA), at P= 6 X 10 mmHg, optimum operating conditions, with and without the effect of magnetic field using Argon gas. It is clear that at Id = 1.2 mA and B= 300 Gauss, a maximum output ion beam current equal to 300 µA can be obtained, while at B = 0, a maximum output ion beam current equal to 150 µA can be obtained. It can be concluded that at P= 6 X10-4 mmHg and B= 300 Gauss, the output ion beam current value is twice its value without magnet. Figure (63) shows the effect of Argon ion beam on Copper Faraday cup for one hour without
107 magnetic field. Figure (80) shows The effect of Argon ion beam on Copper Faraday cup for one hour with magnetic field of strength B= 300 Gauss.
350 DUncov ered emission disc = 5 mm Ar
dA-C = 6 mm B = 300 Gauss 300 dem-F.C = 3 cm
) dmag.- A = 1.5 cm A -4
(µ Dem = 2.5 mm P= 6X10 mmHg b 250 , I
t n e r r
u 200 c m
a B = 0
be 150 n o i
put 100 Out
50
0 0 0.2 0.4 0.6 0.8 1 1.2 1.4
Discharge current , Id (mA)
Fig.(79) Output ion beam current versus discharge current at optimum operating conditions and P= 6 X10-4 mmHg with B = 300 G and without magnet using Argon
gas.
Fig.(80) The effect of Argon ion beam on Copper Faraday cup for one hour with magnetic field of strength B= 300 Gauss.
108 4.6- The optimum parameters of PIG ion source using Nitrogen gas
In this experiment, we made the optimized parameters of cold cathode Penning ion source using Nitrogen gas.
4.6.1- Input characteristics
Figure (81) shows the discharge current, Id (mA), versus the discharge voltage, Vd (KV), at Dem = 2.5 mm, dA-C = 6 mm, Duncovered em. disc = 5 mm, and dem.-F.C.= 3 cm, magnetic field strength, B, equals 300 Gauss for different pressures using Nitrogen gas. It is clear from the figures that the discharge current is increased by increasing the discharge voltage applied on the anode and the discharge voltage starts at lower potential in case of high pressure (9 X10-4 mmHg) than that in case of low pressure (5 X 10-4 mmHg).
2.5 B = 300 G DUncovered emission disc = 5 mm N2 dA-C = 6 mm
dem-F.C=3 cm
dmag.- A= 1.5 cm 2 1 2 Dem= 2.5 mm A) m (
d -4 I 1.5 1 P= 5X10 mmHg ,
t 2 P= 9X10-4 mmHg en r r cu e
g 1 ar sch i D
0.5
0 012345678
Discharge voltage , Vd (KV)
Fig.(81) Discharge current versus discharge voltage at dA-C= 6 mm, Duncovered em. disc = 5 mm, Dem. = 2.5 mm, dem. – F.C = 3 cm, B = 300 G, and different pressures using Nitrogen gas. 109 4.6.2- Output ion beam characteristics
Figure (82) shows output ion beam current, Ib (µA), versus the discharge voltage, Vd (KV), at dA-C= 6 mm, Dem.= 2.5 mm,
Duncovered em. disc = 5 mm, dem. – F.C = 3 cm, magnetic field strength, B, equals 300 Gauss, and for different pressures using Nitrogen gas. It is clear that these figures are similar in shape to the discharge voltage – discharge current curves. In order to increase the output ion beam current through the discharge; we must increase the number of electrons created by the ionization.
300 B = 300 G DUncovered emission disc = 5 mm N2 dA-C = 6 mm
dem-F.C=3 cm 250 1 dmag.- A= 1.5 cm
) Dem= 2.5 mm 1 P= 5X10-4 mmHg µA 200 -4 b (
I 2 P= 9X10 mmHg , t en r r 150
cu 2 am e b
n 100 o i t u p t u
O 50
0 012345678
Discharge voltage , Vd (KV)
Fig.(82) Output ion beam current versus discharge voltage at dA-C= 6 mm, Dem. = 2.5 mm , Duncovered em. disc = 5 mm, dem. – F.C = 3 cm, B = 300 G, and different pressures using Nitrogen gas.
110
Figure (83) shows output ion beam current, Ib (µA), versus the discharge current, Id (mA), at dA-C = 6 mm, Dem. = 2.5 mm,
Duncovered em. disc = 5 mm, dem.– F.C = 3 cm , magnetic field strength, B, equals 300 Gauss for different pressures using Nitrogen gas. It is clear from the figures that the output ion beam current increases with increasing the discharge current and at P = 5 X 10-4 mm Hg, a maximum output ion beam current equals 241 µA can be obtained.
300 B = 300 G DUncovered emission disc = 5 mm N2 dA-C = 6 mm
dem-F.C=3 cm 250 dmag.- A= 1.5 cm 1
Dem= 2.5 mm )
µA 200 1 P= 5X10-4 mmHg b ( I
, 2 P= 9X10-4 mmHg t n e r 150
cur 2 m bea
n 100 o i t u p t u
O 50
0 0 0.5 1 1.5 2 2.5
Discharge current , Id (mA)
Fig.(83) Output ion beam current versus discharge current at dA-C= 6 mm, Dem. = 2.5 mm , Duncovered em. disc = 5 mm, dem. – F.C = 3 cm, B = 300 G, and different pressures using Nitrogen gas.
111 4.7- The cold cathode Penning ion source characteristics using Nitrogen and Argon gases
In this experiment, we made the optimized parameters of the cold cathode Penning ion source using Argon and Nitrogen gases.
4.7.1- Input characteristics
Figure (84) shows discharge current, Id (mA), versus discharge voltage, Vd (KV), the at Dem = 2.5 mm, dA-C = 6 mm, Duncovered em. disc
= 5 mm, and dem.-F.C.= 3 cm, magnetic field strength, B, equals 300 Gauss, P = 9 X 10-4 mm Hg using Argon and Nitrogen gases. It is clear from this figure that the discharge current is increased by increasing the discharge voltage. Nitrogen gas ionization starts at lower potential than that of Argon gas.
2.5 -4 P= 9X10 mmHg B = 300 G
N 2 DUncovered emission disc = 5 mm 2 dA-C = 6 mm
dem-F.C=3 cm
) dmag.- A= 1.5 cm A
m 1.5 Dem= 2.5 mm (
d Ar , I t en r r
u 1 c e g ar sch i D 0.5
0 012345
Discharge voltage , Vd (KV)
Fig.(84) Discharge current versus discharge voltage at dA-C= 6 mm, Duncovered em. disc -4 = 5 mm, Dem. = 2.5 mm, dem. – F.C = 3 cm, B = 300 G, and P = 9 X 10 mm Hg using Nitrogen and Argon gases.
112 4.7.2- Output ion beam characteristics
Figure (85) shows output ion beam current, Ib (µA), versus discharge voltage, Vd (KV) , at dA-C = 6 mm, Dem. = 2.5 mm,
Duncovered em. disc = 5 mm, dem.–F.C = 3 cm, magnetic field strength, B, equals 300 Gauss, and P = 9 X 10-4 mm Hg using Nitrogen and Argon gases. It is clear that this figure is similar in shape to the discharge voltage – discharge current curves. In order to increase the output ion beam current through the discharge; we must increase the number of electrons created by the ionization. Argon gas has higher output ion beam current than Nitrogen gas.
180 -4 P= 9 X10 mmHg Ar B = 300 G 160
140 N2 ) DUncovered emission disc = 5 mm µA
( d = 6 mm b A-C I 120 , dem-F.C=3 cm t n
e 100 dmag.- A= 1.5 cm r r
u Dem= 2.5 mm c
m 80 a
n be 60 o i ut p 40 Out 20
0 012345
Discharge voltage , Vd (KV)
Fig.(85) Output ion beam current versus discharge voltage at dA-C= 6 mm, Dem. = -4 2.5 mm, Duncovered em. disc = 5 mm, dem. – F.C = 3 cm, B = 300 G, and P = 9 X 10 mm Hg using Nitrogen and Argon gases.
113 Figure (86) shows output ion beam current, Ib (µA), versus discharge current, Id (mA), at dA-C = 6 mm, Dem. = 2.5 mm,
Duncovered em. disc = 5 mm, dem.– F.C = 3 cm , magnetic field strength, B, equals 300 Gauss, and P = 9 X 10-4 mmHg using Nitrogen and Argon gases. It is clear from this figure that the output ion beam current increases with increasing the discharge current and a maximum output ion beam current of Argon equals 169 µA can be obtained, while for Nitrogen is 134 µA .
180 -4 DUncovered emission disc = 5 mm P= 9 X10 mmHg Ar dA-C = 6 mm 160 dem-F.C=3 cm d = 1.5 cm N2 A) mag.- A
µ 140 (
b Dem= 2.5 mm I , 120 t n e r r u
c 100 m a B = 300 G be 80 on i
put 60 Out
40
20
0 00.511.522.5
Discharge curre nt , Id (mA)
Fig.(86) Output ion beam current versus discharge voltage at dA-C = 6 mm, Dem. = -4 2.5 mm, Duncovered em. disc = 5 mm, dem. – F.C = 3 cm, B = 300 G, and P = 9 X 10 mm Hg using Nitrogen and Argon gases.
114
4.8 - Effect of negative voltage on Faraday cup
In this experiment, the negative voltage is affected on Faraday cup using Argon gas, the output ion beam current is increased.
Figure (87) shows output ion beam current, Ib(µA), versus discharge current, Id (mA), at dA-C = 6 mm, Dem. = 2.5 mm, Duncovered em.disc =
5 mm, dem.– F.C = 3 cm , magnetic field strength, B, equals 300 Gauss for different negative voltage applied on Faraday cup using Argon gas. The higher negative voltage on Faraday cup has high ion beam current.
350 -4 1 1 V ng = 0 V P= 5X10 mmHg 2 V = -1250 V ng 2 3 Vng = -1500 V
) 300 Ar A D = 5 mm 3
(µ Uncov ered emission disc b
, I dA-C = 6 mm
t dem-F.C= 3 cm
en 250 r dmag.- A= 1.5 cm r D = 2.5 mm
cu em eam b
n 200
o B = 300 G i t u p t u O 150
100 0.5 0.7 0.9 1.1 1.3 1.5 1.7 1.9 2.1
Discharge current , Id (mA)
Fig.(87) Output ion beam current versus discharge current at dA-C= 6 mm, Dem. = 2.5 mm, Duncovered em. disc = 5 mm, dem. – F.C = 3 cm, B = 300 G, and different negative voltages applied on Faraday cup using Argon gas.
115 Figure (88) shows the output ion beam current versus the negative voltage applied on Faraday cup the using Argon gas. It is clear that the higher ion beam current is at higher discharge current value.
There are two minimum points ( Vng = -500 , -1500 V) at which the ion beam current decreased and before and after them, the output ion beam current increased. There is a maximum point ( Vng = -1000 V), at which the output ion beam current increased to reach 350 µA for Id = 9 mA. At Id = 0.4 mA, the output ion beam current and negative voltage relation is nearly linear. But as the value of discharge current increased, the maximum value at Vng = - 1000 V is increased. This is due to the plasma intensity is increased, the output ion beam current increased by applying negative voltage applied on Faraday cup.
116 DUncovered emission disc = 5 mm P= 5X10-4 mmHg Ar dA- C = 6 mm 400 dem-F.C= 3 cm B = 300 G dmag.- A= 1.5 cm
Dem= 2.5 mm 350
) 9 A
(µ 300 b
, I 8 t n
e 250
r 7 r u
c 6
m 5 a 200 4 on be
i 3 150 put t 2 u O 100 1
50
0 0 -200 -400 -600 -800 -1000 -1200 -1400 -1600 -1800 -2000 Negative voltage on F.C., Vng (V)
1 Id = 0.4 mA 6 Id = 1.4 mA 2 Id = 0.6 mA 7 Id = 1.6 mA
3 Id = 0.8 mA 8 Id = 1.8 mA 4 Id = 1 mA 9 Id = 2 mA 5 Id = 1.2 mA
Fig.(88) Output ion beam current versus negative voltage applied on Faraday cup at dA-C= 6 mm, Dem. = 2.5 mm, Duncovered em. disc = 5 mm, dem. – F.C = 3 cm, B = 300 G, and different discharge current using Argon gas.
4.9 - Effect of energy analyzer on extracted ion beam current
In this experiment, the energy analyzer consists of retarding grid and screen grid. This energy analyzer is placed between the emission disc and Faraday cup. The retarding grid is positively and negatively potential, in case of retarding ions and electrons respectively. The dimensions of this analyzer are:
117 - Emission disc- retarding grid distance equals 1 cm. - Retarding grid – screen grid distance equals 1 cm. - Screen grid – Faraday cup distance equals 1 cm. - Diameters of two grids equal 1 cm. - Diameter of holes equal 2 mm.
4.9.1- Ion retarding
In this experiment, the retarding grid is connected to positive potential, while the emission disc and screen grid are connected to ground. Figure (89) shows the relation between the voltage applied the retarding grid Vret (V) versus the output ion beam current at the optimized parameters of the ion source, special pressure P = 9 X 10-4 mm Hg, and two values of discharge voltage ( 2 and 3 KV) using
Argon gas. It is clear from this figure this relation is higher at Vd =
3 KV than Vd = 2 KV. At Vd = 2 KV, output ion beam current is 4 µA for voltage equals 200 V applied on retarding grid. The output ion beam current decreases for retarding voltage < discharge voltage, and saturated for retarding voltage ≥ discharge voltage. Figure (90) shows the effect of Argon ion beam on Copper Faraday cup at optimized parameters in case of positive potential applied on the retarding grid.
118 20 Ar DUncovered emission disc = 5 mm 18 dA- C = 6 mm dem-F.C= 3 cm
dmag.- A= 1.5 cm ) 16 A Dem= 2.5 mm (µ
b 14 B = 300 G , I t n 12 P= 9X10‐4 mmHg rre u
c 10 m
a 1 Vd = 2 KV 2 e 8
n b 2 Vd = 3 KV o i 6
ut 1 p t
u 4 O 2
0 0 1000 2000 3000 4000
Retarding voltage, Vret (V)
Fig.(89) Output ion beam current versus voltage applied on retarding grid at dA-C= 6 mm, Dem. = 2.5 mm, Duncovered em. disc = 5 mm, dem. – F.C = 3 cm, B = 300 G, and P= 9 X 10 -4 mm Hg using discharge voltages 2 and 3 KV Argon gas.
Fig.(90) the effect of Argon ion beam on Copper Faraday cup at optimized parameters in case of retarding grid is positive potential.
119 4.9.2- Energy distribution
Figure (91) shows the energy distribution for the optimized parameters of the ion source at pressure equals 9 X 10-4 mmHg, discharge voltage equals 2 and 3 KV, and using Argon gas. It is clear from the figure that the energy distribution is almost independently of the discharge voltage. The ions emitting from plasma boundary and moving towards the ion exit aperture, accelerates in the field between the plasma boundary and the emission disc. When it becomes fast and collide with the gas atoms, the collision can result in an ion extracting an electron from gas atom, resulting in it becoming a fast neutral atom while the slow atom becomes a slow positive ion. This process does not change the number of the ions in the system, is called charge transfer process with general form:
X+ (Energetic ion)+ X (Slow atom) → X+ (Slow ion)+ X (Fast atom)
120 1.8 ‐4 Ar DUncovered emission disc = 5 mm P= 9X10 mmHg dA- C = 6 mm 1 dem-F.C= 3 cm 1.6 dmag.- A= 1.5 cm 2 Dem= 2.5 mm 1.4 B = 300 Gauss
t 1.2 1 Vd = 2 KV uni y
r 2 Vd = 3 KV a r
t 1 bi r a , 0.8 dV / dI
0.6
0.4
0.2
0 0 200 400 600 800 1000 1200 1400 1600 1800 2000
-0.2 Retarding voltage, VR (V)
Fig.(91) the energy distribution at the optimized parameters at pressure equals 9X10-4 mmHg, different discharge voltage, and using Argon gas.
4.10 – Paschen curve
The law essentially states that, at higher pressures (above a few torr) the breakdown characteristics of a gap are a function (generally not linear) of the product of the gas pressure and the gap length, usually written as V= f( pd ), where p is the pressure, d is the gap distance, and V is the breakdown voltage.
121 4.10.1- Without applying magnetic field
Figure (92) shows the relation between the pressure (torr) multiplied by gap distance between the anode – cathode (cm) versus the discharge voltage (KV) at dA-C = 6 mm, Dem. = 2.5 mm,
Duncovered em.disc = 5 mm, dem.– F.C = 3 cm, and discharge current varies with values 0.5, 0.6, 0.7, 0.8, 0.9, and 1 mA without applying magnetic field using Argon gas. It is clear that discharge voltage decreases as the pressure is high. The lower relation occurs at lower discharge current Id = 0.5 mA.
9 B= 0 DUncovered emission disc= 5mm Ar dA- C = 6 mm 4 Dem= 2.5 mm 8 dem- F.C. = 3 cm 2 ) V 7
(K 1 Id = 0.5 mA d
V 2 Id = 0.7 mA e , 6 3 Id = 0.9 mA ag lt 4 Id = 1 mA vo e g 5 ar sch i D 4 3
1 3 22.5 33.54 Pressure X gab distance ( X 10 -4 torr. Cm)
Fig.(92) Pressure multiplied by gap distance versus discharge current at dA-C= 6 mm, Dem. = 2.5 mm, Duncovered em. disc = 5 mm, dem. – F.C = 3 cm, B = 0, and different discharge current using Argon gas.
122 4.10.2- With applying magnetic field
Figure (93) shows the relation between the pressure (torr) multiplied by gap distance between the anode – cathode (cm) versus the discharge voltage (KV) at dA-C = 6 mm, Dem. = 2.5 mm,
Duncovered em.disc = 5 mm, dem.– F.C = 3 cm, and discharge current varies with values 0.5, 0.6, 0.7, 0.8, 0.9, and 1 mA with applying magnetic field (B = 300 G) using Argon gas. It is clear that discharge voltage decreases as the pressure is high. The lower relation occurs at lower discharge current Id = 0.5 mA.
6 DUncovered emission disc = 5 mm Ar
dA-C = 6 mm d = 3 cm 5.5 em-F.C dmag.- A = 1.5 cm
Dem = 2.5 mm
) 5 B = 300 G 1 Id = 0.5 mA V 2 Id = 0.6 mA (K d 3 Id = 0.7 mA V
e , 4.5 4 Id =0.8 mA ag t l 5 Id = 0.9 mA o v 6 I = 1 mA
e d g r
a 4 h 6 sc i 5 D 4 3.5 3 2 1 3 33.544.555.56
Pressure X gab distance ( X 10 -4 torr. Cm)
Fig.(93) Pressure multiplied by gap distance versus discharge current at dA-C= 6 mm, Dem. = 2.5 mm, Duncovered em. disc = 5 mm, dem. – F.C = 3 cm, B = 300 G, and different discharge current using Argon gas.
123 4.10.3- Without and with applying magnetic field
Figure (94) shows the relation between the discharge voltage, Vd
(KV), versus the discharge current, Id (mA), at dA-C = 6 mm, Dem. = -4 2.5 mm, Duncovered em.disc = 5 mm, dem.– F.C = 3 cm, P= 6 X 10 mm Hg without and with applying magnetic field using Argon gas. It is clear that as the discharge voltage increases, the discharge current increases. With applying magnetic field, the ionization starts at higher discharge voltage than without applying magnetic field.
1.4 -4 DUncovered emission disc = 5 mm P= 6X10 mmHg dA-C = 6 mm 1.2 dem-F.C = 3 cm dmag.- A = 1.5 cm
) Dem = 2.5 mm A 1
(m B = 0 d I , t n 0.8 B = 300 Gauss
rre Ar cu e g r
a 0.6 h c s i D 0.4
0.2
0 33.544.5 55.56
Discharge voltage , Vd (KV)
Fig.(94) Discharge voltage versus discharge current at dA-C= 6 mm, Dem. = 2.5 mm, -4 Duncovered em. disc = 5 mm, dem. – F.C = 3 cm, P = 6 X 10 mm Hg, without and with applying magnetic field using Argon gas.
124 4.11 – Efficiency of this ion source
In this experiment, we can determine the efficiency of the ion source. By drawing the relation between the pressure of the Argon gas versus the output ion beam current and discharge current ratio. Figure (95) shows the relation between the gas pressure (mmHg) versus the efficiency of the ion source at Vd = 3.92 KV, optimized parameters, and using Nitrogen and Argon gases. It is clear that the ion source is more efficient for Argon than Nitrogen gas.
40 DUncov ered emission disc = 5 mm Vd = 3.92 KV dA-C = 6 mm 35 dem-F.C= 3 cm
dmag.- A= 1.5 cm
30 Dem= 2.5 mm B = 300 Gauss 25 0 % Ar 10 20 X d I / b I N 15 2
10
5
0 45678910 Pressure X 10 -4 mm Hg
Fig.(95) Gas pressure versus ion source efficiency at dA-C= 6 mm, Dem. = 2.5 mm, Duncovered em. disc = 5 mm, dem. – F.C = 3 cm, Vd = 3.92 KV, with applying magnetic field using Nitrogen and Argon gases.
125 4.12 – Perveance
Figure (96) shows the relation between the discharge current, Id 3/2 5 3/2 (mA), versus the perveance, [ Ib / Vd ] X 10 in (A/V ), at the optimized parameters of the ion source, pressure equals 7 X 10-4 mmHg, and using Nitrogen and Argon gases. It is clear that by increasing the discharge current, the perveance increases and at discharge current equals 1.3 mA, the perveance reaches 62.3 X 106 (A/V3/2) and 49 X 106 (A/V3/2) for Argon and Nitrogen gases respectively. The perveance in case of Argon gas is higher than that in case of Nitrogen gas.
70 -4 DUncovered emission disc = 5 mm P= 7X10 mmHg
dA- C = 6 mm
dem-F.C= 3 cm 60 dmag.- A= 1.5 cm
Dem= 2.5 mm B = 300 G 50 N2 2 3/
d Ar
/ V 40 b I , 5 10 30 X e c n ea
v 20 r e P
10
0 00.20.40.60.811.21.41.6
Discharge current , Id (mA)
Fig.(96) Perveance versus the discharge current at the optimized parameters of ion source, pressure equals 7 X 10-4 mmHg, and using Argon and Nitrogen gases.
126 4.13 – Operating time of this ion source
Figure (97) shows the output ion beam current, Ib (µA), versus the exposed time, t (min.), at the optimized parameters of the ion source, pressure equals 7 X 10-4 mmHg, and using Argon gas bombarded with Molybdenum specimen. It is clear that the output ion beam current is nearly constant ranging from 130 to 163 µA during the exposed time. It means that the operating time of this ion source is two hours, depending on the insulating materials.
230 P= 7X10-4 mmHg Ar DUncovered emission disc = 5 mm
dA-C = 6 mm 210 dem-F.C= 3 cm
dmag.- A= 1.5 cm
) Dem= 2.5 mm
A 190
(µ B = 300 G b , I t
n 170 e r r Mo u c m
a 150 on be i
130 put t u O
110
90
70 0 20 40 60 80 100 120 Exposed time (min.)
Fig.(97) Output ion beam current versus the exposed time at the optimized parameters of the ion source, pressure equals 7 X 10-4 mmHg, and using Argon gas bombarded with Molybdenum specimen.
127 4.14– Comparison between theoretical and experimental results
By substituting in equation (2.11) presented in chapter (2) by the voltage, charge state, and mass (a.m.u) values for Argon gas, then the theoretical values of output ion beam current can be obtained.
Figure (98) shows the output ion beam current, Ib (µA), versus the discharge current, Id (mA), at the optimized parameters of the ion source, pressure equals 8 X 10-4 mmHg, and for experimental and theoretical results using Argon gas. It is clear that there is symmetry in the values of output ion beam current between the experimental data and the theoretical calculation.
-4 Ar 200 DUncov ered emission disc = 5 mm P= 8X10 mmHg dA-C = 6 mm
dem-F.C= 3 cm
180 dmag.- A= 1.5 cm Dem= 2.5 mm
) B = 300 G
µA 160 b ( I , 1 Experimental result 2 Theoretical result nt e
r 140 r 2 u c m a 120 ion be t u p 1 100 Out
80 0.55 0.65 0.75 0.85 0.95 1.05 1.15
Discharge current , I (mA) d Fig.(98) Output ion beam current versus the discharge current at the optimized parameters of the ion source, pressure equals 8 X 10-4 mmHg, and for experimental and theoretical results using Argon gas.
128 Finally, after we determined the optimized parameters of a cold cathode Penning ion source which give maximum output ion beam current. This ion source is used in applications, specially in polymers specimens.
5.1- Introduction
Ion beams have been used to modify basic processes that control thin film growth and morphology. In recent years, there has been a rapid growth in the utilization of ion sources for a variety of applications, including nuclear physics, isotopes separators, multiampere beams for fusion applications and for industrial production applications. Also they are useful tools in ion implantation, ion sputtering Behrisch et al. [88], ion etching, ion beam machining, ion beam surface modification Rodrguez et al. [89] and neutron generators. As a consequence of this growth, there has been the need for a better understanding of the factors which affect the optical quality Sadahiro et al. [90] of ion beams.
Ion beams have been used for many years in a variety of scientific experiments. More recently they have emerged into use in engineering applications and even in production, for example, sputtering deposition and removal in semi conductor device manufacture Hall [91], fine surface polishing, by ion- implantation doping of semi conductor materials and devices and by the use of ion beams for propulsion of space vehicles. Ion beams offer certain
129 unique advantages that are resulting in their increasing use for semi conductor and other microelectronic applications.
Ions are heavy they have 103 to 106 times the mass of an electron. Thus for a given energy, an ion has approximately 102 to 104 times greater momentum than an electron. As a result of this characteristic, ions can produce quantatively different effects in interaction with crystal lattices.
5.2- Polymers
5.2.1- Brief history of polymers
As far back as 1839, Charles Goodyear first improved the elastic properties of natural rubber by heating with sulfur (vulcanization). The first synthetic polymer, a phenol-formaldehyde polymer, was introduced under the name “Bakelite”, by Leo Baekeland in 1909. Rayon, the first synthetic fiber was developed as a replacement for silk in 1911. It was not until the 1930s that the macromolecule model of rubber was understood. After World War II and through the 1950s rapid developments in synthetic polymers were made.
5.2.2- PM – 355 polymer
In this experiment, the ion beam of argon gas is bombarded to PM-355 polymer specimens at different times. Figure (1) shows the absorbance versus the fluence at optimized parameters of this ion source and different wavelengths.
130
PM- 355 + Ar 1 DUncov ered emission disc = 5 mm
dA-C = 6 mm
dem-F.C = 3 cm 0.9 λ = 300 nm dmag.- A = 1.5 cm
Dem = 2.5 mm 0.8 B = 300 G
0.7 ce n a b r 0.6 so b A
0.5
0.4 λ = 600 nm
0.3 λ = 900 nm
0.2 λ = 1100 nm
0.1 0 2 4 6 8 10121416
Fluence X 10-3 (ions / cm2)
Fig.(1) Absorbance versus fluence at optimized ion source parameters and different wave lengths using argon ion beam bombarded to PM- 355 polymer specimen.
It is clear from this figure that the absorbance increases as the fluence increases. It means that there is cross linking occurs in polymer.
131
132 In this work, the design, construction, and operation of a new shape of cold Molybdenum cathode Penning ion source were made in the Accelerators and Ion Sources Department, Nuclear Research Center, Atomic Energy Authority, Egypt.
The new shape of cold cathode Penning ion source consists of Copper cylindrical hollow anode of 40 mm length, 12 mm diameter, and has two cone ends of 15 mm length, 22 mm upper cone diameter and 12 mm bottom cone diameter. The two movable Molybdenum cathodes are fixed in Perspex insulator and placed symmetrically at two ends of the anode. The Copper emission disc of 2 mm thickness and has central aperture of different diameters is placed at the middle of the anode for ion beam exit. The inner surface of the emission disc is isolated from the anode by Perspex insulator except an area of diameter equals 5 mm (the optimum) to confine the discharge in this area. The movable Faraday cup is placed at different distances from the emission electrode aperture used to collect the output ion beam extracted from the ion source.
It has been found that the glow discharge started between the two cathodes and the anode which acts as a continuous feeding source of the ions to the system. With the increase of the anode potential, the plasma boundary layer is extended to the cathode where the glow discharge takes place. The extracted boundary layer of the plasma is affected by further increase of the potential, which is detected by an increase of the output ion beam current. The ion beam is extracted
133 from the discharge region through central aperture of emission electrode equals 2.5 mm.
From the experimental results of this ion source using Argon gas. It can be concluded that the optimum operating conditions are: • Anode- cathode distance equal to 6 mm • The emission electrode aperture diameter equal to 2.5 mm • The emission electrode aperture – Faraday cup equal to 3cm • The inner diameter of uncovered emission electrode equal to 5mm.
It can be concluded that at the optimum operating conditions, discharge current equals 2 mA, and pressure equals 4 X 10-4 mmHg, a maximum output ion beam current equal to 540 µA can be produced.
The effect of Samarium - Cobalt permanent magnet on the discharge characteristics of this ion source was determined using Argon gas. It can be concluded that at pressure equal to 6 X 10-4 mm Hg, discharge current equal to 1.4 mA, and permanent magnet of intensity equal to 300 Gauss, the output ion beam current value is twice its value without magnet.
The effect of negative voltage applied on the Faraday cup on the output ion beam current from the ion source using Argon gas was determined. It can be concluded that at pressure equal to 5 X 10-4 mmHg, discharge current equal to 2 mA, permanent magnet of
134 intensity equal to 300 Gauss, and Vneg. = - 1000 Volt, a maximum output ion beam current equal to 350 µA can be obtained.
The energy spectrum of the positive ions emerging from the new shape ion source has been measured. The low energy ions are probably due to the charge exchange process taking place inside the ion source. The symmetrical charge transfer process has the general form:
X+ (Energetic ions) + X (Slow atom)→ X+ (Slow ions) + X (Fast atom)
The effect of retarding voltage applied on the retarding grid, while the emission electrode and screen grid are connected to the ground was determined. It can be concluded that at the optimum operating conditions of this ion source, different discharge voltages (2 KV and 3 KV), pressure equal to 9 X10-4 mmHg, and permanent magnet of intensity equal to 300 Gauss, the output ion beam current decreases by increasing the retarding voltage and starts to be constant at retarding voltage greater than the discharge voltage.
The ion source efficiency was determined at the optimum operating conditions, discharge voltage equal to 3.92 KV and different pressures using Nitrogen and Argon gases. It can be concluded that the ion source efficiency reaches 35% and 22 % using Argon and Nitrogen gases respectively.
135 The effect of discharge current on the perveance of this ion source was determined. It can be concluded that at the optimum conditions parameters, pressure equal to 7 X 10 -4 mmHg, permanent magnet of intensity equals 300 Gauss, the perveance is increased by increasing the discharge current and reaches 62.7 X 105 A/ V3/2 and 40.4 X 105 A/ V3/2 using Argon and Nitrogen gases respectively.
Also, it can be concluded that the operating time of this ion source is two hours at the optimum operating conditions, pressure equals 7 X 10 -4 mmHg, permanent magnet of intensity equals 300 Gauss, discharge voltage equals 5 KV, and discharge current equals 1.8 mA.
Finally, it can be concluded that the new shape of cold cathode Penning ion source can be used for different applications such as sputtering, materials surface modification and thin films deposition of different materials.
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144 ﻣﻠﺨﺺ اﻟﺮﺳﺎﻟﺔ
اﻟﻐﺮض ﻣﻦ ه ﺬﻩ اﻟﺮﺳﺎﻟﺔ هﻮ ﺗﺤﺴﻴﻦ أداء ﺷﻜﻞ ﺟﺪﻳﺪ ﻣﻦ ﻣﺼﺪر أﻳﻮﻧﺎت اﻟﺒﻨﻨﺞ ذو اﻟﻤﻬﺒﻂ اﻟﺒﺎرد وذﻟ ﻚ ﻻﺳﺘﺨﺪاﻣﻪ ﻓﻲ اﻟﺘﻄﺒﻴﻘﺎت اﻟﻤﺨﺘﻠﻔﺔ.
ﺗﻢ ﻋﻤﻞ ﻋﺪة ﻣﺤﺎوﻻت ﻟﻠﻮﺻﻮل إﻟ ﻲ اﻷﺑﻌ ﺎد اﻟﻤﺜﻠ ﻲ ﻟﻠﻤ ﺼﺪر اﻷﻳ ﻮﻧﻲ ذو اﻻﺳ ﺘﺨﺮاج اﻟﻤﺤ ﻮري . ﺣﻴ ﺚ ﻳﻤﻜﻦ اﺳﺘﺨﺮاج ﺗﻴﺎر ﻋﺎﻟﻲ ﻣﻦ اﻟﺤﺰﻣﺔ اﻷﻳﻮﻧﻴﺔ ﻓﻲ اﺗﺠﺎﻩ ﻋﻤﻮدي ﻋﻠﻲ ﻣﻨﻄﻘﺔ اﻟﺘﻔﺮﻳﻎ.
وﻳﺘﻜﻮن اﻟﺸﻜﻞ اﻟﺠﺪﻳ ﺪ ﻣ ﻦ ﻣ ﺼﺪر أﻳﻮﻧ ﺎت اﻟﺒﻨ ﻨﺞ ﻣ ﻦ ﻣ ﺼﻌﺪ اﺳ ﻄﻮاﻧﻲ ﻧﺤﺎﺳ ﻲ ﻃﻮﻟ ﻪ ﻳ ﺴﺎوي ٤٠ ﻣ ﻢ، وﻗﻄ ﺮﻩ ﻳ ﺴﺎوي ١٢ ﻣ ﻢ، وﻟ ﻪ ﻧﻬﺎﻳﺘ ﺎن ﻋﻠ ﻲ ﺷ ﻜﻞ ﻣﺨ ﺮوط ﻃﻮﻟ ﻪ ﻳ ﺴﺎوي ١٥ ﻣ ﻢ، ﻗﻄ ﺮﻩ اﻟﻌﻠ ﻮي ﻳ ﺴﺎوي ٢٢ ﻣﻢ، وﻗﻄﺮﻩ اﻟﺴﻔﻠﻲ ﻳﺴﺎوي ١٢ ﻣﻢ. ﻣﻬﺒﻄ ﺎن ﻣﺘﺤﺮآ ﺎن ﻣ ﻦ ﻣ ﺎدة اﻟﻤﻮﻟﻮﺑ ﺪﻧﻴﻢ وﻣﺜﺒﺘ ﺎن داﺧ ﻞ ﻋ ﺎزل ﻣ ﻦ ﻣﺎدة اﻟﺒﻴﺮﺳﺒﻜﺲ وﻣﻮﺿﻮﻋﺎن ﻋﻠﻲ ﺑﻌﺪ ﻣﺘﻤﺎﺛﻞ ﻣﻦ ﻧﻬﺎﻳﺔ اﻟﻤﺼﻌﺪ اﻷﺳ ﻄﻮاﻧﻲ . ﻗﻄ ﺐ اﻻﻧﺒﻌ ﺎث اﻟﻨﺤﺎﺳ ﻲ ذو ﺳ ﻤﻚ ﻳ ﺴﺎوي ٢ ﻣ ﻢ، وﻓﺘﺤ ﺔ ﻣﺮآﺰﻳ ﺔ ﺑﺄﻗﻄ ﺎر ﻣﺨﺘﻠﻔ ﺔ وﺿ ﻊ ﻓ ﻲ ﻣﻨﺘ ﺼﻒ اﻟﻤ ﺼﻌﺪ وذﻟ ﻚ ﻟﺨ ﺮوج اﻟﺤﺰﻣ ﺔ اﻷﻳﻮﻧﻴﺔ. وﻗﺪ ﺗﻢ ﻋﺰل اﻟﺴﻄﺢ اﻟﺪاﺧﻠﻲ ﻟﻘﻄﺐ اﻻﻧﺒﻌﺎث ﺑﻤﺎدة اﻟﺒﻴﺮﺳﺒﻜﺲ ﻣﺎ ﻋﺪا ﻣﺴﺎﺣﺔ ﻗﻄﺮهﺎ ﻳﺴﺎوي ٥ ﻣﻢ وذﻟﻚ ﻟﺘﺮآﻴﺰ اﻟﺘﻔﺮﻳﻎ اﻟﻜﻬﺮﺑﻲ ﻓﻲ هﺬﻩ اﻟﻤﺴﺎﺣﺔ . آﻤﺎ ﺗﻢ وﺿﻊ وﻋﺎء ﻓﺎراداي ﻋﻠﻲ ﻣﺴﺎﻓﺎت ﻣﺨﺘﻠﻔﺔ ﻣﻦ ﻓﺘﺤﺔ ﻗﻄﺐ اﻻﻧﺒﻌﺎث وذﻟﻚ ﻟﺘﺠﻤﻴﻊ اﻟﺤﺰﻣﺔ اﻷﻳﻮﻧﻴﺔ اﻟﺨﺎرﺟﺔ ﻣﻦ اﻟﻤﺼﺪر اﻷﻳﻮﻧﻲ.
ﺗ ﻢ إدﺧ ﺎل ﻏ ﺎزات اﻟﺘ ﺸﻐﻴﻞ إﻟ ﻲ اﻟﻤ ﺼﺪر اﻷﻳ ﻮﻧﻲ ﻣ ﻦ ﺧ ﻼل ﻓﺘﺤ ﺔ ﻓ ﻲ اﻟﻤ ﺼﻌﺪ ﻗﻄﺮه ﺎ ﻳ ﺴﺎوي ٢ ﻣ ﻢ ﺑﻮاﺳﻄﺔ ﺻﻤﺎم إﺑﺮة واﻟﺬي وﺿﻊ ﺑﻴﻦ أﺳﻄﻮاﻧﺔ اﻟﻐﺎز واﻟﻤﺼﺪر اﻷﻳﻮﻧﻲ .
ﺗﻢ ﺗﻌﻴﻴﻦ اﻟﻤﺴﺎﻓﺔ اﻟﻤﺜﻠ ﻲ ﺑ ﻴﻦ اﻟﻤ ﺼﻌﺪ واﻟﻤﻬﺒﻄ ﺎن، ﻗﻄ ﺮ اﻟﻤ ﺴﺎﺣﺔ اﻟﻐﻴ ﺮ ﻣﻐﻄ ﺎة ﻟﻘﻄ ﺐ اﻻﻧﺒﻌ ﺎث، ﻗﻄ ﺮ اﻟﻔﺘﺤ ﺔ اﻟﻤﺮآﺰﻳ ﺔ ﻟﻘﻄ ﺐ اﻻﻧﺒﻌ ﺎث، اﻟ ﻤ ﺴﺎﻓﺔ ﺑ ﻴﻦ ﻗﻄ ﺐ اﻻﻧﺒﻌ ﺎث ووﻋ ﺎء ﻓ ﺎراد يا وذﻟ ﻚ ﺑﺎﺳ ﺘﺨﺪام ﻏ ﺎز اﻷرﺟﻮن. وﻗﺪ وﺟﺪ أن اﻷﺑﻌﺎد اﻟﻤﺜﻠﻲ ﻟ ﻠﻤﺼﺪر اﻷﻳﻮﻧﻲ ﺗﺴﺎوي ٦ ﻣﻢ، ٥ ﻣﻢ، ٢.٥ ﻣﻢ ، ٣ ﺳ ﻢ ﻋﻠ ﻲ اﻟﺘﺮﺗﻴ ﺐ ﺣﻴﺚ ﺗﻔﺮﻳﻎ آﻬﺮﺑﻲ ﻣﺴﺘﻘﺮ وﺗﻴﺎرﻋﺎﻟ اﻲ ﻣﻦ ﻟﺤﺰﻣﺔ اﻷﻳﻮﻧﻴﺔ ﻋﻨﺪ ﺗﻴﺎر ﺗﻔﺮﻳﻎ ﻗﻠﻴﻞ ﻳﻤﻜﻦ اﻟﺤﺼﻮل ﻋﻠﻴﻪ.
ﺗﻢ ﻗﻴﺎس ﺧﺼﺎ ﺋﺺ اﻟﺘﻔﺮﻳﻎ اﻟﻜﻬﺮﺑﻲ، ﺧﺼﺎﺋﺺ اﻟﺤﺰﻣﺔ اﻷﻳﻮﻧﻴ ﺔ وآﻔ ﺎءة اﻟﻤ ﺼﺪر اﻷﻳ ﻮﻧﻲ ﻋﻨ ﺪ ﺷ ﺮوط ﺗﺸﻐﻴﻞ ﻣﺨﺘﻠﻔﺔ وﺿﻐﻮط ﻣﺨﺘﻠﻔﺔ ﺑﺎﺳﺘﺨﺪام ﻏﺎز اﻷرﺟﻮن.
آﻤﺎ ﺗﻢ ﻗﻴﺎس ﺧﺼﺎﺋﺺ اﻟﻤﺼﺪر اﻷﻳﻮﻧﻲ ﻋﻨﺪ ﺷﺮوط اﻟﺘﺸﻐﻴﻞ اﻟﻤﺜﻠﻲ وﺿﻐﻮط ﻣﺨﺘﻠﻔ ﺔ ﺑﺎﺳ ﺘﺨﺪام ﻏ ﺎزي اﻷرﺟ ﻮن واﻟﻨﻴﺘ ﺮوﺟﻴﻦ. وﺗ ﻢ ﺗﻌﻴ ﻴﻦ ﺗ ﺄﺛﻴﺮ اﻟﺠﻬ ﺪ اﻟ ﺴﺎﻟﺐ اﻟﻤﻄﺒ ﻖ ﻋﻠ ﻲ وﻋ ﺎء ﻓ ﺎراد اي ﻋﻠ ﻲ ﺗﻴ ﺎر اﻟﺤﺰﻣ ﺔ اﻷﻳﻮﻧﻴﺔ اﻟﺨﺎرﺟﺔ ﻣﻦ اﻟﻤﺼﺪر اﻷﻳﻮﻧﻲ.
ﺗﻢ ﺗﻌﻴﻴﻦ ﺗﺄﺛﻴﺮ ﻣﺠﺎل ﻣﻐﻨﺎﻃﻴﺴﻲ داﺋﻢ ﻋﻠﻲ ﺧﺼﺎﺋﺺ اﻟﺘﻔﺮﻳﻎ ﻟﻠﻤﺼﺪر اﻷﻳﻮﻧﻲ . ﺣﻴﺚ ﺗ ﻢ اﺳ ﺘﺨﺪام ﻣﺠ ﺎل ﻣﻐﻨﺎﻃﻴ ﺴﻲ ﻣ ﻦ ﻣ ﺎدﺗﻲ ﺳ ﻤﺎر ﻳ ﻢ – آﻮﺑﻠ ﺖ. وﻗ ﺪ وﺟ ﺪ أن اﻟﻤ ﺴﺎﻓﺔ اﻟﻤﺜﻠ ﻲ ﺑ ﻴﻦ اﻟﻤ ﺼﻌﺪ واﻟﻤﻐﻨ ﺎﻃﻴﺲ اﻟ ﺪاﺋﻢ ﺗﺴﺎوي ١,٥ﺳﻢ واﻟﺘﻲ ﺗﻢ اﻟﺤﺼﻮل ﻋﻠﻴﻬﺎ ﻣﻦ ﺗﺠﺎرب ﻋﺪﻳﺪة.
ﺗﻢ ﻗﻴﺎس ﻃﺎﻗﺔ اﻟﺠﺴﻴﻤﺎ ت اﻟﺜﻘﻴﻠﺔ اﻟﻤﺸﺤﻮﻧﺔ ﻟﻠﺒﻼزﻣﺎ داﺧﻞ اﻟﻤﺼﺪر اﻷﻳﻮﻧﻲ ﺑﺎﺳﺘﺨﺪام ﻧﻈﺎم ﻣﺤﻠﻞ اﻟﻄﺎﻗﺔ . . ﺣﻴﺚ ﺗﻢ ﺗﻌﻴﻴﻦ اﻷﻳﻮﻧﺎت اﻟﻤﺘﺄﺧﺮة ﺑﻮﺿﻊ ﺟﻬﺪ ﻣﻮﺟﺐ ﻋﻠﻲ ﺷﺒﻜﺔ اﻟﺘﺄﺧﻴﺮ ، وﻣﻦ اﻟﻨﺘﺎﺋﺞ اﻟﻌﻤﻠﻴ ﺔ ﺗ ﻢ اﻟﺤ ﺼﻮل ﻋﻠﻲ ﺗﻮزﻳﻊ اﻟﻄﺎﻗﺔ.
ﺗﻢ ﺗﻌﻴ ﻴﻦ آﻔ ﺎءة اﻟﻤ ﺼﺪر اﻷﻳ ﻮﻧﻲ ﺑﺎﺳ ﺘﺨﺪام ﻏ ﺎزي اﻟﻨﻴﺘ ﺮوﺟﻴﻦ واﻷرﺟ ﻮن . آﻤ ﺎ ﺗ ﻢ ﺣ ﺴﺎب ﺲاﻟﺒ ﺮ ﻓﻴ ﻨ ﻟﻠﻤﺼﺪر اﻷﻳﻮﻧﻲ ﻣﻦ اﻟﻨﺘﺎﺋﺞ اﻟﻌﻤﻠﻴﺔ ﺑﺎﺳﺘﺨﺪام ﻏﺎزي اﻟﻨﻴﺘﺮوﺟﻴﻦ واﻷرﺟﻮن . وأﻳﻀﺎ ﺗﻢ ﺗﻌﻴﻴﻦ زﻣﻦ اﻟﺘﺸﻐﻴﻞ ﻟﻬﺬا اﻟﻤﺼﺪر اﻷﻳﻮﻧﻲ ﺑﺘﻌﺮﻳﺾ ﻋﻴﻨﺔ ﻣﻦ اﻟﻤﻮﻟﻮﺑﺪﻧﻴﻢ ﻷﻳﻮﻧﺎت ﻏﺎز اﻷرﺟﻮن . آﻤﺎ ﺗﻢ ﻣﻘﺎرﻧﺔ اﻟﻨﺘ ﺎﺋﺞ اﻟﻌﻤﻠﻴ ﺔ ﺑﺎﻟﺤﺴﺎﺑﺎت اﻟﻨﻈﺮﻳﺔ.
وأﺧﻴﺮا ﺗﻢ دراﺳﺔ ﺗﺄﺛﻴﺮ اﻟﺤﺰﻣ ﺔ اﻷﻳﻮﻧﻴﺔ اﻟﺨﺎرﺟﺔ ﻣﻦ اﻟﻤﺼﺪر اﻷﻳﻮﻧﻲ ﻓﻲ اﻟﺘﻄﺒﻴﻘﺎت، وﺧﺎﺻﺔ ﻋﻠ ﻲ ﻋﻴﻨ ﺎت ﻣﻦ اﻟﺒﻮﻟﻴﻤﺮ PM- 355. وﻗﺪ وﺟ ﺪ اﻧ ﻪ ﺑﺰﻳ ﺎدة زﻣ ﻦ ﺗﻌ ﺮﻳﺾ اﻟﻌﻴﻨ ﺎت ﻟ ﻠﺤﺰﻣ ﺔ اﻷﻳﻮﻧﻴ ﺔ ،ﺗﺰﻳ ﺪ اﻟ ﻘ ﺪرة ﻋﻠ ﻲ اﻻﻣﺘﺼﺎص وﺑﺎﻟﺘﺎﻟﻲ ﻳﺤﺪث ﻋﺒﻮر ﻟﻠﺮﺑﻂ داﺧﻞ اﻟﺒﻮﻟﻴﻤﺮ.
إﻧﺸــــﺎء ﻣـــﺼﺪر ﻟﻠﺤــــﺰﻣﺔ اﻷﻳﻮﻧــــﻴﺔ وﺗﻄﺒــــﻴﻘـــﺎﺗﻪ
ﺇﻋﺪﺍﺩ
ﺳﻤﺎح إﺑﺮاهﻴﻢ رﺿﻮان ﺗﺮاب
ﺍﻟﻤﺪﺭﺱ ﺍﻟﻤﺴﺎﻋﺪ ﺑﻘﺴﻢ ﺍﻟﻤﻌﺠﻼﺕ ﻭﺍﻟﻤﺼﺎﺩﺭ ﺍﻷﻳﻮﻧﻴﺔ ﺷﻌﺒﺔ ﺍﻟﻌﻠﻮﻡ ﺍﻟﻨﻮﻭﻳﺔ ﺍﻷﺳﺎﺳﻴﺔ ﻣﺮﻛﺰ ﺍﻟﺒﺤﻮﺙ ﺍﻟﻨﻮﻭﻳﺔ ﻫﻴﺌﺔ ﺍﻟﻄﺎﻗﺔ ﺍﻟﺬﺭﻳﺔ
أ.د/ ﻟﻄﻔﻲ زآﻲ إﺳﻤﺎﻋﻴﻞ أ.د/ ﻋﺎدل ﺟﻤﻌﻪ هﻼل أﺳﺘﺎذ ﻣﺘﻔﺮغ ﻗﺴﻢ اﻟﻔﻴﺰﻳﺎء أﺳﺘﺎذ ﻣﺘﻔﺮغ – ﻗﺴﻢ اﻟﻤﻌﺠﻼت آﻠﻴﺔ اﻟﻌﻠﻮم - ﺟﺎﻣﻌﺔ اﻟﻘﺎهﺮة واﻟﻤﺼﺎدر اﻷﻳﻮﻧﻴﺔ- ﻣﺮآﺰ اﻟﺒﺤﻮث اﻟﻨﻮوﻳﺔ- هﻴﺌﺔ اﻟﻄﺎﻗﺔ اﻟﺬرﻳﺔ - ﻣﺼﺮ
أ.د/ هﺸﺎم اﻟﺨﺒﻴﺮي ﺗﻮﻓﻴﻖ د/ ﺟﻠﻴﻠﻪ ﻣﻬﻴﻨﻪ رﺋﻴﺲ ﻗﺴﻢ اﻟﻤﻌﺠﻼت واﻟﻤﺼﺎدر أﺳﺘﺎذ ﻣﺴﺎﻋﺪ ﺑﻘﺴﻢ اﻟﻔﻴﺰﻳﺎء اﻷﻳﻮﻧﻴﺔ - ﻣﺮآﺰ اﻟﺒﺤﻮث اﻟﻨﻮوﻳﺔ آﻠﻴﺔ اﻟﻌﻠﻮم- ﺟﺎﻣﻌﺔ اﻟﻘﺎهﺮة - هﻴﺌﺔ اﻟﻄﺎﻗﺔ اﻟﺬرﻳﺔ- ﻣﺼﺮ
ﺭﺳﺎﻟﺔ ﻣﻘﺪﻣﺔ ﺇﱄ ﻛﻠﻴﺔ ﺍﻟﻌﻠﻮﻡ ﻛﺠﺰﺀ ﻣﻦ ﻣﺘـﻄﻠﺒﺎﺕ ﺍﳊﺼﻮﻝ ﻋﻠﻲ ﺩﺭﺟ ﺔـ ﺍﻟﺪﻛﺘـﻮﺭﺍﺓ ( ـﻴﺰﻳـﻓ ﺎء اﻟﺒــﻼزﻣﺎ ) ﻗﺴﻢ ﺍﻟﻔﻴــﺰﻳـﺎﺀ ﻛﻠﻴﺔ ﺍﻟﻌـﻠﻮﻡ ـﺟ ﺎﻣﻌﺔ ﺍﻟﻘـﺎﻫﺮﺓ
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إﻧﺸــــﺎء ﻣـــﺼﺪر ﻟﻠﺤــــﺰﻣﺔ اﻷﻳﻮﻧــــﻴﺔ وﺗﻄﺒــــﻴﻘـــﺎﺗﻪ
ﺇﻋﺪﺍﺩ
ﺳﻤﺎح إﺑﺮاهﻴﻢ رﺿﻮان ﺗﺮاب
ﺍﻟﻤﺪﺭﺱ ﺍﻟﻤﺴﺎﻋﺪ ﺑﻘﺴﻢ ﺍﻟﻤﻌﺠﻼﺕ ﻭﺍﻟﻤﺼﺎﺩﺭ ﺍﻷﻳﻮﻧﻴﺔ ﺷﻌﺒﺔ ﺍﻟﻌﻠﻮﻡ ﺍﻟﻨﻮﻭﻳﺔ ﺍﻷﺳﺎﺳﻴﺔ ﻣﺮﻛﺰ ﺍﻟﺒﺤﻮﺙ ﺍﻟﻨﻮﻭﻳﺔ ﻫﻴﺌﺔ ﺍﻟﻄﺎﻗﺔ ﺍﻟﺬﺭﻳﺔ
ﺭﺳﺎﻟﺔ ﻣﻘﺪﻣﺔ ﺇﱄ ﻛﻠﻴﺔ ﺍﻟﻌﻠﻮﻡ ﻛﺠﺰﺀ ﻣﻦ ﻣﺘـﻄﻠﺒﺎﺕ ﺍﳊﺼﻮﻝ ﻋﻠﻲ ﺩﺭﺟ ﺔـ ﺍﻟﺪﻛﺘـﻮﺭﺍﺓ ( ـﻴﺰﻳـﻓ ﺎء اﻟﺒــﻼزﻣﺎ )
ﻗﺴﻢ ﺍﻟﻔﻴــﺰﻳـﺎﺀ ﻛﻠﻴﺔ ﺍﻟﻌـﻠﻮﻡ ـﺟ ﺎﻣﻌﺔ ﺍﻟﻘـﺎﻫﺮﺓ
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