729 research outputs found
Short-Pulse, Compressed Ion Beams at the Neutralized Drift Compression Experiment
We have commenced experiments with intense short pulses of ion beams on the
Neutralized Drift Compression Experiment (NDCX-II) at Lawrence Berkeley
National Laboratory, with 1-mm beam spot size within 2.5 ns full-width at half
maximum. The ion kinetic energy is 1.2 MeV. To enable the short pulse duration
and mm-scale focal spot radius, the beam is neutralized in a 1.5-meter-long
drift compression section following the last accelerator cell. A
short-focal-length solenoid focuses the beam in the presence of the volumetric
plasma that is near the target. In the accelerator, the line-charge density
increases due to the velocity ramp imparted on the beam bunch. The scientific
topics to be explored are warm dense matter, the dynamics of radiation damage
in materials, and intense beam and beam-plasma physics including select topics
of relevance to the development of heavy-ion drivers for inertial fusion
energy. Below the transition to melting, the short beam pulses offer an
opportunity to study the multi-scale dynamics of radiation-induced damage in
materials with pump-probe experiments, and to stabilize novel metastable phases
of materials when short-pulse heating is followed by rapid quenching. First
experiments used a lithium ion source; a new plasma-based helium ion source
shows much greater charge delivered to the target.Comment: 4 pages, 2 figures, 1 table. Submitted to the proceedings for the
Ninth International Conference on Inertial Fusion Sciences and Applications,
IFSA 201
Update on beam-plasma interaction research at PPPL
We have performed experimental and theoretical
studies of beam neutralization by background plasma.
Near-complete space-charge neutralization is
required for the transverse compression of highperveance
ion beams for ion-beam-driven warm
dense matter experiments and heavy ion fusion..
Use of a Linear Paul Trap to Study Random Noise-Induced Beam Degradation in High-Intensity Accelerators
A random noise-induced beam degradation that can affect intense beam transport over long propagation distances has been experimentally studied by making use of the transverse beam dynamics equivalence between an alternating-gradient (AG) focusing system and a linear Paul trap system. For the present studies, machine imperfections in the quadrupole focusing lattice are considered, which are emulated by adding small random noise on the voltage waveform of the quadrupole electrodes in the Paul trap. It is observed that externally driven noise continuously produces a nonthermal tail of trapped ions, and increases the transverse emittance almost linearly with the duration of the noise.close4
Analysis of continuously rotating quadrupole focusing channels using generalized Courant-Snyder theory
By extending the recently developed generalized Courant-Snyder theory for coupled transverse beam dynamics, we have constructed the Gaussian beam distribution and its projections with arbitrary mode emittance ratios. The new formulation has been applied to a continuously rotating quadrupole focusing channel because the basic properties of this channel are known theoretically and could also be investigated experimentally in a compact setup such as the linear Paul trap configuration. The new formulation retains a remarkably similar mathematical structure to the original Courant-Snyder theory, and thus, provides a powerful theoretical tool to investigate coupled transverse beam dynamics in general and more complex linear focusing channels.close
Ion injection optimization for a linear Paul trap to study intense beam propagation
The Paul Trap Simulator Experiment (PTSX) is a linear Paul trap whose purpose is to simulate the nonlinear transverse dynamics of intense charged particle beam propagation in periodic-focusing quadrupole magnetic transport systems. Externally created cesium ions are injected and trapped in the long central electrodes of the PTSX device. In order to have well-matched one-component plasma equilibria for various beam physics experiments, it is important to optimize the ion injection. From the experimental studies reported in this paper, it is found that the injection process can be optimized by minimizing the beam mismatch between the source and the focusing lattice, and by minimizing the number of particles present in the vicinity of the injection electrodes when the injection electrodes are switched from the fully oscillating voltage waveform to their static trapping voltageclose8
Short intense ion pulses for materials and warm dense matter research
We have commenced experiments with intense short pulses of ion beams on the
Neutralized Drift Compression Experiment-II at Lawrence Berkeley National
Laboratory, by generating beam spots size with radius r < 1 mm within 2 ns FWHM
and approximately 10^10 ions/pulse. To enable the short pulse durations and
mm-scale focal spot radii, the 1.2 MeV Li+ ion beam is neutralized in a
1.6-meter drift compression section located after the last accelerator magnet.
An 8-Tesla short focal length solenoid compresses the beam in the presence of
the large volume plasma near the end of this section before the target. The
scientific topics to be explored are warm dense matter, the dynamics of
radiation damage in materials, and intense beam and beam-plasma physics
including selected topics of relevance to the development of heavy-ion drivers
for inertial fusion energy. Here we describe the accelerator commissioning and
time-resolved ionoluminescence measurements of yttrium aluminium perovskite
using the fully integrated accelerator and neutralized drift compression
components.Comment: 7 pages, 9 figure
Studies of emittance growth and halo particle production in intense charged particle beams using the Paul Trap Simulator Experiment
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 in the laboratory frame are equivalent to the spatially periodic magnetic fields applied in the AG system. The transverse emittance of the charge bunch, which is a measure of the area in the transverse phase space that the beam distribution occupies, is an important metric of beam quality. Maintaining low emittance is an important goal when defining AG system tolerances and when designing AG systems to perform beam manipulations such as transverse beam compression. Results are reviewed from experiments in which white noise and colored noise of various amplitudes and durations have been applied to the PTSX electrodes. This noise is observed to drive continuous emittance growth and increase in root-mean-square beam radius over hundreds of lattice periods. Additional results are reviewed from experiments that determine the conditions necessary to adiabatically reduce the charge bunch's transverse size and simultaneously maintain high beam quality. During adiabatic transitions, there is no change in the transverse emittance. The transverse compression can be achieved either by a gradual change in the PTSX voltage waveform amplitude or frequency. Results are presented from experiments in which low emittance is achieved by using focusing-off-defocusing-off waveforms. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3354109close4
Experimental simulations of beam propagation over large distances in a compact linear Paul trap
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 similar 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=omega(2)(p)(0)/2 omega(2)(q), up to 80% of the space-charge limit where self-electric forces balance the applied focusing force. Here, omega(p)(0)=[n(b)(0)e(b)(2)/m(b)epsilon(0)](1/2) is the on-axis plasma frequency, and omega(q) is the smooth-focusing frequency associated with the applied focusing field. Plasmas in PTSX with values of s that are 20% of the limit have been trapped for times corresponding to equivalent beam propagation over 10 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 instantaneous changes in lattice amplitude can be detrimental to transverse confinement of the charge bunch. (c) 2006 American Institute of Physics.close6
Transverse beam compression on the Paul trap simulator experiment
The Paul trap simulator experiment is a compact laboratory Paul trap that simulates a long, thin charged-particle bunch coasting through a kilometers-long magnetic alternating-gradient (AG) transport system by putting the physicist in the beam's frame of reference. The transverse dynamics of particles in both systems are described by similar equations, including all nonlinear space-charge effects. The time-dependent quadrupolar electric fields created by the confinement electrodes of a linear Paul trap correspond to the axially dependent magnetic fields applied in the AG system. Results are presented for experiments in which the lattice period and strength are changed over the course of the experiment to transversely compress a beam with an initial depressed tune of 0.9. Instantaneous and smooth changes are considered. Emphasis is placed on determining the conditions that minimize the emittance growth and the number of halo particles produced by the beam compression process. Both the results of particle-in-cell simulations performed with the warp code and envelope equation solutions agree well with the experimental dataclose9
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