The stability of the gain of the photomultiplier (PMT) camera for the Fluorescence Detector (FD) of the Telescope Array experiment was monitored using an 241Am loaded scintillator pulsers (YAP) and a diffused xenon flasher (TXF) for a selected set of 35 PMT-readout channels. From the monitoring of YAP pulses over four years of FD operation, we found slow monotonic drifts of PMT gains at a rate of -1.7∼+1.7%/year. An average of the PMT gains over the 35 channels stayed nearly constant with a rate of change measured at -0.01±0.31(stat)±0.21(sys)%/year. No systematic decrease of the PMT gain caused by the night sky background was observed. Monitoring by the TXF also tracked the PMT gain drift of the YAP at 0.88±0.14(stat)%/year.
|Number of pages||8|
|Journal||Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment|
|Publication status||Published - 2014 Dec 21|
Bibliographical noteFunding Information:
We gratefully acknowledge Dr. M. Korjik and Prof. M. Kobayashi for elucidating discussions on the construction of the YAP pulser and its performance. The Telescope Array experiment is supported by the Japan Society for the Promotion of Science through Grants-in-Aid for Scientific Research on Specially Promoted Research ( 21000002 ) “Extreme Phenomena in the Universe Explored by Highest Energy Cosmic Rays”, and the Inter-University Research Program of the Institute for Cosmic Ray Research; by the U.S. National Science Foundation awards PHY-0307098 , PHY-0601915 , PHY-0703893 , PHY-0758342 , and PHY-0848320 (Utah) and PHY-0649681 (Rutgers); by the National Research Foundation of Korea ( 2006-0050031 , 2007-0056005 , 2007-0093860 , 2010-0028071 , 2013004883 ); by the Russian Academy of Sciences , RFBR grants 10-02-01406a and 11-02-01528a (INR), IISN project No. 4.4509.10 and Belgian Science Policy under IUAP VI/11 (ULB). The foundations of Dr. Ezekiel R. and Edna Wattis Dumke, Willard L. Eccles and the George S. and Dolores Dore Eccles all helped with generous donations. The State of Utah supported the project through its Economic Development Board, and the University of Utah through the Office of the Vice President for Research. The experimental site became available through the cooperation of the Utah School and Institutional Trust Lands Administration (SITLA), U.S. Bureau of Land Management and the U.S. Air Force. We also wish to thank the people and the officials of Millard County, Utah, for their steadfast and warm support. We gratefully acknowledge the contributions from the technical staffs of our home institutions and the University of Utah Center for High Performance Computing (CHPC). This work was partially supported by the Research Fund of Hanyang University ( HY-2009-O ).
© 2014 Elsevier B.V. All rights reserved.
All Science Journal Classification (ASJC) codes
- Nuclear and High Energy Physics