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Beam emittance measurements at Fermilab

Description: We give short overview of various beam emittance measurement methods, currently applied at different machine locations for the Run II collider physics program at Fermilab. All these methods are based on beam profile measurements, and we give some examples of the related instrumentation techniques. At the end we introduce a multi-megawatt proton source project, currently under investigation at Fermilab, with respect to the beam instrumentation challenges.
Date: January 1, 2008
Creator: Wendt, Manfred; Eddy, Nathan; Hu, Martin; Scarpine, Victor; Syphers, Mike; Tassotto, Gianni et al.
Partner: UNT Libraries Government Documents Department

An Experimentally Robust Technique for Halo Measurement

Description: We propose a model-independent quantity, L/G, to characterize non-Gaussian tails in beam profiles observed with the Fermilab Booster Ion Profile Monitor. This quantity can be considered a measure of beam halo in the Booster. We use beam dynamics and detector simulations to demonstrate that L/G is superior to kurtosis as an experimental measurement of beam halo when realistic beam shapes, detector effects and uncertainties are taken into account. We include the rationale and method of calculation for L/G in addition to results of the experimental studies in the Booster where we show that L/G is a useful halo discriminator.
Date: March 1, 2006
Creator: Amundson, J.; Pellico, W.; Spentzouris, P.; Sullivan, T. & Spentzouris, Linda
Partner: UNT Libraries Government Documents Department

Nanograting-based compact VUV spectrometer and beam profiler for in-situ characterization of high-order harmonic generation light sources

Description: A compact, versatile device for VUV beam characterization is presented. It combines the functionalities of a VUV spectrometer and a VUV beam profiler in one unit and is entirely supported by a standard DN200 CF flange. The spectrometer employs a silicon nitride transmission nanograting in combination with a micro-channel plate based imaging detector. This enables the simultaneous recording of wavelengths ranging from 10 nm to 80 nm with a resolution of 0.25 nm to 0.13 nm. Spatial beam profiles with diameters up to 10 mm are imaged with 0.1 mm resolution. The setup is equipped with an in-vacuum translation stage that allows for in situ switching between the spectrometer and beam profiler modes and for moving the setup out of the beam. The simple, robust design of the device is well suited for non-intrusive routine characterization of emerging laboratory- and accelerator-based VUV light sources. Operation of the device is demonstrated by characterizing the output of a femtosecond high-order harmonic generation light source.
Date: July 9, 2010
Creator: Kornilov, Oleg; Wilcox, Russell & Gessner, Oliver
Partner: UNT Libraries Government Documents Department

A Large L-Band Rectangular Corrugated Horn

Description: This paper describes a lightweight, corrugated-horn antenna, constructed from sheet metal. Over a 1.3-1.7 GHz operating band, its half-power beam width is approximately 20{sup o} in the E-plane and varies from 17{sup o} to 13{sup o} in the H-plane. Quarter-wave choke slots at the aperture help to reduce the E-plane sidelobes below -55 dB at angles greater than 90{sup o}, while the H-plane sidelobes lie in that range both with and without choke slots. Return loss throughout the operating band is -25 dB or below. Critical dimensions are provided, together with useful guidelines for designing similar antennas.
Date: January 1, 1987
Creator: Witebsky, C.; Smoot, G.F.; Levin, S. & Bensadoun, M.
Partner: UNT Libraries Government Documents Department

Quasi-3D space charge simulation

Description: The longitudinal space charge effect is simulated by binning the longitudinal beam profile in order to calculate the force on the bins using the binned particle distribution via FFT, and applying momentum kick based upon this space charge force to macro-particles. Usually, the longitudinal space charge kick is calculated once per turn since the longitudinal profile doesn't change much in a single turn. Besides, the longitudinal profile is used as a weighting factor for the transverse space charge force. The transverse space charge effect is simulated by projecting the 3-D beam to a 2-D Gaussian distribution in order to use the complex error function to compute the transverse space charge force, and applying this space charge force to macro-particles. One transverse space charge calculation per scale length of the beam shape variation requires at least ten transverse space charge force calculations per betatron oscillation.
Date: April 1, 2007
Creator: Yang, Xi
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

Disruption effects on the beam size measurement

Description: At the SLC Final Focus with higher currents and smaller beam sizes, the disruption parameter D{sub y} is close to one and so the pinch effect should produce a luminosity enhancement. Since a flat beam-beam function is fit to deflection scan data to measure the beam size, disruption can affect the measurement. Here the authors discuss the quantitative effects of disruption for typical SLC beam parameters. With 3.5 10{sup 10} particles per pulse, bunch length of 0.8 mm and beam sizes of 2.1 {mu}m horizontally and 0.55 {mu}m vertically, the measured vertical size can be as much as 25% bigger than the real one. Furthermore during the collision the spot size actually decrease, producing an enhancement factor H{sub D} of about 1.25. This would yield to a true luminosity which is 1.6 times that which is estimated from the beam-beam deflection fit.
Date: June 1, 1995
Creator: Raimondi, P.; Decker, F.J. & Chen, P.
Partner: UNT Libraries Government Documents Department

Simulation studies of the LAMPF proton linac

Description: 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, and an electrostatic deflector. The deflector is used to limit the fraction of a macropulse which is seen by the beam diagnostics throughout the linac. The DTL consists of four rf tanks and uses singlet FODO transverse focusing. The focusing period is doubled in the last two tanks by placing a quadrupole only in every other drift-tube. Doublet FDO transverse focusing is used in the SCL. The TR consists of separate transport lines for the H{sup +} and H{sup {minus}} beams. The pathlengths for the two beams differ, by introducing bends, so as to delay arrival of one beam relative to the other and thereby produce the desired macropulse time structure. Peak beam currents typically range from 12 to 18-mA for varying macropulse lengths which give an average beam current of 1-mA. The number of particles per bunch is of the order 10{sup 8}. The work presented here is an extension of previous work. The authors have attempted to do a more complete simulation by including modeling of the LEBT. No measurements of the longitudinal structure of the beam, except phase-scans, are performed at LAMPF. The authors show that, based on simulation results, the primary causes of beam spill are inefficient longitudinal capture and the lack of longitudinal matching. Measurements to support these claims are not presently made at LAMPF. ...
Date: May 1, 1995
Creator: Garnett, R.W.; Gray, E.R.; Rybarcyk, L.J. & Wangler, T.P.
Partner: UNT Libraries Government Documents Department

High power beam profile monitor with optical transition radiation

Description: A simple monitor has been built to measure the profile of the high power beam (800 kW) delivered by the CEBAF accelerator at Jefferson Lab. The monitor uses the optical part of the forward transition radiation emitted from a thin carbon foil. The small beam size to be measured, about 100 {mu}m, is challenging not only for the power density involved but also for the resolution the instrument must achieve. An important part of the beam instrumentation community believes the radiation being emitted into a cone of characteristic angle 1/{gamma} is originated from a region of transverse dimension roughly {lambda}{gamma}; thus the apparent size of the source of transition radiation would become very large for highly relativistic particles. This monitor measures 100 {mu}m beam sizes that are much smaller than the 3.2 mm {lambda}{gamma} limit; it confirms the statement of Rule and Fiorito that optical transition radiation can be used to image small beams at high energy. The present paper describes the instrument and its performance. The authors tested the foil in, up to 180 {mu}A of CW beam without causing noticeable beam loss, even at 800 MeV, the lowest CEBAF energy.
Date: June 1, 1997
Creator: Denard, J.C.; Piot, P.; Capek, K. & Feldl, E.
Partner: UNT Libraries Government Documents Department

Stability and halo formation in axisymmetric intense beams

Description: Beam stability and halo formation in high-intensity axisymmetric 2D beams in a uniform focusing channel are analyzed using particle-in-cell simulations. The tune depression-mismatch space is explored for the uniform (KV) distribution of the particle transverse-phase-space density, as well as for more realistic ones (in particular, the water-bag distribution), to determine the stability limits and halo parameters. The numerical results show an agreement with predictions of the analytical model for halo formation.
Date: October 1, 1997
Creator: Gluckstern, R.L. & Kurennoy, S.S.
Partner: UNT Libraries Government Documents Department


Description: In the Relativistic Heavy ion Collider (RHIC) much larger background signals were occurring at BRAMS, one of the four experiments. This was especially pronounced at the time when vacuum conditions deteriorated due to the beam ionization profile monitor replacements. Recording the beam intensities during the store provided the beam lifetime. Predictions from the beam gas interactions to the above measured values are compared The ionization gauges simultaneously recorded the vacuum pressure data.
Date: June 18, 2001
Partner: UNT Libraries Government Documents Department

Cumulative Beam Breakup in Linear Accelerators with Arbitrary Beam Current Profile

Description: An analytic formalism for the solution of cumulative beam breakup in linacs with arbitrary beam current profile is developed. It is applied to obtain an expression for the transverse displacement of trains of bunches of finite length.The same formalism is used to investigate the beam breakup-enhanced displacement of beams caused by the misalignment of the deflecting structures or focusing elements.
Date: June 1, 2001
Creator: Delayen, J.R.
Partner: UNT Libraries Government Documents Department


Description: During the year 2000 run a total of eight beam scans (Vernier Scans) were performed at various interaction points (IF) at RHIC. During a Vernier Scan the experimental collision rates are recorded while the beams are stepwise scanned across each other. Vernier Scans yield transverse beam sizes as well as maximum luminosity and thus the absolute cross section, which with the limited data from the 2000 run we measured to be {sigma} = 8.9 {+-} 0.3 barn at ({radical}s{sub NN}) = 130 GeV. Also, Vernier Scans permit performance studies of the beam orbit control and local coupling.
Date: June 18, 2001
Creator: DREES,A. & XU,Z.
Partner: UNT Libraries Government Documents Department


Description: The 6.7-MeV, 100-mA proton beam being produced in the Low Energy Demonstration Accelerator (LEDA) RFQ will be injected into a 52-magnet lattice in order to study the formation of beam halo [1]. The LEDA RFQ beam has a rms size of 1 mm. At nine longitudinal locations along the lattice an assembly that incorporates both a wire scanner and a halo-scraper assembly will be placed to make current density measurements of the beam.
Date: October 1, 2000
Partner: UNT Libraries Government Documents Department