Bulletin of the American Physical Society
53rd Annual Meeting of the APS Division of Plasma Physics
Volume 56, Number 16
Monday–Friday, November 14–18, 2011; Salt Lake City, Utah
Session GO7: Particle Beams and Accelerators |
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Chair: Erik Gilson, Princeton Plasma Physics Laboratory Room: Ballroom H |
Tuesday, November 15, 2011 9:30AM - 9:42AM |
GO7.00001: The NDCX-II accelerator facility for Heavy Ion Fusion Science A. Friedman, J.J. Barnard, R.H. Cohen, M. Dorf, D.P. Grote, S.M. Lund, W.M. Sharp, D. Arbelaez, A. Faltens, J. Galvin, W. Greenway, E. Henestroza, J.-Y. Jung, J.W. Kwan, E.P. Lee, B.G. Logan, L.L. Reginato, P.K. Roy, P.A. Seidl, J. Takakuwa, J.-L. Vay, W.L. Waldron, R.C. Davidson, E.P. Gilson, I.D. Kaganovich The Neutralized Drift Compression Experiment-II (NDCX-II) will generate ion beams for studies of Warm Dense Matter, target physics for heavy-ion-driven Inertial Fusion Energy, and intense-beam dynamics. NDCX-II will accelerate a 20-50 nC Li pulse to 1.2-3 MeV, compress it to sub-ns duration in a neutralizing plasma, and focus it onto a target. Construction of the induction accelerator and compression line at LBNL is approaching completion. We briefly describe the NDCX-II ``physics design'' [A. Friedman, et al., Phys. Plasmas 17, 056704 (2010)], the simulation studies that enabled it, variations (e.g., for other ions), plans for commissioning over the next year, and some possible experiments using the machine itself and extensions. [Preview Abstract] |
Tuesday, November 15, 2011 9:42AM - 9:54AM |
GO7.00002: NDCX-II injector with a 10.9 cm diameter Li$^{+}$ ion source P.K. Roy, W.G. Greenway, D.P. Grote, J.Y. Jung, J.W. Kwan, P.A. Seidl, J. Takakuwa, J.L. Vay, W.L. Waldron The Neutralized Drift Compression Experiment II (NDCX-II) is an accelerator facility for warm dense matter studies. It will generate a short Li$^{+}$ ion beam pulse ($\sim $ 1 ns) at up to a few MeV ion kinetic energy to uniformly heat thin targets to $\sim $ 1 eV temperature. The NDCX-II induction linac has a 130 kV injector that produces $\sim $ 100 mA, 0.5 $\mu $s ion current from a 10.9 cm diameter lithium alumino-silicate ion source. The fabrication and operation of the ion source is challenging due to the high current density required, the difficulty in coating the large emitter and the high operating temperature of 1275$^{\circ}$C. Required power to heat the source is 3.4 kW and calculated temperature variation across the surface is 9.8$^{\circ}$C. Details of the NDCX-II injector design and initial beam optics will be presented. [Preview Abstract] |
Tuesday, November 15, 2011 9:54AM - 10:06AM |
GO7.00003: Completion of NDCX-II Facility and Initial Tests Joe Kwan, Diego Arbelaez, Wayne Greenway, Jin-Young Jung, Steve Lidia, Thomas Lipton, Prabir Roy, Peter Seidl, Jeff Takakuwa, William Waldron, Alex Friedman, David Grote, William Sharp, Erik Gilson The Neutralized Drift Compression Experiment-II (NDCX-II) will generate ion beam pulses for studies of Warm Dense Matter and heavy-ion-driven Inertial Fusion Energy.\footnote{see A. Friedman, et al., this meeting} The machine will accelerate 20-50 nC of Li$^{+}$ to 1.2-3 MeV energy, starting from a 10.9-cm alumino-silicate ion source. At the end of the accelerator the ions are focused to a mm spot size on a thin foil (planar) target; and the pulse length compressed to sub-ns during beam transport in a neutralizing plasma. While using solenoids for beam focusing, the acceleration and compression will be done by special voltage waveforms along the induction linac. The construction project started in July 2009 and will be complete by March 2012, or earlier. Progress on construction, component and initial beam tests will be reported. [Preview Abstract] |
Tuesday, November 15, 2011 10:06AM - 10:18AM |
GO7.00004: Beam Phase Space of an Intense Ion Beam in a Neutralizing Plasma Peter A. Seidl, Guillaume Bazouin, Alice Beneytout, Steven M. Lidia, Jean-Luc Vay, David P. Grote The Neutralized Drift Compression Experiment (NDCX-I) generates high intensity ion beams to explore warm dense matter physics. Transverse final focusing is accomplished with an 8-Tesla, 10-cm long pulsed solenoid magnet combined with a background neutralizing plasma to effectively cancel the space charge field of the ion beam. We report on phase space measurements of the beam before the neutralization channel and of the focused ion beam at the target plane. These are compared to WARP particle-in-cell simulations of the ion beam propagation through the focusing system and neutralizing plasma. Due to the orientation of the plasma sources with respect to the focusing magnet, the plasma distribution within the final focusing lens is strongly affected by the magnetic field, an effect which can influence the peak intensity at the target and which is included in the model of the experiment. [Preview Abstract] |
Tuesday, November 15, 2011 10:18AM - 10:30AM |
GO7.00005: Review of Methods for Neutralization of Intense High-Energy Ion Beam Pulses by Electrons Igor D. Kaganovich, Will Berdanier, Ronald C. Davidson, Edward A. Startsev For ballistic propagation of intense ion beam pulses, the beam charge and current have to be neutralized, so that the self-electric and self-magnetic fields do not affect the ballistic propagation of the beam. In this paper we review several neutralization schemes for intense ion beam pulses, including neutralization by emitting filaments positioned near the beam sides, neutralization by gas ionization, neutralization by a grid immersed in the beam path, and neutralization by passing the beam pulse through a background plasma, either a finitesize layer of plasma or a volumetric plasma produced everywhere along the beam path [1]. The most efficient scheme is neutralization by dense volumetric plasma. However, if dense plasma is not available a combination of tenuous plasma and filament emitters may be sufficient. Filaments provide extra electrons to neutralize the ion beam space charge and tenuous plasma short-circuit the electric field. \\[4pt] [1] I. D. Kaganovich, \textit{et al.,} Physics of Plasmas \textbf{17}, 056703 (2010). [Preview Abstract] |
Tuesday, November 15, 2011 10:30AM - 10:42AM |
GO7.00006: Novel Simulation Methods in the Particle-In-Cell Framework Warp J.-L. Vay, D.P. Dave, R.H. Cohen, A. Friedman, M.A. Furman, R. Secondo, M. Venturini, C.G.R. Geddes, E. Cormier-Michel The Particle-In-Cell (PIC) Framework Warp is being developed by the Heavy Ion Fusion Science Virtual National Laboratory (HIFSVNL) to guide the development of accelerators that can deliver beams suitable for high energy density experiments and implosion of inertial fusion capsules. It is also applied to the study and design of existing and next generation high-energy accelerators including the study of electron cloud effects, laser wakefield acceleration, coherent synchrotron radiation, etc. We will present a selection of original numerical methods that were developed by the HIFSVNL, including: PIC with adaptive mesh refinement (AMR), a large-timestep mover for particles of arbitrary magnetized species, a new relativistic leapfrog particle pusher, simulations in Lorentz boosted frames, an electromagnetic solver with tunable numerical dispersion and efficient stride-based digital filtering. Examples of applications of the methods to the abovementioned fields will also be given. [Preview Abstract] |
Tuesday, November 15, 2011 10:42AM - 10:54AM |
GO7.00007: Secondary Electron Emission in the Limit of Low Energy and its Effect on High Energy Physics Accelerators A.N. Andronov, A.S. Smirnov, I.D. Kaganovich, E.A. Startsev, Y. Raitses, R.C. Davidson, V. Demidov Authors of the Letter [1] reported that the secondary electron emission (SEE) coefficient approaches unity in the limit of zero primary electron energy. This occurs due to nearly 100{\%} electron reflection from the surface, for electron energy less than an electron volt. If correct, this finding could have profound implications on electron cloud formation in high-energy accelerators and sheath structure in plasmas, because electrons approaching the wall with energy below an electron volt are reflected from the walls and thus are effectively confined by the walls. In this paper, we summarize comprehensive studies rendering this claim inaccurate; that is most electrons are lost on walls. These studies include theoretical analysis of SEE properties in the limit of low electron energy, analysis of measuring device errors, and experimental observation of the operation of probes collecting electron current. \\[4pt] [1] R. Cimino, \textit{et al}, Phys. Rev. Lett. \textbf{93}, 014801 (2004). [Preview Abstract] |
Tuesday, November 15, 2011 10:54AM - 11:06AM |
GO7.00008: A Self-consistent General Thermal Field Emission Model M.C. Lin Emission of electrons from cold or hot cathode surfaces has attracted a lot of attention in the past century due to its wide applications in vacuum nano-electronics as well as understanding the fundamental surface physics and basics of vacuum breakdown and electrical discharge phenomena. Electron emission is strongly dependent upon not only the work function but the local surface electric field of cathode. A general electron emission equation, namely general thermal field (GTF) equation, was developed to account for both tunneling and thermal emission for general potentials, particularly when both processes are non-negligible. However, the GTF equation was derived without considering the space charge effects on the emission surfaces. Although in most cases, space charge effects are not important, a formula cannot be said to be complete without including the space charges of the emission electrons. In this work, a self-consistent GTF emission model is formulated and the space charge effect on the original GTF equation is studied analytically. We have also implemented the GTF algorithm in VORPAL, a conformal finite-difference time-domain (CFDTD) particle-in-cell (PIC) code. This analytic model could serve as a benchmark standard for the GTF CFDTD PIC simulations. [Preview Abstract] |
Tuesday, November 15, 2011 11:06AM - 11:18AM |
GO7.00009: Recent developments for low energy extreme of ion implantation Ady Hershcovitch Since the invention of the transistor, the trend has been to miniaturize semiconductor devices. Consequently, the technology has been focused on the formation of shallower junctions, and thus lower energy implants. Current density limitation associated with low energy ion beams result in lower beam currents that in turn adversely affects the process throughput. R{\&}D effort has been on mitigating space charge limitations associated with low energy semiconductor ion implantation by developing boron and phosphorous cluster ion sources, and novel deceleration techniques that overcome space limitations. Presently our focus is on carborane (C$_{2}$B$_{10}$H$_{12})$ ions, which are the most stable of the molecular boron ion currently being pursued. Simultaneously, a pure boron ion source was developed that can form the basis for a novel, more efficient, plasma immersion source. And our Berna-Calutron ion source, which in the past produced record currents of steady state high charge phosphorous has been generating~molecular phosphorous P$_{4}^{+}$ that is gas fed. As such the Berna-Calutron has become a universal source capable of switching between~generating~molecular phosphorous P$_{4}^{+}$, high charge state ions, as well as other types of ions. Various results will be presented at the conference. [Preview Abstract] |
Tuesday, November 15, 2011 11:18AM - 11:30AM |
GO7.00010: Emittance measurement of laser produced positrons Hui Chen, J. Sheppard, J. Gronberg, S. Wilks, S. Anderson, A. Hazi, S. Kerr, E. Marley, J. Park, R. Tommasini Intense lasers have been shown to produce a large number ($\sim $10$^{10}$) of quasi monoenergetic positrons in a short (ps) burst [1]. This suggests the possibility of using laser-generated positrons as injector sources for high-energy accelerators. One of the key parameters for evaluating this application is the positron beam emittance, a measure of the beam size and divergence. We performed a series of measurements on the Titan laser at Lawrence Livermore National Laboratory for this purpose. 1-D Pepper-pot, a standard technique, was used for a number of laser and target conditions. The emittance was also calculated using the Electron-Gamma-Shower (EGS4) code. This talk will present the experimental and simulation results, and their implication for this positron source for accelerators. \\[4pt] [1] Hui Chen, et al., PRL 105, 015003 (2010) [Preview Abstract] |
Tuesday, November 15, 2011 11:30AM - 11:42AM |
GO7.00011: Wakefield Generation in Compact Rectangular Dielectric Loaded Structures Using Flat Beams Peter Stoltz, Philippe Piot, Ben Cowan, Francois Lemery, Daniel Mihalcea, Chris Prokop, Jonathan Smith, David Smithe Wakefields with amplitude in the 10s MV/m range can be routinely generated by passing electron beams through dielectric-loaded structures. The main obstacle in obtaining high field amplitude (in the GV/m range) is the ability to focus the high-peak-current electron beam in the transverse plane to micron level, and to maintain the focusing all the way along the dielectric structure. In this paper we explore the use of a flat, high-peak current, electron beams to be produced at the Fermilab NML facility to drive dielectric loaded structures. Based on beam dynamics simulation we anticipate that we can obtain flat beams with very small vertical size (under 100 microns) and peak current is in excess of 1 kA. We present simulations of the wakefield generation based on theoretical models and PIC simulations with VORPAL. [Preview Abstract] |
Tuesday, November 15, 2011 11:42AM - 11:54AM |
GO7.00012: Laser Assisted Ionization Injection for Plasma Wakefield Accelerators: A Plasma Cathode Wei Lu, A. Davidsion, W. An, P.C. Yu, Chan Joshi, Warren Mori, F. Li, X.L. Xu, C.J. Zhang, J.F. Hua In PWFA, controlled injection of high quality electron into the wakefield is of utmost importance. In this talk, a method based on laser ionization injection in a plasma wakefield accelerator is proposed and tested through 2D/3D PIC simulations. In this scheme,an ultrashort high current electron beam ($I_p>~7kA$) is used to drive a nonlinear wake in a preionized or self-ionized plasma, then a short laser pulse (with focused intensity $I~10^{14}W/cm^2$) synchronized to the electron beam driver ionizes a second gas with higher ionization potential (e.g.,Helium) to produce controlled injection when the time delay between the electron driver and the trailing laser is appropriate. The key advantage of this scheme is that the intrinsic normalized emmitance of the generated electron beam could be as small as 0.01 mm mrad due to the very small transverse beam size (~micron) and very small initial transverse momentum (~0.01mc). We will show through 3D PIC simulations that such small emittance is achievable under certain conditions. It is also found that the emitance at high beam current strongly depends on the space charge effect of the generated bunches although the acceleration gradient is thousands times greater than that of the RF photocathode. Methods for optimizing the beam brightness and the overall efficiency will also be discussed. [Preview Abstract] |
Tuesday, November 15, 2011 11:54AM - 12:06PM |
GO7.00013: Growth and phase velocity of self-modulated beam-driven plasma waves Carl Schroeder, Carlo Benedetti, Eric Esarey, Wim Leemans, Florian Gruener A long, relativistic charged particle beam propagating in a plasma is subject to the self-modulation instability. This instability is analyzed and the growth rates are calculated, including the phase relations. The phase velocity of the accelerating field is shown to be significantly less than the drive beam velocity. These results indicate that the energy gain of a plasma accelerator driven by a self-modulated beam will be limited by dephasing. In the long-beam, strongly-coupled regime, dephasing is reached in less than four e-foldings, independent of beam-plasma parameters. [Preview Abstract] |
Tuesday, November 15, 2011 12:06PM - 12:18PM |
GO7.00014: Resonant K-alpha spectroscopy of a hot dense plasma created by the LCLS x-ray free electron laser Byoung-ick Cho, K. Engelhorn, R.W. Falcone, P.A. Heimann, S.M. Vinko, O. Ciricosta, A. Higginbotham, C. Murphy, J.S. Wark, H.-K. Chung, C.R.D. Brown, T. Burian, L. Vysin, L. Juha, H.J. Lee, M. Messersmidt, W. Schlotter, J. Turner, B. Nagler, Y. Ping, R.W. Lee, S. Toleikis, U. Zastrau We present one of the first experimental studies of the interaction of high intensity x-ray free electron laser radiation with solid density matter. In the experiment performed at the LCLS, an intense 80 fs x-ray pulse at 10$^{17}$ Wcm$^{-2}$ with photon energies of 1480 $\sim $ 1560 eV is focused on a thin Al foil and K-alpha emission spectra are observed. Although x-ray photon energy is lower than the absorption edge, because of its high intensity the sample is surprisingly heated up to 100$\sim $200 eV in the pulse duration and a hot dense plasma is created. Observed x-ray spectra indicate this dense plasma resonantly interacts with the x-ray photons. The emission spectra are also simulated using the collisional-radiative code, SCFLY which provides information about the electron temperature and density, the charge state distribution and opacity. The comparison of experiment and simulation provides a detailed description of a dense plasma resonantly interacting with an intense x-ray pulse. [Preview Abstract] |
Tuesday, November 15, 2011 12:18PM - 12:30PM |
GO7.00015: Simulations of High Intensity X-ray Free-Electron Laser Interactions with Matter by use of the SCFLY Code Justin Wark, Orlando Ciricosta, Sam Vinko, Hyun-Kyung Chung, Richard Lee The last few years has seen a revolution in FEL technology such that multi-keV X-ray beams with focussed intensities in excess of 10$^{18}$ Wcm$^{-2}$ can routinely be produced. An understanding of how such radiation interacts with matter requires atomic kinetics codes with the capabilities to model large numbers of configurations, the inclusion of exotic (e.g. double core-hole) states, as well as treating the X-ray heating consistently. We report here on the use of a modified version of the SCFLY\footnote{H.-K. Chung, M.H. Chen, W.L. Morgan, Y. Ralchenko, and R.W. Lee, High Energy Density Physics {\bf 1}, 3, (2005).} code to model experiments where the LCLS beam interacted with in a low density Neon gas,\footnote{L. Young {\it et al}, Nature, {\bf 466}, 56 (2010).}$^,$\footnote{O. Ciricosta, H.-K. Chung, R.W. Lee, and J.S. Wark, High Energy Density Physics, {\bf 7}, 111, (2011).} as well as more recent work where the LCLS beam was focused onto solid aluminum targets. We further demonstrate that at high photon energies the LCLS beam can be used as a non-perturbative probe of pre-exisiting charge states. [Preview Abstract] |
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