DOCSLIB.ORG

Study of Flow, Turbulence and Transport on the Large Plasma Device

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Study of Flow, Turbulence and Transport on the Large Plasma Device University of California Los Angeles Study of Flow, Turbulence and Transport on the Large Plasma Device A dissertation submitted in partial satisfaction of the requirements for the degree Doctor of Philosophy in Physics by David Andrew Schaffner 2013 c Copyright by David Andrew Schaffner 2013 Abstract of the Dissertation Study of Flow, Turbulence and Transport on the Large Plasma Device by David Andrew Schaffner Doctor of Philosophy in Physics University of California, Los Angeles, 2013 Professor Troy A. Carter, Chair The relationships amongst azimuthal flow, radial particle transport and turbulence on the Large Plasma Device (LAPD) are explored through the use of biasable limiters which con- tinuously modify the rotation of the plasma column. Four quarter annulus plates serve as an iris-like boundary between the cathode source and the main plasma chamber. Application of a voltage to the plates using a capacitor bank drives cross-field current which rotates the plasma azimuthally in the electron diamagnetic direction (EDD). With the limiters inserted, a spontaneous rotation in the ion diamagnetic direction is observed; thus, increasing biasing tends to first slow rotation, null it out, then reverse it. This experiment builds on previous LAPD biasing experiments which used the chamber wall as the biasing electrode rather than inserted limiter plates. The use of inserted limiter biasing rather than chamber wall biasing allows for better cross-field current penetration between the plasma source and the electrodes which in turn allow for a finer variation of applied torque on the plasma. The modification of plasma parameter profiles, turbulent characteristics, and radial trans- port are tracked through these varying flow states. Azimuthal flow radial profiles are peaked at the limiter edge. Consequently, the variation in flow states also results in variation of sheared flow. Improved radial particle confinement is observed in states with sheared flow regardless of the direction of rotation. This improvement is indicated by both steepened den- sity profiles and decreased radial particle flux. Conversely, a confinement degradation is seen ii in the minimum sheared flow state. Comparison of density fluctuation power and crossphase between density and radial velocity fluctuations show that both quantities are suppressed by sheared flow, but that the density fluctuation suppression is dominant and contributes most to the decrease in radial particle flux. Also, some observed changes to density and flux profiles suggest disagreement with a purely local model of transport including the formation of a hollow density profile at state of high flow (high bias) and regions where the direction of measured flux is opposite to that predicted by the direction of density gradient. Changes in flux and density gradient with bias are correlated but in a way that is inconsistent with a Fick's Law like model. Changes in turbulent spectra and features are observed with modification of the rotation state. Log-linear spectra with rotation in either azimuthal direction tends to exhibit a linear slope for power versus frequency and versus wavenumber, while spectra curves in the null flow case have an upward concave shape. Time traces corresponding to these spectra indicate a clear presence of Lorentzian structures in flow states but not in the null flow state. Spectral density histograms, showing the distribution of density fluctuation power in both frequency and wavenumber space, indicate that the modes tend to propagate azimuthally in the same direction as the flow. This suggests a large contribution of rotational interchange instability to the plasma turbulence. Regions with significant flow exhibit spectral density distributions which follow narrow curves in frequency and wavenumber space, much like a dispersion relation line. Regions without flow (either the null flow state or the plasma core) have broader, more diffuse distributions. A pair of coherent modes develop with rotation in the EDD direction. The mode fluctua- tion power peaks at the limiter edge; since maximum flow is observed at the limiter edge, the modes are most likely flow driven. Comparison with a linear Braginskii-fluid model eigen- function solver supports this conclusion. The lower frequency mode—first observed at about 1-2kHz|is identified as a pure interchange mode while the higher frequency mode—first observed at about 5-6kHz|is determined to be a coupled drift-wave interchange mode. The frequency of these modes increases with flow velocity; the appearance of sideband modes in iii the frequency spectra also suggests that these mode begin to interact. iv The dissertation of David Andrew Schaffner is approved. Jon Aurnou George Morales Walter Gekelman Troy A. Carter, Committee Chair University of California, Los Angeles 2013 v To Erin, of course. And to my parents for setting me down this path. vi Table of Contents 1 Overview of the Study of Flow, Turbulence, and Transport on the Large Plasma Device :::::::::::::::::::::::::::::::::::::: 1 1.1 Control of Plasma Rotation on LAPD......................1 1.2 Modification of Density Profile and Radial Particle Confinement.......3 1.3 Modification of Turbulence............................5 1.4 Emergence of a Coherent Mode.........................6 1.5 Local Analysis of Turbulence and Transport variation with shearing rate..8 1.6 Summary of Dissertation Chapters.......................8 2 Introduction and Motivation ::::::::::::::::::::::::::: 11 2.1 From H-Mode to Biasing Experiments..................... 12 2.2 Turbulence, Transport and Shear........................ 16 2.2.1 The Role of Rotation Experiments on LAPD.............. 16 2.3 Plasma Flows................................... 17 2.3.1 ExB Drift................................. 17 2.3.2 General Force Drift and Diamagnetic Drift............... 20 2.4 Diffusion: Classical and Bohm.......................... 21 2.4.1 Parallel Diffusion............................. 25 2.4.2 Perpendicular Diffusion.......................... 26 2.4.3 Anomalous Diffusion........................... 28 2.5 Relevant Instabilities on a Linear Device.................... 29 2.5.1 Resistive Drift Wave Instability..................... 29 2.5.2 Rotational Interchange Instability.................... 31 vii 2.5.3 Kelvin-Helmholtz............................. 31 3 LAPD and Diagnostics ::::::::::::::::::::::::::::::: 33 3.1 The Large Plasma Device............................ 33 3.1.1 Axial versus Radial Transport...................... 39 3.2 Diagnostics.................................... 41 3.2.1 Langmuir Probes............................. 41 3.2.2 Swept Probes............................... 42 3.2.3 Mach Probe................................ 43 3.2.4 Nine-Tip Langmuir Probe........................ 48 3.2.4.1 Density............................. 49 3.2.4.2 Floating Potential and Local Electric Field fluctuations... 49 3.2.4.3 Particle Flux, Reynolds Stress and Vorticity......... 50 3.2.5 Data Acquisition Settings........................ 51 3.2.5.1 Probe Axial Positions..................... 51 3.2.6 Fast-Framing Camera........................... 52 4 Bias-driven plasma rotation :::::::::::::::::::::::::::: 54 4.1 The Limiters................................... 54 4.2 The Biasing Circuit................................ 55 4.3 Limiter Voltage and Discharge Current Response with Bias.......... 61 4.3.1 Field Variations.............................. 66 4.4 Modification of Plasma due to the presence of Limiter Plates......... 68 4.5 Setting Plasma Potential, Flow and Shear with Biasing............ 72 4.6 Cross-field Current and Pedersen Conductivity................. 82 viii 5 Modification of LAPD turbulence with steady-state biased rotation ::: 87 5.1 Profile Modification................................ 87 5.1.1 Density and Temperature Profiles.................... 87 5.1.2 Density, Potential and Velocity Fluctuation Profiles.......... 95 5.1.3 Particle Flux and Diffusivity Profiles.................. 100 5.2 Spectrum Modification.............................. 107 5.2.1 Frequency Spectral Distribution..................... 109 5.2.2 Turbulent Spatial Distribution...................... 119 5.2.3 Wavenumber and M-Number Spectra.................. 122 5.3 Mode Analysis.................................. 129 5.3.1 Instability Drive.............................. 131 5.4 Fluctuation Ratios................................ 133 5.5 Linear Analysis Fluid Equations......................... 134 5.5.1 Experimental Spectra vs Linear Growth................ 140 5.5.2 Evaluation of the Coherent Mode.................... 149 5.6 Turbulent Structure and Modification...................... 160 6 Local analysis of the variation of turbulence and transport with shearing rate ::::::::::::::::::::::::::::::::::::::::::::: 167 6.1 Flow and Density................................. 167 6.2 Decorrelation Rate................................ 170 6.3 Density Gradient Modification.......................... 172 6.4 Turbulence and Transport Suppression..................... 174 6.4.1 Density Fluctuations........................... 177 6.4.2 Crossphase................................ 180 ix 6.4.3 Radial Velocity Fluctuations....................... 182 6.4.4 Coherence................................. 182 6.5 Radial Correlation Length............................ 186 7 Quantitative Scaling of turbulent quantities with sheared flow :::::: 189 7.1 Models of Shear Suppression........................... 189 7.2 Experimental Shear Suppression Scaling.................... 191 7.2.1 Density and Velocity Fluctuations.................... 200
Load more

Recommended publications
  • Fluctuation Induced Cross-Field Transport in Hall Thrusters and Tokamaks Michael Lane Garrett
    Fluctuation Induced Cross-Field Transport in Hall Thrusters and Tokamaks by Michael Lane Garrett B.A., Physics, Wesleyan University (1997) S.M., Applied Plasma Physics, M.I.T. (2012) Submitted to the Department of Aeronautics and Astronautics in partial fulfillment of the requirements for the degree of Master of Science in Aeronautics and Astronautics OF TECHNOLOGY at the NOVi22013 MASSACHUSETTS INSTITUTE OF TECHNOLOGY September 2013 LIBRARIES @ Massachusetts Institute of Technology 2013. All rights reserved. Author ......... ......... ...... .................. .. .. ......... Department of Aeronautics and Astronautics A August 22, 2013 Certified by... Manuel Martinez- Sanchez Professor Thesis Supervisor Certified by........ ......... Stephen J. Wukitch Research Scientist Thesis Reader Certified by.... ... .... .... .... ... Felix I. Parra Assistant Professor / a Thesis Reader A ccepted by ........................................... Eytan H. Modiano Professor of Aeronautics and Astronautics Chair, Graduate Program Committee 2 Fluctuation Induced Cross-Field Transport in Hall Thrusters and Tokamaks by Michael Lane Garrett Submitted to the Department of Aeronautics and Astronautics on August 22, 2013, in partial fulfillment of the requirements for the degree of Master of Science in Aeronautics and Astronautics Abstract One area of fundamental plasma physics which remains poorly understood is the transport of particles across magnetic field lines at rates significantly higher than predicted by theory exclusively based on collisions. This "anomalous" transport is observed in many different classes of plasma experiment. Notably, both magnetic confinement fusion devices and Hall thrusters exhibit anomalous cross-field particle diffusion. This higher than predicted "loss" of particles has significant practical im- plications for both classes of experiment. In the case of magnetic confinement fusion experiments, such as tokamaks, the Lawson criterion nTTE > 1021 [keV.
    [Show full text]
  • Nd AAS Meeting Abstracts
    nd AAS Meeting Abstracts 101 – Kavli Foundation Lectureship: The Outreach Kepler Mission: Exoplanets and Astrophysics Search for Habitable Worlds 200 – SPD Harvey Prize Lecture: Modeling 301 – Bridging Laboratory and Astrophysics: 102 – Bridging Laboratory and Astrophysics: Solar Eruptions: Where Do We Stand? Planetary Atoms 201 – Astronomy Education & Public 302 – Extrasolar Planets & Tools 103 – Cosmology and Associated Topics Outreach 303 – Outer Limits of the Milky Way III: 104 – University of Arizona Astronomy Club 202 – Bridging Laboratory and Astrophysics: Mapping Galactic Structure in Stars and Dust 105 – WIYN Observatory - Building on the Dust and Ices 304 – Stars, Cool Dwarfs, and Brown Dwarfs Past, Looking to the Future: Groundbreaking 203 – Outer Limits of the Milky Way I: 305 – Recent Advances in Our Understanding Science and Education Overview and Theories of Galactic Structure of Star Formation 106 – SPD Hale Prize Lecture: Twisting and 204 – WIYN Observatory - Building on the 308 – Bridging Laboratory and Astrophysics: Writhing with George Ellery Hale Past, Looking to the Future: Partnerships Nuclear 108 – Astronomy Education: Where Are We 205 – The Atacama Large 309 – Galaxies and AGN II Now and Where Are We Going? Millimeter/submillimeter Array: A New 310 – Young Stellar Objects, Star Formation 109 – Bridging Laboratory and Astrophysics: Window on the Universe and Star Clusters Molecules 208 – Galaxies and AGN I 311 – Curiosity on Mars: The Latest Results 110 – Interstellar Medium, Dust, Etc. 209 – Supernovae and Neutron
    [Show full text]
  • Annual Report 2011-2012
    Department of Physics Astronomy& ANNUAL REPORT 2011-2012 ANNUAL REPORT 2011-12 Annual Report 2011-12-Final-.indd 1 11/30/12 3:23 PM UCLA Physics and Astronomy Department 2011-2012 Chair James Rosenzweig Chief Administrative Officer Will Spencer Feature Article Alex Levine Design Mary Jo Robertson © 2012 by the Regents of the University of California All rights reserved. Requests for additional copies of the publication UCLA Department of Physics and Astronomy 2011-2012 Annual Report may be sent to: Office of the Chair UCLA Department of Physics and Astronomy 430 Portola Plaza Box 951547 For more information on the Department see our website: http://www.pa.ucla.edu/ Los Angeles California 90095-1547 UCLA DEPARTMENT OF PHYSICS & ASTRONOMY Annual Report 2011-12-Final-.indd 2 11/30/12 3:23 PM Department of Physics Astronomy& 2011-2012 Annual Report UNIVERSITY OF CALIFORNIA, LOS ANGELES ANNUAL REPORT 2011-12 Annual Report 2011-12-Final-.indd 3 11/30/12 3:23 PM CONTENTS FEATURE ARTICLE: EXPLORING THE PHYSICAL FOUNDATION OF EMERGENT PHENOMENA P.7 GIVING TO THE DEPARTMENT P.14 ‘BRILLIANT’ SUPERSTAR ASTRONOMERS P.16 ASTRONOMY & ASTROPHYSICS P.17 ASTROPARTICLE PHYSICS P.24 PHYSICS RESEARCH HIGHLIGHTS P.27 PHYSICS & ASTRONOMY FACULTY/RESEARCHERS P.45 NEW DEPARTMENT FACULTY P.46 RALPH WUERKER 1929-2012 P.47 UCLA ALUMNI P.48 DEPARTMENT NEWS P.49 OUTREACH-ASTRONOMY LIVE P.51 ACADEMICS CREATING AND UPGRADING TEACHING LABS P.52 WOMEN IN SCIENCE P.53 GRADUATION 2011-2012 P.54-55 Annual Report 2011-12-Final-.indd 4 11/30/12 3:24 PM Message from the Chair As Chair of the UCLA Department of Physics and Astronomy, it is with pleasure that I present to you our 2011-12 Annual Report.
    [Show full text]
  • Yang Zhang UC Irvine Phd Thesis V5
    UNIVERSITY OF CALIFORNIA, IRVINE Fast Ions and Shear Alfvén Waves DISSERTATION submitted in partial satisfaction of the requirements for the degree of DOCTOR OF PHILOSOPHY in Physics By Yang Zhang Dissertation Committee: Professor William W. Heidbrink, Co-chair Professor Roger McWilliams, Co-chair Professor Zhihong Lin 2008 ©2008 Yang Zhang The dissertation of Yang Zhang is approved and is acceptable in quality and form for publication on microfilm ________________________ ________________________ ________________________ Committee Chair University of California, Irvine 2008 ii DEDICATION To my wife Lily, and my parents, for their love and support. The LORD is my rock, and my fortress, and my deliverer; my God, my strength, in whom I will trust; my buckler, and the horn of my salvation, and my high tower. Psalm 18:2 iii TABLE OF CONTENTS CONTENTS ………………………………………………………………………………….Page TABLE OF CONTENTS .........................................................................................................iv LIST OF FIGURES .................................................................................................................vi LIST OF TABLES....................................................................................................................ix LIST OF SYMBOLS.................................................................................................................x ACKNOWLEDGMENTS......................................................................................................xiii CURRICULUM VITAE ........................................................................................................
    [Show full text]
  • Study of Fast Ion Transport in Turbulent Waves in the Large Plasma Device (LAPD)
    Study of Fast Ion Transport in Turbulent Waves in the Large Plasma Device (LAPD) Shu Zhou, W. Heidbrink, H. Boehmer, R. McWilliams, University of California, Irvine T. Carter, S. K. P. Tripathi, S. Vincena, University of California, Los Angeles Due to gyroradius averaging and drift-orbit averaging, the transport of fast ions by microturbulence in tokamaks often is smaller than experienced by thermal ions [1]. In this experiment, strong drift wave turbulence (δn/n ~1, f ~5-20 kHz) is observed in LAPD in gradient regions produced by obstacles. Energetic lithium ions ( Efast /E thermal 300 , fast/~ s 10 ) orbit through the turbulent region. Scans with a collimated analyzer and with probes give detailed profiles of the fast ion spatial distribution and of the fluctuating fields. The fast-ion transport decreases rapidly with increasing fast-ion gyroradius, which is explained well by gyro-averaging theory [2]. The characteristics of the fluctuations are modified by changing the plasma species from helium to neon, and by modifying the bias on the obstacle. A transition from non-diffusive to diffusive transport is observed when the fast ion time-of-flight in the waves exceeds its correlation time ( corr ~0 . 1 ms ) with the waves. Different spatial correlation lengths of the wave potential fields also alter the fast ion transport. A Monte Carlo trajectory-following code simulates the interaction of the fast ions with stationary two-dimensional electrostatic wave potential fields and with three-dimensional, time-dependent fields. Comparison between observation and modeling is presented. [1] W. W. Heidbrink, M. Murakami, J. M. Park, et al., Plasma Phys.
    [Show full text]
  • Summary of Basic Plasma Session
    AAPPS‐DPP 2018, 2nd Asia‐Pacific Conference on Plasma physics November 12‐17, 2018 Summary of Basic Plasma Session Y. Kishimoto Kyoto University, Japan Basic Plasma Session : Large number of submission papers • Basic plasma session includes wider areas, which is highly interdisciplinary. BP in 1st Meeting courtesy of A. Sen Plenary : 4 Invited : 56 Oral : 15 Poster : 49 Total : 124 • Strongly coupled complex plasmas, dusty plasmas, quantum plasmas : 9 • Atomic and molecular process in plasmas : 15 • Non‐neutral plasmas and beam plasmas : 5 • Plasma propulsion and discharge for industrial and medical applications : 10 • Plasma sources, electromagnetic waves and radiations, plasma heating : 5 • Simulation and computation of plasmas : 11 • Plasma diagnostics : 2 • Apologies for selective summary without covering all papers. Basic Plasma Session : plenary and invited/oral • Basic plasma session includes wider areas, which is highly interdisciplinary. Basic Plasma Session : Poster • Basic plasma session includes wider areas, which is highly interdisciplinary. Various plasmas in wide parameter region • Basic plasma session includes wider areas, which is highly interdisciplinary. • Plasma, highly nonlinear medium with the freedom interacting with electromagnetic field, exhibits extremely rich dynamics and structure in wider parameter regions, which are very complex while behave with a synchronized an/or coherent manner. • Key : Linear and nonlinear “structure” and “dynamics”, and methodology identifying them courtesy of H. Totsuji Various plasmas in wide parameter region : classical : quantum TT F TTF Infinitesimally small dissipation r d low density high temperature plasmas Events dominant (Long range force dominant ) outside Debye sphere Vlasov‐Maxwellian system High temperature magnetically confined fusion plasmas 1 Dynamics and Structure Various plasmas in wide parameter region 2 2 kT 3 23 Ze n13 Ze 0 B 4 nd 41 1 λd 2 N D 23 rs nZe() 3 33４0kTBD N 0.272 akTB F 1 Dynamics and Structure Atomic and molecular.
    [Show full text]
  • Plasma Science
    Report of the Panel on Frontiers of Plasma Science Plasma: at the frontier of scientific discovery US Department of Energy Office of Science Office of Fusion Energy Science Report of the Panel on Frontiers of Plasma Science Plasma: at the frontier of scientific discovery The production of this report was sponsored by the U.S. Department of Energy, Office of Science, Fusion Energy Sciences in the year 2016. US Department of Energy Office of Science Office of Fusion Energy Science Contents Plasma: at the frontier of scientific discovery v Panel Membership vii Preface ix Executive Summary Chapter 1 1 Extreme States of Matter and Plasmas Chapter 2 23 Understanding the Physics of Coherent Plasma Structures Chapter 3 43 Understanding the Energies of the Plasma Universe Chapter 4 65 The Physics of Disruptive Plasma Technologies Chapter 5 83 Plasmas at the Interface of Chemistry and Biology 100 Appendix A: The Charge 102 Appendix B: Procedural Background 104 Appendix C: List of figures Panel Membership Plasma: at the frontier of scientific discovery Igor Adamovich Donald Lamb The Ohio State University University of Chicago Andre Anders Martin Laming Lawrence Berkeley National Laboratory Naval Research Laboratory Scott Baalrud Michael Mauel (Group Leader) University of Iowa Columbia University Stuart Bale Julia Mikhailova University of California, Berkeley Princeton University Michael Bonitz Philip Morrison (Group Leader) Christian-Albrechts-Universität zu Kiel University of Texas at Austin Alain Brizard Bruce Remington (Group Leader) St. Michael’s
    [Show full text]
  • BIOGRAPHIES of FESAC MEMBERS Troy Carter Is a Professor Of
    BIOGRAPHIES OF FESAC MEMBERS Troy Carter is a Professor of Physics at the University of California, Los Angeles (UCLA). He is a Co-Principal Investigator of the Basic Plasma Science Facility at UCLA, a user facility for studies of basic plasma physics, and is currently chair of the FESAC Long-Range Planning Subcommittee. His research focuses on fundamental processes in magnetized plasmas and is motivated by current issues in magnetic confinement fusion energy research and in space and astrophysical plasmas. He has addressed topics including magnetic reconnection, turbulence and transport in magnetized plasmas, and the nonlinear physics of Alfvén waves. Along with colleagues at Princeton Plasma Physics Laboratory, he was the recipient of the 2002 American Physical Society (APS) Division of Plasma Physics (DPP) Excellence in Plasma Physics Research Award for his work on the role of turbulence in magnetic reconnection. He has an extensive record of service to the plasma physics research community, including serving on: APS committees (DPP Executive Committee, Program Committee, and Rosenbluth and Dawson Award Selection committees); the U.S. Burning Plasma Organization Council; the 2004 FESAC Workforce Panel; the 2009 DOE Committee of Visitors; Program Advisory Committees for the DIII-D and Alcator C-Mod tokamaks and for the Center for Magnetic Self Organization; the University Fusion Association Executive Committee; and the DOE Edge Coordinating Committee. Additionally, he was selected as an APS DPP Distinguished Lecturer for the 2012- 2013 academic year. He received B.S. degrees in Physics and in Nuclear Engineering from North Carolina State University in 1995 and received a Ph.D.
    [Show full text]
  • UNIVERSITY of CALIFORNIA Los Angeles Simulations of Super Alfvénic Laser Ablation Experiments in the Large Plasma Device a Diss
    UNIVERSITY OF CALIFORNIA Los Angeles Simulations of Super Alfv´enic Laser Ablation Experiments in the Large Plasma Device A dissertation submitted in partial satisfaction of the requirements for the degree Doctor of Philosophy in Physics by Stephen Eric Clark 2016 c Copyright by Stephen Eric Clark 2016 ABSTRACT OF THE DISSERTATION Simulations of Super Alfv´enic Laser Ablation Experiments in the Large Plasma Device by Stephen Eric Clark Doctor of Philosophy in Physics University of California, Los Angeles, 2016 Professor Christoph Niemann, Chair Hybrid plasma simulations, consisting of kinetic ions treated using standard Particle- In-Cell (PIC) techniques and an inertialess charge-neutralizing electron fluid, have been used to investigate the properties of collisionless shocks for a number of years. They agree well with sparse data obtained by flying through Earth’s bow shock and have been used to model high energy explosions in the ionosphere. In this doctoral dissertation hybrid plasma simulation is used on much smaller scales to model collisionless shocks in a controlled laboratory setting. Initially a two-dimensional hybrid code from Los Alamos National Laboratory was used to find the best experimental parameters for shock forma- tion, and interpret experimental data. It was demonstrated using the hybrid code that the experimental parameters needed to generate a shock in the laboratory are relaxed compared to previous work that was done[1]. It was also shown that stronger shocks can be generated when running into a density gradient. Laboratory experiments at the University of California at Los Angeles using the high energy kJ-class Nd:Glass 1053 nm Raptor laser, and later the low energy yet high repetition rate 25 J Nd:Glass 1053 nm ii Peening laser have been performed in the Large Plasma Device (LAPD), which have pro- vided some much needed data to benchmark the hybrid simulation method.
    [Show full text]
  • Lithium Ion Sources for Investigations of Fast Ion Transport in Magnetized Plasmas ͒ Y
    REVIEW OF SCIENTIFIC INSTRUMENTS 78, 013302 ͑2007͒ Lithium ion sources for investigations of fast ion transport in magnetized plasmas ͒ Y. Zhang,a H. Boehmer, W. W. Heidbrink, and R. McWilliams Department of Physics and Astronomy, University of California, Irvine, California 92697 D. Leneman and S. Vincena Department of Physics and Astronomy, University of California, Los Angeles, California 90095 ͑Received 3 August 2006; accepted 9 December 2006; published online 10 January 2007͒ In order to study the interaction of ions of intermediate energies with plasma fluctuations, two plasma immersible lithium ion sources, based on solid-state thermionic emitters ͑Li aluminosilicate͒ were developed. Compared to discharge based ion sources, they are compact, have zero gas load, small energy dispersion, and can be operated at any angle with respect to an ambient magnetic field of up to 4.0 kG. Beam energies range from 400 eV to 2.0 keV with typical beam current densities in the 1 mA/cm2 range. Because of the low ion mass, beam velocities of 100–300 km/s are in the range of Alfvén speeds in typical helium plasmas in the large plasma device. © 2007 American Institute of Physics. ͓DOI: 10.1063/1.2431086͔ I. INTRODUCTION source has to be immersed in the plasma puts severe con- straints on the properties of the ion gun. An ideal source for Fast ions ͑FI͒ with energies large compared to those of this research should have these features ͑Table I͒: the background plasma ions play a key role in space plasmas as well as in controlled fusion related laboratory plasmas.
    [Show full text]
  • 3D Two-Fluid Braginskii Simulations of the Large Plasma Device
    Large Plasma Device (LAPD) Model Equations and Numerical Setup Evolution of Turbulence and Transport LAPD Comparisons Conclusions 3D Two-Fluid Braginskii Simulations of the Large Plasma Device Dustin Fishery, Barrett Rogersy, Giovanni Rossi∗, Danny Guice∗ yDepartment of Physics and Astronomy, Dartmouth College, Hanover, New Hampshire 03755, USA ∗Department of Physics and Astronomy , University of California, Los Angeles, California 90095, USA Conclusions: ? 3D global 2-fluid simulations show good agree- ment with data from LAPD in the low-bias pa- rameter regime explored so far. ? KH turbulence at relatively large scales is the dom- inant driver of cross-field transport in the low-bias simulations. ? Biased simulations are currently under study. The work presented here builds upon an initial numerical study [Rogers and Ricci, Phys. Rev. Lett., 104, 2010] of LAPD [Gekelman et al., Rev. Sci. Instrum., 62, 1991] using the Global Braginskii Solver code (GBS) [Ricci et. al., Plasma Phys. Control. Fusion, 54, 2012]. Dustin M. Fisher Sherwood 2015 Modeling the LAPD 1 / 21 Large Plasma Device (LAPD) Model Equations and Numerical Setup Evolution of Turbulence and Transport LAPD Comparisons Conclusions LAPD Primer for a Nominal He Plasma • Plasma 17 m in length, 30 cm in radius • Machine diameter 1m ' • n 2 1012 cm−3 ∼ × • Pulsed at 1 Hz for 10 ms ∼ • Axial magnetic field 1kG ∼ • Te 6 eV and T 0:5 eV ∼ i ∼ • Ion sound gyroradius, ρs 1:4 cm ∼ • Plasma β 10−4 ∼ 012304-2 T. A. Carter and J. E. Maggs Phys. Plasmas 16,012304͑2009͒ Discharge Circuit generation of primary electrons with energy comparable to − + the anode-cathode bias voltage.
    [Show full text]
  • Fourier Coefficients of Triangle Functions
    University of California Los Angeles Fourier Coefficients of Triangle Functions A dissertation submitted in partial satisfaction of the requirements for the degree Doctor of Philosophy in Mathematics by John Garrett Leo 2008 ⃝c Copyright by John Garrett Leo 2008 The dissertation of John Garrett Leo is approved. Don Blasius Troy Carter Richard Elman William Duke, Committee Chair University of California, Los Angeles 2008 ii to Kyoko and Kyle iii Table of Contents 1 Introduction :::::::::::::::::::::::::::::::: 1 2 Triangle Functions :::::::::::::::::::::::::::: 8 2.1 Mappings of Hyperbolic Triangles . 8 2.2 Hecke Groups . 15 3 Fourier Coefficients of Triangle Functions ::::::::::::: 18 3.1 Power Series . 19 3.2 Computer Experiments . 26 3.3 Conjecture . 33 3.4 Cyclotomic Fields . 33 3.5 Dwork's Method . 36 3.6 Main Theorem . 42 4 Modular Forms for Hecke Groups :::::::::::::::::: 44 4.1 Modular Forms and Cusp Forms . 44 4.2 Eisenstein Series . 47 4.3 Eisenstein Series of Weight 4 . 50 4.3.1 The Case m =3........................ 50 4.3.2 The Cases m = 4 and m =6................. 51 4.3.3 The Case m =5........................ 54 iv 5 Conclusion and Future Work ::::::::::::::::::::: 60 References ::::::::::::::::::::::::::::::::::: 62 v Acknowledgments The three mathematics department members of my thesis committee were not only the first professors I met at UCLA but also the most influential and helpful to me here. First and foremost I want to thank my thesis advisor, Bill Duke. Bill not only suggested looking into the problem that led into this thesis, but provided invaluable guidance throughout. In addition he taught me how to approach mathematics and research, and did everything in his power to help make me successful.
    [Show full text]