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in subjects: "Particle Beams 430200* -- Particle Accelerators-- Beam Dynamics, Field Calculations, & Ion Optics"

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Electron-beam envelopes and matching for a combined wiggler and alternating-gradient quadrupole channel

This work studies the electron-beam envelopes and matching for a combined wiggler and alternating-gradient quadrupole field for a free-electron laser (FEL) that will be operated in the VUV or XUV wavelength region. The quadrupole field is assumed to vary continuously along the symmetry axis. The linearized equations of electron motion are solved analytically by using the two-scale perturbation method for a plane polarized wiggler. The electron-beam envelopes and the envelope equations, as well … more

Date: January 1, 1985

Creator: Wang, T. F. & Cooper, R. K.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Three-dimensional free electron laser dispersion relation including betatron oscillations

We have developed a 3-D FEL theory based upon the Maxwell-Vlasov equations including the effects of the energy spread and emittance of the electron beam, and of betatron oscillations. The radiation field is expressed in terms of the Green's function of the inhomogeneous wave equation and the distribution function of the electron beam. The distribution function is expanded in terms of a set of orthogonal functions determined by the unperturbed particle distribution. The coupled Maxwell-Vlasov eq… more

Date: August 1, 1991

Creator: Chin, Y. H.; Kim, K. J. & Xie, M.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Field measurements in pulsed microwigglers

A pulsed microwiggler can provide a large field, greater than 5 T, with a short period, less than 2 mm. It is essential to find a way to measure the field produced in the small bore, with accuracy as well as with high resolution in all three coordinates and the time domain. Conventional field-measuring probes are too large and have poor temporal resolution, but the pulsed-wire technique is well suited to these demands. Los Alamos researchers have made recent improvements to this technique. 9 re… more

Date: January 1, 1991

Creator: Warren, R. (Los Alamos National Lab., NM (United States)) & Preston, D.W. (California State Univ., Hayward, CA (United States))

Item Type: Article

Partner: UNT Libraries Government Documents Department

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The Effect of Wiggler Errors on FEL Gain

For an FEL operating in the exponential regime before saturation, we present an analytic description of the effect on the gain of longitudinal velocity variations arising from wiggler field errors. The average gain reduction and the width of the output power distribution are expressed in terms of the mean square average of the ponderomotive phase shift per gain length. A scheme for correcting the electron trajectory using position monitors and dipole correctors is analyzed. Our work is directly… more

Date: January 1, 1991

Creator: Yu, L. H.; Krinsky, S. (Brookhaven National Lab., Upton, NY (United States)); Gluckstern, R. L. & van Zeijts, J. B. J.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Possibilities of polarized protons in Sp anti p S and other high energy hadron colliders

The requirements for collisions with polarized protons in hadron colliders above 200 GeV are listed and briefly discussed. Particular attention is given to the use of the ''Siberan snake'' to eliminate depolarizing resonances, which occur when the spin precession frequency equals a frequency contained in the spectrum of the field seen by the beam. The Siberian snake is a device which makes the spin precession frequency essentially constant by using spin rotators, which precess the spin by 180/s… more

Date: January 1, 1984

Creator: Courant, E. D.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Variable-energy drift-tube linacs

Practical applications of ion linacs are more viable now than ever before because of the recent development of the radio-frequency quadrupole accelerating structure, as well as other technological advances developed under the Pion Generator for Medical Irradiations program. This report describes a practical technique for varying the energy of drift-tube linacs and thus further broadening the possibilities for linac applications. This technique involves using the post couplers (normally used to … more

Date: January 1, 1981

Creator: Swenson, D. A.; Boyd, T. J.; Potter, J. M. & Stovall, J. E.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Relativistic electron beam cyclotron wave growth in helical slow wave structures

One of the more promising and thoroughly studied proposals for high energy collective ion acceleration is Autoresonant Acceleration: Ions trapped in the electrostatic wells of large amplitude slow cyclotron waves in an unneutralized intense relativistic electron beam are accelerated by the increase of wave phase velocity as the beam propagates along a magnetic guide field of decreasing strength. A critical component of this scheme is growth of coherent, large amplitude waves. A discussion is gi… more

Date: January 1, 1977

Creator: Godfrey, B.B.; Faehl, R.J.; Newberger, B.S.; Shanahan, W.R. & Thode, L.E.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Phenomenological Analysis of Current Limits in Storage Rings

The limitations on the current which can be stored in a storage ring was studied. A simple model is used for the impedance of the beam environment. Feedback systems are assumed to be used to their full capacity to provide beam stability and that in the frequency range where feedback can no longer be used Landau damping will determine how much current can be stored in the ring. Estimates are made for proton storage rings and for electron storage rings of interest as synchrotron radiation sources… more

Date: January 1, 1980

Creator: Pellegrini, C. & Sands, M.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Modeling beam-front dynamics at low gas pressures

The dynamics of space charge neutralization at the front of an intense self-focused electron beam pulse exhibits important differences in different gas pressure regimes. At very low pressures, the beam front is in the so-called ion-focused regime (IFR) where all secondary electrons are expelled from the beam region by the radial electric field without causing significant additional ionization. We estimate the upper pressure boundary of this regime by considering the distance scale length for ca… more

Date: May 13, 1982

Creator: Briggs, R. J. & Yu, S.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Crossing simple resonances

A simple criterion governs the beam distortion and/or loss of protons on a fast resonance crossing. Results from numerical integrations are illustrated for simple sextupole, octupole, and 10-pole resonances.

Date: August 1, 1985

Creator: Collins, T.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Suppression of transverse beam breakup modes in an induction accelerator by gas focusing

The effect of beam-generated positive ions on the beam-breakup instability in linear electron accelerators is calculated using simple models. The strongly nonlinear dependence of the ion focusing force on radius makes a complete suppression of the mode growth possible, in contrast to solenoidal focusing. The predicted gas pressures for significant stabilization of the mode growth in a machine configuration like ATA is relatively low (10/sup -5/ to 10/sup -4/ torr), even for high-Q modes.

Date: April 7, 1980

Creator: Briggs, R. J.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Importance of high order momentum terms in SLC optics

The evaluation of background levels at the SLC relies, in several cases, on the proper representation of how low momentum electrons propagate through the Arcs and the Final Focus System (FFS). For example, beam - gas bremsstrahlung in the arcs causes electrons of up to 6% energy loss to be transported through to the IP; secondary showers on edges of masks and collimators yield debris with a very wide momentum spectrum. This note is a naive attempt at checking the validity of TRANSPORT and TURTL… more

Date: July 10, 1985

Creator: Kozanecki, W.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Collective ion acceleration

Progress achieved in the understanding and development of collective ion acceleration is presented. Extensive analytic and computational studies of slow cyclotron wave growth on an electron beam in a helix amplifier were performed. Research included precise determination of linear coupling between beam and helix, suppression of undesired transients and end effects, and two-dimensional simulations of wave growth in physically realizable systems. Electrostatic well depths produced exceed requirem… more

Date: January 1, 1977

Creator: Godfrey, B.B.; Faehl, R.J.; Newberger, B.S.; Shanahan, W.R. & Thode, L.E.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Initial measurements of beam breakup instability in the advanced test accelerator

This paper reports the measurements of beam breakup (BBU) instability performed on the Advanced Test Accelerator (ATA) up to the end of February, 1984. The main objective was to produce a high current usable electron beam at the ATA output. A well-known instability is BBU which arises from the accelerator cavity modes interacting with the electron beam. The dominant mode is TM/sub 130/ at a frequency of approximately 785 MHz. It couples most strongly to the beam motion and has been observed to … more

Date: May 13, 1985

Creator: Chong, Y.P.; Caporaso, G.J. & Struve, K.W.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Effects of slots/holes in disks on frequencies of TM/sub 01/ and EH/sub 11/ waves in the disk-loaded waveguide

The increase in the BBU threshold current is very important for the high and medium energy electron linacs because of a larger operating current attainable or a smaller emittance available at certain operating current. For this purpose, many means can be used, among which the improvement in the accelerating structure itself is always fundamental. SLAC's three-meter long section is unique with truly constant gradient performance. The theoretical analyses and operating experiences at SLAC have in… more

Date: March 1, 1985

Creator: Yao, C.G.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Beam front accelerators

An intense relativistic electron beam cannot propagate in a metal drift tube when the current exceeds the space charge limit. Very high charge density and electric field gradients (10/sup 2/ to 10/sup 3/ MV/m) develop at the beam front and the electrons are reflected. When a neutral gas or a plasma is present, collective acceleration of positive ions occur, and the resulting charge neutralization enables the beam to propagate. Experimental results, theoretical understanding, and schemes to achi… more

Date: January 1, 1982

Creator: Reiser, M.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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1. 2-GeV damping-ring complex for the Stanford Linear Collider

The choice of parameters, the design, a 2-1/2 year consruction program and the early operation of a high field, high tune research and development damping ring complex for one of the two linear collider beams are described.

Date: July 1983

Creator: Fischer, G. E.; Davies-White, W.; Fieguth, T. & Wiedemann, H.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

New magic angle bumps and magic translation bumps

SLC beams of opposite charge can be transversely deflected in the same direction by RF fields in the accelerating cavities caused by girder tilts, coupler-asymmetries, or manufacturing errors. A symmetric deflection can be corrected by a magic angle bump if the deflection is located adjacent to one of the linac quadrupoles. However, if the deflection is located between quadrupoles, two magic angle bumps or a magic angle bump and a magic translation bump are needed for the correction. Several ex… more

Date: October 28, 1983

Creator: Seeman, J.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Coherent synchro-betatron oscillations excited by the beam-beam interaction

In this note, a third possible coherent instability excited by the beam-beam interaction will be discussed. This time it involves the longitudinal motion of the bunches. What is studied is the possibility of beam-beam excited longitudinal dipole oscillations or coherent synchro-betatron oscillations in which the longitudinal and transverse motions are coupled through the beam-beam collisions. We suggest that such modes of oscillations exist when there is a finite dispersion at the interaction p… more

Date: December 1, 1983

Creator: Kamiya, Y. & Chao, A.W.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Beam deflection into a quadrant by a positionally stationary magnetic bending system

A system of postionally stationary magnets is analyzed for the continuously variable deflection of a 50 MeV electron beam. The system is composed of a collection of horizontal and vertical bending magnets, quadrupoles, and a final deflection magnet that is conical in shape and capable of deflections of plus or minus 50 degrees simultaneously in both horizonal and vertical planes. Throughout the system the beam is assumed to be focused by its own magnetic self-field, the electric self-field bein… more

Date: June 20, 1980

Creator: Paul, A.C. & Neil, V.K.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Reduction of FEL Gain Due to Wiggler Errors

For an FEL operating in the exponential regime before saturation, we consider the effect on the gain of longitudinal velocity variations arising from wiggler field errors. The average gain reduction and the width of the output power distribution are expressed in terms of the mean square average of the ponderomotive phase shift per gain length. A scheme for correcting the electron trajectory using position monitors and dipole correctors is analyzed. Analytic results are compared with numerical s… more

Date: January 1, 1991

Creator: Yu, L. H.; Krinsky, S.; Friedman, A.; Gluckstern, R. L. & van Zeijts, J. B. J.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Electron trajectory program

The SLAC Electron Trajectory Program is described and instructions and examples for users are given. The program is specifically written to compute trajectories of charged particles in electrostatic and magnetostatic focusing systems including the effects of space charge and self-magnetic fields. Starting options include Child's Law conditions on cathodes of various shapes. Either rectangular or cylindrically symmetric geometry may be used. Magntic fields may be specified using arbitrary config… more

Date: November 1, 1979

Creator: Herrmannsfeldt, W.B.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Preliminary study of pseudorandom binary sequence pulsing of ORELA

It has been suggested that pseudorandom binary sequence (PRBS) pulsing might enhance the performance of the Oak Ridge Electron Linear Accelerator (ORELA) for neutron-induced, time-of-flight (TOF) cross-section measurements. In this technical memorandum, equations are developed for expected count rates, statistical variances, and backgrounds for a pulsing scheme in which a PRBS is superimposed on the periodic equalintensity ORELA bursts. Introduction of the PRBS modification permits neutrons of … more

Date: March 1, 1980

Creator: Larson, N. M. & Olsen, D. K.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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ATA operations

Four accelerator parameters were found to control the condition of the electron beam entering the Intergrated Fast Reactor (IFR). These parameters were the matching of the electron beam to the ion channel, the laser timing, the benzene pressure at the entrance to the IFR, and the timing of the accelerator gaps. Manipulation of these parameters make possible the control of the total current, the emittance, the pulse length, the mixture of laser induced current and cathode current, the radial gro… more

Date: June 20, 1986

Creator: Weir, J.T.; Caporaso, G.J.; Chambers, F.W.; Chong, Y.P.; Prono, D.S. & Rainer, F.

Item Type: Article

Partner: UNT Libraries Government Documents Department