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in subjects: "Space Charge"

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Recent experimental results on the beam-beam effects in storage rings and an attempt of their interpretation

The latest available experimental results on the luminosity, the space charge parameters, and the beam blowup as functions of particle energy and beam current are reviewed. The comparison with the phenomenological diffusion theory is done and useful scaling laws are derived. Some implications for anti p p storage rings are discussed.

Date: June 1, 1980

Creator: Kheifets, S.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Application of microfabrication technology to thermionic energy conversion. Progress report 4, 1 May 1980 to 31 July 1980

Two applications of microfabrication technology to thermionic converters have been investigated theoretically. The first is a novel method of maintaining micron or submicron spacings over large areas (>1 cm/sup 2/), using metals of different expansion coefficients to eliminate the shear stresses on the insulating pillars separating the electrodes. The second uses low-voltage field-emission sources to create ions in a large (approx. 1 mm) interelectrode gap for space charge neutralization. The t… more

Date: September 5, 1980

Creator: Brodie, I.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Considerations for high-brightness electron sources

Particle accelerators are now used in many areas of physics research and in industrial and medical applications. New uses are being studied to address major societal needs in energy production, materials research, generation of intense beams of radiation at optical and suboptical wavelengths, treatment of various kinds of waste, and so on. Many of these modern applications require a high intensity beam at the desired energy, along with a very good beam quality in terms of the beam confinement, … more

Date: January 1, 1990

Creator: Jameson, Robert A.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Experiments and prospects for induction linac drivers

In the last three years, the US program in Heavy Ion Fusion has concentrated on understanding the induction linac approach to a power-plant driver. In this method it is important that the beam current be maximized throughout the accelerator. Consequently, it is crucial to understand the space-charge limit in the AG transport system in the linac and, also, to achieve current amplification during acceleration to keep pace with the kinematical increase of this limit with energy. Experimental resul… more

Date: May 1, 1986

Creator: D., Keefe

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Design desiderata for a laminar flow quadrupole-focused acceleration column

The Pierce design acceleration column has been widely used to accelerate high current beams. It operates well in the space charge limited condition, and will produce beams with a temperature comparable with that of the source. It is restricted in current density, however, by the Child-Langmuir relation. If the ion source itself is not the limiting constraint, then the achievable current density is limited by the electric field at which sparking occurs. One sees clearly that the achievable curre… more

Date: January 1, 1983

Creator: Maschke, A.W.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Annotated bibliography on high-intensity linear accelerators. [240 citations]

A technical bibliography covering subjects important to the design of high-intensity beam transport systems and linear accelerators is presented. Space charge and emittance growth are stressed. Subject and author concordances provide cross-reference to detailed citations, which include an abstract and notes on the material. The bibliography resides in a computer database that can be searched for key words and phrases.

Date: January 1, 1978

Creator: Jameson, R.A. & Roybal, E.U.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Stability of space-charge neutralized beams

Consideration is given to the stability of negative ion beams which are neutralized through ionization of a background gas. Two types of instabilities are examined. First, beam-plasma instabilities are analyzed with the dispersion relation showing that they are unimportant if the beam velocity is less than the electron thermal velocity. Second, results of a computer simulation on the flow of a cylindrical beam and the resulting background plasma show that when the background neutral gas density… more

Date: September 22, 1977

Creator: Turnbull, R. J. & Hooper, E. B. Jr.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Model equations for high current transport

The use of distribution functions to model transverse beam dynamics is discussed. Emphasis is placed on envelope equations, moments, the Vlasov equation, and the Kapchinski-Vladimirskij distribution. 10 refs.

Date: June 1, 1985

Creator: Lee, Edward P.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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High current beam transport with multiple beam arrays

Highlights of recent experimental and theoretical research progress on the high current beam transport of single and multiple beams by the Heavy Ion Fusion Accelerator Research (HIFAR) group at the Lawrence Berkeley Laboratory (LBL) are presented. In the single beam transport experiment (SBTE), stability boundaries and the emittance growth of a space charge dominated beam in a long quadrupole transport channel were measured and compared with theory and computer simulations. Also, a multiple bea… more

Date: May 1, 1985

Creator: Kim, C.H.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Transport of intense ion beams. [HIBALL II]

The maximum transportable current for an ion beam is determined by considerations of focal strength, space charge equilibrium and stability, structural practically and emittance. These factors are described within the context of a heavy ion driver for Inertial Confinement Fusion. Recent supporting results from particle-in-cell simulations and transport experiments will be described.

Date: June 1, 1986

Creator: Lee, Edward P.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Report of Working Group on Accelerator Problems

There are many experimental elementary particle objectives which are uniquely achievable with polarized proton beams. These objectives require both higher beam energies and intensities than are presently available. The polarized ion source working group concluded that it looks quite practical to produce polarized H sources with output currents of several mA. The significance of this is best demonstrated by the fact that the ZGS operates at its space charge limit using a 6 mA H/sup -/ impolarize… more

Date: October 18, 1977

Creator: Cho, Y.; Montague, B. W.; Kubischta, W.; Turrin, A.; Courant, E. D. & Ratner, L.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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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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Beam-beam effect and luminosity in SPEAR

Measurements performed at SPEAR have been discussed and scaling laws for the maximum luminosity and the maximum linear tune shift parameter with energy are shown. There are two distinct regimes, one below 2 GeV where the linear tune shift parameter scales like xi/sub y/ approx. E/sup 2/ /sup 4/ and the other regime where this parameter is constant xi/sub y/ approx. = 0.05 to 0.06. In the lower energy regime the limit is reached when the vertical beam size is blown up to the acceptance of the st… more

Date: July 1, 1980

Creator: Wiedemann, H.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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High-brightness injectors for hadron colliders

The counterrotating beams in collider rings consist of trains of beam bunches with N{sub B} particles per bunch, spaced a distance S{sub B} apart. When the bunches collide, the interaction rate is determined by the luminosity, which is defined as the interaction rate per unit cross section. For head-on collisions between cylindrical Gaussian beams moving at speed {beta}c, the luminosity is given by L = N{sub B}{sup 2}{beta}c/4{pi}{sigma}{sup 2}S{sub B}, where {sigma} is the rms beam size projec… more

Date: January 1, 1990

Creator: Wangler, T. P.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Design and construction status of the AGS Booster accelerator

To meet the requirements of new experiments in high energy physics and nuclear physics, a fast cycling Booster accelerator was proposed to fulfill the following three technical objectives: The AGS Booster has three objectives. They are to increase the space charge limit of the AGS, to incrase the intensity of the polarized proton beam by accumulating many linac pulses (since the intensity is limited by the polarized ion source), and to re-accelerate heavy ions from the BNL Tandem Van de Graaff … more

Date: January 1, 1988

Creator: Weng, W. & Lee, Y. Y.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Heavy ion fusion year-end report, April 1, 1983-September 30, 1983

Some highlights of the program during this reporting period are as follows: (1) First results with the completed apparatus of the Single Beam Transport Experiment (SBTE) have shown the stable propagation of a space-charge-dominated cesium-ion beam through 41 periods of an AG focussing lattice. The space-charge effects were large enough to depress the betatron phase advance per cell from sigma/sub 0/ = 60/sup 0/ to sigma = 12/sup 0/. (2) Understanding of the reflection stabilization of longitudi… more

Date: November 1, 1983

Item Type: Report

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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Transportable charge in a periodic alternating gradient system

A simple set of formulas is derived which relate emittance, line charge density, matched maximum and average envelope radii, occupancy factors, and the (space charge) depressed and vacuum values of tune. This formulation is an improvement on the smooth limit approximation; deviations from exact (numerically determined) relations are on the order of +-2%, while the smooth limit values are in error by up to +-30%. This transport formalism is used to determine the limits of transportable line char… more

Date: May 1, 1985

Creator: Lee, E.P.; Fessenden, T.J. & Laslett, L.J.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Space-charge effects in the Main Ring at 8 GeV

This is a note on the effects of space-charge on particle behavior in the Main Ring. At first, to elucidate various basic points, an idealized model of the Main Ring was studied. Then the TEVLAT program was used, with a sample Main Ring lattice. The TEVLAT program was modified to include space-charge kicks. The idealized model mentioned above consisted of linear dynamics with localized nonlinear elements (thin sextupoles). The incoherent space-charge force was included as a series of kicks appl… more

Date: January 1, 1988

Creator: Mane, S.R.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Simulation of transverse combining of space-charge dominated beams

Rms emittance growth in the transverse plane due to the transverse combining of four identical elliptical beams of uniform density has been investigated. The emittance growth can be related by conservation of energy to the change in the electrostatic field energy. Its dependence on initial beam positions and radii has been calculated analytically for round beams and by computer simulation for elliptical beams.

Date: June 1, 1986

Creator: Celata, C. M.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Induction linac drivers for commercial heavy-ion beam fusion

This paper discusses induction linac drivers necessary to accelerate heavy ions at inertial fusion targets. Topics discussed are: driver configurations, the current-amplifying induction linac, high current beam behavior and emittance growth, new considerations for driver design, the heavy ion fusion systems study, and future studies. 13 refs., 6 figs., 1 tab. (LSP)

Date: November 1, 1987

Creator: Keefe, D.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Measurements of stability limits for a space-charge-dominated ion beam in a long A. G. transport channel

The Single Beam Transport Experiment at LBL consists of 82 electrostatic quadrupole lenses arranged in a FODO lattice. Five further lenses provide a matched beam from a high-current high-brightness cesium source for injection into the FODO channel. We call the transport conditions stable if both the emittance and current remain unchanged between the beginning and end of the channel, and unstable if either the emittance grows or the current decreases because of collective effects. We have explor… more

Date: May 1, 1985

Creator: Tiefenback, M.G. & Keefe, D.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Effects of space charge on the acceptance of brightness measuring devices

Attempts to measure high electron beam brightness at low values of beam energy are plagued by the effects of space charge forces. These forces can substantially lower the phase space acceptance of various brightness measuring devices. This report considers several models for the effects of space charge upon the acceptance of both the field free, double aperture system and the magnetic ''emittance selector'' and compares them for some recent experiments on ATA and the High Brightness Test Stand.… more

Date: August 14, 1985

Creator: Caporaso, G.J.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Preliminary design of a 10 MV ion accelerator

At the low energy end of an induction linac HIF driver the beam current is limited by our ability to control space charge by a focusing system. As a consequence, HIF induction accelerator designs feature simultaneous acceleration of many beams in parallel within a single accelerator structure. As the speed of the beams increase, the focusing system changes from electrostatic to magnetic quadrupoles with a corresponding increase in the maximum allowable current. At that point the beams are merge… more

Date: June 1, 1986

Creator: Fessenden, T. J.; Celata, C. M.; Faltens, A.; Henderson, T.; Judd, D. L.; Keefe, D. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department