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Beam matching and halo control

Description: We present an overview of the status of ongoing work on physics models describing beam matching and halo control for particle accelerators, particularly high power ion linacs. We consider moments and various new variables that more naturally describe beam halo evolution. We compute matched beams and ``mode invariants`` (analogs of moment invariants) using primarily symbolic techniques.
Date: September 1, 1997
Creator: Lysenko, W. & Parsa, Z.
Partner: UNT Libraries Government Documents Department

Beam profile analysis for the C{ampersand}MS B231 electron beam welding machines

Description: The electron beams produced by two different welders were examined using computer assisted tomographic (CT) analysis. The machines used are Hamilton Standard welders with 150 kV/50mA maximum. One machine uses a ribbon filament while the other uses a hairpin filament. The objective of this study was to characterize the beam power distribution on each machine to see if weld parameters could easily be transferred between machines. Beam focus, voltage, and current settings were pre-selected to duplicate the welding conditions used in LLNL program applications. The results show that the actual beam currents measured by Faraday cup are 5 to 10% higher for the first machine and 30% lower for the second. The CT analysis of the beam shapes shows that the hairpin filament welder produces an elliptical beam shape in the sharp focus condition that defocuses to a diamond shape. The ribbon filament welder produced less of an elliptical beam shape in the sharp focus condition, but when defocused, acquires an elliptical shape. CT analysis of the effects of defocus on the peak power density shows that the hairpin filament drops in peak power density much more quickly than the ribbon filament for a given amount of defocus. Furthermore, it was more difficult to find and repeat the sharp focus condition for the hairpin filament, particularly at higher beam currents.
Date: June 12, 1997
Creator: Elmer, J. W.; Teruya, A.T. & Gauthier, M.
Partner: UNT Libraries Government Documents Department

Electron Bunch Length Diagnostic With Coherent Smith-Purcell Radiation

Description: The authors have designed a new technique for measuring subpicosecond electron bunch lengths using coherent Smith-Purcell radiation. This new diagnostic technique involves passing the electron beam in close proximity of a grating with a period comparable to the electron bunch length. The emitted Smith-Purcell radiation will have a coherent component whose angular position and distribution are directly related to the electron bunch length and longitudinal profile, respectively. This new diagnostic technique is inherently simple, inexpensive and non-intercepting. The authors show that the new technique is also scaleable to femtosecond regime.
Date: May 12, 1997
Creator: Nguyen, D.C.
Partner: UNT Libraries Government Documents Department

Optical diagnostics on ETA-II for x-ray spot size

Description: Improvements have been made in the performance of the ETA-II accelerator that allow a nominal 2 kA, 6 MeV beam to be focused to a spot size less that 1 mm in diameter. The improvements include reducing the energy sweep to less than +/- 0.5 & over 40 ns of the pulse using a real time energy diagnostic and improving the magnetic tune of the accelerator to reduce the emittance to 8 cm-mrad. Finally, an automated tuning system (MAESTRO) was run to minimize the time dependent centroid motion (corkscrew) by adjusting the steering dipoles over the focusing solenoids. The corkscrew motion was reduced to less than +/- 0.5 mm at the output of the accelerator.
Date: March 22, 1999
Creator: Richardson, R A
Partner: UNT Libraries Government Documents Department

Transverse Beam Profile Measurement Using Scrape Scans

Description: A scraper scan - sending a scraper through a particle beam while measuring the intensity as a function of scraper position - is a common method of determining the profile of the beam. At first glance, this seems to be a rather simple procedure. Nevertheless, some care is required in the acquisition of the data and in the analysis if one is going to achieve an accurate result.
Date: September 13, 2001
Creator: Werkema, Steven J.
Partner: UNT Libraries Government Documents Department

DML and Foil Measurements of ETA Beam Radius

Description: Simultaneous measurements of the ETA beam radius have been made with a quartz foil and a diamagnetic loop (DML). While the measurements agreed at some settings they diverged at others. While the DML measures the rms radius of the total beam, the foil measures mainly the core and the divergence can be explained by the presence of a low density halo. Evidence of such a halo from other measurements is presented.
Date: May 11, 2005
Creator: Nexsen, W & Weir, J
Partner: UNT Libraries Government Documents Department


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

Results from Vernier scans during the RHIC 2008 PP Run

Description: Using the vernier scan or Van der Meer scan technique, where one beam is swept stepwise across the other while measuring the collision rate as a function of beam displacement, the transverse beam profiles, the luminosity and the effective cross section of the detector in question can be measured. This report briefly recalls the vernier scan method and presents results from the 100 GeV 2008 RHIC polarized proton (pp) run.
Date: May 4, 2009
Creator: Drees,A. & D Ottavio, T.
Partner: UNT Libraries Government Documents Department

XUV radiography measurements of direct drive imprint in thin aluminum foils using a Ge x-ray laser on Vulcan

Description: One key aspect for high gain direct drive inertial confinement fusion is the imprint of perturbations in the outer surface of a capsule due to nonuniformities in the direct laser illumination of the capsule. Direct drive implosions are achieved by uniformly irradiating the outside surface of a hollow spherical capsule that contains a layer of fusionable D-T on its inner surface. The intensity of laser irradiation is down with a low intensity ``foot`` at 10{sup 13} W/cm{sup 2} for several nanoseconds before it builds up to more than 10{sup 15} W/cm{sup 2} during the main drive portion of the pulse. Laser ablation of the capsule surface produces a high pressure that accelerates the capsule shell radially inward in a spherical implosion. During this acceleration, perturbations due to surface roughness and due to imprint from spatial nonuniformities in the laser irradiation undergo Rayleigh-Taylor growth, potentially severely degrading performance. Our interest is in studying the imprint process and subsequent Rayleigh-Taylor growth of perturbations in a foil target that is irradiated by a low intensity laser speckle pattern. Previous experiments have been done to study laser imprint with an x-ray laser backlighter at the Nova laser using 0.35 micrometer laser irradiation of a 3 micrometer Si foil. In these experiments we irradiated a 2 micrometer thick Al foil with 0.53 micrometer laser light at 2-8 {times} 10{sup 12} W/cm{sup 2} using the Vulcan laser. We used a Ge x-ray laser as an XUV backlighter to measure the modulation in optical depth of the foil on a CCD during the initial imprint phase and after Rayleigh-Taylor growth with different laser smoothing schemes. 4 refs., 6 figs.
Date: March 29, 1996
Creator: Kalantar, D.H.; Demir, A. & Key, M.H.
Partner: UNT Libraries Government Documents Department

Measurement of sub-picosecond bunch profiles using coherent transition radiation

Description: A technique for measuring the longitudinal profile of sub-picosecond electron bunches based on autocorrelation of coherent transition radiation is reviewed. The technique uses sub-millimeter/far-infrared Michelson interferometry to obtain the autocorrelation of transition radiation emitted from a thin conducting foil placed in the beam path. The theory of coherent radiation from a charged particle beam passing through a thin conducting foil is presented for normal and oblique incidence. Michelson interferometric analysis of this radiation is shown to provide the autocorrelation of longitudinal bunch profile. The details of a noninvasive technique for measuring longitudinal bunch profile using coherent diffraction radiation are discussed.
Date: May 1, 1996
Creator: Barry, W.
Partner: UNT Libraries Government Documents Department

A scanning target profile monitor for the slow extracted beam at the AGS

Description: The purpose of this new instrument is for probing beam halo and obtaining beam profiles of the resonant extracted beam at the AGS. The device described here is a prototype version, to obtain data and prepare for a more permanent device. The goals of the permanent device are to allow emittances of low current, but high intensity slowly extracted beams to be accurately measured and to have a diagnostic for probing the wings of the beam distribution. The device works on secondary emission from thin targets as well as scattering into two scintillator telescopes. The targets are movable over the entire aperture at the device. The performance of this new device has exceeded expectations. The authors were very concerned about singles rates in the area, since the telescopes were located inside the beam enclosure and had effectively no shielding. The singles rates were not insignificant, as high as 1 MHz, but the triple coincidence circuitry had no problems contending with these rates.
Date: July 1, 1997
Creator: Brown, K.A.; Chiang, I.H. & Gassner, D.
Partner: UNT Libraries Government Documents Department

A multi-wire beam profile monitor in the AGS

Description: A multi-wire beam profile monitor which can be used to directly monitor and control the optical matching between the Booster and AGS rings has been installed and tested in the AGS. Placement of a multi-wire monitor directly in the AGS provides profile measurements taken upon injection and the first two or more revolutions of the beam. The data from such measurements can be used to determine the optical properties of the beam transport line leading into the AGS.
Date: July 1, 1997
Creator: Huang, H.; Buxton, W.; Castillo, V. & Glenn, J.W.
Partner: UNT Libraries Government Documents Department

Longitudinal potential well distortion due to the synchrotron radiation wakefield

Description: The effect of the synchrotron radiation free space wakefield on the equilibrium bunch length in an electron storage ring is explored. The equilibrium bunch length, which is obtained numerically, is shown to increase for {alpha}<O and decrease for {alpha}>O.
Date: December 1, 1996
Creator: Bane, K.; Krinsky, S. & Murphy, J.B.
Partner: UNT Libraries Government Documents Department

Design and development of the LEDA slow wire scanner profile measurement

Description: The Low Energy Demonstration Accelerator (LEDA) is being developed at Los Alamos National Laboratory as part of the Accelerator Production of Tritium (APT) project. One of the diagnostics being developed to commission LEDSA is a slow wire scanner beam profile measurement. Initial profile measurements will be made at 6.7 MeV beam energy and 100 mA beam current. The wire scanner is an interceptive device that will move two silicon carbide coated graphite mono-filament fibers (wires) through the beam, in order to obtain the profile. Some of the design considerations discussed are: Mechanical design, wire temperature analysis, secondary electron detection, signal processing, and system control.
Date: December 1998
Creator: O`Hara, J. F.; Power, J. F.; Ledford, J.; Gilpatrick, J. D.; Stettler, M. & Sage, J.
Partner: UNT Libraries Government Documents Department

Particle beams with uniform transverse distribution

Description: A successfully tested method is described which achieves a more uniform illumination of an extended flat target by the charged particle beam from an accelerator, by proper use of a combination of quadrupole and octupole magneto-optical elements.
Date: October 1, 1996
Creator: Tsoupas, N.; Zucker, M.S.; Snead, C.L. & Ward, T.E.
Partner: UNT Libraries Government Documents Department

1996 Design effort for IFMIF HEBT

Description: The paper details the 1996 design effort for the IFMIF HEBT. Following a brief overview, it lists the primary requirements for the beam at the target, describes the design approach and design tools used, introduces the beamline modules, gives the results achieved with the design at this stage, points out possible improvements and gives the names and computer locations of the TRACE3-D and PARMILA files that sum up the design work. The design does not fully meet specifications in regards to the flatness of the distribution at the target. With further work, including if necessary some backup options, the flatness specifications may be realized. It is not proposed that the specifications, namely flatness to {+-}5% and higher-intensity ridges that are no more than 15% above average, be changed at this time. The design also does not meet the requirement that the modules of all beamlines should operate at the same settings. However, the goal of using identical components and operational procedures has been met and only minor returning is needed to produce very similar beam distributions from all beamlines. Significant further work is required in the following areas: TRACE3-D designs and PARMILA runs must be made for the beams coming from accelerators No. 3 and No. 4. Transport of 30-MeV and 35-MeV beams to the targets and beam dump must be studied. Comprehensive error studies must be made. These must result in tolerance specifications and may require design iterations. Detailed interfacing with target-spot instrumentation is required. This instrumentation must be able to check all aspects of the specifications.
Date: January 1, 1997
Creator: Blind, B.
Partner: UNT Libraries Government Documents Department

Techniques for intense-proton-beam profile measurements

Description: In a collaborative effort with industry and several national laboratories, the Accelerator Production of Tritium (APT) facility and the Spallation Neutron Source (SNS) linac are presently being designed and developed at Los Alamos National Laboratory (LANL). The APT facility is planned to accelerate a 100-mA H{sup +} cw beam to 1.7 GeV and the SNS linac is planned to accelerate a 1- to 4-mA-average, H{sup {minus}}, pulsed-beam to 1 GeV. With typical rms beam widths of 1- to 3-mm throughout much of these accelerators, the maximum average-power densities of these beams are expected to be approximately 30- and 1-MW-per-square millimeter, respectively. Such power densities are too large to use standard interceptive techniques typically used for acquisition of beam profile information. This paper summarizes the specific requirements for the beam profile measurements to be used in the APT, SNS, and the Low Energy Development Accelerator (LEDA)--a facility to verify the operation of the first 20-MeV section of APT. This paper also discusses the variety of profile measurement choices discussed at a recent high-average-current beam profile workshop held in Santa Fe, NM, and will present the present state of the design for the beam profile measurements planned for APT, SNS, and LEDA.
Date: December 31, 1998
Creator: Gilpatrick, J.D.
Partner: UNT Libraries Government Documents Department