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Sensitivity and offset calibration for the beam position monitors at the Advanced Photon Source

Description: The beam position monitors (BPMs) play a critically important role in commissioning and operation of accelerators. Accurate determination of the offsets relative to the magnetic axis and sensitivities of individual BPMs is thus needed. We will describe in this paper the schemes for calibrating all of the 360 BPMs for sensitivity and offset in the 7-GeV Advanced Photon Source (APS) storage ring and the results. For the sensitivity calibration, a 2-dimensional map of the BPM response in the aluminum vacuum chamber is obtained theoretically, which is combined with the measured nonlinear response of the BPM electronics. A set of 2-dimensional polynomial coefficients is then obtained to approximate the result analytically. The offset calibration of the BPMs is done relative to the magnetic axis of the quadrupoles using the beam. This avoids the problem arising from various mechanical sources as well as the offset in the processing electronics. The measurement results for the resolution and long-term drift of the BPM electronics shows 0.06-{mu}m/{radical}Hz resolution and 2-{mu}m/hr drift over a period of 1.5 hrs.
Date: July 1, 1995
Creator: Chung, Y.; Barr, D.; Decker, G.; Evans, K. Jr. & Kahana, E.
Partner: UNT Libraries Government Documents Department

Alignment and survey of the elements in RHIC

Description: The Relativistic Heavy Ion Collider (RHIC) consists of two rings with cryogenic magnets at a 4.5K operating temperature. Control of positions of the dipole and quadrupole cold masses (iron laminations) and the beam position monitors (BPM`s) during production and installation is presented. The roll of the dipoles is controlled by a combination of rotating coil measurements with the surveying measurements. The center of the quadrupole magnetic field is obtained by direct measurement of the field shape within a colloidal cell placed inside the quadrupoles. Special attention is given to the triplet quadrupole alignment and determination of the field center position.
Date: May 1, 1995
Creator: Trbojevic, D.; Cameron, P. & Ganetis, G.L.
Partner: UNT Libraries Government Documents Department

The APS booster synchrotron: Commissioning and operational experience

Description: The Advanced Photon Source (APS) at Argonne National Laboratory (ANL) was constructed to provide a large user community with intense and high brightness synchrotron radiation at x-ray wavelengths. A 7-GeV positron beam is used to generate this light. Acceleration of the beam from 450 MeV to 7 GeV is accomplished at a 2-Hz repetition rate by the booster synchrotron. Commissioning of the booster began in the second quarter of 1994 and continued on into early 1995. The booster is now routinely used to provide beam for the commissioning of the APS storage ring. Reported here are our commissioning and operational experiences with the booster synchrotron.
Date: July 1, 1995
Creator: Milton, S.V.
Partner: UNT Libraries Government Documents Department

Toward more precise beam position measurements

Description: For the past year or so we have been examining the properties and limitations of the beam bugs in use in the ETA program at LLNL with a view toward improving the accuracy of beam position and current measurements. When considering measurements of beam position, it is very important to distinguish between relative and absolute position measurements. A relative position measurement determines only the amplitude and direction of the motion of the beam within the transport tube. If one knew where the beam was, one could determine its new position. A relative measurement is essentially independent of errors in mechanical fabrication or electrical components. The minimum measurable displacement is only limited by the strength of the electrical signals or the signal to noise ratio of the position signal. An absolute position measurement is much more challenging. All inaccuracies in mechanical components and fabrication, electrical components, installation and assembly errors must be considered and controlled along with the issues common to relative position measurements. However, if the object is to strike a small specific point on a target or pass the beam through a small hole, absolute beam position measurements are required. The following is a summary of our progress including conclusions and recommendations for developments and improvements. This is, of course, only a step in beam bug development and there is plenty of room for others to contribute.
Date: May 12, 1999
Creator: Clark, J C; Fessenden, T J & Holmes, C
Partner: UNT Libraries Government Documents Department

Operational aspects of experimental accelerator physics

Description: During the normal course of high energy storage ring operations, it is customary for blocks of time to be allotted to something called ``machine studies,`` or more simply, just ``studies.`` It is during these periods of time that observations and measurement of accelerator behavior are actually performed. Almost invariably these studies are performed in support of normal machine operations. The machine physicist is either attempting to improve machine performance, or more often trying to recover previously attained ``good`` operation, for example after an extended machine down period. For the latter activity, a good portion of machine studies time is usually devoted to ``beam tuning`` activities: those standard measurements and adjustments required to recover good operations. Before continuing, please note that this paper is not intended to be comprehensive. It is intended solely to reflect one accelerator physicist`s impressions as to what goes on in an accelerator control room. Many topics are discussed, some in more detail than others, and it is not the intention that the techniques described herein be applied verbatim to any existing accelerator. It is hoped,, however, that by reading through the various sections, scientists, including accelerator physicists, engineers, and accelerator beam users, will come to appreciate the types of operations that are required to make an accelerator work.
Date: July 1, 1995
Creator: Decker, G.A.
Partner: UNT Libraries Government Documents Department

Digital signal processing for the APS transverse and longitudinal damping system

Description: The Advanced Photon Source (APS) at Argonne National Laboratory will be a 7-GeV machine. It is anticipated that for beam operations beyond the baseline design of 100 mA stored beam current, a transverse and longitudinal damping system is needed to damp instabilities. A key part of this digital damping system is digital signal processing. This digital system will be used to process samples taken from the beam and determine appropriate correction values to be applied to the beam. The processing will take the form of a transversal digital filter with adaptable filter weights. Sampling will be done at 176 MHz with a possible correction bandwidth of 88 MHz. This paper concentrates on the digital processing involved in this system, and especially on the adaptive algorithms used for determining the digital filter weights.
Date: July 1, 1995
Creator: Barr, D. & Sellyey, W.
Partner: UNT Libraries Government Documents Department

A low-cost non-intercepting beam current and phase monitor for heavy ions

Description: A low cost ion beam measurement system has been developed for use at ATLAS. The system provides nondestructive phase and intensity measurement of passing ion beam bunches by sensing their electric fields. Bunches traverse a short tubular electrode thereby inducing displacement currents. These currents are brought outside the vacuum jacket where a lumped inductance resonates electrode capacitance at one of the bunching harmonic frequencies. This configuration yields a basic sensitivity of a few hundred millivolts signal per microampere of beam current. Beam induced radiofrequency signals are summed against an offset frequency generated by the master oscillator. The resulting difference frequency conveys beam intensity and bunch phase information which is sent to separate processing channels. One channel utilizes a phase locked loop to stabilize phase readings during microsecond beam drop outs. The other channel uses a linear full-wave active rectifier circuit which converts sine wave signal amplitude to a DC voltage representing beam current. Plans are in progress to install this new diagnostic at several locations in ATLAS which should help shorten the tuning cycle of new ion species.
Date: July 1, 1995
Creator: Bogaty, J.M. & Clifft, B.E.
Partner: UNT Libraries Government Documents Department

The development of beam current monitors in the APS

Description: The Advanced Photon Source (APS) is a third-generation 7-GeV synchrotron radiation source. The precision measurement of beam current is a challenging task in high energy accelerators, such as the APS, with a wide range of beam parameters and complicated noise, radiation, and thermal environments. The beam pulses in the APS injector and storage ring have charge ranging from 50pC to 25nC with pulse durations varying from 30ps to 30ns. A total of nine non- intercepting beam current monitors have been installed in the APS facility (excluding those in the linac) for general current measurement. In addition, several independent current monitors with specially designed redundant interlock electronics are installed for personnel safety and machine protection. This paper documents the design and development of current monitors in the APS,. discusses the commissioning experience in the past year, and presents the results of recent operations.
Date: July 1, 1995
Creator: Wang, X.; Lenkszus, F. & Rotela, E.
Partner: UNT Libraries Government Documents Department

High precision electron beam diagnostic system for high current long pulse beams

Description: As part of the effort to develop a multi-axis electron beam transport system using stripline kicker technology for DARHT II apploications, it is necessary to precisely determine the position and extent of long high energy beams (6-40 MeV, 1-4 kA, 2 microseconds) for accurate position control. The kicker positioning system utilizes shot-to-shot adjustments for reduction of relatively slow (<20 MHz) motion of the beam centroid. The electron beams passing through the diagnostic systems have the potential for large halo effects that tend to corrupt measurements performed using capacitive pickoff probes. Likewise, transmission line traveling wave probes have problems with multi-bounce effects due to these longer pulse widths. Finally, the high energy densities experienced in these applications distort typical foil beam position measurements.
Date: March 24, 1999
Creator: Nelson, S D; Fessenden, T; Chen, Y J; Holmes, C & Selchow, N
Partner: UNT Libraries Government Documents Department

Performance of a beam monitor in the Fermilab Tevatron using synchrotron light

Description: Synclite, the beam monitor in the Fermilab Tevatron using synchrotron light is described. The calibration, monitoring and performance of the system is discussed. Observation of some effects of long range beam-beam interactions seen in the beam monitor will be presented as well as a measurement of DC beam in the Tevatron.
Date: June 4, 2003
Creator: Cheung, Harry W.K.; Hahn, Alan & Xiao, Aimin
Partner: UNT Libraries Government Documents Department

On the Choice of Method to Cancel 60 Hz Disturbances in Beam Position and Energy

Description: Because the voltage applied to magnets in accelerators is likely to be rectified, there can be 60 Hz related fluctuations in beam position and energy. Correcting such errors as well as other less repeatable errors can be done with combinations of feedback, feedforward, real time repetitive control, and batch update repetitive control. This paper studies how to mix these approaches for optimized performance. It is shown that use of feedback control can be counterproductive because of the waterbed effect operating on errors such as BPM noise. Also, it is seen that iterative repetitive control updates can produce significantly better error levels than pure feedforward control. Making corrections of errors for harmonics of 60 Hz that are above the Nyquist frequency can be accomplished, and this can save the expense and integration effort to produce fast beam sampling.
Date: June 1, 2001
Creator: Akogyeram, R.A.; Longman, R.W.; Hutton, Andrew & Juang, J.-N.
Partner: UNT Libraries Government Documents Department

Ion-chamber-based loss monitor system for the Los Alamos Meson Physics Facility

Description: A new loss monitor system has been designed and installed at the Los Alamos Meson Physics Facility (LAMPF). The detectors are ion chambers filled with N{sub 2} gas. The electronics modules have a threshold range of 1:100, and they can resolve changes in beam loss of about 2% of the threshold settings. They can generate a trip signal in 2 {mu}s if the beam loss is large enough; if the response time of the Fast Protect System is included the beam will be shut off in about 37 {mu}s.
Date: May 1, 1995
Creator: Plum, M.A.; Brown, D.; Browman, A. & Macek, R.J.
Partner: UNT Libraries Government Documents Department

Antiproton noise source for the Tevatron

Description: A new system for exciting the beam in the Tevatron has been installed in the A1 service building and in the A17 medium straight section. The purpose of the system is to make betatron tune measurements.
Date: October 26, 1992
Creator: McConnell, D. & Fellenz, B.
Partner: UNT Libraries Government Documents Department

Self triggered single pulse beam position monitor

Description: A self triggered beam position monitor (BPM) has been developed for the NSLS injection system to provide single pulse orbit measurements in the booster synchrotron, linac, and transport lines. The BPM integrates the negative going portion of 3 nS wide bipolar pickup electrode signals. The gated, self triggering feature confines critical timing components to the front end, relaxing external timing specifications. The system features a low noise high speed FET sampler, a fiber optic gate for bunch and turn selection, and an inexpensive interface to a standard PC data acquisition system.
Date: July 1, 1993
Creator: Rothman, J. L. & Blum, E. B.
Partner: UNT Libraries Government Documents Department

An interactive beam position monitor system simulator

Description: A system simulator has been implemented to aid the development of the RHIC position monitor system. Based on the LabVIEW software package by National Instruments, this simulator allows engineers and technicians to interactively explore the parameter space of a system during the design phase. Adjustable parameters are divided into three categories: beam, pickup, and electronics. The simulator uses these parameters in simple formulas to produce results in both time-domain and frequencydomain. During the prototyping phase, these simulated results can be compared to test data acquired with the same software package. The RHIC position monitor system is presented as an example, but the software is applicable to several other systems as well.
Date: March 1, 1993
Creator: Ryan, W. A. & Shea, T. J.
Partner: UNT Libraries Government Documents Department

Description and calibration beamline SEM/Ion Chamber Current Digitizer

Description: This report discusses the following on beamline SEM/ion chamber current digitizers: Module description; testing and calibration; common setup procedures; summary of fault indications and associated causes; summary of input and output connections; SEM conversion constant table; ion chamber conversion constant table; hexadecimal to decimal conversion table; and schematic diagram.
Date: May 1, 1994
Creator: Schoo, D.
Partner: UNT Libraries Government Documents Department

Conceptual Design Report for a Phase 3 upgrade of the National Synchrotron Light Source

Description: Considerable investment by both the Department of Energy and the facility`s Participating Research teams has permitted the NSLS to offer a national facility to a wide range of scientific pursuits. The purpose of the NSLS Phase III project is to maximize the scientific output of this premier 2nd generation synchrotron radiation facility through a number of distinct projects. Over the years the NSLS has made significant improvements in the area of beam reliability which has resulted in deliverable, reproducible beam during 98% and 97% of scheduled operations on the VUV and X-ray rings respectively. This project will focus on improving beam intensity and stability by upgrading the optics and detector systems on a number of beamlines as well as upgrading radio frequency (rf) and beam position monitoring systems in the storage rings. In addition, the project includes plans for the design and procurement of a utility isolation system that would guard against voltage transients that disrupt the facility`s electrical system. Also a new insertion device will be installed at beamline X25 and a 2nd floor will be constructed over the X6 -- X16 region which will provide sorely needed laboratory and office space for the user community. This project requests funding of 22.5 million dollars over a three year period: FY 1996 ($6.3M), FY 1997 ($13.4M) and FY 1998 ($2.8M).
Date: March 1, 1994
Creator: Foyt, W.; Krinsky, S.; Hastings, J. & Finlay, L.
Partner: UNT Libraries Government Documents Department

Advanced Light Source beam diagnostics systems

Description: The Advanced Light Source (ALS), a third-generation synchrotron light source, has been recently commissioned. Beam diagnostics were very important to the success of the operation. Each diagnostic system is described in this paper along with detailed discussion of its performance. Some of the systems have been in operation for two years. Others, in the storage ring, have not yet been fully commissioned. These systems were, however, working well enough to provide the essential information needed to store beam. The devices described in this paper include wall current monitors, a beam charge monitor, a 50 ohm Faraday cup, DC current transformers, broad-hand striplines, fluorescence screens, beam collimators and scrapers, and beam position monitors. Also, the means by which waveforms are digitized and displayed in the control room is discussed.
Date: October 1, 1993
Creator: Hinkson, J.
Partner: UNT Libraries Government Documents Department

A fast model-calibration procedure for storage rings

Description: The ever-increasing demand for better performance from circular accelerators requires improved methods to calibrate the optics model. We present a linear perturbation approach to the calibration problem in which the modeled BPM-to-corrector response matrix is expanded to first order in quadrupole strengths. The result is numerically fit to the measured response matrix yielding quadrupole strength errors, corrector strength errors, and BPM linearity factors. The large number of degrees of freedom in the fit allows a comprehensive error analysis, including the determination of BPM resolutions. In this way, a self-consistent first order optics model of SPEAR was generated which reproduces the measured tunes.
Date: May 1, 1993
Creator: Corbett, W. J.; Lee, M. J. & Ziemann, V.
Partner: UNT Libraries Government Documents Department

Spool pieces at the SSCL

Description: The basic features of the Superconducting Super Collider lattice are the two beamlines formed by superconducting dipoles (7736) and quadrupoles (1564). The dipoles constraint two 20 TeV proton beams into counterrotating closed orbits of 86.2 km. The quadrupoles (FODO) require cryogenic cooling the LHe temperatures. This requirement isolates the main magnets from the outside world. The interface required, the spool, is a crucial component of superconducting lattice design and machine operation. There are over 1588 spools in the Super Collider. We present hear SSCL spool designs which consist of (1) housing for superconducting closed orbit and multipole correction magnets, (2) cryogenic function, magnet quench protection, system power, and instrumentation interfaces, and (3) cold to warm transitions for ware magnet and warm instrumentation drift spaces.
Date: May 1, 1993
Creator: Clayton, T.; Cai, Y.; Smellie, R. & Stampke, S.
Partner: UNT Libraries Government Documents Department

Front end support systems for the Advanced Photon Source

Description: The support system designs for the Advanced Photon Source (APS) front ends are complete and will be installed in 1994. These designs satisfy the positioning and alignment requirements of the front end components installed inside the storage ring tunnel, including the photon beam position monitors, fixed masks, photon and safety shutters, filters, windows, and differential pumps. Other components include beam transport pipes and ion pumps. The designs comprise 3-point kinematic mounts and single axis supports to satisfy various multi-direction positioning requirements from course to ultra-precise. The confined space inside the storage ring tunnel has posed engineering challenges in the design of these devices, considering some components weigh as much as 500 kg. These challenges include designing for mobility during commissioning and initial alignment, mechanical and thermal stability, and precise low profile vertical and horizontal positioning. As a result, novel stages and kinematic mounts have emerged with modular and standard designs. This paper will discuss the diverse group of support systems, including specifications and performance data of the prototypes.
Date: October 1, 1993
Creator: Barraza, J.; Shu, D. & Kuzay, T. M.
Partner: UNT Libraries Government Documents Department

Linac BPM cable phase matching

Description: This report explains the method chosen to phase match cables, it`s accuracy and the effects of mismatched cables on the position output of the Linac Beam Position Module.
Date: August 6, 1993
Creator: Arthur, J.
Partner: UNT Libraries Government Documents Department