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Commissioning results of the narrow-band beam position monitor system upgrade in the APS storage ring.

Description: When using a low emittance storage ring as a high brightness synchrotron radiation source, it is critical to maintain a very high degree of orbit stability, both for the short term and for the duration of an operational fill. A fill-to-fill reproducibility is an additional important requirement. Recent developments in orbit correction algorithms have provided tools that are capable of achieving a high degree of orbit stability. However, the performance of these feedback systems can be severely limited if there are errors in the beam position monitors (BPMs). The present orbit measurement and correction system at the APS storage ring utilizes 360 broad-band-type BPMs that provide turn-by-turn diagnostics and an ultra-stable orbit: < 1.8 micron rms vertically and 4.5 microns rms horizontally in a frequency band of 0.017 to 30 Hz. The effects of beam intensity and bunch pattern dependency on these BPMs have been significantly reduced by employing offset compensation correction. Recently, 40 narrow-band switching-type BPMs have been installed in the APS storage ring, two in each of 20 operational insertion device straight sections, bringing the total number of beam position monitors to 400. The use of narrow-band BPM electronics is expected to reduce sensitivity to beam intensity, bunch pattern dependence, and long-term drift. These beam position monitors are used for orbit correction/feedback and machine protection interlocks for the insertion device beamlines. The commissioning results and overall performance for orbit stability are provided.
Date: April 20, 1999
Creator: Singh, O.
Partner: UNT Libraries Government Documents Department

Single bunch transfer system for the National Synchrotron Light Source

Description: The accelerator system at the National Synchrotron Light Source consists of an S-band 85 MeV linac and three synchrotron rings. The electron beam from the linac is accelerated by the booster ring to 600 MeV and transferred to one of the two storage rings. The smaller of the two rings operates between 300 and 800 MeV emtting photons in the vacuum ultraviolet (VUV), while the larger storage ring operates up to 2.5 GeV and emits photons in the x-ray spectrum. A system is described for loading the storage rings by filling a single-phase space bunch in the booster ring and transferring it at the end of each booster cycle into a selected bucket in one of the storage rings. By controlling the timing of the transfer on successive transfer cycles, many fill patterns may be obtained.
Date: January 1, 1983
Creator: Sheehan, J.; Singh, O. & Rambo, W.
Partner: UNT Libraries Government Documents Department

Electron beam stability and beam peak to peak motion data for NSLS X-Ray storage ring

Description: In the past two years, a significant reduction in electron beam motion has been achieved at the NSLS X-Ray storage ring. The implementation of global analog orbit feedbacks, based on a harmonics correction scheme, has reduced the beam motion globally. Implementation of six local analog feedback systems has reduced the beam motion even further at the corresponding beam line straight sections. This paper presents beam motion measurements, showing the improvement due to the feedback systems. Beam motion is measured using a spectrum analyzer and data is presented at various frequencies, where peaks were observed. Finally, some of the beam motion sources are discussed.
Date: July 1, 1993
Creator: Singh, O.
Partner: UNT Libraries Government Documents Department

Overview of Beam Instrumentation and Diagnostics for the NSLS-II Project

Description: A new, ultra-bright 3rd generation light source, the NSLS-II Project, is planned to be built at Brookhaven National Laboratory. The light source being developed will have unprecedently small beam horizontal emittance and will provide the radiation sources with a brightness of 3 x 10{sup 21} photons/sec/0.1%BW/mm{sup 2}/mrad{sup 2}. In this paper we present the detailed specifications and a comprehensive description of the planned beam instrumentation system and the first results of the ongoing instrumentation R&D activities on beyond state-of-the-art subsystems.
Date: May 4, 2008
Creator: Singh,O.
Partner: UNT Libraries Government Documents Department

Comparative Study of button BPM Trapped Mode Heating

Description: The combination of short bunches and high currents found in modern light sources and colliders can result in the deposition of tens of watts of power in BPM buttons. The resulting thermal distortion is potentially problematic for maintaining high precision beam position stability, and in the extreme case can result in mechanical damage. We present a simple algorithm that uses the input parameters of beam current, bunch length, button diameter, beampipe aperture, and fill pattern to calculate a relative figure-of-merit for button heating. Data for many of the world's light sources and colliders is compiled in a table. Using the algorithm, the table is sorted in order of the relative magnitude of button heating.
Date: May 4, 2009
Creator: Cameron,P. & Singh, O.
Partner: UNT Libraries Government Documents Department

Comparison of RF BPM Receivers for NSLS-II Project

Description: The NSLS-II Light Source being built at Brookhaven National Laboratory requires submicron stability of the electron orbit in the storage ring in order to utilize fully very small emittances and electron beam sizes. This sets high stability requirements for beam position monitors and a program has been initiated for the purpose of characterizing RF beam position monitor (BPM) receivers in use at other light sources. Present state-of-the-art performance will be contrasted with more recently available technologies.
Date: May 4, 2009
Creator: Pinayev,I. & Singh, O.
Partner: UNT Libraries Government Documents Department

60 HZ beam motion reduction at NSLS UV storage ring

Description: A significant reduction in 60 hz beam motion has been achieved in the UV storage ring. From the wide band harmonic beam motion signal, 60 hz signal is extracted by tuned bandpass filter. This signal is processed by the phase and amplitude adjustment circuits and then, it is fed into the harmonic orbit generation circuits. Several harmonics, near the tune, were canceled by employing one circuit for each harmonic. The design and description of this experiment is given in this paper. The results showing reduction in beam motion at 60 hz are also provided.
Date: January 1, 1997
Creator: Singh, O. V.
Partner: UNT Libraries Government Documents Department

Orbit stability improvement at the NSLS x-ray ring

Description: We describe recent improvements in both the short an long-term orbit stability at the NSLS X-Ray Ring. The short-term stability has been improved by increasing the gain and the bandwidth of the global harmonic feedback systems. The long-term horizontal orbit drift over the course of a fill has been reduced by including the rf-frequency in the orbit feedback. Work is in progress to further reduce orbit drift by compensating for thermally induced mechanical motions of the beam position monitors (BPMs).
Date: June 1, 1995
Creator: Safranek, J.; Singh, O. & Solomon, L.
Partner: UNT Libraries Government Documents Department

Magnet power supply control of the NSLS VUV and x-ray storage rings transfer lines

Description: The transfer lines for NSLS VUV and x-ray storage rings have been split. New power supplies have been incorporated with existing ones. The existing microprocessor system has been upgraded in order to control the additional functions. This system expands the input/output port of the microprocessor to an addressable serial/parallel link to each magnet power supply. The implementation of this system will be discussed.
Date: January 1, 1985
Creator: Klein, J.D.; Ramamoorthy, S.; Singh, O. & Smith, J.D.
Partner: UNT Libraries Government Documents Department


Description: In the NSLS2 storage ring, there are four stripline kickers/pickups. Two long striplines with electrode length of 30cm will be used as bunch-by-bunch transverse feedback actuators. Two short stripline kickers/pickups with 15cm length will mainly used for tune measurement excitation or signal pickup for the beam stability monitor. High shunt impedance of the long stripline kickers is demanded to produce 200 {micro}s damping time. Meanwhile the beam impedance should be minimized. The design work for these two types of stripline is discussed in this paper. NSLS2 is a third-generation light source under construction at Brookhaven National Laboratory. The machine will have < 1nm.rad horizontal emittance by using weak dipoles together with damping wigglers. For the storage ring of 792m circumference, geometric impedance, resistive wall impedance and ion effects are expected to be significant. A transverse bunch-by-bunch feedback system has been designed to suppress the coupled bunch instabilities. More information can be found in previous paper.
Date: March 28, 2011
Creator: Cheng, W.; Blednykh, A.; Krinsky, S. & Singh, O.
Partner: UNT Libraries Government Documents Department

Results from a Test Fixture for button BPM Trapped Mode Measurements

Description: A variety of measures have been suggested to mitigate the problem of button BPM trapped mode heating. A test fixture, using a combination of commercial-off-the-shelf and custom machined components, was assembled to validate the simulations. We present details of the fixture design, measurement results, and a comparison of the results with the simulations. A brief history of the trapped mode button heating problem and a set of design rules for BPM button optimization are presented elsewhere in these proceedings. Here we present measurements on a test fixture that was assembled to confirm, if possible, a subset of those rules: (1) Minimize the trapped mode impedance and the resulting power deposited in this mode by the beam. (2) Maximize the power re-radiated back into the beampipe. (3) Maximize electrical conductivity of the outer circumference of the button and minimize conductivity of the inner circumference of the shell, to shift power deposition from the button to the shell. The problem is then how to extract useful and relevant information from S-parameter measurements of the test fixture.
Date: May 4, 2009
Creator: Cameron,P.; Bacha, B.; Blednykh, A.; Pinayev, I. & Singh, O.
Partner: UNT Libraries Government Documents Department

Preliminary Design of Pinhole camera for NSLS-II Project.

Description: The NSLS-II Light Source being built at Brookhaven National Laboratory is expected to provide very small emittances and electron beam sizes. High resolution imaging systems are required in order to provide robust measurements. The pinhole camera will utilize 6-fold magnification with a pinhole placed inside a crotch absorber. The pinhole is protected from high power synchrotron radiation with a filter made of refractory metal. In this paper we provide resolution analyses, heat load calculations, and optimization details for the NSLS-II pinhole camera, including beamline design.
Date: May 4, 2009
Creator: Pinayev,I.; Kosciuk, B. & Singh, O.
Partner: UNT Libraries Government Documents Department

Orbit compensation for the time-varying elliptically polarized wiggler with switching frequency at 100 hz

Description: In October 1996, the elliptically polarized wiggler, installed in the X13 straight section of the NSLS X-ray ring, was commissioned at an operating frequency of 100 hz. This wiggler generates circularly polarized photons in the energy range of 0.1 to 10 keV with AC modulation of polarization helicity. The vertical magnetic field is produced by a hybrid permanent magnet structure, and the horizontal magnetic field is generated by an electromagnet capable of switching at frequencies up to 100 hz. Here, the authors discuss the compensation of the residual vertical and horizontal orbit motion utilizing a time-domain algorithm employing a function generator to drive trim coils at the wiggler ends, and the wideband high precision orbit measurement system of the X-ray ring. The residual orbit motion has been reduced to a level below 1 micron, and the device has been run in regular operations with no negative effect on other users.
Date: July 1, 1997
Creator: Singh, O. & Krinsky, S.
Partner: UNT Libraries Government Documents Department

Operations with the digital orbit feedback system in the NSLS x-ray ring

Description: The digital filtering and eigenvector decomposition-based orbit correction is performed by two dedicated HP 742/743 rt micros which communicate with Motorola CPU based orbit-measuring and orbit-correction systems. The correction algorithm in the DFbk was orthogonalized with respect of the analog global harmonic feedback. Operational results concerning improvements in the noise suppression at low frequencies and especially in the dc drift as well as in the orbit stability are shown. Efforts are underway to improve the resolution of the orbit measuing system and the sampling rate using 16 bit 400 kHz ADC`s which will allow orbit sampling with high resolution at 4 kHz frequency.
Date: May 1, 1996
Creator: Bozoki, E.; Rammamorthy, S.; Singh, O.; Tang, Y. & Friedman, A.
Partner: UNT Libraries Government Documents Department

X-ray BPM-based feedback system at the APS storage ring

Description: At the Advanced Photon Source (APS) storage ring, the X-ray beam position monitors (X-BPMs) measure accurate photon position down to the submicron level. This level of stable measurement has been possible due to (1) superior thermal insulation and vibration damping of the X-ray BPM support structure, (2) minimal dependence on the bunch pattern and intensity variations, and (3) use of ultrastable preamplifiers and processing electronics. A new X-BPM interface is under development and will be discussed here. This interface will be integrated into the existing rf-based orbit feedback systems. To study preliminary results, an experimental X-BPM orbit feedback set-up was developed and implemented in one of the bending magnet beamlines. The results from this set-up are encouraging. For an operational fill, a typical orbit drift of 30 microns (at X-ray BPMs) has been reduced to less than 5 microns. The fill-to-fill photon orbit reproducibility has been improved from 75 microns to less than 10 microns.
Date: May 17, 2000
Creator: Singh, O.; Erwin, L.; Decker, G.; Laird, R. & Lenkszus, F.
Partner: UNT Libraries Government Documents Department

Upgrade of NSLS timing system

Description: We report on the progress of the new NSLS timing system. There are three types of requirements for NSLS timing system: clocks, synchronization and trigger circuits. All ring revolution frequency clocks are generated using ECL and high speed TTL logic. The synchronization circuits allows to fill both storage rings with any bunch pattern. The triggers are generated by using commercially available digital delay generators. The delay unit`s outputs are ultrastable, with a resolution of 5 ps, and are programmed by computer via IEEE 488 interface. The block diagrams, description of all major timing components and the present status are provided in this paper.
Date: May 1, 1995
Creator: Singh, O.; Ramamoorthy, S.; Sheehan, J. & Smith, J.
Partner: UNT Libraries Government Documents Department

Automatic steering of x-ray beams from NSLS insertion devices using closed orbit feedback

Description: By the middle of this year (1989); there will be five insertion devices installed in the NSLS x-ray electron storage ring. X-ray beams from these devices will be stabilized by local automatic steering systems to reduce beam motion at the end of the beamline. Both the position of the source and the direction of the radiation will be controlled using beam position feedback to the closed orbit. Another system will be installed to stabilize the electron orbit for the LEGS Compton backscattering experiment. Each feedback system will employ at least one x-ray beam position detector; some will also utilize rf electron beam positron monitors. Analog hardware with a digital interface has been designed and will be installed in the near future. A totally digital realization of the feedback controller is under consideration. 6 refs., 6 figs.
Date: January 1, 1989
Creator: Nawrocky, R.J.; Galayda, J.; Klein, J.D.; Singh, O. & Yu, L.H.
Partner: UNT Libraries Government Documents Department

Automatic local beam steering systems for NSLS x-ray storage ring: Design and implementation

Description: Recently, two local automatic steering systems, controlled by microprocessors, have been installed and commissioned in the NSLS X- Ray storage ring. In each system, the position of the electron beam is stabilized at two locations by four independent servo systems. This paper describes three aspects of the local feedback program: design; commissioning; and limitation. The system design is explained by identifying major elements such as beam position detectors, signal processors, compensation amplifiers, ratio amplifiers, trim equalizers and microprocessor feedback controllers. System commissioning involves steps such as matching trim compensation, determination of local orbit bumps, measurement of open loop responses and design of servo circuits. Several limitations of performance are also discussed. 7 refs., 2 figs.
Date: January 1, 1991
Creator: Singh, O.V.; Nawrocky, R. & Flannigan, J.
Partner: UNT Libraries Government Documents Department

An automatic beam steering system for the NSLS X-17T beam line using closed orbit feedback

Description: Initial observations of motion of the undulator radiation in the NSLS X-17T beam line clearly indicated that the beam had to be stabilized in both directions to be usable for the planned soft x-ray imaging experiments. The low frequency spectra of beam motion contained peaks in the range from dc to 60 Hz and at higher frequencies. A beam steering system employing closed orbit feedback has been designed and installed to stabilize the beam in both planes. In each plane of motion, beam position is measured with a beam position detector and a correction signal is fed back to a local four magnet orbit bump to dynamically control the angle of the radiation at the source. This paper describes the design and performance of the beam steering system.
Date: January 1, 1987
Creator: Nawrocky, R.J.; Ma, Li; Rarback, H.M.; Singh, O.V. & Yu, L.H.
Partner: UNT Libraries Government Documents Department

A digital feedback system for orbit stabilization

Description: The authors are reporting on the design and preliminary results of a prototype digital feedback system for the storage rings at the NSLS. The system will use a nonlinear eigenvector decomposition algorithm. It will have a wide dynamic range and will be able to correct noise in the orbit over a bandwidth in excess of 60 Hz. A Motorola-167 CPU board is used to sample the PUE`s at a minimum rate of 200 Hz and an HP-742rt board is used to read the sampled signals and to generate a correction signal for the orbit correctors.
Date: July 1, 1993
Creator: Friedman, A.; Bozoki, E.; Singh, O. & Smith, J.
Partner: UNT Libraries Government Documents Department


Description: A visible synchrotron light monitor (SLM) beam line has been designed at the NSLS2 storage ring, using the bending magnet radiation. A retractable thin absorber will be placed in front of the first mirror to block the central x-rays. The first mirror will reflect the visible light through a vacuum window. The light is guided by three 6-inch diameter mirrors into the experiment hutch. In this paper, we will describe design work on various optical components in the beamline. The ultra high brightness NSLS-II storage ring is under construction at Brookhaven National Laboratory. It will have 3GeV, 500mA electron beam circulating in the 792m ring, with very low emittance (0.9nm.rad horizontal and 8pm.rad vertical). The ring is composed of 30 DBA cells with 15 fold symmetry. Three damping wigglers will be installed in long straight sections 8, 18 and 28 to lower the emittance. While electrons pass through the bending magnet, synchrotron radiation will be generated covering a wide spectrum. There are other insertion devices in the storage ring which will generate shorter wavelength radiation as well. Synchrotron radiation has been widely used as diagnostic tool to measure the transverse and longitudinal profile. Three synchrotron light beam lines dedicated for diagnostics are under design and construction for the NSLS-II storage ring: two x-ray beam lines (pinhole and CRL) with the source points from Cell 22 BM{_}A (first bending in the DBA cell) and Cell22 three-pole wiggler; the third beam line is using visible part of radiation from Cell 30 BM{_}B (second bending magnet from the cell). Our paper focuses on the design of the visible beam line - SLM.
Date: March 28, 2011
Creator: Cheng, W.; Fernandes, H.; Hseuh, H.; Kosciuk, B.; Krinsky, S. & Singh, O.
Partner: UNT Libraries Government Documents Department

BPM Button Optimization to Minimize Distortion Due to Trapped Mode Heating

Description: The outer circumference of a BPM button and the inner circumference of the button housing comprise a transmission line. This transmission line typically presents an impedance of a few tens of ohms to the beam, and couples very weakly to the 50 ohm coaxial transmission line that comprises the signal path out of the button. The modes which are consequently excited and trapped often have quality factors of several hundred, permitting resonant excitation by the beam. The thermal distortion resulting from trapped mode heating is potentially problematic for achieving the high precision beam position measurements needed to provide the sub-micron beam position stability required by light source users. We present a button design that has been optimized via material selection and component geometry to minimize both the trapped mode heating and the resulting thermal distortion.
Date: May 4, 2009
Creator: Cameron,P.; Blednyk, A.; Kosciuk, B.; Pinayev, I.; Ravindranath, I. & Singh, O
Partner: UNT Libraries Government Documents Department