DOCSLIB.ORG

A Comparison of Gamma and Proton Radiation Effects in 200 Ghz Sige Hbts Akil K

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
A Comparison of Gamma and Proton Radiation Effects in 200 Ghz Sige Hbts Akil K 2358 IEEE TRANSACTIONS ON NUCLEAR SCIENCE, VOL. 52, NO. 6, DECEMBER 2005 A Comparison of Gamma and Proton Radiation Effects in 200 GHz SiGe HBTs Akil K. Sutton, Student Member, IEEE, Becca M. Haugerud, Student Member, IEEE, A. P. Gnana Prakash, Member, IEEE, Bongim Jun, Member, IEEE, John D. Cressler, Fellow, IEEE, Cheryl J. Marshall, Member, IEEE, Paul W. Marshall, Member, IEEE, Ray Ladbury, Member, IEEE, Fernando Guarin, Member, IEEE, and Alvin J. Joseph, Member, IEEE Abstract—We present the results of gamma irradiation on third-generation SiGe HBTs demonstrate an increased proton third-generation, 200 GHz SiGe HBTs. Pre- and post-radiation dc tolerance over previous SiGe technology nodes. In this work we figures-of-merit are used to quantify the tolerance of the raised present the first study of the gamma tolerance of these devices. extrinsic base structure to Co-60 gamma rays for varying device geometries. Additionally, the impact of technology scaling on the The third-generation SiGe HBTs investigated here were fab- observed radiation response is addressed through comparisons to ricated at IBM Microelectronics (IBM 8HP) [5], and achieve a second generation, 120 GHz SiGe HBTs. Comparisons to previous peak cutoff frequency (peak ) of 200 GHz. This improvement proton-induced degradation results in these 200 GHz SiGe HBTs in peak over previous technology nodes [6], [7] was realized are also made, and indicate that the STI isolation oxide of the through fundamental changes in the physical structure of the de- device shows increased degradation following Co-60 irradiation. The EB spacer oxide, on the other hand, demonstrates increased vice, yielding a novel, reduced thermal cycle “raised extrinsic susceptibility to proton damage. Low dose rate proton testing base” structure. The SiGe base region features an uncondition- was also performed and indicate that although there is a proton ally stable, 25% peak Ge, and a C-doped SiGe profile deposited dose rate effect present in these devices, it cannot fully explain the using UHV/CVD epitaxial growth techniques [5]. Conventional observed trends. Similar trends have previously been observed for deep trench (DT) and shallow trench isolation (STI), in addition buried oxides and isolation oxides in several MOS technologies and have been attributed to increased charge yield in these oxides for to an in-situ doped polysilicon emitter, were maintained from 1.2 MeV Co-60 gamma rays when compared to 63 MeV protons. prior technology nodes. Previous investigations identified the emitter-base (EB) and STI oxide interfaces as the areas most Index Terms—EB spacer, ELDRS, gamma radiation, proton ra- diation, radiation sources, SiGe, SiGe HBT, shallow trench isola- prone to the formation of radiation induced traps. A represen- tion, technology scaling. tative 2D-MEDICI cross-section of the region of interest is de- picted in Fig. 1 (after [8]). These 200 GHz SiGe HBTs demonstrate increased proton tol- I. MOTIVATION erance when compared to earlier SiGe HBT technology nodes HE inherent robust total dose tolerance, typically to multi- (first-generation 50 GHz (IBM 5HP) and second-generation 120 T Mrad(Si) levels, of Silicon-Germanium Hetero-junction GHz (IBM 7 HP) SiGe HBTs) [4]. The aim of the present work Bipolar Transistors (SiGe HBTs) make them prime contenders is therefore two-fold; first we seek to analyze the impact of for a variety of terrestrial and space-borne integrated circuit ap- technology scaling on gamma-induced radiation damage, and plications. SiGe HBT performance characteristics continue to secondly, we wish to compare the degradation response mech- match those of III-V materials, while sharing a unique seam- anisms for proton and gamma irradiation. less integration platform with traditional low cost, high yield Si CMOS fabrication [1]. Single event upset (SEU) is a known II. EXPERIMENT concern for high-speed SiGe HBT digital circuits, and a variety A. Sample Preparation of mitigation techniques are currently under investigation to ad- dress these issues [2]. Previous studies [3], [4] have shown that Devices of varying geometry across the second- and third technology generations were chosen for testing. Third-genera- tion devices with an emitter-area of m and Manuscript received July 2005; revised December 2005. This work was sup- ported in part by DTRA under the Radiation Hardened Microelectronics Pro- m were chosen as the primary device geometries gram, in part by NASA-GSFC under the NASA Electronic Parts and Packaging of interest for comparing proton and gamma radiation damage. (NEPP) Program, in part by IBM, in part by DARPA, and in part by the Georgia Additional devices ( m m Electronic Design Center at Georgia Tech. A. K. Sutton, B. M. Haugerud, A. P. G. Prakash, B. Jun, and J. D. Cressler and m ) were included in the examina- are with the School of Electrical and Computer Engineering, Georgia Institute tion of geometrical dependence, proton dose rate effects, and of Technology, Atlanta, GA 30308 USA (e-mail:[email protected]). high temperature annealing. The impact of technology scaling C. J. Marshall and P. W. Marshall are with the NASA-GSFC, Greenbelt, MD 20771 USA. on gamma-induced radiation degradation included second-gen- R. L. Ladbury is with the Muinez Engineering, Houston, TX 77001 USA. eration devices with m and m . F. Guarin is with the IBM Microelectronics, East Fishkill, NY 12533 USA. Samples were received on wafer and were diced and pack- A. J. Joseph is with the IBM Microelectronics, Essex Junction, VT 05452 USA. aged into 28-pin DIPs with two or three devices bonded out per Digital Object Identifier 10.1109/TNS.2005.860728 package. All terminals (emitter, base, collector and substrate) of 0018-9499/$20.00 © 2005 IEEE SUTTON et al.: COMPARISON OF GAMMA AND PROTON RADIATION EFFECTS IN 200 GHz SiGe HBTs 2359 TABLE I APPROXIMATE INCREMENTAL DOSE RATE COMPARISON FOR THE PROTON AND GAMMA IRRADIATION OF SECOND AND THIRD-GENERATION DEVICES TABLE II APPROXIMATE INCREMENTAL DOSE RATE COMPARISON FOR THE PROTON AND GAMMA IRRADIATION OF THIRD-GENERATION DEVICES Fig. 1. MEDICI simulation cross section showing the EB and CB space charge regions and their proximity to the trap regions of interest. the devices were grounded during the irradiation. Pre-radiation Cumulative dose rates in this case ranged from 100 krad(Si) to characterization was done at the facility and each device irradi- 3Mrad(Si) as depicted in Table II. Sample sizes for this exper- ated to a given dose with measurements being made in between iment ranged from two to four devices per geometry each ex- incremental dose steps (stepped-stress technique). posed in a stepped-stress fashion. The results of several experiments are presented in this work, each with varying sample sizes. The comparisons between the C. Proton Exposure Facility second and third generation technologies as well as the proton The 63.3 MeV proton irradiation was performed at the dose rate experiments featured sample sizes of one transistor Crocker Nuclear Laboratory at the University of California at per geometry and radiation source. Additional experiments fo- Davis. The dosimetry measurements used a five-foil secondary cusing only on the differences in the gamma and proton response emission monitor calibrated against a Faraday cup. The radi- of the third-generation device featured two to four transistors ation source (Ta scattering foils) was located several meters per geometry and radiation source. In such cases results are pre- upstream of the target to establish a beam spatial uniformity of sented as the ensemble average with error bars representing the about 15% over a 2.0 cm radius circular area. Beam currents maximum and minimum data bounds. from about 20 to 100 nA allowed testing with proton fluxes from to proton/cm sec. The dosimetry system B. Gamma Exposure Facility has been previously described [9], [10], and is accurate to about The 1.2 MeV Gamma irradiation was performed using a 10%. Shepard Model 81 Co-60 source at the NASA Goddard Space A total of three proton experiments are reported on in this Flight Center Radiation Effects Facility. The dose rate was work. As with the gamma investigation, samples were exposed held constant at approximately 30 rad(Si)/s and the dose was with all terminals grounded for all irradiations. In the first exper- uniform to within 10% across all test samples, as determined iment, comparing second and third generation devices, proton using an ion chamber probe. In accordance with MIL-STD 883 fluences ranged from p/cm to p/cm , cor- Method 1019.6, a Pb/Al box was used to decrease the flux of responding to equivalent gamma doses of 135 krad(Si) to 6 733 secondary gammas and ensure a monochromatic gamma ray krad(Si) as depicted in Table I. The dose rate was 2 krad(Si)/s spectrum. and one device per geometry was exposed in a stepped-stress A total of two gamma experiments are reported on in this fashion. work. In both cases, all devices were irradiated with all termi- The second experiment focused only on the third-generation nals grounded inside of a black conductive foam, housed in a devices which were exposed to proton fluences ranging from conductive black box. In both experiments, samples were im- p/cm to p/cm corresponding to equiv- mediately measured after each incremental dose and then irra- alent gamma doses of approximately 100 krad(Si) to 3 Mrad(Si) diated to the next dose level. In the first experiment, measure- respectively as depicted in Table II. The dose rate was constant ments were taken at various cumulative gamma doses from 92 at approximately 1 krad(Si)/s. Two to four devices per geometry krad(Si) to 3 792 krad(Si) as depicted in Table I.
Load more

Recommended publications
  • R-Process Elements from Magnetorotational Hypernovae
    r-Process elements from magnetorotational hypernovae D. Yong1,2*, C. Kobayashi3,2, G. S. Da Costa1,2, M. S. Bessell1, A. Chiti4, A. Frebel4, K. Lind5, A. D. Mackey1,2, T. Nordlander1,2, M. Asplund6, A. R. Casey7,2, A. F. Marino8, S. J. Murphy9,1 & B. P. Schmidt1 1Research School of Astronomy & Astrophysics, Australian National University, Canberra, ACT 2611, Australia 2ARC Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D), Australia 3Centre for Astrophysics Research, Department of Physics, Astronomy and Mathematics, University of Hertfordshire, Hatfield, AL10 9AB, UK 4Department of Physics and Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139, USA 5Department of Astronomy, Stockholm University, AlbaNova University Center, 106 91 Stockholm, Sweden 6Max Planck Institute for Astrophysics, Karl-Schwarzschild-Str. 1, D-85741 Garching, Germany 7School of Physics and Astronomy, Monash University, VIC 3800, Australia 8Istituto NaZionale di Astrofisica - Osservatorio Astronomico di Arcetri, Largo Enrico Fermi, 5, 50125, Firenze, Italy 9School of Science, The University of New South Wales, Canberra, ACT 2600, Australia Neutron-star mergers were recently confirmed as sites of rapid-neutron-capture (r-process) nucleosynthesis1–3. However, in Galactic chemical evolution models, neutron-star mergers alone cannot reproduce the observed element abundance patterns of extremely metal-poor stars, which indicates the existence of other sites of r-process nucleosynthesis4–6. These sites may be investigated by studying the element abundance patterns of chemically primitive stars in the halo of the Milky Way, because these objects retain the nucleosynthetic signatures of the earliest generation of stars7–13.
    [Show full text]
  • Experimental Γ Ray Spectroscopy and Investigations of Environmental Radioactivity
    Experimental γ Ray Spectroscopy and Investigations of Environmental Radioactivity BY RANDOLPH S. PETERSON 216 α Po 84 10.64h. 212 Pb 1- 415 82 0- 239 β- 01- 0 60.6m 212 1+ 1630 Bi 2+ 1513 83 α β- 2+ 787 304ns 0+ 0 212 α Po 84 Experimental γ Ray Spectroscopy and Investigations of Environmental Radioactivity Randolph S. Peterson Physics Department The University of the South Sewanee, Tennessee Published by Spectrum Techniques All Rights Reserved Copyright 1996 TABLE OF CONTENTS Page Introduction ....................................................................................................................4 Basic Gamma Spectroscopy 1. Energy Calibration ................................................................................................... 7 2. Gamma Spectra from Common Commercial Sources ........................................ 10 3. Detector Energy Resolution .................................................................................. 12 Interaction of Radiation with Matter 4. Compton Scattering............................................................................................... 14 5. Pair Production and Annihilation ........................................................................ 17 6. Absorption of Gammas by Materials ..................................................................... 19 7. X Rays ..................................................................................................................... 21 Radioactive Decay 8. Multichannel Scaling and Half-life .....................................................................
    [Show full text]
  • 3 Gamma-Ray Detectors
    3 Gamma-Ray Detectors Hastings A Smith,Jr., and Marcia Lucas S.1 INTRODUCTION In order for a gamma ray to be detected, it must interact with matteu that interaction must be recorded. Fortunately, the electromagnetic nature of gamma-ray photons allows them to interact strongly with the charged electrons in the atoms of all matter. The key process by which a gamma ray is detected is ionization, where it gives up part or all of its energy to an electron. The ionized electrons collide with other atoms and liberate many more electrons. The liberated charge is collected, either directly (as with a proportional counter or a solid-state semiconductor detector) or indirectly (as with a scintillation detector), in order to register the presence of the gamma ray and measure its energy. The final result is an electrical pulse whose voltage is proportional to the energy deposited in the detecting medhtm. In this chapter, we will present some general information on types of’ gamma-ray detectors that are used in nondestructive assay (NDA) of nuclear materials. The elec- tronic instrumentation associated with gamma-ray detection is discussed in Chapter 4. More in-depth treatments of the design and operation of gamma-ray detectors can be found in Refs. 1 and 2. 3.2 TYPES OF DETECTORS Many different detectors have been used to register the gamma ray and its eneqgy. In NDA, it is usually necessary to measure not only the amount of radiation emanating from a sample but also its energy spectrum. Thus, the detectors of most use in NDA applications are those whose signal outputs are proportional to the energy deposited by the gamma ray in the sensitive volume of the detector.
    [Show full text]
  • Sources of Gamma Radiation in a Reactor Core Matts Roas
    AE-19 Sources of gamma radiation in a reactor core Matts Roas AKTIEBOLAGET ATOMENERGI STOCKHOLM • S\\ HDJtN • 1959 AE-19 ERRATUM The spectrum in Fig. 3 has erroneously been normalized to 7. 4 MeV/capture. The correct spectrum can be found by mul- tiplying the ordinate by 0. 64. AE-19 Sources of gamma radiation in a reactor core Matts Roos Summary: - In a thermal reactor the gamma ray sources of importance for shielding calculations and related aspects are 1) fission, 2) decay of fission products, 3) capture processes in fuel, poison and other materials, 4) inelastic scattering in the fuel and 5) decay of capture products. The energy release and the gamma ray spectra of these sources have been compiled or estimated from the latest information available, and the results are presented in a general way to permit 235 application to any thermal reactor, fueled with a mixture of U and 238 U • As an example the total spectrum and the spectrum of radiation escaping from a fuel rod in the Swedish R3-reactor are presented. Completion of manuscript April 1959 Printed Maj 1959 LIST OF CONTENTS Page Introduction ........... 1 1. Prompt fis sion gamma rays i 2. Fission product gamma rays 2 3. Uranium capture gamma rays 4 O -2 Q 4. U inelastic scattering gamma rays 5 5. Gamma rays from capture in poison, construction materials and moderator .....*•»..•........ 8 6. Gamma rays from disintegration of capture products. 8 7. Total gamma spectra. Application to the Swedish R3 -reactor 9 SOURCES OF GAMMA RADIATION IN A REACTOR CORE.
    [Show full text]
  • Slow Neutrons and Secondary Gamma Ray Distributions in Concrete Shields Followed by Reflecting Layers
    oo A. R. E. A. E. A. / Rep. 318 w ARAB REPUBLIC OF EGYPT ATOMIC ENERGY AUTHORITY REACTOR AND NEUTRON PHYSICS DEPART SLOW NEUTRONS AND SECONDARY GAMMA RAY DISTRIBUTIONS IN CONCRETE SHIELDS FOLLOWED BY REFLECTING LAYERS BY A.S. MAKARI.OUS, Y;I. SWILEM, Z. AWWAD AND T. BAYOMY 1993 INFORMATION AND DOCUMENTATION CENTER ATOMIC ENERGY POST OFFICE CAIRO, A.R;I:. VOL 2 7 id Q 7 AREAEA/Rep.318 ARAB REPUBLIC OF EGYPT ATOMIC ENERGY AUTHORITY REACTOR AND NEUTRON PHYSICS DEPART, SLOW NEUTRONS AND SECONDARY GAMMA RAY DISTRIBUTIONS IN CONCRETE SHIELDS FOLLOWED BY REFLECTING LAYERS BY A,S.M\KARIOUS, Y.I.SWILEM, 2.AWWAD AND T.BAYOMY INFORMATION AND DUCUMENTATICN CENTER ATOMIC ENERGY POST OFFICE CAIRO, A.R«E. CONTENTS x Page ABSTRACT *<,..».»••... i INTRODUCTION . *« . *.*,...... 1 EXPERIMENTAL DETAILS ••»*«•««»« • • a • » « •»»«*««* *»»*«•»»»«»<>• — RESULTS AND DISCUSSION ..,.••+ .*.....•...•.. 4 ACKNOWLEDGEMENTS ...,.......•..<...»,..>......... 10 REFERENCES „...»,«.**»» 11 ABSTRACT Slow neutrons and secondary gamma r>ay distributions in concrete shields with and without a reflecting layer behind the concrete shield have been investigated first in case of' using a bare reactor beam and then on using & B.C filtered beam. The total and capture secondary gair-m-a ray coefficient (B^and B^) , the ratio of the reflected (Thermal neutron (S ) the ratio of the secondary gamma rays caused by reflected neutrons to those caused by transmitted neutrons ( and the effect of inserting a blocking l&yer (a B^C layer) between the concrete shield and the reflector on the sup- pression of the produced secondary gamma rays have been investigated, It was found that the presence of the reflector layer behind the concrete shield reflects sor/so thermal neutrons back to the concrete shields end so it increases the number of thermal neutrons at the interface between the concrete shield and the reflector.
    [Show full text]
  • Gamma-Ray Bursts and Magnetars
    GAMMA-RAY BURSTS AND MAGNETARS How USRA scientists helped make major advancements in high-energy astrophysics. During the 1960s, the second Administrator Frank J. Kerr (1918 - 2000) of the University of NASA, James E. Webb, sought a university- of Maryland was appointed by USRA to based organization that could serve the manage its programs in astronomy and needs of NASA as well as the space research astrophysics. Kerr was a highly-regarded radio community. In particular, Webb sought to astronomer, originally from Australia. He had have university researchers assist NASA in been the Director of the Astronomy Program the planning and execution of large, complex at the University projects. The result of Webb’s vision was of Maryland, the Universities Space Research Association and at the time (USRA), which was incorporated as a non- of his USRA proft association of research universities on appointment 12 March 1969. in 1983, he was Provost of As described in the previous essay, USRA’s the Division of frst major collaboration with NASA was the Physical and Apollo Exploration of the Moon. The vehicle Mathematical by which USRA assisted NASA and the space Sciences and research community was the Lunar Science Engineering at Institute, later renamed the Lunar and the University. Frank Kerr Planetary Institute. In support of Another major project was undertaken in MSFC and NRL, USRA brought astronomers 1983, when USRA began to support NASA to work closely with NASA researchers in in the development of the Space Telescope the development of instrumentation and Project at NASA’s Marshall Space Flight the preparation for analyses of data for Center (MSFC).
    [Show full text]
  • Fission Product Gamma Spectra
    LA-7620-MS Informal Report UC-34c Issued: January 1979 Fission Product Gamma Spectra E. T. Jurney P. J. Bendt T. R. England -—• — NOTICE I Hiu report J-J*. pn-fviifii .,•. .111 j, i-i-ii V.itiei the 1 ' -i!r.: S-v. r. .• lit I ni!e.. S'jif FISSION PRODUCT GAMMA SPECTRA by E. T. Jurney, P. J. Bendt, and T. R. England ABSTRACT The fission product gamma spectra of 233U, 23SU, and 239Pu have been measured at 12 cooling times following 20 000-s irradiations in the thermal column of the Omega West Reactor. The mean cooling times ranged from 29 s to 146 500 s. The total gamma energies were obtained by inte- grating over the energy spectra, and both the spectra and the total energies are compared with calculations using the CINDER-10 code and ENDF/B-IV data base. The measured and calculated gamma spectra are compared in a series of figures. The meas- ured total gamma energies are *M4? larger than the calculated energies during the earliest counting period (4 s to 54 s cooling time). For 23SU, the measured and calculated total gamma energies are nearly the same after 1200 s cooling time, and the measurements are 2% to 6% lower at longer cooling times. For 239Pu, the measured and calculated total gamma energies are nearly the same at cooling times longer than 4 000 s, and for 233U this condition prevails at cooling times longer than 10 000 s. I. INTRODUCTION o o o o o c o o o The fission product gamma spectra of II, U, and "' Pu have been meas- ured at 12 cooling times following 20 000-s irradiations in the thermal column of the Omega West Reactor.
    [Show full text]
  • Gamma-Ray Diagnostics of Energetic Ions in JET
    EFDA–JET–CP(01)08-02 V.G.Kiptily, F.E.Cecil, O.N.Jarvis, M.J.Mantsinen, S.E.Sharapov, L.Bertalot, S.Conroy, L.C.Ingesson, K.D.Lawson, S.Popovichev and JET EFDA Contributors Gamma-ray Diagnostics of Energetic Ions in JET . Gamma-ray Diagnostics of Energetic Ions in JET V.G.Kiptily, F.E.Cecil1, O.N.Jarvis, M.J.Mantsinen2, S.E.Sharapov, L.Bertalot3, S.Conroy4, L.C.Ingesson5, K.D.Lawson, S.Popovichev and JET EFDA Contributors EURATOM-UKAEA Fusion Association, Culham Science Centre, Abingdon, OX14 4XB, United Kingdom. 1Department of Physics, Colorado School of Mines, Golden, Colorado 80401, USA 2Helsinki University of Technology, Association Euratom-Tekes, P.O.Box 2200, FIN-02015 HUT, Finland 3Ass. Euratom/ENEA/CNR sulla Fusione, Centro Ricerche Energia ENEA-Frascati 00044 Frascati, Rome 4INF, Uppsala University, Euratom-VR Association, Box 535, 75 121 Uppsala, Sweden 5FOM-Inst. Plasmafysica “Rijnhuizen”, Ass. Euratom-FOM, TEC, PO Box 1207, 3430 BE Nieuwegein, NL *See Annex of J. Pamela et al., “Overview of Recent JET Results and Future Perspectives”, Fusion Energy 2000 (Proc. 18th Int. Conf. Sorrento, 2000), IAEA, Vienna (2001). Preprint of Paper to be submitted for publication in Proceedings of the 7th IAEA TCM on Energetic Particles, (Gothenburg, 8-11 October 2001) “This document is intended for publication in the open literature. It is made available on the understanding that it may not be further circulated and extracts or references may not be published prior to publication of the original when applicable, or without the consent of the Publications Officer, EFDA, Culham Science Centre, Abingdon, Oxon, OX14 3DB, UK.” “Enquiries about Copyright and reproduction should be addressed to the Publications Officer, EFDA, Culham Science Centre, Abingdon, Oxon, OX14 3DB, UK.” ABSTRACT An overview of recent gamma-ray diagnostic measurements of energetic ions in JET is presented.
    [Show full text]
  • Lawrence Berkeley National Laboratory Recent Work
    Lawrence Berkeley National Laboratory Recent Work Title ELECTRON CAPTURE AND THE AUGER EFFECT IN THE HEAVIEST ELEMENTS Permalink https://escholarship.org/uc/item/47h087z3 Author Gray, Peter Rygaard. Publication Date 1955-08-01 eScholarship.org Powered by the California Digital Library University of California UCRL a1o¥ ·I,. .. .. UNIVERSITY OF CALIFORNIA adiation TWO-WEEK LOAN COPY This is a library Circulating Copy which may be borrowed for two weeks. For a personal retention copy, call Tech. Info. Dioision, Ext. 5545 BERKELEY, CALIFORNIA DISCLAIMER This document was prepared as an account of work sponsored by the United States Government. While this document is believed to contain correct information, neither the United States Government nor any agency thereof, nor the Regents of the University of California, nor any of their employees, makes any warranty, express or implied, or assumes any legal responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by its trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof, or the Regents of the University of California. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof or the Regents of the University of California. UCRL-3104 UNIVERSITY OF CALIFORNIA Radiation Laboratory Berkeley, California i .. Contract No. W-7405-eng-48 ' ELECTRON CAPTURE AND THE AUGER EFFECT IN THE HEAVIEST ELEMENTS Peter Rygaard Gray (Thesis) August 1955 ·-.
    [Show full text]
  • The Psyche Gamma-Ray and Neutron Spectrometer: Characterizing the Composition of a Metal-Rich Body Using Nuclear Spectroscopy
    47th Lunar and Planetary Science Conference (2016) 1622.pdf THE PSYCHE GAMMA-RAY AND NEUTRON SPECTROMETER: CHARACTERIZING THE COMPOSITION OF A METAL-RICH BODY USING NUCLEAR SPECTROSCOPY. David J. Lawrence1, Patrick N. Peplowski1, John O. Goldsten1, Morgan Burks2, Andrew W. Beck1, Linda T. Elkins-Tanton3, Insoo Jun4, Timothy J. McCoy5, Carol A. Polanskey4, Thomas H. Prettyman6, 1Johns Hopkins University Applied Physics La- boratory, Laurel, MD 20723, USA ([email protected]); 2Lawrence Livermore National Laboratory, Livermore, CA 94550; 3Arizona State University, Tempe, AZ 85287; 4NASA Jet Propulsion Laboratory, Pasadena, CA, 91109, USA; 5Smithsonian Institution, Washington, DC, 20560, USA; 6Planetary Science Institute, Tucson, AZ 85719, USA. Introduction: The asteroid 16 Psyche is the largest The Psyche GRNS is a high-heritage design based on of the metal asteroids, and is thought to be the exposed the successful MESSENGER GRNS [13] and the Lu- core of a larger differentiated body, or may possibly be nar Prospector Neutron Spectrometer (LP-NS)[14]. composed of primordial material having accreted from Specifically, gamma rays are measured with a cry- highly reduced metal-rich material [1]. In the latest ocooled high-purity Ge (HPGe) sensor surrounded by a round of NASA Discovery mission proposals, an or- borated-plastic anticoincidence shield (ACS). The bital mission to 16 Psyche was selected for a Phase A ACS serves to both reduce the charged-particle back- study with possible launch in late 2020 [2]. The sci- ground in the Ge sensor, and to measure epithermal ence goals of the Psyche mission include understand- (neutron energy, En between 0.4 eV and 500 keV) and ing planetary iron cores, examining the interior of a fast neutrons (0.5<En<10) as was done on the Lunar differentiated body, and exploring a new type of world, Prospector [14], Mars Odyssey [15], Dawn [16], and namely a metal planet.
    [Show full text]
  • Gamma-Ray Interactions with Matter
    2 Gamma-Ray Interactions with Matter G. Nelson and D. ReWy 2.1 INTRODUCTION A knowledge of gamma-ray interactions is important to the nondestructive assayist in order to understand gamma-ray detection and attenuation. A gamma ray must interact with a detector in order to be “seen.” Although the major isotopes of uranium and plutonium emit gamma rays at fixed energies and rates, the gamma-ray intensity measured outside a sample is always attenuated because of gamma-ray interactions with the sample. This attenuation must be carefully considered when using gamma-ray NDA instruments. This chapter discusses the exponential attenuation of gamma rays in bulk mater- ials and describes the major gamma-ray interactions, gamma-ray shielding, filtering, and collimation. The treatment given here is necessarily brief. For a more detailed discussion, see Refs. 1 and 2. 2.2 EXPONENTIAL A~ATION Gamma rays were first identified in 1900 by Becquerel and VMard as a component of the radiation from uranium and radium that had much higher penetrability than alpha and beta particles. In 1909, Soddy and Russell found that gamma-ray attenuation followed an exponential law and that the ratio of the attenuation coefficient to the density of the attenuating material was nearly constant for all materials. 2.2.1 The Fundamental Law of Gamma-Ray Attenuation Figure 2.1 illustrates a simple attenuation experiment. When gamma radiation of intensity IO is incident on an absorber of thickness L, the emerging intensity (I) transmitted by the absorber is given by the exponential expression (2-i) 27 28 G.
    [Show full text]
  • Chapter 3 Gamma-Ray and Neutron Sources R.J. Holmes
    123 CHAPTER 3 GAMMA-RAY AND NEUTRON SOURCES R.J. HOLMES 125 1. GAMMA-RAY SOURCES Most y-ray sources in commercial use do not occur in nature because their half-lives are small compared with geological times. They must be produced from naturally occurring nuclides by a suitable nucle?r reaction; often this is by irradiation in a nuclear reactor. Some examples of radioisotope production are given below: 59Co (n,y)60Co T^ 5.26 y 123Sb (n,y)mSb T^ 60 d 6Li (n,a)3H T^ 12.3 y 55Mn (p,n)55Fe T, 2.7 y Commercially available sources are sealed in chemically inert capsules. The choice of the most suitable source for a particular application usually depends on the energy of the y-rays that are emitted and on the half-life of the radioisotope. In many applications, a monoenergetic source of long half-life is preferred. Calibration corrections for source decay can be made using the familiar equation - 0.693t/T, = Io e where I is the initial source intensity/ I(t) is its intensity at time o t, and T, is the half-life. Selection of the appropriate y-ray energy depends on such criteria as the energy threshold for a desired nuclear reaction and whether absorption should be due predominantly to the photoelectric effect or Compton scattering. Table 1 lists the commonly used y-ray sources together with their y-ray energies and half-lives. 2. X-RAY SOURCES Sources of radiation below an energy of about 150 keV are usually referred to as X-ray sources, although technically some of them are low energy y-ray sources, e.g.
    [Show full text]