1,357 Matching Results

Search Results

Advanced search parameters have been applied.

A Linear, Transparent Beam Integrator

Description: Abstract: "A fast, linear air-ionization chamber has been developed for integrating and monitoring external heavy-particle beams. It consists of a thin-windowed air chamber in which the beam ionization light is viewed by a photomultiplier whose output is fed directly to a standard electrometer."
Date: February 12, 1954
Creator: Kitchen, Sumner W.
Partner: UNT Libraries Government Documents Department


Description: The purpose of this paper is twofold: to introduce the reader to the subject of instabilities exhibited by relativistic particle beams, and to summarize the present state of our knowledge concerning these phenomena. Most of the material in the first part of the paper is not new. It has been known to some specialists for a good many years; what is new is that the problems that can be solved are now of much more interest to the general community of accelerator physicists. Consequently, many accelerator physicists who have not paid much attention to these matters may now want to become informed; it is my hope that this paper will provide an introduction to the field. The second part of the article consists of two sections. The first summarizes the experimental information presently available, with emphasis upon the degree to which it confirms or disagrees with theory. Our current level of understanding is delineated: considering the generality and reliability of the theoretical analysis as well as the degree of experimental confirmation, the author expresses his opinion as to what can be considered relatively well established. The final section contains a discussion of subjects needing further investigation and, consequently, supplements the discussion of areas of understanding by describing the peripheral areas of uncertainty.
Date: October 4, 1965
Creator: Sessler, Andrew M.
Partner: UNT Libraries Government Documents Department


Description: In accord with recent custom, the organizing committee for this conference has scheduled this review paper on beam instabilities. In view of the various review papers which already exist and the fact that the fundamentals of the subject have even been treated in a textbook, I thought this paper might best be devoted to a limited part of the rather large field of beam instabilities. Thus, I have selected only an aspect of the general subject, but an aspect which has during the last years been very much at the center of activity, and will--if my judgment is correct--be even more so in the years to come. I wish to concentrate, here, on the interaction of a relativistic particle beam with itself which is a result of the coupling of the beam with its surroundings. Before approaching this topic, a few remarks on the existing review papers are in order. A comprehensive treatment of beam instabilities may be found in Ref. 1, where, also, the reader will find some 48 references to the original literature. In Refs. 2 and 3, the General subject is approached from other points of view. Reference 4 is concerned with some special topics, but treats them in depth; and the text of Ref. 5 closely follows the original papers.
Date: February 1, 1971
Creator: Sessler, Andrew M.
Partner: UNT Libraries Government Documents Department


Description: The stability of a coasting beam against self-bunching (negative mass instability) may be expressed in terms of a beam coupling impedance. The impedance has contributions from self-fields, wall impedance, and curvature effects. This paper describes procedures for measuring the wall and curvature contributions to the coupling impedance by means of an analog in which the beam is replaced by a conductor propagating a TEM-like mode. Conditions are derived under which the measurements are valid, various measurement procedures are described and results of the application of the method to the compressor of an electron ring accelerator are reported.
Date: August 1, 1971
Creator: Faltens, A.; Hartvig, E.C.; Mohl, D. & Sessler, A.M.
Partner: UNT Libraries Government Documents Department

DML and Foil Measurements of ETA Beam Radius

Description: Simultaneous measurements of the ETA beam radius have been made with a quartz foil and a diamagnetic loop (DML). While the measurements agreed at some settings they diverged at others. While the DML measures the rms radius of the total beam, the foil measures mainly the core and the divergence can be explained by the presence of a low density halo. Evidence of such a halo from other measurements is presented.
Date: May 11, 2005
Creator: Nexsen, W & Weir, J
Partner: UNT Libraries Government Documents Department

Transverse Beam Profile Measurement Using Scrape Scans

Description: A scraper scan - sending a scraper through a particle beam while measuring the intensity as a function of scraper position - is a common method of determining the profile of the beam. At first glance, this seems to be a rather simple procedure. Nevertheless, some care is required in the acquisition of the data and in the analysis if one is going to achieve an accurate result.
Date: September 13, 2001
Creator: Werkema, Steven J.
Partner: UNT Libraries Government Documents Department

Particle-beam approach to collective instabilities -- application to space-charge dominated beams

Description: Nonlinear dynamics deals with parametric resonances and di#11;usion. The phenomena are usually beam-intensity independent and rely on a particle Hamiltonian. Collective instabilities deal with beam coherent motion, where the Vlasov equation is frequently used in conjunction with a beam-intensity dependent Hamiltonian. We ad- dress the questions: Are the two descriptions the same? Are collective instabilities the results of encountering parametric resonances whose driving force is intensity depen- dent? We study here the example of a space-charge dominated beam governed by the Kapchinskij-Vladimirskij (K-V) envelope equation [1]. The stability and instability regions as functions of tune depression and envelope mismatch are compared in the two approaches. The study has been restricted to the simple example of a uniformly focusing channel.
Date: November 1, 1998
Creator: Lee, K.Y. Ng and S.Y.
Partner: UNT Libraries Government Documents Department

Particle-beam profiling techniques on the APS storage ring

Description: Characterization of the Advanced Photon Source storage ring particle beams includes transverse and longitudinal profile measurements using synchrotron radiation-based techniques. Both optical (OSR) and x-ray synchrotron radiation stations are now installed. Spatial resolution of about {sigma}=55{mu}m was obtained at low current in the visible field initially. This is expected to improve during commissioning. UV/visible light from the storage ring bending magnet was used to measure the particle beam with a resolution of {sigma}{approximately}80{mu}m and allow operation at 100 mA with the initial x-ray pinhole setup. Early OSR measurements of beam size are consistent with 8.2 nm-rad emittance and 2-3% vertical coupling. Early results with the x-ray pinhole camera are also presented.
Date: December 31, 1996
Creator: Yang, B.X. & Lumpkin, A.H.
Partner: UNT Libraries Government Documents Department

Particle diffusion in overlapping resonances

Description: Longitudinal bunch dilution was studied in the IUCF Cooler Ring with phase modulation of a higher-order harmonic rf. Diffusion in the presence of overlapping parametric resonances has been identified as the dilution mechanism. We found that fast growth is associated with the rapid particle motion along separatrices of dominant parametric resonances, slow growth is related to particle diffusion in the chaotic sea, and saturation occurs when particles are bounded by an invariant torus.
Date: January 1, 1998
Creator: Ng, K.Y.
Partner: UNT Libraries Government Documents Department


Description: In this paper the authors consider applications of methods from wavelet analysis to nonlinear dynamical problems related to accelerator physics. In this approach they take into account underlying algebraical, geometrical and topological structures of corresponding problems.
Date: March 31, 2000
Partner: UNT Libraries Government Documents Department


Description: A working model for the proposed JHF project is the AGS facility at BNL. Research that is being planned at the JHF represent extensions of present AGS experiments. The AGS presently holds the record for beam intensity from a synchrotron. Experience gained and lessons learned over the years from operation of the AGS is invaluable to a new facility like JHF. Presented here is a brief description of the AGS facility with emphasis on the separated particle beam lines that are presently being used for studying strangeness -1 and -2 systems.
Date: March 4, 1998
Creator: PILE,P.H.
Partner: UNT Libraries Government Documents Department

Fixed-Target Electron Accelerators

Description: A tremendous amount of scientific insight has been garnered over the past half-century by using particle accelerators to study physical systems of sub-atomic dimensions. These giant instruments begin with particles at rest, then greatly increase their energy of motion, forming a narrow trajectory or beam of particles. In fixed-target accelerators, the particle beam impacts upon a stationary sample or target which contains or produces the sub-atomic system being studied. This is in distinction to colliders, where two beams are produced and are steered into each other so that their constituent particles can collide. The acceleration process always relies on the particle being accelerated having an electric charge; however, both the details of producing the beam and the classes of scientific investigations possible vary widely with the specific type of particle being accelerated. This article discusses fixed-target accelerators which produce beams of electrons, the lightest charged particle. As detailed in the report, the beam energy has a close connection with the size of the physical system studied. Here a useful unit of energy is a GeV, i.e., a giga electron-volt. (ne GeV, the energy an electron would have if accelerated through a billion volts, is equal to 1.6 x 10{sup -10} joules.) To study systems on a distance scale much smaller than an atomic nucleus requires beam energies ranging from a few GeV up to hundreds of GeV and more.
Date: November 2001
Creator: Brooks, William K.
Partner: UNT Libraries Government Documents Department

Betatron tune shifts and Laslett image coefficients

Description: The complicated expressions of betatron tune shifts in terms of Laslett image coefficients are explained. The expressions of image coefficients for a centered or off-centered beam inside an elliptical or rectangular vacuum chamber are gathered. Typos in earlier literature are corrected.
Date: July 20, 2001
Creator: Ng, K. Y.
Partner: UNT Libraries Government Documents Department


Description: A Fixed Field Alternating Gradient (FFAG) arc can be used to reduce the cost of a recirculating accelerator. Path length variation with energy in such an arc can limit its usefulness, however, due to phase offset at the linac. This paper examines the dynamics of the reference particle in an FFAG recirculating accelerator, and describes the limitations on the design because of path length variation with energy.
Date: July 1, 2001
Creator: BERG,J.S.
Partner: UNT Libraries Government Documents Department

Entropy and emittance of particle and photon beams

Description: The emittance as the available phase space area is defined as the product of the elementary cell area {delta}{Omega} and exp(S), where S is the normalized entropy of a particle beam. The definition is based on the fact that the factor exp(S) can be interpreted as the number of the occupied cells. For particle beams, a closed expression for the emittance in terms of the phase space distribution function is obtained which is independent of {delta}{Omega}. To compute the emittance of the radiation beam, it is necessary to find the eigenvalues of the correlation operator. An explicit solution is found for the case of a partially coherent radiation beam which is a stochastic superposition of coherent Gaussian beams with a Gaussian probability distribution. Such a beam is a reasonable model for undulator radiation by beam of electrons. From the requirement that the radiation emittance reproduces the particle beam emittance in the incoherent limit, the elementary cell area {delta}{Omega} is determined unambiguously to be {lambda}, the radiation wavelength. The emittance in the incoherent limit then becomes {lambda}.
Date: April 1, 1995
Creator: Kim, K.J. & Littlejohn, R.G.
Partner: UNT Libraries Government Documents Department

GeV C. W. Electron Microtron Design Report

Description: Rising interest in the nuclear physics community in a GeV C.W. electron accelerator reflects the growing importance of high-resolution short-range nuclear physics to future advances in the field. In this report major current problems are reviewed and the details of prospective measurements which could be made with a GeV C.W. electron facility are discussed, together with their impact on an understanding of nuclear forces and the structure of nuclear matter. The microtron accelerator has been chosen as the technology to generate the electron beams required for the research discussed because of the advantages of superior beam quality, low capital and operating cost and capability of furnishing beams of several energies and intensities simultaneously. A complete technical description of the conceptual design for a 2 GeV double-sided C.W. electron microtron is presented. The accelerator can furnish three beams with independently controlled energy and intensity. The maximum current per beam is 100 mircoamps. Although the precise objective for maximum beam energy is still a subject of debate, the design developed in this study provides the base technology for microtron accelerators at higher energies (2 to 6 GeV) using multi-sided geometries.
Date: May 1982
Creator: Jackson, H. E.
Partner: UNT Libraries Government Documents Department

A National CW GeV Electron Microtron Laboratory

Description: Rising interest in the nuclear physics community in a CW GeV electron accelerator reflects the growing importance of high-resolution short-range nuclear physics to future advances in the field. To meet this need, Argonne National Laboratory proposes to build a CW GeV Electron Microtron (GEM) laboratory as a national user facility. The microtron accelerator has been chosen as the technology to generate the electron beams required for the research discussed because of the advantages of superior beam quality, low capital and operating costs and capability of furnishing beams of several energies and intensities simultaneously. A complete technical description of the conceptual design for a six-sided CW microtron (hexatron) is presented. The hexatron and three experimental areas will be housed in a well-shielded complex of existing buildings that provide all utilities and services required for an advanced accelerator and an active research program at a savings of $30 to 40 million. Beam lines have been designed to accommodate the transport of polarized beams to each area. The total capital cost of the facility will be $78.6 million and the annual budget for accelerator operations will be $12.1 million. Design and construction of the facility will require four and one half years. Staged construction with a 2 GeV phase costing $65.9 million is also discussed.
Date: December 1982
Creator: Argonne National Laboratory
Partner: UNT Libraries Government Documents Department

Coherent parasitic energy loss of the recycler beam

Description: Parasitic energy loss of the particle beam in the Recycler Ring is discussed. The long beam confined between two barrier waves has a spectrum that falls off rapidly with frequency. Discrete summation over the revolution harmonics must be made to obtain the correct energy loss per particle per turn, because only a few lower revolution harmonics of real part of the longitudinal impedance contribute to the parasitic energy loss. The longitudinal impedances of the broadband rf cavities, the broadband resistive-wall monitors, and the resistive wall of the vacuum chamber are discussed. They are the main sources of the parasitic energy loss.
Date: July 14, 2004
Creator: Ng, K.Y.
Partner: UNT Libraries Government Documents Department

Design Considerations for Plasma Accelerators Driven by Lasers or Particle Beams

Description: Plasma accelerators may be driven by the ponderomotive force of an intense laser or the space-charge force of a charged particle beam. The implications for accelerator design and the different physical mechanisms of laser-driven and beam-driven plasma acceleration are discussed. Driver propagation is examined, as well as the effects of the excited plasma wave phase velocity. The driver coupling to subsequent plasma accelerator stages for high-energy physics applications is addressed.
Date: June 1, 2010
Creator: Schroeder, C. B.; Esarey, E.; Benedetti, C.; Toth, Cs.; Geddes, C. G. R. & Leemans, W.P.
Partner: UNT Libraries Government Documents Department

Interactive visualization of particle beams for accelerator design

Description: We describe a hybrid data-representation and rendering technique for visualizing large-scale particle data generated from numerical modeling of beam dynamics. The basis of the technique is mixing volume rendering and point rendering according to particle density distribution, visibility, and the user's instruction. A hierarchical representation of the data is created on a parallel computer, allowing real-time partitioning into high-density areas for volume rendering, and low-density areas for point rendering. This allows the beam to be interactively visualized while preserving the fine structure usually visible only with slow point based rendering techniques.
Date: January 15, 2002
Creator: Wilson, Brett; Ma, Kwan-Liu; Qiang, Ji & Ryne, Robert
Partner: UNT Libraries Government Documents Department