Estimation and measurement of effective beam position monitor offsets by using a stored beam

Citation
K. Soutome et al., Estimation and measurement of effective beam position monitor offsets by using a stored beam, NUCL INST A, 459(1-2), 2001, pp. 66-77
Citations number
15
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Spectroscopy /Instrumentation/Analytical Sciences","Instrumentation & Measurement
Journal title
NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT
ISSN journal
0168-9002 → ACNP
Volume
459
Issue
1-2
Year of publication
2001
Pages
66 - 77
Database
ISI
SICI code
0168-9002(20010221)459:1-2<66:EAMOEB>2.0.ZU;2-I
Abstract
In general, a closed orbit distortion is observed as the sum of beam orbit and various noises such as beam position monitor (BPM) setting errors, BPM' s electric response errors, etc. In order to obtain a beam with high perfor mance in a low emittance ring with strong sextupole magnets, it is importan t to pick up information only of the beam orbit and perform orbit correctio ns by using this information. For this purpose we developed a new method of estimating BPM offsets to suppress the noise in the orbit data, based on t he concept of "two-stage magnet alignment with common girders". This alignm ent scheme, adopted in an 8 GeV electron storage ring at SPring-8, reduces high harmonic Fourier components of the orbit which results from magnet mis alignment. Then, the main part of high harmonic components of a measured cl osed orbit is the artificial noise, and these harmful high harmonic compone nts can be extracted as "effective" BPM offsets by filtering a measured clo sed orbit. This method was applied to the SPring-8 storage ring and found t o be effective for reducing residual orbit distortions and a leakage of the dispersion function. To check the reliability of the resulting effective o ffsets, a beam-based measurement was also carried out at some BPMs and the beam position was measured with respect to the center of a nearby quadrupol e magnet. The results were compared with the effective offsets and a reason able agreement was found. (C) 2001 Elsevier Science B.V. All rights reserve d.