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in creator/contributor: "Gray, E. R."

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Alignment and steering scenarios for the APT linac

The Accelerator for the Production of Tritium (APT) requires a very high proton beam current (100 mA cw). Requirement for hands-on maintenance limits the beam spill to less than 0.2 nA/m along most of the linac. To achieve this, it is important to understand the effects of fabrication, installation and operational errors, establish realistic tolerances, and develop techniques for mitigating their consequences. A new code, PARTREX, statistically evaluates the effects of alignment, quadrupole fie… more

Date: September 1, 1996

Creator: Stovall, J. E.; Gray, E. R.; Nath, S.; Takeda, H.; Wood, R. L.; Young, L. M. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Basis for low beam loss in the high-current APT linac

The present evidence that the APT proton linac design will meet its goal of low beam loss operation. The conclusion has three main bases: (1) extrapolation from the understanding of the performance of the 800-MeV LANSCE proton linac at Los Alamos, (2) the theoretical understanding of the dominant halo-forming mechanism in the APT accelerator from physics models and multiparticle simulations, and (3) the conservative approach and key principles underlying the design of the APT linac, which are a… more

Date: December 31, 1998

Creator: Wangler, T. P.; Gray, E. R.; Krawczyk, F. L.; Kurennoy, S. S.; Lawrence, G. P.; Ryne, R. D. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Beam dynamics aspects for the APT integrated linac

The accelerator-based production of tritium calls for a high-power cw proton linac. The current Los Alamos design uses an integrated approach in terms of accelerating structure. The front part of the accelerator uses normal-conducting (NC) structures while most (>80%) of the linac structure is superconducting (SC). Here, the authors report the beam-dynamics rationale used in the integrated design and present particle simulation results.

Date: August 1, 1997

Creator: Nath, S.; Gray, E. R. & Wangler, T. P.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Design and construction of the photocathode electron gun cavity

A 1300-MHz, two-cell rf accelerator cavity has been constructed for the high-brightness photocathode electron source program. Each cell has an rf drive. Cell one has a replacement photocathode plug on the back wall and has a shape designed for linear radial fields. Cell two has a more standard high-shunt-impedance shape. SUPERFISH values for shunt impedances are, respectively, 29.5 and 45.8 M/Omega//m. Peak surface field maximums are 58.9 and 32.1 MV/m for an electron acceleration of 0.9 and 1.… more

Date: January 1, 1988

Creator: Gray, E.R. & Fraser, J.S.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Development of a commissioning plan for the APT linac

The Accelerator Production of Tritium (APT) facility is based on a linac which incorporates both normal-conducting and superconducting RF technology and accelerates a 100-mA cw proton beam to an energy of 1,030 MeV or higher, depending on the desired production rate. Commissioning plans to achieve full power operation with minimum beam-induced activation of components have been evolving. This paper presents the main issues and the basic approaches that are now being discussed.

Date: December 1998

Creator: Funk, L. W.; Crandall, K. R.; Gilpatrick, J. D.; Gray, E. R.; Regan, A. H.; Rohlev, A. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Dynamics of beam halo in mismatched beams

High-power proton linacs for nuclear materials transmutation and production, and new accelerator-driven neutron spallation sources must be designed to control beam-halo formation, which leads to beam loss. The study of particle-core models is leading to a better understanding of the causes and characteristics of beam halo produced by space-charge forces in rms mismatched beams. Detailed studies of the models have resulted in predictions of the dependence of the maximum amplitude of halo particl… more

Date: September 1, 1996

Creator: Wangler, T. P.; Garnett, R. W.; Gray, E. R.; Ryne, R. D. & Wang, T. S.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

High-brightness photoemitter development for electron accelerator injectors

Free-electron-laser (FEL) oscillators require a train of high-brightness bunches. Conventional subharmonic bunchers are currently used with rf linacs to generate pulse trains, but the resulting dilution of the transverse phase space and lower beam brightness are unacceptable for high-performance FELs. Recent developments suggest that photoemitters of high quantum efficiency combined with rapid acceleration can produce pulse trains of higher brightness than has been achieved before.

Date: January 1, 1985

Creator: Fraser, J.S.; Sheffield, R.L. & Gray, E.R.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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High-frequency cavity applications and measurements of high-temperature superconductors

A potentially important application of high-temperature superconductors will be high-frequency accelerating cavities. Currently these materials are not competitive with Nb at liquid helium temperature or with Cu at room temperature. However, available data on high-quality single crystals suggest that the relatively poor rf properties (high surface resistance and low surface magnetic field) of bulk and film specimens are due to materials properties that can be eliminated by improved processing t… more

Date: January 1, 1989

Creator: Cooke, D.W. & Gray, E.R.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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The Los Alamos Photoinjector Program

Free-electron lasers (FELS) require electron beams of high peak brightness. In this presentation, we describe the design of a compact high-brightness electron source for driving short-wavelength FELs. The experiment uses a laser-illuminated Cs/sub 3/Sb photoemitter located in the first rf cavity of an injector linac. The photocathode source and associated hardware are described. The doubled YAG laser (532 nm), which is used to drive the photocathode, produces 75-ps micropulses at 108-MHz repeti… more

Date: September 1, 1987

Creator: Sheffield, R.L.; Gray, E.R. & Fraser, J.S.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Microwave characterization of high-temperature superconductors

Thick (10-15 {mu}m) Tl-Ba-Ca-Cu-O films have been deposited onto yttria-stabilized zirconia and Ag substrates by d.c. magnetron sputtering techniques. Direct deposition onto 1'' diameter yttria-stabilized zirconia yields films with typical 22 GHz surface resistance (R{sub s}) values of 5.2 {plus minus} 2 m{Omega} and 52 {plus minus} 2 m{Omega} at 10 K and 77 K, respectively. For comparison, R{sub s} of Cu at this same frequency is 10 m{Omega} at 4 K and 22 m{Omega} at 77 K. Tl-Ba-Ca-Cu-O films … more

Date: January 1, 1989

Creator: Cooke, D. W.; Gray, E. R.; Arendt, P. N.; Beery, J. G.; Bennett, B. L.; Brown, D. R. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Microwave properties of HTS (high temperature superconductor) films

High-frequency applications of high-temperature superconductors generally fall into two categories: devices that require low values of surface resistance R{sub s} in ambient surface magnetic fields H{sub rf}, and devices that require low R{sub s} in modest fields. Moreover, many applications can be realized with small-surface-area films whereas others require larger areas-radiofrequency (rf) cavities, for example. Regardless of the application, the potential of HTS films is predicated on satisf… more

Date: January 1, 1990

Creator: Cooke, D. W.; Arendt, P. N.; Gray, E. R.; Muenchausen, R. E.; Bennett, B. L.; Foltyn, S. R. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

New high-brightness electron injector for free-electron lasers driven by rf linacs

A free-electron laser oscillator, driven by an rf linac, requires a train of electron bunches delivered to an undulator. The brightness requirement exceeds that available from a conventional linac with rf bunchers. The demonstrated high brightness of laser-illuminated photoemitters indicates that the conventional buncher system might be eliminated entirely, thereby avoiding the usual loarge loss in brightness that occurs in bunchers. A photoemitter with a current density of about 200 A/cm/sup 2… more

Date: January 1, 1985

Creator: Fraser, J.S.; Sheffield, R.L. & Gray, E.R.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

New high power linacs and beam physics

New high-power proton linacs must be designed to control beam loss, which can lead to radioactivation of the accelerator. The threat of beam loss is increased significantly by the formation of beam halo. Numerical simulation studies have identified the space-charge interactions, especially those that occur in rms mismatched beams, as a major concern for halo growth. The maximum-amplitude predictions of the simulation codes must be subjected to independent tests to confirm the validity of the re… more

Date: August 1, 1997

Creator: Wangler, T. P.; Gray, E. R.; Nath, S.; Crandall, K. R. & Hasegawa, K.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Overview of the APT high-energy beam transport and beam expanders

The APT high energy beam transport (HEBT) and beam expanders convey the 1700-MeV, 100-mA cw proton beam from the linac to the tritium target/blanket assembly, or a tuning beam stop. The HEBT includes extensive beam diagnostics, collimators, and beam jitter correction, to monitor and control the 170-MW beam prior to expansion. A zero-degree beamline conveys the beam to the beam stop, and an achromatic bend conveys the beam to the tritium production target. Nonlinear beam expanders make use of hi… more

Date: August 1, 1997

Creator: Shafer, R. E.; Blind, B. & Gray, E. R.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Photocathodes in accelerator applications

Some electron accelerator applications require bursts of short pulses at high microscopic repetition rates and high peak brightness. A photocathode, illuminated by a mode-locked laser, is well suited to filling this need. The intrinsic brightness of a photoemitter beam is high; experiments are under way at Los Alamos to study the brightness of short bunches with high space charge after acceleration. A laser-illuminated Cs/sub 3/Sb photoemitter is located in the first rf cavity of an injector li… more

Date: January 1, 1987

Creator: Fraser, J.S.; Sheffield, R.L.; Gray, E.R.; Giles, P.M.; Springer, R.W. & Loebs, V.A.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Preparation and properties of Y-124 superconductor made by a chemical precipitation method

We have prepared the thermodynamically stable YBCO-124 high temperature superconductor in powder form by a chemical precipitation method and have characterized the material by a number of chemical and physical methods, including carbon content, x-ray diffraction, thermogravimetry, scanning electron microscopy, surface area, thermally stimulated luminescence, and the superconducting transition and magnetization curves. We have also started to consolidate the powders by hot pressing. 21 refs., 6 … more

Date: January 1, 1990

Creator: Laquer, H. L. (CryoPower Associates, Los Alamos, NM (USA)); Gaines, J. R., Jr.; Brainard, S.; Hutson, S. D.; Pisanelli, J. (Superconductive Components, Inc., Columbus, OH (USA)); Cooke, D. W. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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A radio-frequency quadrupole accelerator longitudinal field stabilizer

The fields in a 600-MHz model of a radio-frequency quadrupole (RFQ) accelerator have been longitudinally stabilized over 86% of its length. The stabilizing elements consist of four external transverse electromagnetic (TEM) lines. Each line is coupled to the RFQ by two magnetic loops attached to voltage maxima of the TEM line. These resonant lines stabilize the RFQ fields by providing an alternate longitudinal power flow path in the RFQ. Stabilization depends on the TEM line Q and the TEM line R… more

Date: January 1, 1988

Creator: Gray, E. R.; Spalek, G. & Shapiro, A.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Recent developments for high-intensity proton linacs

High-intensity proton linacs are being proposed for new projects around the world, especially for tritium production, and for pulsed spallation neutron sources. Typical requirements for these linacs include peak beam current of about 100 mA, and final energies of 1 GeV and higher, APT, a tritium production linac, requires cw operation to obtain sufficient average tritium production linac, requires cw operation to obtain sufficient average beam power, and H{sup +} ion sources appear capable of p… more

Date: April 1, 1996

Creator: Wangler, T. P.; Garnett, R. W.; Gray, E. R. & Nath, S.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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An rf-driven lasertron

An rf-driven lasertron has been built and is being tested. It is designed to produce over 1 MW of power at 1.3 GHz, with over 60% conversion efficiency between the beam's kinetic energy and microwaves. The design and experiment are discussed, and calculations are presented that show lasertrons can operate at frequencies up to 20 GHz. 3 refs., 5 figs.

Date: January 1, 1988

Creator: Tallerico, P. J.; Sheffield, R. L.; Cornelius, W. D.; Gray, E. R.; Wilson, M. T.; Nguyen, D. C. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Rf photoelectron gun experimental performance

Free-electron lasers require electrons beams of high peak brightness. In this paper, we describe the performance of a compact high-brightness electron source for driving short-wavelength free-electron lasers. The experiment uses a laser-illuminated photoemitter located in the first rf cavity of a two-cavity linac. The photocathode source and associated hardware are described. The doubled ND:YAG laser (532 nm), which is used to drive the photocathode, produces 75-ps micropulses at a 108-MHz repe… more

Date: January 1, 1988

Creator: Sheffield, R. L.; Cornelius, W. D.; Nguyen, D. C.; Springer, R. W.; Lamartine, B. C.; Gray, E. R. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

RF properties of high temperature superconductors: Cavity methods

A description of cavities used in the study of the microwave properties of the high-temperature superconductors is followed by a lumped-circuit analysis of the coupling of transmission lines and resonators. The frequency dependence of the reflected and transmitted microwave power and the character of transient cavity response are analyzed. Techniques are discussed for the introduction of samples of the high-temperature superconductors into microwave cavities. Following a discussion of sample su… more

Date: January 1, 1990

Creator: Portis, A.M. (California Univ., Berkeley, CA (USA)); Cooke, D.W. & Gray, E.R. (Los Alamos National Lab., NM (USA))

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Rf superconductivity research and development at Los Alamos National Laboratory

Los Alamos National Laboratory is engaged in two distinct areas of rf superconductivity research and development. One program is devoted to studying the rf properties of high-temperature superconductors (HTS) and assessing their potential for accelerator-cavity applications. Our best results to date have come from YBa{sub 2}Cu{sub 3}O{sub 7} films (0.8 {mu}m) electron-beam deposited onto LaGaO{sub 3} substrates. A typical surface resistance value is 0.2 {plus minus} 0.1 m{Omega} measured at 22 … more

Date: January 1, 1989

Creator: Cooke, D. W.; Gray, E. R.; Houlton, R. J.; Lawrence, G. P.; McGill, J. A.; Meyer, E. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Simulated performance of the superconducting section of the APT linac under various fault and error conditions

The current design for the production of tritium uses both normal-conducting (NC) and superconducting (SC) structures. To evaluate the performance of the superconducting part of the linac which constitutes more than 80% of the accelerator, studies have been made to include the effects of various error and fault conditions. Here, the authors present the simulation results of studies such as effects of rf phase and amplitude errors, cavity/klystron failure, quadrupole misalignment errors, quadrup… more

Date: August 1, 1997

Creator: Gray, E. R.; Nath, S. & Wangler, T. P.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Simulation studies of the LAMPF proton linac

The LAMPF accelerator consists of two 0.75-MeV injectors, one for H{sup +} and the other for H{sup {minus}}, a separate low-energy beam transport (LEBT) line for each beam species, a 0.75 to 100-MeV drift-tube linac (DTL) operating at 201.25-MHz, a 100-MeV transition region (TR), and a 100 to 800-MeV side-coupled linac (SCL) operating at 805-MHz. Each LEBT line consists of a series of quadrupoles to transport and transversely match the beam. The LEBT also contains a prebuncher, a main buncher, … more

Date: May 1, 1995

Creator: Garnett, R. W.; Gray, E. R.; Rybarcyk, L. J. & Wangler, T. P.

Item Type: Article

Partner: UNT Libraries Government Documents Department