Study of Resistive Plate Chamber with high rate capability

抵抗板室（RPC）是充电粒子的探测器之一。在日本，这是大型RPC系统第一次被用于在KEK B工厂检测KL和Muons的BELLE实验。这些RPC是用玻璃制成的。A gas mixture for BELLE experiment is 30%Ar，8%Butane，62%freon（134 a） as a standard gas mixture。RPCs在许多不同的流媒体模式下运行，因此，速率能力更差，因为检测电荷颗粒的有效性小于90%，约0.3赫兹/厘米^2。在贝尔，由于光束电流和亮度的增加，外盖帽的RPC受到了影响，背景下~ 1Hz/cm^2，由于光束隧道中的中子，所以效率从98%下降到60%。本研究的目的是提高速率能力，我们通过测量宇宙射线测试了10个玻璃RPCs的性能，当RPCs的单计数<60>率手动改变时，我们发现效率和单计数率之间的关系是一个公式， η= 1-τ·f，η是一个有效的， τ an有效的死亡时间（s·cm^2）， f a单计数率（Hz/cm^2）。If τ is smaller， η will be higher even if the background rate （f） is higher。用于standard gas mixture的标准gas 0.47 （s·cm^2）。As a result of studying the gas mixture， the？becomes 0. 15（s·cm^2） for the gas mixture of 50%Ar，8%Butane，37%freon，5%SF_6。在有效的死亡时间里，这三次会有更好的改善。If we supply high voltage to keep plateau efficiency， the？becomes 0.05 （s· cm^2） which is ~ 10 times better。这一改进是在1Hz/cm^95%的有效性。这些结果于9月在JPS会议上提出。2004年10月，IEEE 2004年国际会议。

A resistive plate chamber (RPC) is one of detectors of charged particles. In Japan, it was the first time that the large RPCs system was used to detect KL and muons in BELLE experiment at KEK B-factory. Those RPCs were made from glass. A gas mixture for BELLE experiment is 30% Ar, 8 % Butane, 62% freon (134a) as a standard gas mixture. The RPCs have been operated in streamer mode with many advantages, however a rate capability is worse as an efficiency of detecting charge particles is less than 90% at about 0.3Hz/cm^2. In BELLE, as an increasing of beam currents and luminosity, the RPCs of outer-layer at endcap have been affected by background of ~ 1Hz/cm^2 due to neutrons from beam tunnel, so that the efficiency drooped to about 60% from 98%. A purpose of this study is to improve the rate capability.We tested a performance of 10 glass RPCs by measuring cosmic rays, when single count rates of RPCs were changed manually by using ^<60>Co. We found a relation between the efficiency and single count rate to be a formula, η= 1-τ・f, where η is an efficiency, τ an effective dead time (s・cm^2), f a single count rate (Hz/cm^2). If τ is smaller, η will be higher even if the background rate (f) is higher. The τ is 0.47 (s・cm^2) for the standard gas mixture. As a result of studying the gas mixture, the τ becomes 0.15 (s・cm^2) for the gas mixture of 50% Ar, 8% Butane, 37% freon, 5% SF_6. This is three times better improvement in the effective dead time. If we supply high voltage to keep plateau efficiency, the τ becomes 0.05 (s・ cm^2) which is ~ 10 times better. This improvements is the efficiency to be ~ 95 % at 1Hz/cm^2.These results were presented at JPS meeting in Sept. 2004, International conference of IEEE2004 in Oct.2004.