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Bench test of a residual gas ionization profile monitor (RGIPM)

Description: An RGIPM has been designed1, constructed and bench tested to verify that all components are functioning properly and that the desired resolution of about 50 {micro}m rms can be achieved. This paper will describe major considerations that went into the bench test and some results.
Date: January 1, 2001
Creator: Sellyey, W. C. (William C.); Gilpatrick, J. D. (John Douglas) & Senior, R. (Ralph)
Partner: UNT Libraries Government Documents Department

ANALOG FRONT-END ELECTRONICS FOR BEAM POSITION MEASUREMENT ON THE BEAM HALO MEASUREMENT

Description: Enhancements have been made to the log-ratio analog front-end electronics based on the Analog Devices 8307 logarithmic amplifier as used on the LEDA accelerator. The dynamic range of greater than 85 dB, has been extended to nearly the full capability of the AD8307 from the previous design of approximately 65 dB through the addition of a 350 MHz band-pass filter, careful use of ground and power plane placement, signal routing, and power supply bypassing. Additionally, selection of high-isolation RF switches (55dB) has been an integral part of a new calibration technique, which is fully described in another paper submitted to this conference. Provision has also been made for insertion of a first-stage low-noise amplifier for using the circuit under low-signal conditions.
Date: January 1, 2001
Creator: Shurter, R. B. (Robert B.); Cote, T. J. (Thomas J.) & Gilpatrick, J. D. (John Douglas)
Partner: UNT Libraries Government Documents Department

Characterizing proton beam of 6.7 MeV LEDA RFQ by fitting HEBT wire-scanner profiles to improved model.

Description: Quadrupole scans in the HEBT of the 6.7 MeV LEDA RFQ were analyzed to characterize the transverse phase space at the RFQ exit. In previous work, the profiles measured by the wire scanner were fit to various models (HEBT simulations from the RFQ exit to the wire scanner) in an effort to determine the transverse Courant-Snyder parameters (a, p, and t) at the RFQ exit. Unfortunately, at the larger quadrupole settings, the measured profiles showed features that were not present in the simulations. This made good fits impossible. Here we describe our latest analysis, which resulted in very good fits by using an improved model for the beam at the RFQ exit. The model beam was generated by the RFQ simulation code TOUTATIS. In the fitting code, this beam was distorted by linear transformations that changed the Courant-Snyder parameters to whatever values were required by the nonlinear optimizer while preserving the high-order features of the phase-space distribution. This present success indicates that there has not been any missing physics in the codes, which gives us increased confidence in our accelerator designs. In addition, we have learned that details in the RFQ beam can make a significant difference in observed behavior downstream of the RFQ.
Date: January 1, 2002
Creator: Lysenko, W. P. (Walter P.); Gilpatrick, J. D. (John Douglas); Qiang, J. (Ji); Ryne, Robert; Rybarcyk, L. J. (Lawrence J.); Schneider, J. D. (J. David) et al.
Partner: UNT Libraries Government Documents Department

Position measurements for the isotope production facility and the switchyard kicker upgrade projects

Description: The Los Alamos Neutron Science Center (LANSCE) is installing two beam lines to both improve operational tuning and provide new capabilities within the facility. The Isotope Production Facility (IPF) will provide isotopes for medical purposes by using the H' beam spur at 100 MeV and the Switchyard Kicker Upgrade (SYK) will allow the LANSCE 800-MeV H beam to be rapidly switched between various beam lines within the facility. The beam position measurements for both of these beam lines uses a standard micro-stripline beam position monitor (BPM) with both a 50-mm and 75-mm radius. The cable plant is unique in that it unambiguously provides a method of verifying the operation of the complete position measurement. The processing electronics module uses a log ratio technique with error corrections such that it has a dynamic range of -12 dBm to -85 dBm with errors less than 0.15 dB within this range. This paper will describe the primary components of these measurement systems and provide initial data of their operation.
Date: January 1, 2003
Creator: Gilpatrick, J. D. (John Douglas); Barr, D. S. (Dean S.); O'Hara, J. F. (James F.); Shurter, R. B. (Robert B.); Stettler, M. W. (Matthew W.) & Martinez, D. G. (Derwin G.)
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

BEAM-PROFILE INSTRUMENTATION FOR BEAM-HALO MEASUREMENT : OVERALL DESCRIPTION AND OPERATION

Description: Within the halo experiment presently being conducted at the Low Energy Demonstration Accelerator at Los Alamos National Laboratory, specific beam instruments that acquire horizontally and vertically projected particle-density distributions out to greater than 10{sup 5}:1 dynamic range are located throught the 52-magnet halo lattice.
Date: January 1, 2001
Creator: Gilpatrick, J. D. (John Douglas); Barr, D. S. (Dean S.); Day, L. A. (Lisa A.); Kerstiens, D. M. (Debora M.); Stettler, M. W. (Matthew W.); Valdiviez, R. (Robert) et al.
Partner: UNT Libraries Government Documents Department

BEAM-PROFILE INSTRUMENTATION FOR BEAM-HALO MEASUREMENT : OVERALL DESCRIPTION, OPERATION, AND BEAM DATA.

Description: The halo experiment presently being conducted at the Low Energy Demonstration Accelerator (LEDA) at Los Alamos National Laboratory (LANL) has specific instruments that acquire horizontally and vertically projected particle-density beam distributions out to greater than 10{sup 5}:1 dynamic range. They measure the core of the distributions using traditional wire scanners, and the tails of the distribution using water-cooled graphite scraping devices. The wire scanner and halo scrapers are mounted on the same moving frame whose location is controlled with stepper motors. A sequence within the Experimental Physics and Industrial Control System (EPICS) software communicates with a National Instrument LabVIEW virtual instrument to control the motion and location of the scanner/scraper assembly. Secondary electrons from the wire scanner 0.03-mm carbon wire and protons impinging on the scraper are both detected with a lossy-integrator electronic circuit. Algorithms implemented within EPICS and in Research Systems Interactive Data Langugage (IDL) subroutines analyse and plot the acquired distributions. This paper describes this beam profile instrument, describes their experience with its operation, compares acquired profile data with simulations, and discusses various beam profile phenomena specific to the halo experiment.
Date: January 1, 2001
Creator: Gilpatrick, J. D. (John Douglas); Barr, D. S. (Dean S.); Day, L. A. (Lisa A.); Stettler, M. W. (Matthew W.); Valdiviez, R. (Robert); Gruchalla, M. (Michael) et al.
Partner: UNT Libraries Government Documents Department

An experimental study of microwave stability near transition in the PSR

Description: We have undertaken a study of microwave stability in the PSR storage ring under a variety of beam conditions near transition, including variable intensity and machine impedance, which can be independently controlled in the PSR. Results indicate that the general features of a linear stability model are valid, namely that the instability threshold becomes very small sufficiently close to transition. In addition, many nonlinear features are apparent and the results suggest an extended operating regime is possible with saturated, but otherwise benign, longitudinal fluctuations. Details of the linear model experimental results and corresponding simulations will be presented.
Date: January 1, 2003
Creator: Colestock, P. L. (Patrick L.),; Beltran, C. (Chris); Browman, A. A. (Andrew A.); Gilpatrick, J. D. (John Douglas); Macek, R. J. (Robert J.); McCrady, R. C. (Rodney C.) et al.
Partner: UNT Libraries Government Documents Department

EXPERIENCE WITH THE LOW ENERGY DEMONSTRATION ACCELERATOR (LEDA) HALO EXPERIMENT BEAM INSTRUMENTATION

Description: A 52 quadrupole-magnet FODO lattice has been assembled and operated at the Los Alamos National Laboratory. The purpose of this lattice is to provide a platform to measure the resulting beam halo as the first few magnets of the lattice produce various mismatch conditions. These data are then compared with particle simulation so that halo formation mechanisms may be better understood. The lattice is appended to the LEDA 6.7-MeV radio frequency quadrupole (RFQ) and is followed by a short high-energy beam transport (HEBT) that safely dumps the beam into a 670-kW beam stop.
Date: January 1, 2001
Creator: Gilpatrick, J. D. (John Douglas); Barr, D. S. (Dean S.); Colestock, P. L. (Patrick L.),; Day, L. A. (Lisa A.); Sellyey, W. C. (William C.); Shurter, R. B. (Robert B.) et al.
Partner: UNT Libraries Government Documents Department

Final mechanical design, fabrication, and commissioning of a wire scanner and scraper assembly for halo-formation measurements in a proton beam

Description: The 6.7 MeV, 100 mA proton beam being produced in the Low Energy Demonstration Accelerator (LEDA) RFQ is being injected into a 52 magnet lattice in order to study the charged-beam phenomenon known as beam halo [1]. Quadrupole magnets in the lattice are purposely mismatched to cause or amplify halo formation in the beam. Interceptive diagnostics that consist of a thin wire and a paddle type device called a scraper are placed in the beam to obtain charge-distribution data. The charge-distribution data is used to create a current-density distribution plot of the beam at the probed location [2]. This paper describes the mechanical design, fabrication, and commissioning of the interceptive diagnostic devices and the assembly that carries them.
Date: April 1, 2001
Creator: Valdiviez, R. (Robert); Martinez, F. A. (Felix A.); Rendon, Armando M.; Wright, T. O. (Tony O.); Ledford, J. E. (John E.); Patterson, N. K. (Norman K.) et al.
Partner: UNT Libraries Government Documents Department

High order beam features and fitting quadrupole scan data to particle code model.

Description: Quadrupole scans in the HEBT of the 6.7 MeV LEDA RFQ were analyzed to characterize the RFQ output beam. In previous work, profiles measured by the wire scanner were fit to models (beam parameterizations and HEBT simulations) to determine the transverse Courant-Snyder parameters {alpha}, {beta}, and {epsilon} at the RFQ exit. Unfortunately, at the larger quadrupole settings, the measured profiles showed features that were not present in any of our simulations. Here we describe our latest analysis, which resulted in very good fits by using an improved model for the RFQ output beam. The model beam was generated by the RFQ simulation code TOUTATIS. In our fitting code, this beam was distorted by linear transformations that changed the Courant-Snyder parameters to whatever values were required by the nonlinear optimizer while preserving the high-order features of the phase-space distribution. No new physics in the HEBT was required to explain our quad-scan results, just an improved initial beam. High-order features in the RFQ output beam apparently make a significant difference in behavior downstream of the RFQ. While this result gives us increased confidence in our codes, we still have a mystery: exactly what high-order features in the beam are responsible for the the strange behavior downstream. Understanding this phenomenon may be helpful to understanding our halo-experiment data. We have begun to study this by comparing higher-order moments of the TOUTATIS distribution with other distributions.
Date: January 1, 2003
Creator: Lysenko, W. P. (Walter P.); Garnett, R. W. (Robert W.); Gilpatrick, J. D. (John Douglas); Qiang, J. (Ji); Rybarcyk, L. J. (Lawrence J.); Ryne, Robert 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