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Understanding the nonlinear beam dynamics of the Advanced Light Source

Description: Frequency map analysis is used to study the single particle transverse beam dynamics in ALS. The maps, which provide details about the diffusion of orbits and limits on long term stability, are generated by a postprocessor attached to a tracking code. This paper describes the method and shows how the map is changed when the 12- fold symmetry of the linear lattice is perturbed by including measured magnetic field imperfections. Also the long term stability of orbits that reside in regions of large diffusion is studied.
Date: September 18, 1996
Creator: Robin, D. & Laskar, J.
Partner: UNT Libraries Government Documents Department

Orbit dynamics for unstable linear motion

Description: A treatment is given of the orbit dynamics for linear unstable motion that allows for the zeros in the beta function and makes no assumptions about the realness of the betatron and phase functions. The phase shift per turn is shown to be related to the beta function and the number of zeros the beta function goes through per turn. The solutions of the equations of motion are found in terms of the beta function.
Date: July 1997
Creator: Parzen, G.
Partner: UNT Libraries Government Documents Department

Particle motion in the stable region near the edge of a linear sum resonance stopband

Description: This paper studies the particle motion when the tune is in the stable region close to the edge of linear sum resonance stopband. Results are found for the tune and the beta functions. Results are also found for the two solutions of the equations of motion. The results found are shown to be also valid for small accelerators where the large accelerator approximation may not be used.
Date: December 1, 1995
Creator: Parzen, G.
Partner: UNT Libraries Government Documents Department

Quadrupole shunt experiments at SPEAR

Description: As part of a program to align and stabilize the SPEAR storage ring, a switchable shunt resistor was installed on each quadrupole to bypass a small percentage of the magnet current. The impact of a quadrupole shunt is to move the electron beam orbit in proportion to the off-axis beam position at the quadrupole, and to shift the betatron tune. Initially, quadrupole shunts in SPEAR were used to position the electron beam in the center of the quadrupoles. This provided readback offsets for nearby beam position monitors, and helped to steer the photon beams with low-amplitude corrector currents. The shunt-induced tune shift measurements were then processed in MAD to derive a lattice model.
Date: May 1, 1996
Creator: Corbett, W.J.; Hettel, R.O. & Nuhn, H.-D.
Partner: UNT Libraries Government Documents Department

Performance optimization of synchrotron light sources

Description: This paper will present work done at the NSLS to tailor the electron beam properties so as to maximize the performance of the photon beamlines. The electron beam properties of most importance to photon users are the total stored current, emittance, lifetime, and transverse stability. Recent and planned improvements in each of these properties will be discussed as well as the ultimate limits for each. The discussion of transverse stability will include high frequency motion, which can reduce the effective brightness, as well as slow drift during a fill and fill-to-fill reproducibility.
Date: Summer 1996
Creator: Safranek, J
Partner: UNT Libraries Government Documents Department

Orbit stability of the ALS storage ring

Description: The Advanced Light Source (ALS) storage ring, a synchrotron light source of the third generation, is specified to maintain its electron orbit stable within one tenth of the rms beam size. In the absence of a dedicated orbit feed-back system, several orbit-distorting effects were investigated, aided by a new interactive simulation tool, the code TRACY V. The effort has led to a better understanding of the behavior of a variety of accelerator subsystems and in consequence produced a substantial improvement in day-to-day orbit stability.
Date: May 1, 1997
Creator: Keller, R.; Nishimura, H. & Biocca, A.
Partner: UNT Libraries Government Documents Department

Advances in orbit drift correction in the advanced photon source storage ring

Description: The Advanced Photon Source storage ring is required to provide X-ray beams of high positional stability, specified as 17 {mu}m rms in the horizontal plane and 4.4 {mu}m rms in the vertical plane. The author reports on the difficult task of stabilizing the slow drift component of the orbit motion down to a few microns rms using workstation-based orbit correction. There are two aspects to consider separately the correction algorithm and the configuration of the beam position monitors (BPMs) and correctors. Three notable features of the correction algorithm are: low-pass digital filtering of BPM readbacks; {open_quotes}despiking{close_quotes} of the filtered orbit to desensitize the orbit correction to spurious BPM readbacks without having to change the correction matrix; and BPM intensity-dependent offset compensation. The BPM/corrector configuration includes all of the working BPMs but only a small set of correctors distributed around the ring. Thus only those orbit modes that are most likely to be representative of real beam drift are handled by the correction algorithm.
Date: June 1, 1997
Creator: Emery, L. & Borland, M.
Partner: UNT Libraries Government Documents Department

Skew chromaticity in large accelerators

Description: The 2-D ``skew chromaticity`` vector k is introduced when the standard on-momentum description of linear coupling is extended to include off-momentum particles. A lattice that is well decoupled on-momentum may be badly decoupled off-momentum, inside the natural momentum spread of the beam. There are two general areas of concern: (1) the free space in the tune plane is decreased; (2) collective phenomena may be destabilized. Two strong new criteria for head-tail stability in the presence of off-momentum coupling are derived, which are consistent with experimental and operational observations at the Tevatron, and with tracking data from RHIC.
Date: May 1, 1995
Creator: Peggs, S. & Dell, G.F.
Partner: UNT Libraries Government Documents Department

Design and implementation of a slow orbit control package at Thomas Jefferson National Accelerator Facility

Description: The authors describe the design and implementation of a C++ client/server based slow orbit and energy control package based on the CDEV software control bus. Several client applications are described and operational experience is given.
Date: June 1, 1997
Creator: Zeijts, J. van; Witherspoon, S. & Watson, W.A.
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

Survey, alignment, and beam stability at the Advanced Light Source

Description: This paper describes survey and alignment at the Lawrence Berkeley Laboratories Advanced Light Source (ALS) accelerators from 1993 to 1997. The ALS is a third generation light source requiring magnet alignment to within 150 microns. To accomplish this, a network of monuments was established and maintained. Monthly elevation surveys show the movement of the floor over time. Inclinometers have recently been employed to give real time information about magnet, vacuum tank and magnet girder motion in the ALS storage ring.
Date: October 1, 1997
Creator: Krebs, G.F.
Partner: UNT Libraries Government Documents Department

Orbit correction using virtual monitors at Jefferson Lab

Description: An orbit correction algorithm is developed to achieve the following goals for the CEBAF accelerator at Jefferson Lab.: (1) Pre-processing of orbit input to account for estimated misalignment and monitor errors. (2) Automatic elimination of blind spots caused by response matrix degeneracy. (3) Transparency of exception handling to interchangeable generic steering engines. (4) CEBAF-specific demands on control of injection angle, path length, orbit effects on optics, simultaneous multiple pass steering, and orbit control at un-monitored locations. All of the above can be accomplished by the introduction of virtual monitors into the processed input orbit, whose theoretical basis is to be discussed in this report. Implementation of all or part of these features and operational experience during the CEBAF variable energy runs will also be discussed.
Date: August 1, 1997
Creator: Chao, Yu-Chiu; Bowling, B.; Witherspoon, S.; Zeijts, J. van & Watson, W.A. III
Partner: UNT Libraries Government Documents Department

Analysis of ultra-relativistic charged particle beam and stretched wire measurement interactions with cylindrically symmetric structures

Description: The beam impedance and wakefield are quantities which describe the stability of charged particles in their trajectory within an accelerator. The stretched wire measurement technique is a method which estimates the beam impedance and wakefield. Definitions for the beam impedance, the wakefield, and the stretched wire measurement are presented. A pillbox resonator with circular beampipes is studied for its relatively simple profile and mode structure. Theoretical predictions and measurement data are presented for the interaction of various charged particle beams and center conductor geometries between the cavity and beampipe. Time domain predictions for the stretched wire measurement and wakefield are presented and are shown to be a linear interaction.
Date: December 31, 1996
Creator: Deibele, C.E.
Partner: UNT Libraries Government Documents Department

Orbit control at the ALS based on sensitivity matrices

Description: A third-generation synchrotron-light source storage ring requires accurate orbit correction because its lattice is very sensitive to magnet imperfections and misalignments. If model-based control is used, calibration of this model is required in advance. Therefore, it is preferable to prepare some kind of model-free orbit control scheme that is complementary to model-based control. A sensitivity matrix (S matrix) works effectively as the kernel of a model-free orbit control system for a given optics of a lattice. This paper describes recent efforts in this respect at Advanced Light Source (ALS).
Date: April 1, 1995
Creator: Nishimura, H.; Schachinger, L. & Ohgaki, H.
Partner: UNT Libraries Government Documents Department

The advanced photon source

Description: The Advanced Photon Source (APS) is a 7-GeV third-generation synchrotron radiation storage ring and full-energy positron injector. Construction project funding began in 1989, and ground breaking took place on 5 May 1990. Construction of all accelerator facilities was completed in January 1995 and storage ring commissioning is underway. First observation of x-rays from a bending magnet source took place on 26 March 1995. Nearly all performance specifications of the injector have been reached, and first observations indicate that the reliability, dynamic aperture, emittance, and orbit stability in the storage ring are satisfactory. Observation of radiation from the first of 20 insertion device beamlines is scheduled for October 1995. Start of regular operations is expected to take place well before the APS Project target date of December 1996.
Date: July 1, 1995
Creator: Galayda, J.N.
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

Particle motion inside and near a linear half-integer stopband

Description: This paper studies the motion of a particle whose tune is inside and near a linear half-integer stopband. Results are found for the tune and beta functions in the stable region close to an edge of the stopband. Results are found for the growth rates and for the exponentially growing particle motion inside the stopband. It is shown that the eigenvalues and the eigenfunctions of the transfer matrix are real inside the stopband. All the results found are also valid for small accelerators where the large accelerator approximation is not used.
Date: July 1, 1995
Creator: Parzen, G.
Partner: UNT Libraries Government Documents Department

Linearized error analysis for an accelerator and application to the APS injector synchrotron

Description: This paper presents a tolerance budget for accelerators dictated by the linear transverse dynamics of particle motion. The linearized equations satisfied by the particle motion when errors in the lattice are present are given along with the solution to these equations. The forms of these errors giving rise to the linearized equation are stated. These results are used to derive a tolerance budget for the Advanced Photon Source (APS) injector synchrotron.
Date: July 1, 1995
Creator: Koul, R.K. & Mills, F.E.
Partner: UNT Libraries Government Documents Department

On the feasibility of tracking with differential-algebra maps in long-term stability studies for large hadron colliders

Description: A time-saving alternative to conventional element-by-element tracking in long-term stability studies is the use of truncated Taylor maps. This report discusses how the non-symplecticity of a moderately high-order truncated Taylor map affects its reliability when the map is used for tracking over several thousand turns. Various machines and two different map-constructing programs are compared. It is found that the discrepancies between the Taylor map results and those obtained by direct tracking grow with amplitude. Thus, such maps are not guaranteed to be sufficient for long-term tracking over millions of turns without suitable symplectification.
Date: January 1, 1992
Creator: Kleiss, R.; Schmidt, F. & Yan, Y.
Partner: UNT Libraries Government Documents Department

Integrated Global Orbit Feedback with Slow and Fast Correctors

Description: The NSLS-II Light Source, which is planned to be built at Brookhaven National Laboratory, provides users with ultra-bright synchrotron radiation sources and is designed for horizontal beam emittances < 1 nm. Full utilization of the very small emittances and beam sizes requires sub-micron orbit stability in the storage ring. This can be provided by means of a wide bandwidth orbit feedback system. Traditional approach is to utilize a uniform set of fast correctors or use two separate systems with strong slow and weaker fast correctors. In the latter case two systems needed to communicate to suppress transients associated with different update rates of corrector settings. In this paper they consider an integrated system with two types of correctors. Its main feature is that setpoints of slow correctors are updated with the same rate as fast correctors; however the bandwidth is limited in order to stay in linear regime. Possible architectures and technical solutions as well as achievable performance are discussed.
Date: June 23, 2008
Creator: Pinayev,I.
Partner: UNT Libraries Government Documents Department

SPEAR3 Accelerator Physics Update

Description: The SPEAR3 storage ring at Stanford Synchrotron Radiation Laboratory has been delivering photon beams for three years. We will give an overview of recent and ongoing accelerator physics activities, including 500 mA fills, work toward top-off injection, long-term orbit stability characterization and improvement, fast orbit feedback, new chicane optics, low alpha optics & short bunches, low emittance optics, and MATLAB software. The accelerator physics group has a strong program to characterize and improve SPEAR3 performance
Date: November 2, 2007
Creator: Safranek, James A.; Corbett, W.Jeff; Gierman, S.; Hettel, R.O.; Huang, X.; Nosochkov, Yuri et al.
Partner: UNT Libraries Government Documents Department

A Comprehensive Study of Nanometer Resolution of the IPBPM at ATF2

Description: High-resolution beam position monitors (IPBPMs) have been developed in order to measure the electron beam position at the focus point of ATF2 to a few nanometers in the vertical plane. To date, the IPBPM system has operated in test mode with a highest demonstrated resolution of 8.7 nm in the ATF extraction line during 2008. After expected noise source calculations there still remains 7.9 nm of noise of unexplained origin. We summarize the experimental work on the IPBPM system since this measurement and outline the possible origins of these sources. We then present a study plan to be performed at the ATF2 facility designed to identify and to improve the resolution performance and comment on the expected ultimate resolution of this system. The Accelerator Test Facility 2 (ATF2) is a test beamline for ILC final focus system in the framework of the ATF international collaboration which was constructed to extend the extraction line at ATF, located at KEK, Japan. There are two goals of the ATF2: firstly to demonstrate focusing to 37 nm vertical beam size, secondly to achieve a few nanometer level beam orbit stability at the focus point in the vertical plane. High-resolution beam position monitors (IPBPMs) for the interaction point (IP) have been developed in order to measure the electron beam position at the focus point of the ATF2 to a few nanometers in the vertical plane. The previous measured position resolution of IPBPMs was 8.7 nm for a 0.68 x 10{sup 10} e/bunch beam with a dynamic range of 5 {mu}m. The intrinsic noise of the system was estimated to be 2.6 nm at 10{sup 10} e/bunch. It is scaled to 3.8 nm at 0.68 x 10{sup 10} e/bunch which means that 7.9 nm of unknown noise remains. The origin of the unknown noise must be ...
Date: December 13, 2011
Creator: Kim, Y.I.; Park, H.; U., /Kyungpook Natl.; Boogert, S.T.; /Oxford U., JAI; Frisch, J. et al.
Partner: UNT Libraries Government Documents Department

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

Impact-generated atmospheric plumes: The threat to satellites in low-earth orbit

Description: Computational simulations of the impacts of comet Shoemaker-Levy 9 (SL9) fragments on Jupiter provide a framework for interpreting the observations. A reasonably consistent picture has emerged, along with a more detailed understanding of atmospheric collisional processes. The knowledge gained from the observations and simulations of SL9 has led us to consider the threat of impact-generated plumes to satellites in low-Earth orbit (LEO). Preliminary simulations suggest that impacts of a size that recur about once per century on Earth generate plumes that rise to nearly 1000 km over an area thousands of km in diameter. Detailed modeling of such plumes is needed to quantify this threat to satellites in LEO. Careful observations of high-energy atmospheric entry events using both satellite and ground- based instruments would provide validation for these computational models.
Date: February 1, 1996
Creator: Boslough, M.B. & Crawford, D.A.
Partner: UNT Libraries Government Documents Department