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Further improvements on TRACE 3-D

Description: TRACE 3-D, an interactive beam-dynamics program that calculates the envelopes of a bunched beam (including linear space-charge forces) through a user-defined transport system, has undergone several upgrades in physics, coding, and capabilities. Recent modifications include centroid tracking (and misalignment capabilities) and an improved beam description that allows study of some nonlinear effects such as wakefields. The Fortran code has been made portable and runs on numerous platforms. It can be used with a variety of graphics packages. The additional beamline elements, new commands, expanded fitting capabilities, improved beam description, and coding modifications have extended TRACE 3-D`s usefulness and applicability to the accelerator community. These changes are documented in the third edition of TRACE 3-D Documentation.
Date: August 1, 1997
Creator: Rusthoi, D.P.; Lysenko, W.P. & Crandall, K.R.
Partner: UNT Libraries Government Documents Department

New high power linacs and beam physics

Description: 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 results. Consequently, the authors compare predictions from the particle-core halo models with computer simulations to test their understanding of the halo mechanisms that are incorporated in the computer codes. They present and discuss scaling laws that provide guidance for high-power linac design.
Date: August 1, 1997
Creator: Wangler, T.P.; Gray, E.R.; Nath, S.; Crandall, K.R. & Hasegawa, K.
Partner: UNT Libraries Government Documents Department

Room-temperature LINAC structures for the spallation neutron source

Description: Los Alamos National Laboratory is building room-temperature rf accelerating structures for the Spallation Neutron Source (SNS). These structures, for H{sup -} ions, consist of six 402.5-MHz, 2-MW drift-tube linac (DTL) tanks from 2.5 to 87 MeV followed by four 805-MHz, 4-MW coupled-cavity linac (CCL) modules to 186 MeV. The DTL uses permanent magnet quadrupoles inside the drift tubes arranged in a 6{beta}{lambda} FFODDO lattice with every third drift tube available for diagnostics and steering. The CCL uses a 13{beta}{lambda} FODO electromagnetic quadrupole lattice. Diagnostics and magnets occupy the 2.5{beta}{lambda} spaces between 8-cavity segments. This paper discusses design of the rf cavities and low-power modeling work.
Date: April 1, 2001
Creator: Billen, J. H. (James H.); Young, L. M. (Lloyd M.); Kurennoy, S. (Sergey) & Crandall, K. R. (Kenneth R.)
Partner: UNT Libraries Government Documents Department

Development of a commissioning plan for the APT linac

Description: 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.
Partner: UNT Libraries Government Documents Department

Alignment and steering scenarios for the APT linac

Description: 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 field, and rf phase and amplitude errors in the linac. This paper reviews the effects of quadrupole misalignments and present two steering algorithms that minimize the potential for particle loss from the beam halo. These algorithms were tested on the 8-to-20 MeV portion of the APT linac.
Date: September 1, 1996
Creator: Stovall, J.E.; Gray, E.R.; Nath, S.; Takeda, H.; Wood, R.L.; Young, L.M. et al.
Partner: UNT Libraries Government Documents Department

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

Description: 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 aimed at minimizing beam halo and providing large apertures to reduce beam loss to a very low value.
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.
Partner: UNT Libraries Government Documents Department

Beam Loss Studies for Rare Isotope Driver Linacs Final Report

Description: The Fortran 90 RIAPMTQ/IMPACT code package is a pair of linked beam-dynamics simulation codes that have been developed for end-to-end computer simulations of multiple-charge-state heavy-ion linacs for future exotic-beam facilities. These codes have multiple charge-state capability, and include space-charge forces. The simulations can extend from the low-energy beam-transport line after an ECR ion source to the end of the linac. The work has been performed by a collaboration including LANL, LBNL, ANL, and MSU. The code RIAPMTQ simulates the linac front-end beam dynamics including the LEBT, RFQ, and MEBT. The code IMPACT simulates the beam dynamics of the main superconducting linac. The codes have been benchmarked for rms beam properties against previously existing codes at ANL and MSU. The codes allow high-statistics runs on parallel supercomputing platforms, particularly at NERSC at LBNL, for studies of beam losses. The codes also run on desktop PC computers for low-statistics work. The code package is described in more detail in a recent publication [1] in the Proceedings of PAC07 (2007 US Particle Accelerator Conference). In this report we describe the main activities for the FY07 beam-loss studies project using this code package.
Date: March 26, 2008
Creator: Wangler, T P; Kurennoy, S S; Billen, J H; Crandall, K R; Qiang, J; Ryne, R D et al.
Partner: UNT Libraries Government Documents Department

Beam halo in mismatched proton beams.

Description: Progress was made during the past decade towards a better understanding of halo formation caused by beam mismatch in high-intensity beams. To test these ideas an experiment was carried out at Los Alamos with proton beams in a 52-quadrupole focusing channel. Rms emittances and beam widths were obtained from measured beam profiles for comparison with the maximum emittance growth predictions of a free-energy model and the maximum haloamplitude predictions of a particle-core model. The experimental results are also compared with multiparticle simulations. In this paper we will present the experimental results and discuss the implications with respect to the validity of both the models and the simulations. Keywords: beam halo, emittance growth, beam profiles, simulations, space charge, mismatch
Date: January 1, 2002
Creator: Wangler, Thomas P.,; Allen, C. K. (Christopher K.); Chan, D. (Dominic); Colestock, P. L. (Patrick L.),; Crandall, K. R. (Kenneth R.); Qiang, J. (Ji) et al.
Partner: UNT Libraries Government Documents Department

Experimental study of proton beam halo in mismatched beams

Description: We report measurements of transverse beam-halo formation in mismatched proton beams in a 52-quadrupole FODO-transport channel following the 6.7 MeV RFQ at the Low-Energy Demonstration Accelerator (LEDA) at Los Alamos. Beam profiles in both transverse planes were measured using a new diagnostic device that consists of a movable carbon filament for measurement of the beam core, and scraper plates for measurement of the outer part of the distributions. The initial results indicate a surprisingly strong growth rate of the rms emittance even for the modest space-charge tune depressions of the experiment. Our results are consistent with the complete transfer of free energy of the mismatched beams into emittance growth within 10 envelope oscillations for both the breathing and the quadrupole modes.
Date: January 1, 2002
Creator: Allen, C. K. (Christopher K.); Chan, K. D. (Kwok-Chi D.); Colestock, P. L. (Patrick L.),; Garnett, R. W. (Robert W.); Gilpatrick, J. D. (John Douglas); Qiang, J. (Ji) et al.
Partner: UNT Libraries Government Documents Department

EXPERIMENTAL STUDY OF PROTON-BEAM HALO INDUCED BY BEAM MISMATCH IN LEDA.

Description: We report measurements of transverse beam halo in mismatched proton beams in a 52-quadrupole FODO transport channel following the 6.7-MeV LEDA RFQ. Beam profiles in both transverse planes are measured using beam-profile diagnostic devices that consist of a movable carbon filament for measurement of the dense beam core, and scraper plates for measurement of the halo. The gradients of the first four quadrupoles can be independently adjusted to mismatch the RFQ output beam into the beam-transport channel. The properties of the measured mismatched beam profiles in the transport channel will be compared with predictions from multiparticle beam-dynamics simulations.
Date: January 1, 2001
Creator: Wangler, Thomas P.,; Allen, C. K. (Christopher K.); Colestock, P. L. (Patrick L.),; Chan, K. D. (Kwok-Chi D.); Crandall, K. R. (Kenneth R.); Garnett, R. W. (Robert W.) et al.
Partner: UNT Libraries Government Documents Department

Characterization of the proton beam at the output of the 6.7MeV LEDA RFQ.

Description: The present configuration of the Low-Energy Demonstration Accelerator (LEDA) consists of a 75-keV proton injector, a 6.7-MeV 350-MHz cw radio-frequency quadrupole (RFQ) with associated high-power and lowlevel rf systems, a 52-magnet periodic lattice followed by a short high-energy beam transport (HEBT) and highpower (670-kW cw) beam stop. The rms beam emittance was measured prior to the installation of the 52-magnet lattice, based on wire-scanner measurements of the beam profile at a single location in the HEBT. New measurements with additional diagnostic hardware have been performed to determine the rms transverse beam properties of the beam at the output of the 6.7-MeV LEDA RFQ. The 52-magnet periodic lattice also includes ten beam position monitors (BPMs) evenly spaced in pairs of two. The BPMs provide a measure of the bunched beam current that exhibits nulls at different locations in the lattice. Model predictions of the locations of the nulls and the strength of the bunched beam current are made to determine what information this data can provide regarding the longitudinal beam emittance.
Date: January 1, 2001
Creator: Allen, C. K. (Christopher K.); Colestock, P. L. (Patrick L.),; Gilpatrick, J. D. (John Douglas); Lysenko, W. P. (Walter P.); Rybarcyk, L. J. (Lawrence J.); Schneider, J. D. (J. David) et al.
Partner: UNT Libraries Government Documents Department