分类： 物理学 >> 核物理学 提交时间： 2016-09-13
DONG Ming-Yi
XIU Qing-Lei
WU Ling-Hui
WU Zhi
QIN Zhong-Hua
SHEN Pin
AN Fen-Fen
JU Xu-Dong
LIU Yi
ZHU Kai
OU-YANG Qun
CHEN Yuan-Bo
摘要： As the main tracking detector of BESIII, the drift chamber works for accurate measurements of the tracking and the momentum of the charged particles decayed from the reaction of BEPCII e+ and e-. After operation six years, the drift chamber is suffering from aging problems due to huge beam related background. The gains of the cells in the first ten layers experience an obvious decrease, reaching a maximum of about 29% for the first layer cells. Two calculation methods for the gains change (Bhabha events and accumulated charges with 0.3% aging ratio for inner chamber cells) get almost the same results. For the Malter effect encountered by the inner drift chamber in Jan., 2012, about 0.2% water vapor was added to MDC gas mixture to solve this cathode aging problem. These results provide an important reference for MDC operation high voltage setting and the upgrade of the inner drift chamber.
分类： 物理学 >> 核物理学 提交时间： 2016-09-13
GUO Yue
WANG Liang-Liang
JU Xu-Dong
WU Ling-Hui
XIU Qing-Lei
WANG Hai-Xia
DONG Ming-Yi
HU Jing-Ran
LI Wei-Dong
LI Wei-Guo
LIU Huai-Min
OU-YANG Qun
SHEN Xiao-Yan
YUAN Ye
ZHANG Yao
摘要： Considering the aging effects of existing Inner Drift Chamber (IDC) of BES\uppercase\expandafter{\romannumeral3}, a GEM based inner tracker is proposed to be designed and constructed as an upgrade candidate for IDC. This paper introduces a full simulation package of CGEM-IT with a simplified digitization model, describes the development of the softwares for cluster reconstruction and track fitting algorithm based on Kalman filter method for CGEM-IT. Preliminary results from the reconstruction algorithms are obtained using a Monte Carlo sample of single muon events in CGEM-IT.
分类： 物理学 >> 核物理学 提交时间： 2016-08-31
摘要： The optimization of resistive anode for two dimensional imaging detectors which consists of a series of high resistive square pads surrounding by low resistive strips has been studied by both numerical simulations and experimental tests. It has been found that to obtain good detector performance, the resistance ratio of the pad to the strip should be larger than 5, the nonuniformity of the pad surface resistivity had better be less than 20%, a smaller pad width leads to a smaller spatial resolution and when the pad width is 6mm, the spatial resolution (σ) can reach about 105μm. Based on the study results, a 2-D GEM detector prototype with the optimized resistive anode is constructed and a good imaging performance is achieved.
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