R&D of Muon Trigger Chamber for the Use in Proton-proton Collider Experiment

大型强子对撞机（LHC）ATLAS实验中μ子触发室的薄隙室（TGC）已经完成了研制工作。根据1995年的实验结果，从检测效率的角度考虑，CO_2+正戊烷的混合气体是合适的。因此在1996年对这种气体混合物进行了老化试验。将该室暴露于辐射量与ATLAS实验中预期的辐射量相对应的β射线10年，并检查室性能的劣化。在辐照过程中没有观察到放大因子和时间分辨率的显著劣化。在100 kHz/cm ~ 2的辐射率下，探测效率接近100%，由于预期的最大辐射率为1 kHz/cm ~ 2，这种混合气体可以安全地用于ATLAS实验。由于电子漂移速度较慢，CO_2+正戊烷的时间分辨率略差于CF_4+异丁烷。为了提高这种时间分辨率，构造并测试了具有较小线间距的室。在ATLAS实验中，时间分辨率得到了提高，从而可以分辨出连续的交叉束团，从相互作用点出射的μ子以5-40度的入射角进入TGC。测量了时间分辨率与入射角的关系，发现与Monte Carlo模拟的结果一致。总之，我们详细地研究了CO_2+n-pentane混合气体薄间隙室的各种特性，发现它们满足ATLAS实验的要求。

R&D study has been performed for the Thin Gap Chambers (TGC), which will be used for the muon trigger chamber in the ATLAS experiment of Large Hadron Collider (LHC). Based on the results in 1995, it turned out that the gas mixture of CO_2n+n-pentane was suitable from the viewpoint of detection efficiency. So that the aging tests for this gas mixture were carried out in 1996. The chamber was exposed to the beta rays whose radiation amount corresponded to the expected one for 10 years in the ATLAS experiment, and the deterioration of the chamber performance was examined. No significant deterioration was observed during the irradiation for the amplification factor and for the time resolution. The detection efficiency was found to be nearly 100% up the radiation rate of 100kHz/cm^2, and this gas mixture will be safely used in the ATLAS experiment since the expected radiation rate is at maximum 1kHz/^2The time resolution of CO_2+n-pentane is slightly worse than that of CF_4+iso-butane due to its slower electron drift velocity. In order to improve this time resolution, the chamber with smaller wire spacing was constructed and tested. The time resolution was improved so that we can identify successive crossing bunches in the ATLAS experiment.In is known that the muons emerging from the interaction point enter the TGC with the incident angle of 5-40 degrees. The dependence of the time resolution on this incident angle was measured and and found to be consistent with the expectation from the Monte Carlo simulation.In summary, the various properties of Thin Gap Chambers with the gas mixture of CO_2+n-pentane were examined in detail, and we found that they satisfy the requirements of ATLAS experiment.