Bulletin of the American Physical Society
2005 47th Annual Meeting of the Division of Plasma Physics
Monday–Friday, October 24–28, 2005; Denver, Colorado
Session LI2: Education and Outreach; Intense Beam Transport |
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Chair: Sudeep Banerjee, University of Nebraska; Rick Lee, General Atomics Room: Adam's Mark Hotel Plaza Ballroom EF |
Wednesday, October 26, 2005 2:00PM - 2:30PM |
LI2.00001: Fusion/Astrophysics Teacher Research Academy Invited Speaker: In order to engage California high school science teachers in the area of plasma physics and fusion research, LLNL's Fusion Energy Program has partnered with the UC Davis Edward Teller Education Center, ETEC (http://etec.ucdavis.edu), the Stanford University Solar Center (http://solar-center.stanford.edu) and LLNL's Science {\&} Technology Education Program, STEP (http://education.llnl.gov). A four-level ``Fusion {\&} Astrophysics Research Academy'' has been designed to give teachers experience in conducting research using spectroscopy with their students. Spectroscopy, and its relationship to atomic physics and electromagnetism, provides for an ideal plasma `bridge' to the CA Science Education Standards (http://www.cde.ca.gov/be/st/ss/scphysics.asp). Teachers attend multiple-day professional development workshops to explore new research activities for use in the high school science classroom. A Level I, 3-day program consists of two days where teachers learn how plasma researchers use spectrometers followed by instructions on how to use a research grade spectrometer for their own investigations. A 3rd day includes touring LLNL's SSPX (http://www.mfescience.org/sspx/) facility to see spectrometry being used to measure plasma properties. Spectrometry classroom kits are made available for loaning to participating teachers. Level I workshop results (http://education.llnl.gov/fusion{\_}astro/) will be presented along with plans being developed for Level II (one week advanced SKA's), Level III (pre-internship), and Level IV (summer internship) research academies. [Preview Abstract] |
Wednesday, October 26, 2005 2:30PM - 3:00PM |
LI2.00002: Training The Next Generation Of Fusion Scientists And Engineers: Summer High School Fusion Science Workshop Invited Speaker: The goal of the education and outreach activities of the Hampton University Center for Fusion Research and Training (HU CFRT) is to create a high school-to-Ph.D. pipeline in plasma physics, fusion science, and related sciences for underrepresented minorities and female students. The HU CFRT Summer High School Fusion Research Workshop is an integral component of this pipeline. This workshop has been extraordinarily successful. The workshop participants are chosen from a national pool of young and talented minority and female high school students through the NASA SHARP program. These students come to HU from all over US and its possessions for eight weeks during the summer. Over the last ten years, these workshops have provided one-on-one high quality research experiences in fusion science to the best and the brightest minority and female high school students in the nation. Our high school students have presented over 25 contributed papers at APS/DPP annual meetings, twice reached semi-finalist positions in Siemens-Westinghouse competitions, won awards and prizes, admissions and scholarships to prestigious universities, and won high praises from the fusion research community and other educators and researchers. We wish to emphasize that we have been able to achieve these results with limited human and fiscal resources and a meager infrastructure. Here we will present the details of how this workshop has evolved over the years, the approaches, the activities, and the structure that we have used to train, motivate, and provide valuable research experiences to the next generation of our national leaders in science. We thank the U.S. DOE OFES for supporting these efforts. We also thank Dr. Allen Boozer and Dr. Thomas Simonen for their invaluable help in the workshop and in all our efforts. [Preview Abstract] |
Wednesday, October 26, 2005 3:00PM - 3:30PM |
LI2.00003: Plasma modeling of beam-electron cloud instabilities in circular accelerators Invited Speaker: A 3D Particle-In-Cell model for continuous modeling of beam and electron cloud interaction in a circular accelerator is presented. A simple model for lattice structure, mainly the Quadruple and dipole magnets and chromaticity have been added to a plasma PIC code, QuickPIC, used extensively to model plasma wakefield acceleration concept. The code utilizes parallel processing techniques with domain decomposition in both longitudinal and transverse domains to overcome the massive computational costs of continuously modeling the beam-cloud interaction. Through parallel modeling, we have been able to simulate long-term beam propagation in the presence of electron cloud in many existing and future circular machines around the world. The exact dipole lattice structure has been added to the code and the simulation results for CERN-SPS and LHC with the new lattice structure have been studied. The code is also used to model electron cloud effects in PEP-II storage ring at SLAC. The pipe geometry in this ring is much bigger than the beam cross section that the boundary conditions turned out to be inconsequential on beam dynamics, therefore smaller pipe cross section is used in the modeling to reduce the computational costs. Also the simulation results are compared to the results from the two macro-particle modeling for strong head-tail instability. It is shown that the simple two macro-particle model can capture some of the physics involved in the beam- electron cloud interaction qualitatively. [Preview Abstract] |
Wednesday, October 26, 2005 3:30PM - 4:00PM |
LI2.00004: Space-charge-limited flow in quantum regime Invited Speaker: Space-charge-limited (SCL) flow has been an area of active research in the development of non-neutral plasma physics, high current diodes, high power microwave sources, vacuum microelectronics and sheath physics. According to the classical Child-Langmuir (CL) law for the planar diodes, the current density scales as 3/2's power of gap voltage and to the inverse squared power of gap spacing. In the past decade, there have been renewed interests in extending the classical CL law to multi-dimensional models both numerically and analytically. The study of SCL flow in quantum regime has also attracted considerable interests in the past 3 years [1-3]. With the recent advances in nanotechnology, electron beam with very high current density may be transported in a nano-scale gap with a relatively low gap voltage.~In this new operating regime, where the electron wavelength is comparable or larger than the gap spacing, the quantum effects become important. In this talk, the quantum theory of CL law will be introduced to reveal that the classical CL law is enhanced by a large factor due to electron tunneling and exchange-correlation effects, and there is a new quantum scaling for the current density, which is proportional to the 1/2's power of gap voltage, and to the inverse fourth-power of gap spacing [1-2]. Quasi-2D and 3D models with finite emission area will be shown [3]. We will also show that the classical properties of the SCL flow such as bipolar flow, beam-loaded capacitance, transit time and noise will require a complete revision in the quantum regime. The implications of the emission law of Fowler-Nordheim in the presence of intense space charge over the nanometer scale will be discussed.\newline \newline [1] L. K. Ang, T. J. T. Kwan, and Y. Y. Lau, ``New Scaling of Child-Langmuir Law in the Quantum Regime,'' Phys. Rev. Lett. 91, 208303 (2003). \newline [2] L. K. Ang, Y. Y. Lau, and T. J. T. Kwan, ``Simple Derivation of Quantum Scaling in Child-Langmuir law,'' IEEE Trans Plasma Sci. 32, 410 (2004). \newline [3] W. S. Koh, L. K. Ang, and T.J.T. Kwan, ``Three-dimensional Child-Langmuir law for uniform hot electron emission,'' Phys. Plasmas 12, 053107 (2005). [Preview Abstract] |
Wednesday, October 26, 2005 4:00PM - 4:30PM |
LI2.00005: Experimental Simulations of Intense Beam Propagation Over Large Distances in a Compact Linear Paul Trap Invited Speaker: The Paul Trap Simulator Experiment (PTSX) is a compact laboratory experiment that places the physicist in the frame-of-reference of a long, charged-particle bunch coasting through a kilometers-long magnetic alternating-gradient (AG) transport system. The transverse dynamics of particles in both systems are described by the same set of equations, including nonlinear space-charge effects. The time-dependent voltages applied to the PTSX quadrupole electrodes are equivalent to the axially-oscillating magnetic fields applied in the AG system. Experiments concerning the quiescent propagation of intense beams over large distances can then be performed in a compact and flexible facility. An understanding and characterization of the conditions required for quiescent beam transport, minimum halo particle generation, and precise beam compression and manipulation techniques, are essential, as accelerators and transport systems demand that ever-increasing amounts of space-charge be transported. Application areas include ion-beam-driven high energy density physics, high energy and nuclear physics accelerator systems, etc. One-component cesium plasmas have been trapped in PTSX that correspond to normalized beam intensities, s, up to 80\% of the limit where the self-electric forces would destroy the transverse confinement. Plasmas in PTSX have been trapped with twice the value of s to be employed in the Spallation Neutron Source, corresponding to equivalent beam propagation over 20 km. Results are presented for experiments in which the amplitude of the quadrupole focusing lattice is modified as a function of time. It is found that beams can be transversely compressed by a gradual increase in quadrupole lattice amplitude that takes place over only 15 lattice periods. Instantaneous changes in lattice amplitude are quite detrimental to transverse confinement of the charge bunch. [Preview Abstract] |
Wednesday, October 26, 2005 4:30PM - 5:00PM |
LI2.00006: Commissioning of the University of Maryland Electron Ring (UMER) Invited Speaker: The University of Maryland Electron Ring (UMER) is a low-energy, high current recirculator for beam physics research. The ring is completed for multi-turn operation of beams over a broad range of intensities and initial conditions. UMER is an extremely versatile experimental platform with a beam current of up to 100 mA and pulse length as long as 100 ns. Beam current profiles are adjustable in both space and time. Intercepting and non-intercepting diagnostic equipment is in position every 20 degrees of the ring which allow time resolved measurements of position, beam current density, and emittance. UMER is addressing issues in beam physics with relevance to many applications that rely on intense beams of high quality. Examples are advanced accelerators, free electron lasers, spallation neutron sources, and future heavy-ion drivers for inertial fusion. We review the motivation, ring layout and operating conditions of UMER. The primary focus of this presentation will be the areas of beam physics that UMER is currently investigating, and others that are part of the commissioning plan. These topics include transverse beam dynamics (matching, halo formation, strongly asymmetric beams, space-charge waves, etc), longitudinal dynamics (bunch capture/shaping, evolution of energy spread, longitudinal space-charge waves, etc.), and computer simulation benchmarking and refinement. Future upgrades and planned research (acceleration and resonance traversal, modeling of galactic dynamics, etc.) will also be presented. [Preview Abstract] |
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