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Commissioning results of the APS storage ring rf beam position monitors

Description: The commissioning of the 360 rf beam position monitors (BPMs) in the Advanced Photon Source (APS) storage ring (SR) is nearing completion. After using the single-turn capability of the BPM electronics in the early ring commissioning phase, resolution measurements versus current and bandwidth were successfully performed. In the standard Sr vacuum chamber geometry, the resolution was measured with beam as 0.16 {micro}mA/{radical}(Hz). For the insertion device vacuum chamber geometry, the resolution was measured to be 0.1 {micro}mA/{radical}(Hz). Since the photon beam stability requirement for the users is only 4.5 microns rms in the vertical direction, investigations of rf BPM offset versus current and bunch pattern have also been initiated. Both single bunch and multibunch beam patterns with varying intensity were used to determine offset stability for both the global and the local orbit feedback applications.
Date: July 1, 1996
Creator: Kahana, E. & Chung, Y.
Partner: UNT Libraries Government Documents Department

Synthesis and analysis of nickel dithiolene dyes in a nematic liquid crystal host. 1998 summer research program for high school juniors at the University of Rochester`s Laboratory for Laser Energetics: Student research reports

Description: The Liquid Crystal Point Diffraction Interferometer (LCPDI) can be employed to evaluate the Omega Laser system for optimum firing capabilities. This device utilizes a nickel dithiolene infrared absorbing liquid crystal dye dissolved in a liquid crystal host medium (Merck E7). Three nickel dithiolene dyes were characterized for both their solubility in the E7 host and their infrared spectral absorption.
Date: March 1, 1999
Creator: Lippa, I.
Partner: UNT Libraries Government Documents Department

Particle physics: CP violation in hyperon decays

Description: The primary research activities under this grant were in E871 (HyperCP) at Fermilab, a search for CP violation in hyperon decays which completed data taking in January, 2000. HyperCP is an experiment designed to perform a sensitive search for direct CP violation in the decays of cascade ({Xi}) and {Lambda} hyperons by looking for an asymmetry between particle and antiparticle decay parameters. The experiment is expected to achieve a sensitivity {approx}10{sup -4} in the decay parameters. Standard model predictions for this CP-violating asymmetry range from 0.3 to 5 x 10{sup -4}. A difference between the decay parameters for particle and antiparticle is direct evidence that CP symmetry is violated. A non-zero asymmetry would be the first evidence for CP violation outside of the K{sup o} system. Recent results from KTeV indicate a direct CP violation in K{sup o} decays, which suggests that CP violation will appear in other decays. In addition, we will look at a number of rare hyperon decays involving muons. These probe important new physics topics such as Majorana neutrinos and lepton number violating processes. The latter are of great current interest because new evidence for neutrino oscillations indicate lepton flavor violation does occur. Our data will lead to an improvement in the limits on branching ratios for these processes typically by three to four orders-of-magnitude. The muon detector construction and data resulting from it have been the responsibility of the Michigan group. We are now leading the analysis of the rare muon-related decay modes, and were responsible for the muon system and beam monitor upgrades for the 1999 run.
Date: October 31, 2000
Creator: Longo, Michael J.
Partner: UNT Libraries Government Documents Department

ET: EPICS TCL/TK interface

Description: This document describes the tc1 command and command types which are used to communicate with EPICS database servers. The application libraries upon which et is built include tc1, tk, tc1-dp, and blt. The reader of this document is assumed to be familiar with tc1/tk.
Date: February 1995
Creator: Daly, B.
Partner: UNT Libraries Government Documents Department

The Advanced Photon Source list of parameters

Description: The Advanced Photon Source (APS) is a third-generation synchrotron radiation source that stores positrons in a storage ring. The choice of positrons as accelerating particles was motivated by the usual reason: to eliminate the degradation of the beam caused by trapping of positively charged dust particles or ions. The third-generation synchrotron radiation sources are designed to have low beam emittance and many straight sections for insertion devices. The parameter list is comprised of three basic systems: the injection system, the storage ring system, and the experimental facilities system. The components of the injection system are listed according to the causal flow of positrons. Below we briefly list the individual components of the injection system, with the names of people responsible for managing these machines in parentheses: the linac system; electron linac-target-positron linac (Marion White); low energy transport line from linac to the PAR (Michael Borland); positron accumulator ring or PAR (Michael Borland); low energy transport line from PAR to injector synchrotron (Michael Borland); injector synchrotron (Stephen Milton); high energy transport line from injector synchrotron to storage ring (Stephen Milton). The storage ring system, managed by Glenn Decker, uses the Chasman-Green lattice. The APS storage ring, 1104 m in circumference, has 40 periodic sectors. Six are used to house hardware and 34 serve as insertion devices. Another 34 beamlines emit radiation from bending magnets. The experimental facilities system`s parameters include parameters for both an undulator and a wiggler.
Date: July 1, 1996
Creator: Bizek, H.M.
Partner: UNT Libraries Government Documents Department

The art and science of magnet design: Selected notes of Klaus Halbach. Volume 2

Description: This volume contains a compilation of 57 notes written by Dr. Klaus Halbach selected from his collection of over 1650 such documents. It provides an historic snapshot of the evolution of magnet technology and related fields as the notes range from as early as 1965 to the present, and is intended to show the breadth of Dr. Halbach`s interest and ability that have long been an inspiration to his many friends and colleagues. As Halbach is an experimental physicist whose scientific interests span many areas, and who does his most innovative work with pencil and paper rather than at the workbench or with a computer, the vast majority of the notes in this volume were handwritten and their content varies greatly--some reflect original work or work for a specific project, while others are mere clarifications of mathematical calculations or design specifications. As the authors converted the notes to electronic form, some were superficially edited and corrected, while others were extensively re-written to reflect current knowledge and notation. The notes are organized under five categories which reflect their primary content: Beam Position Monitors, (bpm), Current Sheet Electron Magnets (csem), Magnet Theory, (thry), Undulators and Wigglers (u-w), and Miscellaneous (misc). Within the category, they are presented chronologically starting from the most recent note and working backwards in time.
Date: February 1, 1995
Partner: UNT Libraries Government Documents Department

Computer-aided design and modeling of nickel dithiolene near-infrared dyes. 1998 summer research program for high school juniors at the University of Rochester`s Laboratory for Laser Energetics: Student research reports

Description: Recent advances in computational chemistry have made it feasible to design many types of molecules and predict their properties theoretically. The author applied these techniques to the design of organometallic transition-metal dyes absorbing in the near-infrared region of the spectrum which possess the combination of a large molar extinction coefficient, good chemical and thermal stability, and a high solubility in liquid crystal (LC) hosts. These properties are required for the dye to function as a near-infrared (IR) attenuator in a liquid crystal point diffraction interferometer (LCPDI) device that will be used as a beam diagnostic on the 60-beam OMEGA solid-state Nd:glass laser system at the University of Rochester`s Laboratory for Laser Energetics. Using commercially available software, both the absorption spectra and solubility characteristics of bis[1,2-di-(p-n alkoxyphenyl)ethane-1,2-dithione] nickel dye complexes were modeled in an isotropic host (cyclohexane) and, in most cases, excellent agreement was found with experimental data. Two additional compounds utilizing the same nickel dithiolene core but with alkylthio and phenylalkylthio terminal groups have been designed and show excellent potential to produce dramatic improvements in both solubility and optical density (absorbance) in liquid crystalline hosts. Based upon my work, a new dye not previously reported, 2(C{sub 4}S)2(C{sub 4}SPh)DTNi, has been proposed to satisfy the LCPDI device requirements. The nickel dithiolene dyes may also find important applications in other technology areas such as near-IR photography and laser-based near-IR communications.
Date: March 1, 1999
Creator: Corsello, S.
Partner: UNT Libraries Government Documents Department

A front end design for the advanced photon source

Description: X-ray sources on next generation low emittance/high brilliance synchrotrons such as the 7-GeV Advanced Photon Source (APS)(1) have unique properties which directly affect the design of the front end of the beam line. The most striking of these are the large peak photon power densities expected for the insertion device (ID) x-ray sources. Undulators, for example, can have highly peaked photon power distributions with central densities approaching 300 kW/mrad{sup 2}. Large power distributions can also be expected for some of the high critical energy wigglers. Front end components which intercept the photon beam produced by IDs must be able to absorb and safety dissipate the heat loads associated with their power distributions. In addition, detection of the position of the photon beam in some cases requires a precision in the range of a few microns. The information from such photon beam monitors is used primarily in the particle beam control loop in order to maintain the position and take-off angle of the particle beam within some fraction of the beam size and angular divergence dictated by the emittance of the lattice. In most cases, these photon beam detectors must function in the high flux environment of the x-ray beam.
Date: April 1, 1988
Creator: Viccaro, P.J.
Partner: UNT Libraries Government Documents Department

Analyzing algorithms for nonlinear and spatially nonuniform phase shifts in the liquid crystal point diffraction interferometer. 1998 summer research program for high school juniors at the University of Rochester`s Laboratory for Laser Energetics: Student research reports

Description: Phase-shifting interferometry has many advantages, and the phase shifting nature of the Liquid Crystal Point Diffraction Interferometer (LCPDI) promises to provide significant improvement over other current OMEGA wavefront sensors. However, while phase-shifting capabilities improve its accuracy as an interferometer, phase-shifting itself introduces errors. Phase-shifting algorithms are designed to eliminate certain types of phase-shift errors, and it is important to chose an algorithm that is best suited for use with the LCPDI. Using polarization microscopy, the authors have observed a correlation between LC alignment around the microsphere and fringe behavior. After designing a procedure to compare phase-shifting algorithms, they were able to predict the accuracy of two particular algorithms through computer modeling of device-specific phase shift-errors.
Date: March 1, 1999
Creator: Jain, N.
Partner: UNT Libraries Government Documents Department

Measurement of short bunches

Description: In recent years, there has been increasing interest in short electron bunches for different applications such as short wavelength FELs, linear colliders, and advanced accelerators such as laser or plasma wakefield accelerators. One would like to meet various requirements such as high peak current, low momentum spread, high luminosity, small ratio of bunch length to plasma wavelength, and accurate timing. Meanwhile, recent development and advances in RF photoinjectors and various bunching schemes make it possible to generate very short electron bunches. Measuring the longitudinal profile and monitoring bunch length are critical to understand the bunching process and longitudinal beam dynamics, and to commission and operate such short bunch machines. In this paper, several commonly used measurement techniques for subpicosecond bunches and their relative advantages and disadvantages are discussed. As examples, bunch length related measurements at Jefferson lab are presented. At Jefferson Lab, bunch lengths s short as 84 fs have been systematically measured using a zero-phasing technique. A highly sensitive Coherent Synchrotron Radiation (CSR) detector has been developed to noninvasively monitor bunch length for low charge bunches. Phase transfer function measurements provide a means of correcting RF phase drifts and reproducing RF phases to within a couple of tenths of a degree. The measurement results are in excellent agreement with simulations. A comprehensive bunch length control scheme is presented.
Date: October 1, 1996
Creator: Wang, D.X.
Partner: UNT Libraries Government Documents Department

Automated CCD camera characterization. 1998 summer research program for high school juniors at the University of Rochester`s Laboratory for Laser Energetics: Student research reports

Description: The OMEGA system uses CCD cameras for a broad range of applications. Over 100 video rate CCD cameras are used for such purposes as targeting, aligning, and monitoring areas such as the target chamber, laser bay, and viewing gallery. There are approximately 14 scientific grade CCD cameras on the system which are used to obtain precise photometric results from the laser beam as well as target diagnostics. It is very important that these scientific grade CCDs are properly characterized so that the results received from them can be evaluated appropriately. Currently characterization is a tedious process done by hand. The operator must manually operate the camera and light source simultaneously. Because more exposures means more accurate information on the camera, the characterization tests can become very length affairs. Sometimes it takes an entire day to complete just a single plot. Characterization requires the testing of many aspects of the camera`s operation. Such aspects include the following: variance vs. mean signal level--this should be proportional due to Poisson statistics of the incident photon flux; linearity--the ability of the CCD to produce signals proportional to the light it received; signal-to-noise ratio--the relative magnitude of the signal vs. the uncertainty in that signal; dark current--the amount of noise due to thermal generation of electrons (cooling lowers this noise contribution significantly). These tests, as well as many others, must be conducted in order to properly understand a CCD camera. The goal of this project was to construct an apparatus that could characterize a camera automatically.
Date: March 1, 1999
Creator: Silbermann, J.
Partner: UNT Libraries Government Documents Department

Design of a diagnostic area-type beam position monitor for x-ray beamlines at the National Synchrotron Light Source

Description: We have built a area-type beam position monitor for use as a diagnostic tool at the National Synchrotron Light Source. The device is compact and fits into a vacuum cross. We completed range and resolution tests of the device at beamline X-19A at the NSLS and concluded that such a monitor can be placed in the confines of the vacuum cross.
Date: October 1, 1996
Creator: Corridon, D.
Partner: UNT Libraries Government Documents Department

Ray tracing through the liquid crystal point diffraction interferometer. 1998 summer research program for high school juniors at the University of Rochester`s Laboratory for Laser Energetics: Student research reports

Description: The Omega laser is a system with many different parts that may cause imperfections. There are a multitude of lenses and mirrors, for example, that may not be polished correctly and can cause the laser wave front to have aberrations. The Liquid Crystal Point Diffraction Interferometer (L.C.P.D.I.) is a device whose main purpose is to read the wave front of the laser and measure any aberrations that may be on it. The way the L.C.P.D.I. reads the laser wave front and measures these aberrations is very complicated and has yet to be perfected. A ray-tracing model of the L.C.P.D.I. has been built, which calculates and models the ray trajectories, the optical paths of the rays, the O.P.D. between the object and reference beams, the absorption of the rays in the liquid crystal, and the intensities of each beam. It can predict an actual experiment by manipulating the different parameters of the program. It will be useful in optimization and further development of the L.C.P.D.I. Evidently, it is necessary to develop a liquid crystal solution with an O.D. greater than 0.3, and possibly as high as 2.0. This new solution would be able to reduce the intensity of the object beam sufficiently to make it comparable with the reference beam intensity. If this were achieved, the contrast, or visibility of the fringes would be better, and the interferogram could be used to diagnose the aberrations in the laser beam front. Then the cause of the aberrations could be fixed. This would result in a near-perfect laser front. If this were achieved, then it is possible that laser fusion could be made more efficient and possibly used as an energy source.
Date: March 1, 1999
Creator: Turner, A.
Partner: UNT Libraries Government Documents Department

Tests of the APS X-ray transmitting beam position monitors at ESRF

Description: Two different types of synthetic diamond-based X-ray transmitting beam position monitor (XBPM) prototypes have been studied with an undulator white beam at the European Synchrotron Radiation Facility (ESRF) ID-6 beamline. Of particular interest was the possibility of designing an integral window and filter-photon beam position monitor for the Advanced Photon Source (APS) high heat flux insertion device beamlines. The photoelectron-emission type transmitting XBPM prototype uses a 25-mm-diameter, 175-micron-thick CVD-diamond disk with 0.2-micron-thick electrically isolated patterns of aluminum coating on one side of the diamond disk. The photoelectron emission signal was collected from the aluminum-coat surface to provide the beam position information. A novel photoconductive-type transmitting XBPM prototype uses the same CVD-diamond disk, but patterns of aluminum coating were applied on both sides of the diamond disk. A DC bias voltage was used to generate the current signal, which is based on photoconductive properties of the CVD-diamond. Test results are presented in the paper.
Date: October 1, 1997
Creator: Shu, D.; Barraza, J.; Kuzay, T.M.; Naylor, G. & Elleaume, P.
Partner: UNT Libraries Government Documents Department

Laser diagnostic for high current H{sup {minus}} beams

Description: In the last 5 years, significant technology advances have been made in the performance, size, and cost of solid-state diode-pumped lasers. These developments enable the use of compact Q-switched Nd:YAG lasers as a beam diagnostic for high current H{sup {minus}} beams. Because the threshold for photodetachment is only 0.75 eV, and the maximum detachment cross section is 4 {times} 10{sup {minus}17} cm{sup 2} at 1.5 eV, a 50 mJ/pulse Q-switched Nd:YAG laser can neutralize a significant fraction of the beam in a single 10-ns wide pulse. The neutral beam maintains nearly identical parameters as the parent H{sup {minus}} beam, including size, divergence, energy, energy spread, and phase spread. A dipole magnet can separate the neutral beam from the H{sup {minus}} beam to allow diagnostics on the neutral beam without intercepting the high-current H{sup {minus}} beam. Such a laser system can also be used to extract a low current proton beam, or to induce fluorescence in partially stripped heavy ion beams. Possible beamline diagnostic systems will be reviewed, and the neutral beam yields will be calculated.
Date: May 5, 1998
Creator: Shafer, R.E.
Partner: UNT Libraries Government Documents Department

Study of a non-intrusive electron beam radius diagnostic

Description: The authors have evaluated the usefulness and limitation of a non-intrusive beam radius diagnostic which is based on the measurement of the magnetic moment of a high-current electron beam in an axisymmetric focusing magnetic field, and relates the beam root-mean-square (RMS) radius to the change in magnetic flux through a diamagnetic loop encircling the beam. An analytic formula that gives the RMS radius of the electron beam at a given axial position and a given time is derived and compared with results from a 2-D particle-in-cell code. The study has established criteria for its validity and optimal applications.
Date: December 1, 1997
Creator: Kwan, T.J.T.; DeVolder, B.G.; Goldstein, J.C. & Snell, C.M.
Partner: UNT Libraries Government Documents Department

Fast PIN-diode beam loss monitors at Tevatron

Description: The article is devoted to results of fine time structure of particle losses in Tevatron with use of fast beam loss monitors (BLM) based on PIN-diodes. An ultimate goal of the new BLMs is to distinguish losses of protons and antiprotons from neighbor bunches with 132 ns bunch spacing in the Tevatron collider upgrade. The devices studied fit well to the goal as they can recognize even seven times closer - 18.9 ns - spaced bunches` losses in the Tevatron fixed target operation regime. We have measured main characteristics of the BLM as well as studied the proton losses over 10 decades of time scale - from dozen of minutes to dozen of nanoseconds. Power spectral density of the losses is compared with spectra of the proton beam motion.
Date: July 1, 1997
Creator: Shiltsev, V.
Partner: UNT Libraries Government Documents Department

Characterization of beam position monitors for measurement of second moment

Description: A dual-axis beam position monitor (BPM) consists of four electrodes placed at 90{degree} intervals around the probe aperture. The response signals of these lobes can be expressed as a sum of moments. The first order moment gives the centroid of the beam. The second order moment contains information about the rms size of the beam. It has been shown previously that the second order moment can be used to determine beam emittance. To make this measurement, the authors must characterize the BPM appropriately. The approach to this problem is to use a pulsed wire test fixture. By using the principle of superposition, they can build up a diffuse beam by taking the signals from different wire positions and summing them. This is done two ways: first by physically moving a wire about the aperture and building individual distributions, and, second, by taking a two dimensional grid of wire positions versus signal and using a computer to interpolate between the grid points to get arbitrary wire positions and, therefore, distributions. The authors present the current results of this effort.
Date: May 1, 1995
Creator: Russell, S.J.; Gilpatrick, J.D.; Power, J.F. & Shurter, R.B.
Partner: UNT Libraries Government Documents Department

Optimization of four-button beam position monitor configuration for small-gap vacuum chambers

Description: Induced charges on a four-button beam position monitor (BPM) system attached on a beam chamber of narrow rectangular cross sections are calculated as a 2-D electrostatic problem of image charges. The calculation shows that for a narrow chamber of width/height (2w/2h) {much_gt} 1, over 90% of the induced charges are distributed within a distance of 2h from the charged beam position in the direction of the chamber width. Therefore, a four-button system with a button diameter of (2--2.5)h and no button offset from the beam position is the most efficient configuration. The four-button BPMs used for 8-mm and 5-mm chambers in the APS have relatively low sensitivities because the button locations are outside the range where the induced charge densities are low and the button diameters are less than 2h. Using derived formulae, button sensitivities and beam position coefficients are calculated for the buttons of the most efficient case and of the 8-mm and 5-mm chambers. The formulae may be used to validate the method of computer modeling for BPM buttons on a beam chamber of an arbitrary cross section.
Date: March 27, 1998
Creator: Kim, S.H.
Partner: UNT Libraries Government Documents Department

Observation of the spread of the readings in the Linac toroids and BPMs

Description: The readback accuracy on the high-energy toroids is about 0.26 mA. This does not consider, completely, the relative offsets among the toroids, just the accuracy of one reading on one toroid. Similarly, if you remove the way in which the beam moves in the beam pipe and ignore the relative offsets of the BPMs themselves, then the absolute accuracy of the reading on a BPM is 35 microns.
Date: November 9, 2001
Creator: McCrory, Elliott S
Partner: UNT Libraries Government Documents Department


Description: This is the final report of a three-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The purpose of this LDRD project was to develop new, inexpensive, simple electron beam bunch-length diagnostics with resolutions below 1/4 picosecond (ps). Our approach to this problem was three pronged. First, it was our intent to build a streak camera with 1/2 ps resolution. This conventional diagnostic was to be used to verify the results of two novel measurement techniques. Second, we wished to investigate the utility of off-axis coherent Smith-Purcell radiation as a bunch-length diagnostic. Finally, we planned to demonstrate a measurement of the electron bunch-length using a transversely deflecting RF field and a beam position monitor (BPM).
Date: June 1, 2000
Creator: RUSSELL, S. & AL, ET
Partner: UNT Libraries Government Documents Department


Description: The cluster klystron project required a beam monitor to check the quality of the hollow beam shape. Since the power density of the beam is very large, a common phosphorescent screen doesn't work. We investigated varies types of monitors. The related problems were also discussed.
Date: August 21, 2001
Creator: ZHAO,Y.
Partner: UNT Libraries Government Documents Department

A method for calculating longitudinal phase space distribution when given the time profile of the bunch

Description: We will show in this paper a method for calculating the longitudinal phase space distribution when the time profile of the bunch as measured by a wall current monitor is given. The key to this method is the assumption that the bunch is matched to the bucket. With this assumption, we will show that the method boils down to solving a simple upper triangular matrix equation. We will also illustrate the method with two examples and show the method's shortcomings.
Date: July 30, 2001
Creator: Tan, Cheng-Yang
Partner: UNT Libraries Government Documents Department

A bipolar integrator for secondary emission profile monitors at the SSCL

Description: Many invasive techniques for monitoring beam profile and intensity require secondary emission signals in order to make the measurement. Signal acquisition and processing can take many forms. This paper describes a bipolar integration technique which uses the Burr-Brown ACF2101 Dual Switched Integrator chip and applications for accelerator beam instrumentation.
Date: January 1, 1994
Creator: Datte, P.; Beechy, D. & Webber, R.
Partner: UNT Libraries Government Documents Department