High precision, low disturbance calibration system for the CMS Barrel Electromagnetic Calorimeter High Voltage apparatus. (30th January 2017)

• Record Type: Journal Article
• Authors: Fasanella, G.
• Is Part Of: Journal of instrumentation. Volume 12:Number 1(2017:Jan.)
• Page Start: C01090
• Page End: C01090
• Publication Date: 2017-01-30
• Subjects: Calorimeters -- Hardware and accelerator control systems; Scientific apparatus and instruments -- Periodicals; 502.84
• DOI: 10.1088/1748-0221/12/01/C01090
• Languages: English
• ISSNs: 1748-0221

Abstract

Abstract: The CMS Electromagnetic Calorimeter utilizes scintillation lead tungstate crystals, with avalanche photodiodes (APD) as photo-detectors in the barrel part. 1224 HV channels bias groups of 50 APD pairs, each at a voltage of about 380 V. The APD gain dependence on the voltage is 3%/V. A stability of better than 60 mV is needed to have negligible impact on the calorimeter energy resolution. Until 2015 manual calibrations were performed yearly. A new calibration system was deployed recently, which satisfies the requirement of low disturbance and high precision. The system is discussed in detail and first operational experience is presented.