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

对将用于大型强子对撞机（LHC） ATLAS实验的μ子触发室的薄间隙室（TGC）进行了研发研究。根据1995年的结果，从检测效率的角度来看，CO_2n+正戊烷混合气体是合适的。因此，1996年对这种气体混合物进行了老化试验。在ATLAS实验中，将实验室连续10年暴露于与预期辐射量相符的β射线中，并对实验室性能的恶化情况进行了检测。在辐照过程中，放大因子和时间分辨率均未见明显恶化。当辐射率为100kHz/cm^2时，检测效率接近100%，预期辐射率最高可达1kHz/ cm^2，可安全用于ATLAS实验。CO_2+正戊烷由于电子漂移速度较慢，其时间分辨率略低于CF_4+异丁烷。为了提高这一时间分辨率，构建了导线间距较小的腔室并进行了测试。提高了时间分辨率，使我们能够在ATLAS实验中识别连续的交叉束。已知从相互作用点出来的介子以5-40度的入射角进入TGC。测量了该入射角对时间分辨率的依赖性，并发现与蒙特卡罗模拟的期望一致。综上所述，我们对CO_2+正戊烷混合气体的薄壁腔的各种性能进行了详细的测试，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.