DOCSLIB.ORG

Ion Acoustic Waves in Plasma

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Ion Acoustic Waves in Plasma Ion Acoustic Waves in Plasma Physics 480W (Dated: Sp19) I. INTRODUCTION TO THE EXPERIMENT A. Goals of the experiments The basic goals of these experiments are to help famil- iarize us with the fourth state of matter: plasma, and to get to know a simple way of creating laboratory plasma for research purpose (a cartoon of which is shown in fig- ure 1). Further, we want to understand how Langmuir probes work. The Langmuir probe (see references 1 & 2 in the background readings section), is the one the most versatile diagnostic for plasma physics research. The stu- dent will learn how to interpret the data gathered by Langmuir probes in order to determine plasma param- eters such as plasma density (ne), temperature (kTe), and how these parameters depend on the discharge pa- rameters of a magnetically confined thermionic discharge plasma (figure 2). The description of these experiments is followed by a brief introduction to the plasma state of matter itself in section II, followed by more references. Among those references you'll find a paper very perti- nent to these experiments, which have been done before in similar devices? . The student is aware at this point in the semester of how useful it is to look at previous results wherever this is possible. Finally, parameters measured FIG. 1. Not just any collection of charged particles, with with Langmuir probes will be used to make theoretical roughly equal concentrations of positive and negative charges, predictions regarding ion acoustic waves. The phase ve- exhibit collective behavior distinctive of the plasma state of locity of ion acoustic waves may be measured directly matter. The electron and ion densities have to be great using the tone-burst technique (see ref. 5 in the back- enough and these populations have to be hot enough for `medium like' behavior to become important. Plasma crowns ground reading sections and described briefly below) de- our planet, above and below (the aurora), surrounds it (iono- pend on the electron temperature, and the model we use sphere, magnetosphere), and heats it (the sun and all stars are to assess the phase velocity, the dispersion relationship, in the plasma state, and most are made of classical plasma) permits us to predict the speed of the waves, and so to compare theory with experiment. This is essentially the point of these experiments. B. Procedure To summarize, the main results and deliverables for the experiments described here are Plasmas can be created when energetic particles meet neutral atoms and molecules, causing ionization, and 1. Use the planar Langmuir probe diagnostic to infer when sufficiently high plasma density results. In the plasma density and electron temperature measure- plasma physics experiments conducted here at USD, the ments for a variety of plasma discharge conditions, plasma is created by accelerating thermionically emitted and to use kinetic theory generally to try to account electrons from hot filaments (Tf > 2400K) biased to a for the dependence of those plasma parameters on negative potential (the so-called discharge current) with the discharge parameters. respect to the vacuum chamber wall, as shown in figure 2. When the discharge voltage significantly exceeds the ion- 2. Measure the group velocity of the ion acoustic ization potential of the feed gas (argon, in our case), the waves for a relative hot plasma and a relatively energetic electrons (called `primary electrons'), may cre- cold plasma, and test simplified perturbation the- ate an ion, electron pair, in an ionization collision, ory results, that is, the dispersion relationship for e− + Ar −! Ar+ + e− + e−; (1) ion acoustic waves, and from a direct measurement p p of kTe using the Langmuir probe, compare the- where the subscript denotes the primary electron, which ory (calculating the phase velocity given the elec- must loose energy at the expense of the ionization po- tron temperature) with experiment (measuring the tential of the neutral (and any internal energy imparted phase velocity using the tone-burst method). to the ion), and where ion-electron pair primarily com- pose the plasma. Of course, the entire collection of ions, 2 Idis;Vdis; and po, and the probe area. In your lab note- book, tape in a hardcopy of a good I − V characteristic, and a semi-log plot of the electron branch of the I − V characteristic, marking the location of the plasma po- tential and the floating potential, and demonstrate the calculation of ne and Te. Obtain I −V characteristics at different discharge cur- rents (500ma < Idis < 1; 500ma) and fixed discharge voltage and neutral pressure, (Vdis = 80V , say, and −4 po5 × 10 torr), and do the same for different neutral −5 −4 pressures (1 × 10 < po < 8 × 10 torr) for fixed dis- charge voltage and discharge current (say, 60V and 1amp, respectively). Evaluate the results and show how the plasma density, temperature, and potential depend on the discharge current, and neutral pressure. Plot the data and tape the hardcopy into your notebook, and try to account for the curves qualitatively. Calculate the frac- tional ionization of the plasma as a function of neutral pressure. Does the result surprise you? In your paper, you'll want to capture the essence of the parameter stud- ies and try to interpret the trends in the graphs. The background reference help a great deal here, especially MacKenzie's paper. C. Part II: collective effects—ion acoustic waves FIG. 2. Schematic of a basic device for producing a plasma, a multi-dipole hot filament plasma device with a Langmuir The plasma state of matter supports a variety of col- ~ disk probe. The plasma is produced by electron impact ion- lective effects one of which is longitudinal (k k E), elec- ization of argon atoms by electrons that are thermionically trostatic (B~ = 0) waves. These low frequency waves emitted and accelerated from a hot tungsten (W) filament. follow as the result of introducing a perturbation of the To enhance the ionization efficiency, the walls of the chamber ion density which thereafter propagates in the medium are lined with rows of permanent magnets of opposite polar- (the plasma). Your mission is to introduce such a per- ity. The lower diagram is an end view showing the arrange- turbation into the plasma and then to measure the speed ment of magnets. The magnetic field lines are sketched as of propagation. These waves are weird. They are analo- the dotted curves. In this magnetic cusp configuration, the gous to sound waves in air, but the ions do not provide bulk plasma is essentially magnetic field-free. This caption was shamelessly lifted from reference 2. the pressure swings: the electrons do. How and why does that work? What is the speed of the waves? A worksheet will be provided to lead through the steps to derive it, beginning from simple assumptions, arriving at electrons, and neutrals compose the plasma, and the col- lection deserves the name if it exhibits collective effects. C2k2 !2 = s ; (2) Rows of permanent magnets of alternating polarity line 1 + k2λ2 the exterior of the vacuum chamber to confine the ener- D getic primaries so that each energetic electrons can suffer p where Cs = Te=M, is the phase velocity of ion acoustic many ionizing collisions before being lost to the anode waves in the limit of long wavelengths, also called the ion (the chamber wall). The magnetic fields also help slow acoustic speed, ! and k have their usual meanings, and the loss of plasma electrons (and thus, plasma ions). The λD is called the Debye length. net loss of charge from the plasma to the boundary is zero, but there is a current driven by the discharge volt- age from the filaments to the chamber wall, and this is called the discharge current. A very good overview of discharge physics is given by Braithwaite5 D. Sketch of procedure: Tone-burst pulse delay Measure the I−V (current-voltage) characteristic for a Method planar Langmuir probe (see references 1 & 2 cited above, and a worksheet will be provided to help with this) in a Capacitively couple the Agilent function generator (fg) steady state discharge, using a simple probe-bias sweeper to the Wave Launching Grid. The Langmuir probe will circuit. Mark the plasma space potential, Vs, the float- be used as the detector, as shown in figure 3. It to will ing potential, Vf , electron saturation current, Ies, and be capacitively coupled to ground so as to make a high ion saturation current, Iis. Subtract Iis from I(V ), and pass filter (fc ≈ 50kHz). The signal across the termi- so plot the electron current on log-linear (semi-log) axes. nation resistor can go to the scope, say Ch.2 (any scope Determine the electron temperature, Te, and the elec- could be used but the Tektronix TDS series scopes have tron plasma density, ne. Note the discharge parameters, the best digitizers). The output the fg should go also 3 FIG. 3. Block diagram of wave set-up. 2. Understanding Langmuir probe current-voltage characteristics, R. Merlino, Am. J. Phys. 75, 1048, (2007). 3. Propagation and Damping of Ion Acoustic Waves in Highly Ionized Plasmas A. Y. Wong, N. D'Angelo, and R. W. Motley Phys. Rev. Lett. 9, 415-416 (1962) 4. Controlled Landau Damping of Ion-Acoustic Waves I. Alexeff, W. D. Jones, and D. Montgomery Phys. FIG. 4. Grid and probe are separated by some variable dis- Rev. Lett. 19, 422-425 (1967). tance; the time delay between the tone burst applied to the grid and the moment of its appearance on the probe can be 5. Chapter IV, \Ion Acoustic Waves", sections 1,2, varied by changing this distance.
Load more

Recommended publications
  • Optimization of Ion Flow Rates in a Helicon Injected IEC Fusion System
    Aeronautics and Aerospace Open Access Journal Research Article Open Access Optimization of ion flow rates in a helicon injected IEC fusion system Abstract Volume 4 Issue 2 - 2020 The Helicon Injected Inertial Electrostatic Confinement (IEC) offers an attractive D-D Qiheng Cai, George H Miley neutron source for neutron commercial and homeland security activation neutron analysis. Department of Nuclear, Plasma & Radiological Engineering, Designs with multiple injectors also provide a potential route to an attractive small fusion University of Illinois at Champaign-Urbana, USA reactor. Use of such a reactor has also been studied for deep space propulsion. In addition, a non-fusion design been studied for use as an electric thruster for near-term space Correspondence: Qiheng Cai, Department of Nuclear, Plasma applications. The Helicon Inertial Plasma Electrostatic Rocket (HIIPER) is an advanced & Radiological Engineering, University of Illinois at Champaign- space plasma thruster coupling the helicon and a modified IEC. A key aspect for all of these Urbana, Urbana, IL, 61801, Tel +15712679353, systems is to develop efficient coupling between the Helicon plasma injector and the IEC. Email This issue is under study and will be described in this presentation. To analyze the coupling efficiency, ion flow rates (which indicate how many ions exit the helicon and enter the IEC Received: May 01, 2020 | Published: May 21, 2020 device per second) are investigated by a global model. In this simulation particle rate and power balance equations are solved to investigate the time evolution of electron density, neutral density and electron temperature in the helicon tube. In addition to the Helicon geometry and RF field design, the use of a potential bias plate at the gas inlet of the Helicon is considered.
    [Show full text]
  • Plasma Physics I APPH E6101x Columbia University Fall, 2016
    Lecture 1: Plasma Physics I APPH E6101x Columbia University Fall, 2016 1 Syllabus and Class Website http://sites.apam.columbia.edu/courses/apph6101x/ 2 Textbook “Plasma Physics offers a broad and modern introduction to the many aspects of plasma science … . A curious student or interested researcher could track down laboratory notes, older monographs, and obscure papers … . with an extensive list of more than 300 references and, in particular, its excellent overview of the various techniques to generate plasma in a laboratory, Plasma Physics is an excellent entree for students into this rapidly growing field. It’s also a useful reference for professional low-temperature plasma researchers.” (Michael Brown, Physics Today, June, 2011) 3 Grading • Weekly homework • Two in-class quizzes (25%) • Final exam (50%) 4 https://www.nasa.gov/mission_pages/sdo/overview/ Launched 11 Feb 2010 5 http://www.nasa.gov/mission_pages/sdo/news/sdo-year2.html#.VerqQLRgyxI 6 http://www.ccfe.ac.uk/MAST.aspx http://www.ccfe.ac.uk/mast_upgrade_project.aspx 7 https://youtu.be/svrMsZQuZrs 8 9 10 ITER: The International Burning Plasma Experiment Important fusion science experiment, but without low-activation fusion materials, tritium breeding, … ~ 500 MW 10 minute pulses 23,000 tonne 51 GJ >30B $US (?) DIII-D ⇒ ITER ÷ 3.7 (50 times smaller volume) (400 times smaller energy) 11 Prof. Robert Gross Columbia University Fusion Energy (1984) “Fusion has proved to be a very difficult challenge. The early question was—Can fusion be done, and, if so how? … Now, the challenge lies in whether fusion can be done in a reliable, an economical, and socially acceptable way…” 12 http://lasco-www.nrl.navy.mil 13 14 Plasmasphere (Image EUV) 15 https://youtu.be/TaPgSWdcYtY 16 17 LETTER doi:10.1038/nature14476 Small particles dominate Saturn’s Phoebe ring to surprisingly large distances Douglas P.
    [Show full text]
  • Plasma Waves
    Plasma Waves S.M.Lea January 2007 1 General considerations To consider the different possible normal modes of a plasma, we will usually begin by assuming that there is an equilibrium in which the plasma parameters such as density and magnetic field are uniform and constant in time. We will then look at small perturbations away from this equilibrium, and investigate the time and space dependence of those perturbations. The usual notation is to label the equilibrium quantities with a subscript 0, e.g. n0, and the pertrubed quantities with a subscript 1, eg n1. Then the assumption of small perturbations is n /n 1. When the perturbations are small, we can generally ignore j 1 0j ¿ squares and higher powers of these quantities, thus obtaining a set of linear equations for the unknowns. These linear equations may be Fourier transformed in both space and time, thus reducing the differential equations to a set of algebraic equations. Equivalently, we may assume that each perturbed quantity has the mathematical form n = n exp i~k ~x iωt (1) 1 ¢ ¡ where the real part is implicitly assumed. Th³is form descri´bes a wave. The amplitude n is in ~ general complex, allowing for a non•zero phase constant φ0. The vector k, called the wave vector, gives both the direction of propagation of the wave and the wavelength: k = 2π/λ; ω is the angular frequency. There is a relation between ω and ~k that is determined by the physical properties of the system. The function ω ~k is called the dispersion relation for the wave.
    [Show full text]
  • Problems for the Course F5170 – Introduction to Plasma Physics
    Problems for the Course F5170 { Introduction to Plasma Physics Jiˇr´ı Sperka,ˇ Jan Vor´aˇc,Lenka Zaj´ıˇckov´a Department of Physical Electronics Faculty of Science Masaryk University 2014 Contents 1 Introduction5 1.1 Theory...............................5 1.2 Problems.............................6 1.2.1 Derivation of the plasma frequency...........6 1.2.2 Plasma frequency and Debye length..........7 1.2.3 Debye-H¨uckel potential.................8 2 Motion of particles in electromagnetic fields9 2.1 Theory...............................9 2.2 Problems............................. 10 2.2.1 Magnetic mirror..................... 10 2.2.2 Magnetic mirror of a different construction...... 10 2.2.3 Electron in vacuum { three parts............ 11 2.2.4 E × B drift........................ 11 2.2.5 Relativistic cyclotron frequency............. 12 2.2.6 Relativistic particle in an uniform magnetic field... 12 2.2.7 Law of conservation of electric charge......... 12 2.2.8 Magnetostatic field.................... 12 2.2.9 Cyclotron frequency of electron............. 12 2.2.10 Cyclotron frequency of ionized hydrogen atom.... 13 2.2.11 Magnetic moment.................... 13 2.2.12 Magnetic moment 2................... 13 2.2.13 Lorentz force....................... 13 3 Elements of plasma kinetic theory 14 3.1 Theory............................... 14 3.2 Problems............................. 15 3.2.1 Uniform distribution function.............. 15 3.2.2 Linear distribution function............... 15 3.2.3 Quadratic distribution function............. 15 3.2.4 Sinusoidal distribution function............. 15 3.2.5 Boltzmann kinetic equation............... 15 1 CONTENTS 2 4 Average values and macroscopic variables 16 4.1 Theory............................... 16 4.2 Problems............................. 17 4.2.1 RMS speed........................ 17 4.2.2 Mean speed of sinusoidal distribution........
    [Show full text]
  • The Database for Comparison of Plasma Parameters of the JET Tokamak in Various Regimes of Its Operation
    Czech Technical University Faculty of Nuclear Sciences and Physical Engineering Department of Physics The database for comparison of plasma parameters of the JET tokamak in various regimes of its operation (Research project) Martin Kubiˇc Supervisor: Ing. Ivan Duran,ˇ Ph.D Submitted: 24.9.2008 Contents Abstract 2 List of Abbreviations 3 1 Thermonuclear Fusion 4 1.1 Introduction ................................... 4 1.2 Tokamak ..................................... 5 1.3 JET tokamak .................................. 6 1.3.1 Introduction ............................... 6 1.3.2 Description of the JET tokamak .................... 7 2 JET operating regimes 9 2.1 Introduction ................................... 9 2.2 H-mode ..................................... 9 2.3 Internal transport barrier ............................ 11 3 Results 14 3.1 Introduction ................................... 14 3.2 MDB database ................................. 15 3.3 Set-up and evaluation of the database ..................... 16 3.3.1 Impurities ................................ 17 3.3.2 Temperature and density profile .................... 18 3.3.3 Radiation pattern ............................ 18 3.3.4 Energy balance ............................. 21 Summary 22 Bibliography 24 1 Abstract Presently, one of the main responsibilities of JET tokamak is to prepare the operating regimes for future fusion experimental reactor ITER, which is being built in Cadarache, France. The main aim of this report is to compare some aspects of the two ITER candidate operating scenarios, ELMy H-mode and advanced regime with internal transport barrier. For this purpose statistical approach was chosen compiling a large number of JET edge and core plasma quantities across a large discharge database to assess the level of similarity of each type of scenario. The report is focused on influence of gas impurities on plasma performance in both regimes.
    [Show full text]
  • Virtual Cathode in a Spherical Inertial Electrostatic Confinement
    JP0055056 Virtual Cathode in a Spherical Inertial Electrostatic Confinement Hiromu Momota and George H. Miley Dept. Nuclear Engineering, University of Illinois at Urbana-Champaign, 214 Nuclear Engineering Lab. 103 S. Goodwin Avenue, Urbana, IL 61801, USA INTRODUCTION The Spherical Inertia Electrostatic Confinement (SIEC) is widely accepted as one of the simplest candidate among various fusion approaches for controlled fusion. Indeed, it has no externally applied magnetic field and ions are focused in the small volume near the spherical center. Fig. 1 shows a cross section of the single-grid Spherical IEC. When deuterium is used, ions produced in the discharge are extracted from the plasma by the cathode grid, accelerated, and focused in the center. The grid provides recirculation of ions, increasing the ion density. Consequently a very high-density core of fuel ions is created in the center region. This might enhance fusion reactions, since the reaction rate is proportional to the square of the fuel density. Nevertheless, the high density of ions produces a high potential hill, which decreases the kinetic energy of incoming ions and consequently reduces fusion reactions. Electron effects are thought to change the potential shape in such a way as to avoid this problem. In an experiment at high currents, a potential structure develops in the non-neutral plasma, creating virtual electrodes that further enhance ion containment and recirculation [1-2]. (see Fig.2). Hirsch [3] pointed out firstly an existence of the potential well or a virtual cathode structure in the potential hill. Nevertheless, discussions on the virtual cathode have still continued. This is attributed to the fact that Hirsch have discussed only a simple case where the charged particles are monoenergetic and have no angular momentum.
    [Show full text]
  • Plasma Generation and Plasma Sources
    Plasma Sources Sci. Technol. 9 (2000) 441–454. Printed in the UK PII: S0963-0252(00)17858-2 Plasma generation and plasma sources H Conrads and M Schmidt INP Greifswald, Institut fur¨ Niedertemperatur-Plasmaphysik e.V., Friedrich Ludwig-Jahn-Str. 19, D-17489 Greifswald, Germany Received 1 October 1999, in final form 27 September 2000 Abstract. This paper reviews the most commonly used methods for the generation of plasmas with special emphasis on non-thermal, low-temperature plasmas for technological applications. We also discuss various technical realizations of plasma sources for selected applications. This paper is further limited to the discussion of plasma generation methods that employ electric fields. The various plasmas described include dc glow discharges, either operated continuously (CW) or pulsed, capacitively and inductively coupled rf discharges, helicon discharges, and microwave discharges. Various examples of technical realizations of plasmas in closed structures (cavities), in open structures (surfatron, planar plasma source), and in magnetic fields (electron cyclotron resonance sources) are discussed in detail. Finally, we mention dielectric barrier discharges as convenient sources of non-thermal plasmas at high pressures (up to atmospheric pressure) and beam-produced plasmas. It is the main objective of this paper to give an overview of the wide range of diverse plasma generation methods and plasma sources and highlight the broad spectrum of plasma properties which, in turn, lead to a wide range of diverse technological and technical applications. Introduction Plasmas are generated by supplying energy to a neutral gas causing the formation of charge carriers (figure 1) [1–3]. Electrons and ions are produced in the gas phase when electrons or photons with sufficient energy collide with the neutral atoms and molecules in the feed gas (electron-impact ionization or photoionization).
    [Show full text]
  • Lecture Notes in Physics Introduction to Plasma Physics
    Lecture Notes in Physics Introduction to Plasma Physics Michael Gedalin ii Contents 1 Basic definitions and parameters 1 1.1 What is plasma . 1 1.2 Debye shielding . 2 1.3 Plasma parameter . 4 1.4 Plasma oscillations . 5 1.5 ∗Ionization degree∗ ............................ 5 1.6 Summary . 6 1.7 Problems . 7 2 Plasma description 9 2.1 Hierarchy of descriptions . 9 2.2 Fluid description . 10 2.3 Continuity equation . 10 2.4 Motion (Euler) equation . 11 2.5 State equation . 12 2.6 MHD . 12 2.7 Order-of-magnitude estimates . 14 2.8 Summary . 14 2.9 Problems . 15 3 MHD equilibria and waves 17 3.1 Magnetic field diffusion and dragging . 17 3.2 Equilibrium conditions . 18 3.3 MHD waves . 19 3.4 Alfven and magnetosonic modes . 22 3.5 Wave energy . 23 3.6 Summary . 24 3.7 Problems . 24 iii CONTENTS 4 MHD discontinuities 27 4.1 Stationary structures . 27 4.2 Discontinuities . 28 4.3 Shocks . 29 4.4 Why shocks ? . 31 4.5 Problems . 32 5 Two-fluid description 33 5.1 Basic equations . 33 5.2 Reduction to MHD . 34 5.3 Generalized Ohm’s law . 35 5.4 Problems . 36 6 Waves in dispersive media 37 6.1 Maxwell equations for waves . 37 6.2 Wave amplitude, velocity etc. 38 6.3 Wave energy . 40 6.4 Problems . 44 7 Waves in two-fluid hydrodynamics 47 7.1 Dispersion relation . 47 7.2 Unmagnetized plasma . 49 7.3 Parallel propagation . 49 7.4 Perpendicular propagation . 50 7.5 General properties of the dispersion relation .
    [Show full text]
  • Introduction the Dimensionless Generalized Ohm's
    The impact of the Hall term on tokamak plasmas P.-A. Gourdain, Extreme State Physics Laboratory, Department of Physics and Astronomy, University of Rochester, NY 14627 USA Introduction The Hall term has often been neglected in MHD codes as it is difficult to compute. Nevertheless, setting it aside for numerical reasons led to ignoring it altogether. This is especially problematic when dealing with tokamak physics as the Hall term cannot be neglected as this paper shows. In general, the Hall term is strongly expressed when the ion motion decouples from the electron motion [1]. This is often the case in tokamaks when non ambipolar flows are present [2]. This paper demonstrates the importance of the Hall effect by first deriving a global, dimensionless version of the generalized Ohm’s law (GOL). While the standard dimensionless version of the GOL use local plasma quantities as scaling factors, this paper recast the GOL using global plasma quantities, such as average plasma density or vacuum toroidal field. In this approach, universal tokamak parameters like the Greenwald-Murakami- Hugill [3] density limit, the edge q factor [4] or the torus aspect ratio can be used to rescale the GOL, highlighting where the Hall term matters. After this short introduction, we derived in great detailed a dimensionless version of the GOL using global (i.e. average) plasma parameters. This scaling is done self-consistently with the other MHD equations, reducing the total number of free parameters. We then apply this dimensionless GOL to tokamak plasmas and show that the Hall term can rarely be neglected.
    [Show full text]
  • Parametric Study of a Cylindrical Inertial Electrostatic Confinement Fusion Device and Its Application Thursday, 27 June 2019 16:00 (1H 30M)
    PPPS 2019 Contribution ID: 609 Type: Either 4P32 - Parametric Study of a Cylindrical Inertial Electrostatic Confinement Fusion Device and its Application Thursday, 27 June 2019 16:00 (1h 30m) Portable and cheap neutron sources are in demand for various applications such as cancer therapy, fusion ma- terial study, explosive materials etc. Among various neutron sources, inertial electrostatic confinement fusion (IECF) is an extremely simple device that produces neutron yield typically ~ 108 DD n/s. IECF is basically a fusion concept where the lighter fuel ions (deuterium, tritium) are trapped in a converging electrostatic field inside a cylindrical or spherical geometry. A compact cylindrical IECF device is under operation at Centre of Plasma Physics-Institute for Plasma Re- search. This device mainly comprises of a cylindrical grid assembly housed inside a cylindrical vacuumcham- ber, a vacuum pumping system, a gas injection system, a high voltage feedthrough and a high voltage negative polarity power supply. Deuterium plasma is produced in it by the filamentary glow discharge as well as cold cathode discharge. The plasma is characterized using electrostatic probes. Plasma parameters such as theelec- tron temperature (Te), plasma potential (Vp) and plasma density (ni) are evaluated. The plasma temperature and density are estimated at optimum experimental conditions and it is noted that the plasma temperature is 3 eV in the case of hot cathode discharge whereas 10 eV in the case of the cold cathode discharge. The plasma − density as determined is two orders more in the case of the hot cathode discharge (1015m 3) than the other. Neutron Production Rate of the order 106 n/s is measured in this device by applying 80 kV to the cathode grid.
    [Show full text]
  • NRL: Plasma Formulary 5B
    Naval Research Laboratory Washington, DC 20375-5320 NRL/PU/6790--04-477 NRL Plasma Formulary Revised 2004 Approved for public release; distribution is unlimited. Form Approved Report Documentation Page OMB No. 0704-0188 Public reporting burden for the collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to a penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. 1. REPORT DATE 2. REPORT TYPE 3. DATES COVERED 2004 N/A - 4. TITLE AND SUBTITLE 5a. CONTRACT NUMBER NRL: Plasma Formulary 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) 5d. PROJECT NUMBER 5e. TASK NUMBER 5f. WORK UNIT NUMBER 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 8. PERFORMING ORGANIZATION REPORT NUMBER Naval Research Laboratory Washington, DC 20375-5320 9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSOR/MONITOR’S ACRONYM(S) 11. SPONSOR/MONITOR’S REPORT NUMBER(S) 12. DISTRIBUTION/AVAILABILITY STATEMENT Approved for public release, distribution unlimited 13. SUPPLEMENTARY NOTES 14. ABSTRACT 15. SUBJECT TERMS 16. SECURITY CLASSIFICATION OF: 17.
    [Show full text]
  • A Computational Study of a Lithium Deuteride Fueled Electrothermal Plasma Mass Accelerator
    A Computational Study of a Lithium Deuteride Fueled Electrothermal Plasma Mass Accelerator Gerald Edward Gebhart III Thesis submitted to the faculty of the Virginia Polytechnic Institute and State University in partial fulfillment of the requirements for the degree of Master of Science In Mechanical Engineering Leigh Winfrey Mark A. Pierson Brian Vick May 2nd, 2013 Blacksburg, Virginia Keywords: Tokamak fueling, electrothermal plasma, mass accelerator, pellet injector, plasma launcher, plasma disruption mitigation. Copyright 2013 A Computational Study of a Lithium Deuteride Fueled Electrothermal Plasma Mass Accelerator Gerald Edward Gebhart III Abstract Future magnetic fusion reactors such as tokamaks will need innovative, fast, deep-fueling systems to inject frozen deuterium-tritium pellets at high speeds and high repetition rates into the hot plasma core. There have been several studies and concepts for pellet injectors generated, and different devices have been proposed. In addition to fueling, recent studies show that it may be possible to disrupt edge localized mode (ELM) formation by injecting pellets or gas into the fusion plasma. The system studied is capable of doing either at a variety of plasma and pellet velocities, volumes, and repetition rates that can be controlled through the formation conditions of the plasma. In magnetic or inertial fusion reactors, hydrogen, its isotopes, and lithium are used as fusion fueling materials. Lithium is considered a fusion fuel and not an impurity in fusion reactors as it can be used to produce fusion energy and breed fusion products. Lithium hydride and lithium deuteride may serve as good ablating sleeves for plasma formation in an ablation-dominated electrothermal plasma source to propel fusion pellets.
    [Show full text]