Development of the GEM tracker for the J-PARC E16 experiment

作者：Komatsu Yusuke^*; Aoki Kazuya; Aramaki Yoki; En'yo Hideto; Kanno Koki; Kawama Daisuke; Masumoto Shinichi; Nakai Wataru; Obara Yuki; Ozawa Kyoichiro; Sekimoto Michiko; Shibukawa Takuya; Takahashi Tomonori; Watanabe Yosuke; Yokkaichi Satoshi

来源：Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment , 2013, 732: 241-244.

DOI：10.1016/j.nima.2013.08.024

• Tracker
• GEM
• Position resolution

The J-PARC E16 experiment has been proposed to measure the mass spectrum of phi mesons in nuclear matter to study the origin of QCD mass. The phi mesons are identified in the e(+) e(-) decay channel and the mass of these phi mesons is reconstructed using the momenta of the e(+) and e(-) pairs. A tracking detector for this experiment is composed of a position sensitive device that employs Gas Electron Multipliers (GEMs) with a two-dimensional readout board. The ionization electrons are amplified with a triple-GEM stack. The required position resolution is 100 mu m up to an incidence angle of 30 degrees.
Position resolutions and efficiencies of the tracking device are evaluated using a pi(-) beam with a momentum of 1.0 GeV/c at the J-PARC K1.1 BR beam line. A position resolution of better than 100 mu m is obtained by calculating the center of gravity of the charges on the readout strips when tracks arrive perpendicularly at the detector plane. Timing information of charge clusters is essential to improve the position resolutions for the inclined tracks. The arrival times of the charge clusters are derived from the wave forms collected by flash ADC modules. Using the arrival times of the clusters, the obtained position resolution is better than 100 mu m for the track inclinations of 15 degrees and 30 degrees. The detection efficiency is also investigated as a function of the GEM gains, and the operational voltage is optimized.

• 出版日期2013-12-21