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Reducing current dependence in position measurements of BPM systems by using pilot tone: Quasi-constant power approach

DOI: 10.18429/JACoW-IBIC2017-TUPWC09 DOI Help

Authors: G. Brajnik (Elettra-Sincrotrone Trieste) , S. Bassanese (Elettra-Sincrotrone Trieste) , G. Cautero (Elettra-Sincrotrone Trieste) , R. De Monte (Elettra-Sincrotrone Trieste) , M. Ferianis (Elettra-Sincrotrone Trieste) , G. Rehm (Diamond Light Source)
Co-authored by industrial partner: No

Type: Conference Paper
Conference: 6th International Beam Instrumentation Conference
Peer Reviewed: No

State: Published (Approved)
Published: March 2018

Open Access Open Access

Abstract: In BPM systems, the dependence of measured position on beam current is a well-known behaviour due to many factors. Measurements were carried out at Diamond Light Source with the pilot-tone compensated RF front end developed at Elettra and they evidenced a strong link between that issue and the integral non-linearity (INL) of the ADCs. A potential way to reduce this dependence is to change the gain of the preamplifiers following the beam current variation, trying to coerce the ADC into working as close as possible to a specific level. In this paper, along with the results of the tests performed at Diamond, which confirm once again the effectiveness of the front end and of the compensation strategy, an alternative technique is proposed to mitigate the current dependence by using the pilot tone itself. The idea is to maintain constant the total amplitude at the input of the ADCs, which is composed of the signal from the beam plus the pilot tone. Our data demonstrate how, by changing the latter in a convenient way during the current variations, we can achieve a reduction of the dependence by a factor of 10 considering an equivalent current ramp from 10 to 300 mA.

Journal Keywords: ion; storage-ring; controls; operation; electron

Subject Areas: Technique Development, Physics


Technical Areas: RF

Documents:
tupwc09.pdf