Comparison of Electron Cloud Simulation and Experiments in the High-Current Experiment

Cohen, R. H.; Friedman, A.; Covo, M. Kireeff; Lund, Steven M.; Molvik, A.W.; Bieniosek, F.M.; Seidl, P.A.; Vay, J.-L.; Verboncoeur, John; Stoltz, Peter; Veitzer, Seth

doi:10.2172/15011579

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“…When the e-suppression voltage is turned off at the end of the four quadrupoles (see figure 4), large electron populations build up in the last magnet, strongly affecting the magnitude and distribution of the beam space-charge, resulting in significant Z-shaped distortions of the beam phase-space exiting the last magnet. Figure 5 compares the beam V x -x phase-space measured with a slit scanner at the beam exit, with threedimensional self-consistent simulations [8] of the electron cloud resulting from ingress of secondary electrons coming off the end diagnostics which terminate the beam. The simulations show a distortion of the beam phase-space very similar to that measured.…”

Section: High-current Experiments (Hcx)mentioning

confidence: 99%

Overview of US heavy ion fusion research

et al. 2005

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Significant experimental and theoretical progress has been made in the U.S. heavy ion fusion program on high-current sources, injectors, transport, final focusing, chambers and targets for high energy density physics (HEDP) and inertial fusion energy (IFE) driven by induction linac accelerators. One focus of present research is the beam physics associated with quadrupole focusing of intense, space-charge dominated heavy-ion beams, including gas and electron cloud effects at high currents, and the study of long-distance-propagation effects such as emittance growth due to field errors in scaled experiments. A second area of emphasis in present research is the introduction of background plasma to neutralize the space charge of intense heavy ion beams and assist in focusing the beams to a small spot size. In the near future, research will continue in the above areas, and a new area of emphasis will be to explore the physics of neutralized beam compression and focusing to high intensities required to heat targets to high energy density conditions as well as for inertial fusion energy. IF/1-2 2 I. IntroductionA coordinated beam physics program by the Lawrence Berkeley National Laboratory, Lawrence Livermore National Laboratory, and Princeton Plasma Physics Laboratory (the Heavy-Ion Fusion Virtual National Laboratory), together with collaborators at Mission Research Corporation, Sandia National Laboratories, and the University of Maryland, pursues intense space-charge-dominated beam science in support of applications of heavy-ion beams to high energy density physics and to inertial fusion energy. A unifying research theme for the US program is to address a key scientific question of fundamental importance to both high energy density physics and inertial fusion energy-"How can heavy ion beams be compressed to the high intensities required for creating high energy density matter and fusion ignition conditions". The primary scientific challenge is to compress intense ion beams in time and space sufficiently to heat targets to the desired temperatures with pulse durations of order or less than the target hydrodynamic expansion time. Present experiments, theory and simulations investigate key technical issues that can affect the brightness (focusability) of space-charge dominated beams, including the effects of gas and electron cloud interactions, as well as emittance growth during focusing of such intense beams, including the effects of neutralizing background plasma. Section II describes selected highlights of recent research since the 2002 IAEA Fusion Energy Conference. In particular, recent particle-in-cell simulations of planned near-term experiments of modest scale indicate that intense heavy ion beams injected with an appropriate head-to-tail velocity gradient ("tilt") into a long neutralizing background plasma column may be compressed by more than a factor of 100 in length and focused by a factor greater than 20 in radius (> 40,000 increase in intensity). Section III describes newly developed research plans ...

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Section: High-current Experiments (Hcx)mentioning

confidence: 99%