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Conceptual foundation of the Fokker-Planck approach to space-charge effects

Description: An rms-mismatched beam can evolve rapidly to a configuration of quasiequilibrium under the influence of space-charge forces. As sit evolves, its emittance grows and a diffuse halo forms. The beam`s distribution function accounts for all the complicated dynamics. Unfortunately, the distribution function is difficult to calculate inasmuch as the physics lies at the interface between classical mechanics and thermodynamics. This paper presents the foundation for a statistical theory of the dynamics… more
Date: July 1, 1996
Creator: Bohn, C. L.
Partner: UNT Libraries Government Documents Department
open access

Space-charge-dominated beam dynamics simulations using the massively parallel processors (MPPs) of the Cray T3D

Description: Computer simulations using the multi-particle code PARMELA with a three-dimensional point-by-point space charge algorithm have turned out to be very helpful in supporting injector commissioning and operations at Thomas Jefferson National Accelerator Facility (Jefferson Lab, formerly called CEBAF). However, this algorithm, which defines a typical N{sup 2} problem in CPU time scaling, is very time-consuming when N, the number of macro-particles, is large. Therefore, it is attractive to use massiv… more
Date: October 1, 1996
Creator: Liu, H.
Partner: UNT Libraries Government Documents Department
open access

Solitary waves in particle beams

Description: Since space charge waves on a particle beam exhibit both dispersive and nonlinear character, solitary waves or solitons are possible. Dispersive, nonlinear wave propagation in high current beams is found to be similar to ion-acoustic waves in plasmas with an analogy between Debye screening and beam pipe shielding. Exact longitudinal solitary wave propagation is found for potentials associated with certain transverse distributions which fill the beam pipe. For weak dispersion, the waves satisfy … more
Date: July 1, 1996
Creator: Bisognano, J. J.
Partner: UNT Libraries Government Documents Department
open access

Longitudinal space charge in the SLC, FFTB and NLC final-focus systems

Description: In a final-focus system, space-charge forces can be significant even for very high beam energies. The reason is the inherent large chromaticity of such a system, which needs to be compensated to a high precision. The longitudinal space-charge force causes an energy variation along the bunch, which depends on beam size, beam-pipe radius, and bunch population. Since this energy variation is location-dependent, it may affect the chromatic correction and, thereby, increase the IP spot size. The spa… more
Date: June 1, 1996
Creator: Zimmermann, F. & Raubenheimer, T.O.
Partner: UNT Libraries Government Documents Department
open access

Transverse match of high peak-current beam into the LANSCE DTL using PARMILA

Description: A new algorithm that uses a multiparticle PARMILA-based code to match high peak current H{sup +} beam ({approx}21 mA) into the Los Alamos Neutron Science Center (LANSCE) drift tube linac (DTL) has been developed. Two single cell rf bunchers in the low energy beam transport (LEBT) prepare the initially unbunched beam for DTL capture. The transverse distribution at the entrance to the DTL is set with four quadrupoles in the 1.26 m between the last transverse emittance measuring station and the DT… more
Date: September 1, 1996
Creator: Merrill, F.E. & Rybarcyk, L.J.
Partner: UNT Libraries Government Documents Department
open access

A tracking code for injection and acceleration studies in synchrotrons

Description: CAPTURE-SPC is a Monte-Carlo-based tracking program that simulates the injection and acceleration processes in proton synchrotrons. The time evolution of a distribution of charged particles is implemented by a symplectic, second-order-accurate integration algorithm. The recurrence relations follow a time-stepping leap--frog method. The time-step can be varied optionally to reduce computer time. Space-charge forces are calculated by binning the phase-projected particle distribution. The statisti… more
Date: November 1, 1996
Creator: Lessner, E. & Symon, K.
Partner: UNT Libraries Government Documents Department
open access

Emittance growth of a short electron bunch in circular motion

Description: A short electron bunch undergoing circular motion produces space-charge forces that do not decrease with increasing bunch energy, unlike those induced by straight-line motion. These energy-independent forces can be separated into a noninertial space-charge force and a coherent synchrotron radiation force. These forces result in an energy spread in the bunch, and can lead to a potentially large emittance growth. These effects can take place in both (1) bunch compression systems used to increase … more
Date: September 1996
Creator: Carlsten, B. E. & Goldstein, J. C.
Partner: UNT Libraries Government Documents Department
open access

Optimization and nonlinear solver experiences in high-intensity rf ion linac problems

Description: Optimization techniques and nonlinear equation solvers have long been used as tools for advanced problems in high-intensity rf ion linacs. It is expected that the use of these tools will increase dramatically in the future, as computer software and hardware facilitates their development and use. Three such problems are discussed: development of an rf field tuning method to work around a systematic error in the LAMPF linac, investigation of this tuning method to identify why it does not always c… more
Date: October 1, 1996
Creator: Jameson, Robert A.
Partner: UNT Libraries Government Documents Department
open access

Beam-bunching with a linear-ramp including space-charge force effects cylinder model

Description: The voltage-amplitude requirement of a saw tooth waveform buncher is calculated to give a desired degree of bunching for a given beam current and particle species. This calculation includes the effect of space-charge forces with and without adjacent beam buckets. The results are compared to TRACE-3D calculations which do not include the space-charge effects of adjacent bunches. It appears that TRACE- 3D calculations underestimate the bunching voltage required. The methodology and a listing of t… more
Date: September 1, 1996
Creator: Wadlinger, E.A.
Partner: UNT Libraries Government Documents Department
open access

TRACE 3-D code improvements

Description: TRACE 3-D is an interactive beam-transport code for bunched beams that includes accelerating elements and linear space-charge forces. It has been integrated with an improved GUI (graphic user interface) based on the Shell for Particle Accelerator Related Codes. Recent modifications to the code include centroid tracking and an improved beam description consisting of a set of beam slices, each having its own 6D centroid and sigma matrix. This allows one to study some nonlinear effects, such as wa… more
Date: November 1, 1996
Creator: Lysenko, W. P.; Rusthoi, D. P.; Chan, K. C. D.; Gillespie, G. H. & Hill, B. W.
Partner: UNT Libraries Government Documents Department
open access

Extensions of the longitudinal envelope equation

Description: Recently, longitudinal space charge effects have become of increased importance in a variety of dynamical situations. The CEBAF FEL injector beam dynamics shows large space-charge effects, even at 10 MeV ({gamma} {approx} 20). Space-charge dominated longitudinal motion has also been studied in the IUCF ion storage ring. Previously a longitudinal envelope equation with a self-consistent phase-space distribution has been developed, and has been of considerable use in analyzing the motion of these… more
Date: December 1, 1996
Creator: Neuffer, D.
Partner: UNT Libraries Government Documents Department
open access

Induction-accelerator heavy-ion fusion: Status and beam physics issues

Description: Inertial confinement fusion driven by beams of heavy ions is an attractive route to controlled fusion. In the U.S., induction accelerators are being developed as {open_quotes}drivers{close_quotes} for this process. This paper is divided into two main sections. In the first section, the concept of induction-accelerator driven heavy-ion fusion is briefly reviewed, and the U.S. program of experiments and theoretical investigations is described. In the second, a {open_quotes}taxonomy{close_quotes} … more
Date: January 26, 1996
Creator: Friedman, A.
Partner: UNT Libraries Government Documents Department
open access

Longitudinal dynamics and stability in beams for heavy-ion fusion

Description: Successful transport of induction-driven beams for heavy-ion fusion requires careful control of the longitudinal space charge. The usual control technique is the periodic application of time-varying longitudinal electric fields, called `ears`, that on the average, balance the space-charge field. this technique is illustrated using a fluid/envelope code CIRCE, and the sensitivity of the method to errors in these ear fields is illustrated. The possibility that periodic ear fields also excite the … more
Date: January 5, 1996
Creator: Sharp, W. M.; Callahan, D. A. & Grote, D. P.
Partner: UNT Libraries Government Documents Department
open access

Development and testing of an ion probe for tightly-bunched particle beams

Description: Many high-energy physics experiments require a high-quality and well-diagnosed charged-particle beam (CPB). Precise knowledge of beam size, position, and charge distribution is often crucial to the success of the experiment. It is also important in many applications that the diagnostic used to determine the beam parameters be nonintercepting and nonperturbing. This requirement rules out many diagnostics, such as wire scanners, thin foils which produce Cerenkov or transition radiation, and even … more
Date: June 1, 1996
Creator: Ngo, M. & Pasour, J.
Partner: UNT Libraries Government Documents Department
open access

Beyond the Brillouin limit with the Penning fusion experiment

Description: Several years ago, it was proposed that a dense nonneutral plasma could be produced in a Penning trap. Nonneutral plasmas have excellent confinement. Thus, such a dense plasma might produce simultaneously high density and good confinement (as needed for fusion). Recently, this theoretical conjecture has been demonstrated in a small (3 mm radius) electron experiment (PFX). Densities up to 35 times the Brillouin density (limiting number density in a static trap) have been inferred from the observ… more
Date: November 9, 1996
Creator: Barnes, D. C.; Mitchell, T. B. & Schauer, M. M.
Partner: UNT Libraries Government Documents Department
open access

Beam dynamics simulations using a parallel version of PARMILA

Description: The computer code PARMILA has been the primary tool for the design of proton and ion linacs in the United States for nearly three decades. Previously it was sufficient to perform simulations with of order 10000 particles, but recently the need to perform high resolution halo studies for next-generation, high intensity linacs has made it necessary to perform simulations with of order 100 million particles. With the advent of massively parallel computers such simulations are now within reach. Par… more
Date: December 1, 1996
Creator: Ryne, R.D.
Partner: UNT Libraries Government Documents Department
open access

Zero-field {mu}{sup +}SR study of the collossal magnetoresistance material La{sub 0.67}Ca{sub 0.33}MnO{sub 3}

Description: Zero-field {mu}{sup +}SR and resistivity experiments on La{sub 0. 67}Ca{sub 0.33}MnO{sub 3} powder shows that the ferromagnetic transition temperature (Tc = 274 K) and resistivity peak temperature coincide to within 1K, about 10 K higher that T{sub c} determined from the bulk magnetization. The sublattice magnetization v{sub mu}(T) is well described for T {<=} T{sub c} by (1-T/T{sub c}){sup beta}, where {beta} = 0.345 {+-} 0.015. Unusual relaxational dynamics suggest a wide distribution of Mn-i… more
Date: April 1, 1996
Creator: Heffner, R.H.; Le, L.P. & Hundley, M.F.
Partner: UNT Libraries Government Documents Department
open access

Emittance concept and growth mechanisms

Description: The authors present an introduction to the subjects of emittance and space-charge effects in charged-particle beams. This is followed by a discussion of three important topics that are at the frontier of this field. The first is a simple model, describing space-charge-induced emittance growth, which yields scaling formulas and some physical explanations for some of the surprising results. The second is a discussion of beam halo, an introduction to the particle-core model, and a brief summary of… more
Date: May 1, 1996
Creator: Wangler, T. P.
Partner: UNT Libraries Government Documents Department
open access

Conceptual foundation of the Fokker-Planck approach to space-charge effects

Description: An rms-mismatched beam can evolve rapidly to a configuration of quasiequilibrium under the influence of space-charge forces. As sit evolves, its emittance grows and a diffuse halo forms. The beam's distribution function accounts for all the complicated dynamics. Unfortunately, the distribution function is difficult to calculate in as much as the physics lies at the interface between classical mechanics and thermodynamics. This paper presents the foundation for a statistical theory of the dynami… more
Date: July 1, 1996
Creator: Bohn, C.L.
Partner: UNT Libraries Government Documents Department
open access

Space charge and coherent effects in the NSNS storage ring

Description: The goal of the proposed National Spallation Neutron Source (NSNS) is to provide a short pulse proton beam of about 0.5 {mu}s with average beam power of 1-2 MW. To achieve such a purpose, a proton storage ring operate at 60 Hz with 1-2 x 10 {sup 14} protons per pulse at 1 GeV is required. The proton storage ring is one of the major systems in the design of the NSNS. The function of the storage ring is to take the 1.0 GeV proton beam from the Linac and convert the long Linac beam of about 1 ms i… more
Date: July 1996
Creator: Ruggiero, A. G.; Weng, W. T. & Zhang, S. Y.
Partner: UNT Libraries Government Documents Department
open access

Solitary waves in particle beams

Description: Since space charge waves on a particle beam exhibit both dispersive and nonlinear character, solitary waves or solitons are possible. Dispersive, nonlinear wave propagation in high current beams is found to be similar to ion-acoustic waves in plasmas with an analogy between Debye screening and beam pipe shielding. Exact longitudinal solitary wave propagation is found for potentials associated with certain transverse distributions which fill the beam pipe. For weak dispersion, the waves satisfy … more
Date: July 1, 1996
Creator: Bisognano, J.J.
Partner: UNT Libraries Government Documents Department
open access

Aspects of operation of the Fermilab Booster RF System at very high intensity

Description: The purpose of this note is to examine the likelihood and problems associated with operation of the Fermilab Booster rf systems as it presently exists, or with only minor modifications, at beam intensity approaching 5x10{sup 13} protons per pulse. Beam loading of the rf system at such an intensity will be one order of magnitude larger than at the present operation level. It is assumed that the injection energy will be raised to 1 GeV with no major increase in the injected energy spread (longitu… more
Date: April 1, 1996
Creator: Griffin, J.E.
Partner: UNT Libraries Government Documents Department
open access

Spectroscopic techniques for measuring ion diode space-charge distributions and ion source properties

Description: We are using time- and space-resolved visible spectroscopy to measure applied-B ion diode dynamics on the 20 TW Particle Beam Fusion Accelerator II. Doppler broadening of fast Li atoms, as viewed parallel to the anode, is used in a charge-exchange model to obtain the Li{sup +} ion divergence within 100 {mu}m of the anode surface. The characteristic Stark/Zeeman shifts in spectra of alkali neutrals or singly-ionized alkaline-earths are used to measure the strong electric (10{sup 9} V/m) and magn… more
Date: July 1, 1996
Creator: Filuk, A. B.; Bailey, J. E. & Adams, R. G.
Partner: UNT Libraries Government Documents Department
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