Paper  Title  Page 

TUZBAB01  Experiments on Transverse Bunch Compression on the Princeton Paul Trap Simulator Experiment  810 


Funding: Research supported by the U. S. Department of Energy. The Paul Trap Simulator Experiment is a compact laboratory Paul trap that simulates a long, thin chargedparticle bunch coasting through a kilometerslong magnetic alternatinggradient (AG) transport system by putting the physicist in the beam's frameofreference. The transverse dynamics of particles in both systems are described by the same sets of equations, including all nonlinear spacecharge effects. The timedependent quadrupolar electric fields created by the confinement electrodes of a linear Paul trap correspond to the axiallydependent magnetic fields applied in the AG system. Results are presented from experiments in which the lattice period and strength are changed over the course of the experiment to transversely compress a beam with an initial depressedtune 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 after the beam compression. The results of PIC simulations performed with the WARP code agree well with the experimental data. Initial results from a newly installed laserinduced fluorescence diagnostic will also be discussed. 

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WEZC02  Extreme Compression of Heavy Ion Beam Pulses: Experiments and Modeling  2030 


Funding: Research supported by the U. S. Department of Energy. Intense heavy ion beam pulses need to be compressed in both the transverse and longitudinal directions for warm dense matter and heavy ion fusion applications. Previous experiments and simulations utilized a drift region filled with highdensity plasma in order to neutralize the spacecharge and current of a 300 keV K^{+} beam, and achieved transverse and longitudinal focusing separately to a radius < 2 mm and pulse width < 5 ns, respectively. To achieve simultaneous beam compression, a strong solenoid is employed near the end of the drift region in order to transversely focus the beam to the longitudinal focal plane. Simulations of nearterm experiments predict that the ion beam can be focused to a submm spot size coincident with the longitudinal focal plane, reaching a peak beam density in the range 10^{12}  10^{13} cm^{3}, provided that the plasma density is large enough for adequate neutralization. Optimizing the compression under the appropriate experimental constraints offers the potential of delivering higher intensity per unit length of accelerator to the target, thereby allowing more compact and costeffective accelerators and transport lines to be used as ion beam drivers. 

Slides  
THPAN085  TwoStream Instability Analysis For Propagating Charged Particle Beams With a Velocity Tilt  3417 


Funding: This research was supported by the U. S. DOE through Lawrence Berkeley National Laboratory, Princeton Plasma Physics Laboratory for the Heavy Ion Fusion ScienceVirtual National Laboratory.
The linear growth of the twostream instability for a charged particle beam that is longitudinally compressing as it propagates through a background plasma (due to an applied velocity tilt) is examined. Detailed, 1D particleincell simulations are carried out to examine the growth of a wave packet produced by a small amplitude density perturbation in the background plasma. Recent analytic and numerical work by Startsev and Davidson [1] predicted reduced linear growth rates, which are indeed observed in the simulations. Here, smallsignal asymptotic gain factors are determined in a semianalytic analysis and compared with the simulation results in the appropriate limits. Nonlinear effects in the PIC simulations, including wave breaking and particletrapping, are found to limit the linear growth phase of the instability for both compressing and noncompressing beams.
[1] Phys. Plasmas 13, 62108 (2006) 

THPAS006  A Solenoid Final Focusing System with Plasma Neutralization for Target Heating Experiments  3519 


Intense bunches of lowenergy heavy ions have been suggested as means to heat targets to the warm dense matter regime (0.1 to 10 eV). In order to achieve the required intensity on target (~1 eV heating), a beam spot radius of approximately 0.5 mm, and pulse duration of 2 ns is required with an energy deposition of approximately 1 J/cm^{2}. This translates to a peak beam current of 8A for ~0.4 MeV K+ ions. To increase the beam intensity on target, a plasmafilled highfield solenoid is being studied as a means to reduce the beam spot size from several mm to the submm range. We are building a prototype experiment to demonstrate the required beam dynamics. The magnetic field of the pulsed solenoid is 5 to 8 T. Challenges include suitable injection of the plasma into the solenoid so that the plasma density near the focus is sufficiently high to maintain spacecharge neutralization of the ion beam pulse. Initial experimental results for a peak current of ~1A will be presented.
This work was supported by the Office of Fusion Energy Sciences, of the U. S. Department of Energy under Contract No. DEAC0205CH11231, W7405Eng48, DEAC0276CH3073 for HIFSVNL. 

THPAS080  Initial Density Profile Measurements using a LaserInduced Fluorescence Diagnostic in the Paul Trap Simulator Experiment  3666 


Funding: Research supported by the U. S. Department of Energy. Installation of a laserinduced fluorescence (LIF) diagnostic system has been completed and initial measurement of the beam density profile has been performed on the Paul trap simulator experiment (PTSX). The PTSX device is a linear Paul trap that simulates the collective processes and nonlinear transverse dynamics of an intense charged particle beam propagating through a periodic focusing quadrupole magnetic configuration. Although there are several visible transition lines for the laser excitation of barium ions, the transition from the metastable state has been considered first mainly because an operating, stable, broadband, and highpower laser system is available for experiments in this region of the red spectrum. The LIF system is composed of a dye laser, fiber optic cables, a line generator, which uses a Powell lens, collection optics, and a CCD camera system. Singlepass mode operation of the PTSX device is employed for the initial tests of the LIF system to make optimum use of the metastable ions. By minimizing the background light level, it is expected that enough signal to noise ratio can be obtained to reconstruct the radial density profile of the ion beam. 

THPAS081  ParticleinCell Simulations of Halo Particle Production in Intense Charged Particle Beams Propagating Through a Quadrupole Focusing Field with Varying Lattice Amplitude  3669 


Funding: Research supported by the U. S. Department of Energy. The transverse compression and dynamics of intense charged particle beams, propagating through a periodic quadrupole lattice, play an important role in many accelerator physics applications. Typically, the compression can be achieved by means of increasing the focusing strength of the lattice along the beam propagation direction. However, beam propagation through the lattice transition region inevitably leads to a certain level of beam mismatch and halo formation. In this paper we present a detailed analysis of these phenomena using particleincell (PIC) numerical simulations performed with the WARP code. A new definition of beam halo is proposed in this work that provides the opportunity to carry out a quantitative analysis of halo production by a beam mismatch. 

THPAS082  MeterLong Plasma Source for Heavy Ion Beam Space Charge Neutralization  3672 


Funding: Research supported by the U. S. Department of Energy. Plasmas are sources of electrons for charge neutralizing ion beams to allow them to focus to small spot sizes and compress their axial pulse length. Sources must operate at low pressures and without strong electric/magnetic fields. To produce meterlong plasmas, sources based on ferroelectric ceramics with large dielectric coefficients were developed. The sources use BaTiO3 ceramic to form plasma. The drift tube inner wall of the Neutralized Drift Compression Experiment (NDCX) is covered with ceramic and ~7 kV is applied across the wall of the ceramics. A 20cmlong prototype source produced plasma densities of 5·10^{11} cm^{3}. It was integrated into the Neutralized Transport Experiment and successfully neutralized the K+ beam. A onemeterlong source comprised of five 20cmlong sources has been tested and characterized, producing relatively uniform plasma over the length of the source in the 1·10^{10} cm^{3} range. This source was integrated into NDCX for beam compression experiments. Experiments with this source yielded compression ratios ~80. Future work will consider longer and higher plasma density sources to support beam compression and high energy density experiments. 

THPAS083  Charge and Current Neutralization of an Ion Beam Pulse by Background Plasma in Presence of Applied Magnetic Field and Gas Ionization  3675 


Funding: *Research supported by the U. S. Department of Energy under the auspices of the Heavy Ion Fusion Science Virtual National Laboratory. Background plasma can be used as a convenient tool for manipulating intense charge particle beams, for example, for ballistic focusing and steering, because the plasma can effectively reduce the spacecharge potential and selfmagnetic field of the beam pulse. We previously developed a reduced analytical model of beam charge and current neutralization for an ion beam pulse propagating in a cold background plasma. The reducedfluid description provides an important benchmark for numerical codes and yields useful scaling relations for different beam and plasma parameters. This model has been extended to include the additional effects of a solenoidal magnetic field and gas ionization. Analytical studies show that a sufficiently large solenoidal magnetic field can increase the degree of current neutralization of the ion beam pulse. The linear system of equations has been solved analytically in Fourier space. For a strong enough applied magnetic field, poles emerge in Fourier space. These poles are an indication that whistler waves and lower hybrid waves are excited by the beam pulse. 

THPAS084  Calculation of the Chargechanging Cross Sections of Ions or Atoms colliding with Fast Ions using the Classical Trajectory Method  3678 


Funding: Research supported by the U. S. Department of Energy under the auspices of the Heavy Ion Fusion Science Virtual National Laboratory.
Evaluation of ionatom chargechanging cross sections is needed for many accelerator applications. The validity of the classical trajectory approximation has been studied by comparing the results of simulations with available experimental data and full quantummechanical calculations [1]. Additionally, a theoretical criterion has been developed for the validity of the classical trajectory approximation [2]. For benchmarking purposes, a Classical Trajectory Monte Carlo simulation (CTMC) is used to calculate ionization and charge exchange cross sections for most simple, hydrogen and helium targets in collisions with various ions. The calculated cross sections compare favorably with the experimental results for projectile velocities near the projectile velocity corresponding to the maximum of cross section as a function of projectile velocity. At higher or lower velocities, quantummechanical effects become more significant and the CTMC results agree less well with the experimental values of the cross sections.
[1] I. D. Kaganovich, et al., , New Journal of Physics 8, 278 (2006). 

THPAS085  Kinetic Equilibrium and Stability Properties of 3D HighIntensity Charged Particle Bunches  3681 


Funding: Research supported by the U. S. Department of Energy. In 3D highintensity bunched beams, the collective effects associated with strong coupling between the longitudinal and transverse dynamics are of fundamental importance. A direct consequence of this coupling is that the particle dynamics does not conserve transverse energy and longitudinal energy separately, and there exists no exact kinetic equilibrium which has an anisotropic energy in the transverse and longitudinal directions. The strong coupling also introduces a mechanism for the electrostatic Harristype instability driven by strong temperature anisotropy, which exists naturally in beams that have been accelerated to large velocities. The selfconsistent VlasovMaxwell equations are applied to highintensity bunched beams, and a generalized lownoise deltaf particle simulation algorithm is developed for bunched beams with or without energy anisotropy. Systematic studies are carried out that determine the particle dynamics, the approximate equilibrium, and stability properties under conditions corresponding to strong 3D nonlinear spacecharge force. Finite bunchlength effects on collective excitations and anisotropydriven instabilities are also investigated. 

FRPMS092  Kinetic Description of Nonlinear Wave and Soliton Excitations in Coasting Charged Particle Beams  4291 


Funding: Research supported by the U. S. Department of Energy.
This paper makes use of a onedimensional kinetic model based on the VlasovMaxwell equations to describe nonlinear wave and soliton excitations in coasting charged particle beams. The kinetic description makes use of the recentlydeveloped gfactor model [1] that incorporates selfconsistently the effects of transverse density profile shape at moderate beam intensities. The nonlinear evolution of wave and soliton excitations is examined for disturbances both moving faster and moving slower than the sound speed, incorporating the important effects of wave dispersion [2]. Analytical solutions are obtained for nonlinear traveling wave pulses with and without trapped particles, and the results of nonlinear perturabtive particleincell simulations are presented that describe the stability properties and longtime evolution.
[1] R. C. Davidson and E. A. Startsev, Phys. Rev. ST Accel. Beams 7, 024401 (2004).[2] R. C. Davidson, Phys. Rev. ST Accel. Beams 7, 054402 (2004). 

FRPMS093  Numerical Studies of the Electromagnetic Weibel Instability in Intense Charged Particle Beams with Large Temperature Anisotropy Using the Nonlinear BEST Darwin Deltaf Code  4297 


Funding: Research supported by the U. S.Department of Energy. A numerical scheme for the electromagnetic particle simulation of highintensity chargedparticle beams has been developed which is a modification of the Darwin model. The Darwin model neglects the transverse induction current in Ampere?s law and therefore eliminates fast electromagnetic (light) waves from the simulations. The model has been incorporated into the nonlinear deltaf Beam Equilibrium Stability and Transport(BEST) code. As a benchmark, we have applied the model to simulate the transverse electromagnetic Weibeltype instability in a singlespecies chargedparticle beam with large temperature anisotropy. Results are compared with previous theoretical and numerical studies using the eighenmode code bEASt. The nonlinear stage of the Weibel instability is also studied using BEST code, and the mechanism for nonlinear saturation is identified. 