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Status of flat electron beam production

Description: Last year at LINAC2000 [1] the authors reported their initial verification of the round beam (comparable transverse emittances) to flat beam (high transverse emittance ratio) transformation described by Brinkmann, Derbenev, and Floettmann [2]. Further analysis of the data has confirmed that a transverse emittance ratio of approximately 50 was observed. Graphics representing observational detail are included here, and future plans outlined.
Date: August 24, 2001
Creator: al., Donald A. Edwards et
Partner: UNT Libraries Government Documents Department

Roll bar x-ray spot size measurement technique

Description: A time dependent x-ray spot size measurement is critical to understanding beam target physics such as target plasma generated beam instabilities. The so-called roll bar measurement uses a heavy metal material which is optically thick to X-rays, to form a 1D shadow of the x-ray origination spot. This spot is where an energetic electron beam interacts with a high Z target to produce the x-rays. The material (the �roll bar�) has a slight radius to avoid alignment problems. If a beam profile is assumed (or measured by other means), the equivalent x-ray spot size can be calculated from the x-ray shadow cast by the roll bar. Typically a radiographic film is exposed over the duration of the beam pulse, and the shadow is analyzed for a time integrated measurement. This paper explores various techniques to convert the x-rays to visible photons which can be imaged using a gated camera or streak camera for time evolved x-ray spot size. Data will be presented from the measurements on the ETA II induction linac.
Date: August 14, 1998
Creator: Houck, T L & Richardson, R A
Partner: UNT Libraries Government Documents Department


Description: Two different parameters for the quantitative description of beam halo are introduced, both based on moments of the particle distribution. One parameter is a measure of spatial halo formation and has been defined previously by Wangler and Crandall [3], termed the profile parameter. The second parameter relies on kinematic invariants to quantify halo formation in phase space; we call it the halo parameter. The profile parameter can be computed from experimental beam profile data. The halo parameter provides a theoretically more complete description of halo in phase space, but is difficult to obtain experimentally.
Date: June 1, 2001
Creator: ALLEN, C.K. & WANGLER, T.P.
Partner: UNT Libraries Government Documents Department


Description: In the Spallation Neutron Source (SNS) ring, multi-turn injection is employed to obtain a large transverse beam size which significantly reduces the space-charge tune shift of the accumulated beam. Careful choice of the painting scheme and bump function is required to obtain the desired beam profile together with low beam loss. In this paper we examine, both analytically and numerically, the effect of the space charge on the beam profile during multi-turn injection painting.
Date: June 18, 2001
Partner: UNT Libraries Government Documents Department


Description: A method to split off a few percent of the 6 x 10{sup 13} AGS beam delivered to the Slow External Beam (SEB) lines and send it down the Fast External Beam line (FEB) has been developed. The mission is to feed a counter experiment off the FEB that directly measures the neutrino mass using the muon storage ring. The use of normal thin septum splitters would have an excessive loss overhead and been optically difficult. The AGS Slow Extraction uses a third integer resonance with sextuple strength so the resonance width is a few percent of the beam width. This results in a low density tail which will be clipped by a bent crystal and deflected into the FEB channel. This clipping off of the tail should reduce losses in the SEB transport line. Details of modeled orbits, particle distribution and extraction trajectories into and out off the crystal will be given.
Date: June 18, 2001
Partner: UNT Libraries Government Documents Department


Description: A new diagnostic has been designed and commissioned that measures the profile of the beam in the halo channel of the Low Energy Demonstration Accelerator at the Los Alamos National Laboratory. This paper describes the algorithms written to analyze the data from that diagnostic, a combined wire scanner and halo scraper. These algorithms determine the safe insertions limit of the scrapers, spatially differentiate the scraper signal, amalgamate the wire scanner data with the differentiated scraper data, determine when both the core and combined distributions rise above the noise floor, and compute the moments of the combined distribution. Results of applying the algorithms to data acquired during experiments matching the beam into the halo channel are presented.
Date: May 1, 2001
Partner: UNT Libraries Government Documents Department


Description: In this paper we review the present picture of km halo in proton linacs. Space-charge forces acting in mismatched beams have been identified as a major cause of beam-halo. We present a definition of halo based on a ratio of moments of the distribution of the beam coordinates. We find from our initial studies that for halo detined in this way, a beam can have rms emittance growth without halo growth, but halo growth is always accompanied by rms emittance growth. We describe the beam-halo experiment that is in preparation at Los Alamos, which will address questions about the beam profiles, maximum particle amplitudes, and rms emittance growth associated with the halo.
Date: August 1, 2000
Partner: UNT Libraries Government Documents Department


Description: Four ionization beam profile monitors (IPM's) are in RHIC to measure vertical and horizontal profiles in the two rings. Each IPM collects and measures the distribution of electrons in the beamline resulting from residual gas ionization during bunch passage. The IPM's performed well during the 1999 commissioning run and early in the 2000 run. However as the bunch intensity increased there was a beam-induced ringing that increased in amplitude until it saturated the amplifiers and made the IPM's unusable. Near the end of the run the cause of the ringing was found and one IPM was fixed. At the start of the 2001 run all four IPM have EM1 shielding installed.
Date: June 18, 2001
Partner: UNT Libraries Government Documents Department

A high-precision cryogenically-cooled crystal monochromator for the APS diagnostics beamline

Description: A high-precision cryogenically-cooled crystal monochromator has been developed for the APS diagnostics beamline. The design permits simultaneous measurements of the particle beam size and divergence. It provides for a large rotation angle, {minus}15{degree} to 180{degree}, with a resolution of 0.0005{degree}. The roll angle of the crystal can be adjusted by up to {+-}3{degree} with a resolution of 0.0001{degree}. A vertical translational stage, with a stroke of {+-}25 mm and resolution of 8 {micro}m, is provided to enable using different parts of the same crystal or to retract the crystal from the beam path. The modular design will allow optimization of cooling schemes to minimize thermal distortions of the crystal under high heat loads.
Date: July 24, 2000
Creator: Rotela, E.; Yang, B.; Sharma, s. & Barcikowski, A.
Partner: UNT Libraries Government Documents Department

Multipass beam position, profile and polarization measurements using intense photon target

Description: The Compton scattering of a circularly polarized laser beam condensed by an optical resonator can be used for multipass measurement of beam profile, position, and polarization in CEBAF's 250-m-long linac straight sections. The position and profile of the beam will be measured with an accuracy of {approximately}10 {mu}m in about 200 seconds and beam polarization with 10% accuracy in 100 seconds when the lowest beam energy is 500 MeV and the beam current is 100 {mu}A. For higher energies the times for measurement are much less. The photon target is within an optical resonator having a quality factor of 50. The Nd:Yag 5 W CW laser photon beam at wavelength {lambda} = 0.532 nm will have a waist {omega}{sub o} {approximately}30 {mu}m and a Rayleigh range of about 10 mm. Scanning the electron beams in the linac sections by this photon beam at a crossing angle of 0.1 rad will send to a proportional detector installed after the spreader magnet scattered photons with energies sharply correlated with the energy of the electrons.
Date: May 1, 1994
Creator: Karabekov, I.P.; Neil, G.; Karabekian, S. & Musakhanian, V.
Partner: UNT Libraries Government Documents Department

Evaluation of round colliding beams for Tevatron

Description: This paper presents investigation of round beams for increasing the luminosity in colliders. The main idea of round beams is briefly discussed. Numerical simulations of round colliding beams for the Tevatron are much in favor of round beams, because they provide reduction of harmful impact of beam-beam forces on beam sizes particles diffusion and better stability with respect to errors and imperfections.
Date: June 11, 1997
Creator: Danilov, V.V.
Partner: UNT Libraries Government Documents Department

A low diffraction beam technique for scanning in the shallow ocean

Description: The Localized Wave pulse project has created the concept of highly localized, pulsed wave energy. We have confirmed, and developed the technique in a series of experimental and numerical tests. This technique generates radiation, mechanical or electromagnetic, from an array. LW generation sends a broad frequency bandwidth pulse of energy along the array axis. The pulse has no sidelobes and maintains the frequency bandwidth and pulse amplitude better than any other method proposed to date. Confirmation of the theory by acoustic experiments show that the effect is real, and that the advantages of the technique can be realized in a laboratory environment. Numerical studies have shown that this effect is extendible to the microwave (vector field) and elastodynamic (tensor field) regimes as well as the stratified ocean environment. The main features of the LW beam are (1) the pulses are broad bandwidth and maintain that bandwidth over their entire working range; (2) the beam generates no side lobes; (3) the LW effect is accomplished in the linear regime, so that small errors in beam generation result in a less effective beam not the loss of the effect; and (4) the beam can be generated using present technology in the acoustic realm. The LW beam has a wide range of applications. As an active source, it offers a unique method of variable beam forming from spatially wide to the narrowest possible beam. Its uses include oceanographic sound velocity profile estimation and attenuation measurements. Since the pulse characteristics are changeable through the source signal parameters, it also offers the possibility of adaptive beam forming in real time. Passively, the LW array can use a wide spatial width listening pattern until something of interest occurs. Instantaneously, the listening pattern could be changed to a very narrow, steerable beam with a broad bandwidth. These ...
Date: December 1, 1994
Creator: Lewis, D.K.
Partner: UNT Libraries Government Documents Department

Multivideo image processing for beam profile monitoring system

Description: Some experiments at Jefferson Lab demand tight beam size ({approx} 100 {mu}m) and very low energy spread (< 5 x 10{sup {minus}5}). These experiments also require simultaneous and continuous monitoring of these quantities. This paper focuses on the development of the image processing aspects of the beam profile monitoring system. A pipelined image processor, Datacube's MaxVideo MV200, calculates beam sizes and positions from two beam profile monitors simultaneously at 10 Hz rate. Multiplexing software in the EPICS environment allows a single digitizer to process several input channels at high speed. This system makes the profile monitors usable for tuning the accelerator, as well as delivering critical information to the end stations. This paper discusses the issues related to the daily operational use of the system. The availability and reliability of the monitoring system became acceptable only after the implementation of programs that automatically setup and periodically check the monitors and digitizer. The system permits additional video channels without significant additional hardware cost.
Date: May 1, 2000
Creator: Hardy, D.; Chevstov, P.; Denard, J-C. & Dickson, R.
Partner: UNT Libraries Government Documents Department

Bunched beam echos in the AGS

Description: Beam echos have been measured at FNAL and CERN in coasting beams. A coherent oscillation introduced by a short RF burst decoheres quickly, but a coherent echo of this oscillation can be observed if the decohered oscillation is bounced off a second RF burst. In this report the authors describe first longitudinal echo measurements of bunched beam in the AGS accelerator. They applied a method proposed by Stupakov for transverse beam echos, where the initial oscillation is produced by a dipole kick and is bounced off a quadrupole kick. In the longitudinal case the dipole and quadrupole kicks are produced by cavities operating at a 90 and 0{degree} phase shift, respectively.
Date: August 1, 1998
Creator: Kewisch, J. & Brennan, J.M.
Partner: UNT Libraries Government Documents Department

Bunch heating by coherent synchrotron radiation

Description: The authors discuss here effects which define the steady-state rms energy spread of a microbunch in a storage ring. It is implied that the longitudinal microwave instability is controlled by low {alpha} lattice. In this case the coherent synchrotron radiation, if exists, may be the main factor defining the bunch temperature. Another effect comes from the fact that a nonlinear momentum compaction of such lattices makes Haissinskii equation not applicable, and the coherent synchrotron radiation may effect not only bunch lengthening but the energy spread as well.
Date: October 1, 1995
Creator: Heifets, S.A. & Zolotorev, M.
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

Beam Profile Measurement at 30 GeV Using Optical Transition Radiation

Description: We present results of measurements of spot size and angular divergence of a 30 GeV electron beam through use of optical transition radiation (OTR). The OTR near field pattern and far field distribution are measured as a function of beam spot size and divergence at wavelengths of 441, 532, and 800 nm, for both the single and double foil configurations. Electron beam spot sizes of 50 {micro}m rms have been resolved, demonstrating the utility of OTR for measurement of small beam spot sizes of high energy (30 GeV) electron beams. Two-foil interference was clearly observed and utilized electron beam angular divergences of {approximately} 100 {micro}rad.
Date: July 10, 1999
Creator: Whittum, David H
Partner: UNT Libraries Government Documents Department

Beam distributions beyond RMS

Description: The beam is often represented only by its position (mean) and the width (rms = root mean squared) of its distribution. To achieve these beam parameters in a noisy condition with high backgrounds, a Gaussian distribution with offset (4 parmeters) is fitted to the measured beam distribution. This gives a very robust answer and is not very sensitive to background subtraction techniques. To get higher moments of the distribution, like skew or kurtosis, a fitting function with one or two more parameters is desired which would model the higher moments. In this paper we will concentrate on an Asymmetric Gaussian and a Super Gaussian function that will give something like the skew and the kurtosis of the distribution. This information is used to quantify special beam distribution. Some are unwanted like beam tails (skew) from transverse wakefields, higher order dispersive aberrations or potential well distortion in a damping ring. A negative kurtosis of a beam distribution describes a more rectangular, compact shape like with an over-compressed beam in z or a closed to double-homed energy distribution, while a positive kurtosis looks more like a ``Christmas tree`` and can quantify a beam mismatch after filamentation. Besides the advantages of the quantification, there are some distributions which need a further investigation like long flat tails which create background particles in a detector. In particle simulations on the other hand a simple rms number might grossly overestimate the effective size (e.g. for producing luminosity) due to a few particles which are far away from the core. This can reduce the practical gain of a big theoretical improvement in the beam size.
Date: September 1, 1994
Creator: Decker, F.J.
Partner: UNT Libraries Government Documents Department

Potential-well distortion in barrier Rf

Description: Head-tail asymmetry has been observed in the longitudinal beam profiles in the Fermilab Recycler Ring where protons or antiprotons are stored in rf barrier buckets. The asymmetry is caused by the distortion of the rf potential well in the presence of resistive impedance. Gaussian energy distribution can fit the observed asymmetric beam profile but not without discrepancy. It can also fit the measured energy distribution. On the other hand, generalized elliptic distribution gives a better fit to the beam profile. However, it fails to reproduce the observed energy distribution.
Date: April 29, 2004
Creator: Ng, King
Partner: UNT Libraries Government Documents Department

Small-business technology transfer program, case number 93119 - second harmonic generation for Lee Laser Inc.: Resonator designs

Description: The author has investigated several resonator designs for Lee Laser Inc. as outlined in the Short-Term Technical Assistance Project, case number 93119. The scope of this work was to identify various resonator options which would be suitable for use in an intra-cavity doubled Nd:YAG laser and compatible with Lee Laser hardware. This work consisted of computer modeling of laser resonators to identify mirror curvatures, distances, beam sizes, and sensitivity to thermal loading of the laser rod.
Date: September 2, 1994
Creator: Erbert, G.V.
Partner: UNT Libraries Government Documents Department


Description: We present studies of space-charge-induced beam profile broadening at high intensities in the Proton Storage Ring (PSR) at Los Alamos National Laboratory. Previous work has associated the observed broadening in the vertical direction with the coherent half integer resonance. Here, we study the effect of the space charge environment on this resonance; specifically, we investigate the strength of the resonance versus beam intensity, longitudinal bunching factor, transverse lattice tune, and two different beam injection scenarios. For each case, detailed particle-in-cell simulations are combined with experimental results to elucidate the behavior and sensitivity of the beam resonance response.
Date: June 3, 2002
Partner: UNT Libraries Government Documents Department

FNAL booster: Experiment and modeling

Description: We present measurements of transverse and longitudinal beam phase space evolution during the first two hundred turns of the FNAL Booster cycle. We discuss the experimental technique, which allowed us to obtain turn-by-turn measurements of the beam profile. The experimental results are compared with the prediction of the Synergia 3D space charge simulation code.
Date: June 2, 2003
Creator: Spentzouris, Panagiotis & Amundson, James
Partner: UNT Libraries Government Documents Department

Application of a transverse phase-space measurement technique for high-brightness, H{sup {minus}} beams to the GTA H{sup {minus}} beam

Description: The Ground Test Accelerator (GTA) had the objective Of Producing a high-brightness, high-current H-beam. The major components were a 35 keV injector, a Radio Frequency Quadrupole (RFQ), an intertank matching section (IMS), and a drift tube linac (DTL), consisting of 10 modules. A technique for measuring the transverse phase-space of high-power density beams has been developed and tested. This diagnostic has been applied to the GTA H-beam. Experimental results are compared to the slit and collector technique for transverse phase-space measurements and to simulations.
Date: May 1, 1995
Creator: Johnson, K.F.; Garcia, R.C.; Rusthoi, D.P.; Sander, O.R.; Sandoval, D.P.; Shinas, M.A. et al.
Partner: UNT Libraries Government Documents Department