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SPEAR III: A brighter source at SSRL

Description: By replacing the magnets and vacuum chamber for the 3 GeV SPEAR II storage ring, the natural emittance of the machine can be reduced from 130 to 18 nm-rad and the stored current can be raised from 100 to 200 mA with a 50 h lifetime. This configuration increases focused photon flux for insertion device beamlines by an order of magnitude and the photon brightness for future undulators would exceed 10{sup 18} at 5 keV. Due to a higher critical energy, the photon flux in the 20 keV range for bending magnet beamlines increases by more than two orders of magnitude. We present preliminary SPEAR III design study results and plans to implement the facility upgrade with minimal downtime for SSRL users.
Date: June 2, 1997
Creator: Hettel, R.; Boyce, R. & Brennan, S.
Partner: UNT Libraries Government Documents Department

Effect of synchrotron motion on the closed orbit distortion in crossing beams

Description: When beams collide with non-zero crossing angles, there is a dipole component to the beam-beam force, thus introducing a closed orbit distortion. If the force experienced by a particle is antisymmetric about the collision center, then the distorted orbit still passes through the collision center but with a changed slope, resulting in a shift from the nominal crossing angle. This antisymmetry in the force occurs for coasting beams, while for bunched beams, it is the case for particles at the center of the bunches, assuming that the bunches overlap exactly around the collision center. The presence of synchrotron motion means that the beam- beam force experienced by a particle modulates as the particle moves back amd forth within the bunch. Specifically, a symmetric component to the force is introduced. If the synchrotron period is much longer tham the betatron period, the modulation of the force is adiabatic, and so the effect is a modulation of the closed orbit. The symmetric compoment of the dipole force causes; shift in the closed orbit at the collision center. This indicates a tendency for the beams to separate, which in turn changes the mature of the force between the two beams. The closed orbit shift is calculated. Some comments on self-consistency are made. It is indicated how under certain circumstances, a self-consistent solution may not exist. The case of SPEAR is considered. It is shown that for small crossing angles, the orbit shift at the collision center is larger than the beam size, indicating a major effect. Further-more, it is argued that a self-consistent solution cannot exist. For coasting beams, small angle crossings can be designed so that only the antisymmetric component of the dipole force is prcsemt. Thus, the predominant effect is a shift in the nominal crossing angle. (auth)
Date: January 29, 1974
Creator: Month, M.
Partner: UNT Libraries Government Documents Department

Effects of damping wigglers on beam dynamics in the NLC damping rings

Description: To achieve the required damping time in the main damping rings for the Next Linear Collider (NLC), a wiggler will be required in each ring with integrated squared field strength up to 110 T{sup 2}m. There are concerns that nonlinear components of the wiggler field will damage the dynamic aperture of the ring, leading to poor injection efficiency. Severe effects from an insertion device have been observed and corrected in SPEAR 2. In this paper, we describe a model that we have developed to study the effects of the damping wiggler, compare the predictions of the model with actual experience in the case of the SPEAR 2 wiggler, and consider the predicted effects of current damping wiggler design on the NLC main damping rings.
Date: June 16, 2001
Creator: Wolski, Andrzej & Wu, Ying
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

Accelerator modeling at SPEAR

Description: The response matrix, consisting of the closed orbit change at each beam position monitor (BPM) due to corrector magnet excitations, was measured and analyzed in order to calibrate a linear optics model of SPEAR. The model calibration was accomplished by varying model parameters to minimize the chi-square difference between the measured and the model response matrices. The singular value decomposition (SVD) matrix inversion method was used to solve the simultaneous equations. The calibrated model was then used to calculate corrections to the operational lattice. The results of the calibration and correction procedures are presented.
Date: May 23, 1997
Creator: LeBlanc, G. & Corbett, W.J.
Partner: UNT Libraries Government Documents Department

Performance of the elliptically polarizing undulator on SPEAR

Description: This is a description of the first tests of the Elliptically Polarizing Undulator (EPU) on the SPEAR storage ring at SSRL. The EPU is the first device of its type; it is capable of producing plane polarized light in the vertical and horizontal, and right and left circularly polarized light in the 500-1000 eV range. Tests of the EPU were done to characterize its effect on the electron beam in SPEAR. Even at minimum gap, motion of the EPU magnets to vary the polarization of the output radiation caused negligible changes in the tune or the steering of the electron beam, even with no compensation of the steering trim coils. We also measured the polarization of x-rays generated by the EPU using a newly developed multilayer polarimeter built to be efficient in the EPU`s energy range. The EPU produces nearly 100% plane and circularly polarized x-rays. Using left and right circularly polarized radiation, we also performed tests of magnetic circular dichroism on magnetic multilayers.
Date: October 1, 1995
Creator: Carr, R.; Kortright, J.B.; Rice, M. & Lidia, S.
Partner: UNT Libraries Government Documents Department

Effect of Insertion Devices in SPEAR3

Description: The SPEAR3 upgrade lattice will provide much reduced beam emittance to increase the brightness of synchrotron radiation beams from wigglers and undulators. Seven existing insertion devices will be used in the lattice. In this paper we review the wiggler parameters, outline the wiggler compensation scheme, and evaluate wiggler effect on the optics and dynamic aperture.
Date: August 19, 1999
Creator: Corbett, William
Partner: UNT Libraries Government Documents Department

Multipole Spill-Down Effects in the SPEAR3 Dipole Magnets

Description: The main SPEAR3 dipole magnets are 1.45 m long with a pole contour designed to horizontally deflect and vertically focus the electron beam. At the nominal beam energy (3 GeV), the field and gradient along the magnet centerline are 1.3 T and 3.3 T/m (k = {minus}0.33 m{sup {minus}2}), respectively. Due to the straight core construction, the beam passes through each dipole with up to 16.6 mm trajectory offset relative to the centerline. This paper describes a method used to characterize the spilldown effect from magnetic multipole fields as observed by the beam traversing the dipole magnets. Results of tracking studies utilizing the longitudinal variation of multipole fields are discussed.
Date: August 19, 1999
Creator: Corbett, William
Partner: UNT Libraries Government Documents Department

Dynamic Aperture Studies for SPEAR 3

Description: The SSRL is investigating an accelerator upgrade project to replace the present 130 nm.rad FODO lattice with an 18 nm.rad double bend achromat lattice: SPEAR 3. In this paper, we review the methods used to maximize the SPEAR 3 dynamic aperture including optimization of linear optics, betatron tune, chromaticity and coupling correction, and effects of machine errors and insertion devices.
Date: August 19, 1999
Creator: Nosochkov, Yuri
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

An optimized low emittance lattice for SPEAR

Description: An alternate lattice for SPEAR is presented, which has a similar or smaller emittance and improved stability compared to the presently used Low Emittance Lattice. It allows the removal of one and the movement of another of the Low Beta quadrupole families. This creates two long drift spaces of up to 18 m, that can be utilized to accept special insertion devices including long undulators. A phased approach will be used to implement the new lattice starting in 1994.
Date: June 1, 1994
Creator: Nuhn, H. D.
Partner: UNT Libraries Government Documents Department

Nonlinear beam dynamics experimental program at SPEAR

Description: Since nonlinear effects can impose strict performance limitations on modern colliders and storage rings, future performance improvements depend on further understanding of nonlinear beam dynamics. Experimental studies of nonlinear beam motion in three-dimensional space have begun in SPEAR using turn-by-turn transverse and longitudinal phase-space monitors. This paper presents preliminary results from an on-going experiment in SPEAR.
Date: March 1, 1995
Creator: Tran, P.; Pellegrini, C.; Cornacchia, M.; Lee, M. & Corbett, W.
Partner: UNT Libraries Government Documents Department


Description: A dispersion relation, including strong turbulence, is derived for short-wavelength longitudinal self-perturbations of bunched electron beams. The effects of radiation damping and quantum excitation are included. Assuming that turbulence stabilizes coherent oscillations allows the derivation of a formula for bunch length which gives excellent fits to the data from SPEAR. As a special case of the formalism, an integral equation which describes the longitudinal self-perturbations of proton beams is derived.
Date: November 1, 1975
Creator: Channell, Paul J. & Sessler, Andrew M.
Partner: UNT Libraries Government Documents Department


Description: High energy physics, perhaps more than any other branch of science, is driven by technology. It is not the development of theory, or consideration of what measurements to make, which are the driving elements in our science. Rather it is the development of new technology which is the pacing item. Thus it is the development of new techniques, new computers, and new materials which allows one to develop new detectors and new particle-handling devices. It is the latter, the accelerators, which are at the heart of the science. Without particle accelerators there would be, essentially, no high energy physics. In fact. the advances in high energy physics can be directly tied to the advances in particle accelerators. Looking terribly briefly, and restricting one's self to recent history, the Bevatron made possible the discovery of the anti-proton and many of the resonances, on the AGS was found the {mu}-neutrino, the J-particle and time reversal non-invariance, on Spear was found the {psi}-particle, and, within the last year the Z{sub 0} and W{sup {+-}} were seen on the CERN SPS p-{bar p} collider. Of course one could, and should, go on in much more detail with this survey, but I think there is no need. It is clear that as better acceleration techniques were developed more and more powerful machines were built which, as a result, allowed high energy physics to advance. What are these techniques? They are very sophisticated and ever-developing. The science is very extensive and many individuals devote their whole lives to accelerator physics. As high energy experimental physicists your professional lives will be dominated by the performance of 'the machine'; i.e. the accelerator. Primarily you will be frustrated by the fact that it doesn't perform better. Why not? In these lectures, six in all, you should receive some appreciation ...
Date: July 1, 1984
Creator: Sessler, A.M.
Partner: UNT Libraries Government Documents Department


Description: Two-photon interactions have been studied with the SLAC-LBL Mark II magnetic detector at SPEAR. The cross section for {eta}' production by the reaction e{sup +}e{sup -} {yields} e{sup +}e{sup -}{eta}' has been measured at beam energies from 2.0 GeV to 3.7 GeV. The radiative width {Lambda}{sub {gamma}{gamma}}({eta}') has been determined to be 5.8 {+-} 1.1 keV ({+-}20% systematic uncertainty). Upper limits on the radiative widths of the f(1270), A{sub 2}(1310) and f'(1515) tensor mesons have been determined. A search has been made for production of the E(1420) by {gamma}{gamma} collisions, but no signal is observed.
Date: June 1, 1981
Creator: Jenni, P.; Burke, D.L.; Telnov, V.; Alam, M.S.; Boyarski, A.M.; Breidenbach, M. et al.
Partner: UNT Libraries Government Documents Department

The Storage Ring Magnets of the Australian Synchrotron

Description: A 3 GeV Synchrotron Radiation Source is being built in Melbourne, Australia. Commissioning is foreseen in 2006. The Storage ring has a circumference of 216 m and has a 14 fold DBA structure. For the storage ring the following magnets will be installed: 28 dipoles with a field of 1.3 T, and a gradient of 3.35 T/m; 56 quadrupoles with a gradient of 18 T/m and 28 with a gradient of 10 T/m; 56 sextupoles with a strength of B'' = 350 T/m and 42 with 150 T/m. The sextupoles are equipped with additional coils for horizontal and vertical steering and for a skew quadrupole. The pole profile was determined by scaling the pole profile of the SPEAR magnets [1] to the aperture of the ASP magnets. The magnets are to be supplied by Buckley Systems Ltd in Auckland, New Zealand.
Date: May 11, 2005
Creator: Barg, B.; Jackson, A.; LeBlanc, G.; U., /Melbourne; Huttel, E.; /Karlsruhe, Forschungszentrum et al.
Partner: UNT Libraries Government Documents Department

SPEAR 3 Commissioning Software

Description: The short SPEAR 3 startup time required precommissioned software for machine setup, beam measurements and data analysis. To accomplish this goal, we used Matlab with the Accelerator Toolbox (AT), the Channel Access Toolbox (MCA) and Middle Layer software to integrate code and streamline production. This paper outlines the software architecture, describes the Middle Layer component and provides examples from SPEAR 3 commissioning.
Date: May 9, 2005
Creator: Corbett, W.J.; Portmann, G.J.; Safranek, J.A.; Terebilo, A. & /SLAC, SSRL
Partner: UNT Libraries Government Documents Department

The SPEAR 3 Diagnostic Beamlines

Description: SPEAR 3 has two diagnostic beam lines: an x-ray pinhole camera and a visible/UV laboratory. The pinhole camera images {approx}8 keV dipole radiation on a phosphor screen with a remote computer to capture digital images and a parallel video signal to the control room. The visible/UV beam line features an 8 mm high GlidCop ''cold finger'' to remove the x-ray core of the beam. The remaining light is deflected horizontally onto an optical bench where it is focused via reflective (Cassegrain) or refractive optics. The visible beam can be split into branch lines for a variety of experimental applications. This paper describes the experimental set up and projected use of both systems.
Date: March 14, 2006
Creator: Corbett, W.J.; Limborg-Deprey, C.; Mok, W.Y.; Ringwall, A. & /SLAC
Partner: UNT Libraries Government Documents Department

Non Linear Beam Dynamics Studies at SPEAR

Description: The frequency map analysis of a Hamiltonian system recently introduced to accelerators physics in combination with turn-by-turn phase space measurements opens new experimental opportunities for studying non linear dynamic in storage rings. In this paper we report on the experimental program at SPEAR having the goal of measuring the frequency map of the machine. In this paper we discuss the accuracy of the instantaneous tune extraction from experimental data and demonstrate the possibility of the frequency map measurement. The instantaneous tune extraction technique can be applied to experimental tracking data with reasonable accuracy. Frequency map can be experimentally determined using the existing turn-by-turn phase space measurement techniques and NAFF instantaneous tune extraction.
Date: September 12, 2011
Creator: Terebilo, A.; Pellegrini, C.; /UCLA; Cornacchia, M.; Corbett, J.; Martin, D. et al.
Partner: UNT Libraries Government Documents Department

SPEAR 3: the First Year of Operation

Description: The first electrons were accumulated in the newly completed 3-GeV SPEAR 3 storage ring on December 15, 2003, five days after the beginning of commissioning. By mid-January of 2004, 100 mA were stored, the maximum current allowed in the first phase of SPEAR 3 operation, and ring characterization and tuning continued until early March when the first photon beam line was opened for users. After the first year of operation the SPEAR 3 beam properties and ring performance had been extensively measured. These include micron stability using slow orbit feedback, an emittance coupling of {approx}0.1% and 50-h lifetimes. The performance of SPEAR 3 during its first year of commissioning and operation and the improvement plans are described.
Date: February 10, 2006
Creator: Hettel, R.O.
Partner: UNT Libraries Government Documents Department

A control system upgrade of the spear synchrotron and injector

Description: The SPEAR electron synchrotron is an old and venerable facility with a history of great physics. When this storage ring was converted to serve as a full-time synchrotron light source, it was evident that the facility was due for an overhaul of its control system. Outdated hardware interfaces, custom operator interfaces, and the control computer itself were replaced with off-the-shelf distributed intelligent controllers and networked X-workstations. However, almost all applications and control functions were retained by simply rewriting the layer of software closest to each new device. The success of this upgrade prompted us to do a similar upgrade of our Injector system. Although the Injector was already running an X-windows based control system, it was non-networked and Q-bus based. By using the same Ethernet based controllers that were used at SPEAR, we were able to integrate the two systems into one that resembles the ``standard model`` for control systems, and at the same time preserve the applications software that has been developed over the years on both systems.
Date: November 1, 1995
Creator: Garrett, R.; Howry, S.; Wermelskirchen, C. & Yang, J.
Partner: UNT Libraries Government Documents Department

Multi-Bunch Instability Diagnostics via Digital Feedback Systems at PEP-II, DAFNE, ALS and SPEAR

Description: Longitudinal feedback systems based on a common programmable DSP architecture have been commissioned at 4 laboratories. In addition to longitudinal feedback and beam diagnostics these flexible systems have been programmed to provide diagnostics for transverse motion. The diagnostic functions are based on transient domain techniques which record the response of every bunch while the feedback system manipulates the beam. Operational experience from 4 installations is illustrated via experimental results from PEP-II, DAFNE, ALS and SPEAR. Modal growth and damping rates for transverse and longitudinal planes are measured via short (20 ms) transient excitations for unstable and stable coupled-bunch modes. Data from steady-state measurements are used to identify unstable modes, noise-driven beam motion, and noise sources. Techniques are illustrated which allow the prediction of instability thresholds from low-current measurements of stable beams. Transverse bunch train grow-damp sequences which measure the time evolution of instabilities along the bunch train are presented and compared to signatures expected from ion and fast ion instabilities.
Date: April 28, 1999
Creator: Fox, John D
Partner: UNT Libraries Government Documents Department

Multi-Bunch Longitudinal Dynamics and Diagnostics via a Digital Feedback System at PEP-II, DAFNE, ALS and SPEAR

Description: A bunch-by-bunch longitudinal feedback system based on a programmable DSP architecture is used to study coupled-bunch motion and its sources. Experimental results are presented from PEP-II, DA{Phi}NE, ALS and SPEAR to highlight the operational experience from 4 installations, plus show novel accelerator diagnostics possible with the digital processing system. Modal growth and damping rates are measured via short (20 ms) transient recordings for unstable and stable coupled-bunch modes. Data from steady-state measurements are used to identify unstable modes and noise-driven beam motion. A novel impedance measurement technique is presented which reveals the longitudinal impedance as a function of frequency. This technique uses the measured synchronous phase and charge of every bucket to calculate the impedance seen by the beam at revolution harmonics.
Date: April 19, 1999
Creator: Fox, John D
Partner: UNT Libraries Government Documents Department