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Title: Tuning the narrow-band beam position monitor sampling clock to remove the aliasing errors in APS storage ring orbit measurements.

Abstract

The Advanced Photon Source storage ring employs a real-time orbit correction system to reduce orbit motion up to 50 Hz. This system uses up to 142 narrow-band rf beam position monitors (Nbbpms) in a correction algorithm by sampling at a frequency of 1.53 kHz. Several Nbbpms exhibit aliasing errors in orbit measurements, rendering these Nbbpms unusable in real-time orbit feedback. The aliasing errors are caused by beating effects of the internal sampling clocks with various other processing clocks residing within the BPM electronics. A programmable external clock has been employed to move the aliasing errors out of the active frequency band of the real-time feedback system (RTFB) and rms beam motion calculation. This paper discusses the process of tuning and provides test results.

Authors:
;  [1]
  1. (Accelerator Systems Division (APS))
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1014787
Report Number(s):
ANL/ASD/CP-59537
TRN: US1102747
DOE Contract Number:
DE-AC02-06CH11357
Resource Type:
Conference
Resource Relation:
Conference: Particle Accelerator Conference (PAC07); Jun. 25, 2007 - Jun. 29, 2007; Albuquerque, NM
Country of Publication:
United States
Language:
ENGLISH
Subject:
43 PARTICLE ACCELERATORS; ACCELERATORS; ADVANCED PHOTON SOURCE; ALGORITHMS; BEAM POSITION; FEEDBACK; MONITORS; PROCESSING; SAMPLING; STORAGE RINGS; TUNING

Citation Formats

Sun, X., and Singh, O.. Tuning the narrow-band beam position monitor sampling clock to remove the aliasing errors in APS storage ring orbit measurements.. United States: N. p., 2007. Web. doi:10.1109/PAC.2007.4440019.
Sun, X., & Singh, O.. Tuning the narrow-band beam position monitor sampling clock to remove the aliasing errors in APS storage ring orbit measurements.. United States. doi:10.1109/PAC.2007.4440019.
Sun, X., and Singh, O.. Mon . "Tuning the narrow-band beam position monitor sampling clock to remove the aliasing errors in APS storage ring orbit measurements.". United States. doi:10.1109/PAC.2007.4440019.
@article{osti_1014787,
title = {Tuning the narrow-band beam position monitor sampling clock to remove the aliasing errors in APS storage ring orbit measurements.},
author = {Sun, X. and Singh, O.},
abstractNote = {The Advanced Photon Source storage ring employs a real-time orbit correction system to reduce orbit motion up to 50 Hz. This system uses up to 142 narrow-band rf beam position monitors (Nbbpms) in a correction algorithm by sampling at a frequency of 1.53 kHz. Several Nbbpms exhibit aliasing errors in orbit measurements, rendering these Nbbpms unusable in real-time orbit feedback. The aliasing errors are caused by beating effects of the internal sampling clocks with various other processing clocks residing within the BPM electronics. A programmable external clock has been employed to move the aliasing errors out of the active frequency band of the real-time feedback system (RTFB) and rms beam motion calculation. This paper discusses the process of tuning and provides test results.},
doi = {10.1109/PAC.2007.4440019},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}

Conference:
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  • 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 ringmore » 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.« less
  • This paper will present the final tests of the APS storage ring BPM electronic system. The final configuration includes the filter-comparator installed in the accelerator tunnel and the signal conditioning and digitizing unit (SCDU) in a VXI configuration. The SCDU includes an AM/PM monopulse receiver at 352 MHz. Extensive testing was performed on the system. The key parameters measured were the null cancellation better than 45 db, dynamic range of better than 40 db, single bunch capability with 0.01 mA sensitivity, and a resolution better than 10 micron for 512 averaged turns. This last critical performance was tested using amore » moving wire to simulate the beam. This report will concentrate on the wire test results. Also, the actual production hardware will be presented.« less
  • This paper will present the final tests of the APS storage ring BPM electronic system. The final configuration includes the filter-comparator installed in the accelerator tunnel and the signal conditioning and digitizing unit (SCDU) in a VXI configuration. The SCDU includes an AM/PM monopulse receiver at 352 MHz. Extensive testing was performed on the system. The key parameters measured were the null cancellation better than 45 db, dynamic range of better than 40 db, single bunch capability with 0.01 mA sensitivity, and a resolution better than 10 micron for 512 averaged turns. This last critical performance was tested using amore » moving wire to simulate the beam. This report will concentrate on the wire test results. Also, the actual production hardware will be presented.« less
  • Beam position monitors (BPMs) are used in accelerators and ion experiments to measure currents, position, and azimuthal asymmetry. These usually consist of discrete arrays of electromagnetic field detectors, with detectors located at several equally spaced azimuthal positions at the beam tube wall. The discrete nature of these arrays introduces systematic errors into the data, independent of uncertainties resulting from signal noise, lack of recording dynamic range, etc. Computer simulations were used to understand and quantify these aliasing errors. If required, aliasing errors can be significantly reduced by employing more than the usual four detectors in the BPMs. These simulations showmore » that the error in measurements of the centroid position of a large beam is indistinguishable from the error in the position of a filament. The simulations also show that aliasing errors in the measurement of beam ellipticity are very large unless the beam is accurately centered. The simulations were used to quantify the aliasing errors in beam parameter measurements during early experiments on the DARHT-II accelerator, demonstrating that they affected the measurements only slightly, if at all.« less
  • A high-current Proton Storage Ring (PSR) is being constructed at Los Alamos to accumulate intense pulses of 800-MeV protons from LAMPF for delivery to neutron production targets. The beam's transverse location in the injection channel, ring, and extraction channel will be determined by a beam position monitor (BPM) system. The beam will be detected by stripline sensors that generate 4-quadrant position signals from the spectral components of the beam. Sixty sensors are planned for the installation, with their outputs selected by broadband RF multiplexers. The sensor outputs are processed by a differential phase correlator detector to produce an analog signalmore » proportional to the position of the beam centroid. Digital conversion and processing will give overall resolution of the horizontal and vertical position of the beam at each sensor location to +-2 mm. The monitor will operate over the intensity range of 3 x 10/sup 8/ protons/bunch to 5 x 10/sup 13/ protons/bunch. The beam-position system contains CAMAC-based instrumentation for display in three formats, including an azimuth histogram, a time plot, and a numerical readout. The monitor system also includes a microprocessor-based check and exerciser unit to serve as a design aid and maintenance tool.« less