Publications (172) View all
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Article: Implementation of a Software Feedback Control for the CMS Monitoring Lasers
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ABSTRACT: Light monitoring will play a crucial role in maintaining the energy resolution of the CMS lead tungstate crystal electromagnetic calorimeter (ECAL) in situ at LHC. Since 2001, a laser based monitoring system has been used in the CMS ECAL beam tests at CERN. While the stability of the laser pulse energy and width, measured in 24 hours, is at a level of 3%, a long term degradation of both the laser pulse energy and the width were observed, as well as a drift of the laser pulse center timing at 2 ns/day. This degradation and drift, caused by the natural aging of the DC Kr lamp, would affect respectively the monitoring precision and the synchronization between the laser pulse and the ECAL ADC clock. This paper presents a design and implementation of a software feedback control which stabilizes the laser pulse energy, width and timing. With the software feedback implemented, a stability of the laser pulse energy and width at 3% level and a pulse timing jitter at 2 ns were observed in laser runs lasted for more than 3 months. The 0.5% energy resolution of the CMS crystal ECAL is maintained after applying the laser monitoring corrections in a beam irradiation test.IEEE Transactions on Nuclear Science 03/2008; · 1.45 Impact Factor -
Conference Proceeding: Implementation of a Software Feedback Control for the CMS Monitoring Lasers
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ABSTRACT: Light monitoring will play a crucial role in maintaining energy resolution for the CMS lead tungstate crystal calorimeter in situ at LHC. Since 2003, a laser based monitoring system in its final design has been installed and used in beam tests at CERN. While the stability of the laser pulse energy and FWHM width, measured in 24 hours, is at 3% level, a long term degradation and a drift of the laser pulse center timing at 2 ns/day were observed. The degradation and drift were caused by the aging of the DC Kr lamp used to pump the Nd:YLF laser, and would affect the monitoring precision. This paper presents the design and implementation of a software feedback control which stabilizes laser pulse energy, width and timing by trimming the Nd:YLF laser pumping current. For laser runs lasted for more than 650 hours a stability of pulse energy and FWHM width at 3% level and a pulse timing jitter at 2 ns have been achieved when the laser pulse center timing is used as the feedback parameter.Nuclear Science Symposium Conference Record, 2006. IEEE; 12/2006 -
Article: Fast Neutron Induced Nuclear Counter Effect in Hamamatsu Silicon PIN Diodes and APDs
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ABSTRACT: Neutron induced nuclear counter effect in Hama-matsu silicon PIN diodes and APDs was measured by irradiating fast neutrons from a pair of 252 Cf sources directly to these de-vices. It was found that the entire kinetic energy of these neutrons may be converted into electron signals in these devices, leading to anomalous signals of up to a few million electrons in a single isolated calorimeter readout channel. Signals of such amplitude represent equivalent energy of several hundred GeV and a few GeV for PWO and LSO/LYSO crystals respectively assuming the corresponding light yields of 4 and 800 p.e./MeV. The overall rate of the neutron induced nuclear counter effect in APDs is found to be more than an order of magnitude less than that in PIN diodes. Increasing the APD gain was also found to reduce the neutron induced nuclear counter effect. An intelligent front-end chip capable of selecting un-contaminated signal is proposed to eliminate completely the nuclear counter effect without significant cost increase.IEEE Transactions on Nuclear Science 01/2011; 1. · 1.45 Impact Factor -
Article: LSO/LYSO Crystals for Future HEP Experiments
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ABSTRACT: Because of their high stopping power (X0 = 1.14 cm), fast (t = 40 ns) and bright (4 times of BGO) scintillation and good radiation hardness, cerium doped silicate based heavy crystal scintillators (LSO and LYSO) have attracted a broad interest in the high energy physics community pursuing precision electromagnetic calorimeter in severe radiation environment. We present in this paper current status of large size LSO and LYSO crystals adequate for HEP applications. The optical and scintillation properties and their radiation hardness are discussed.J. Phys.: Conf. Ser. 01/2011; 293215220. -
Conference Proceeding: Gamma ray induced radiation damage in PWO and LSO/LYSO crystals
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ABSTRACT: This paper compares ¿-ray induced radiation damage effect in two kinds of heavy crystal scintillators: PWO and LSO/LYSO. Scintillation emission, optical transmission, light output, decay kinetics and light response uniformity were measured for PWO and LSO/LYSO crystal samples of large size before and after ¿-ray irradiations. ¿-ray induced phosphorescence was also measured, and the corresponding readout noise was determined.Nuclear Science Symposium Conference Record (NSS/MIC), 2009 IEEE; 12/2009
