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TY - CONF AU - Brajnik, G. AU - Bassanese, S. AU - Cautero, G. AU - De Monte, R. AU - Ferianis, M. AU - Rehm, G. ED - Liu, Zhengzheng ED - Lidia, Steven ED - McCausey, Amy ED - Schaa, Volker RW TI - Reducing Current Dependence in Position Measurements of BPM Systems by Using Pilot Tone: Quasi-Constant Power Approach J2 - Proc. of IBIC2017, Grand Rapids, MI, USA, 20-24 August 2017 C1 - Grand Rapids, MI, USA T2 - International Beam Instrumentation Conference T3 - 6 LA - english AB - 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. PB - JACoW CP - Geneva, Switzerland SP - 301 EP - 303 KW - ion KW - storage-ring KW - controls KW - operation KW - electron DA - 2018/03 PY - 2018 SN - 978-3-95450-192-2 DO - 10.18429/JACoW-IBIC2017-TUPWC09 UR - http://jacow.org/ibic2017/papers/tupwc09.pdf ER -