The ALICE muon trigger (MTR) system consists of 72 Resistive Plate Chamber (RPC) detectors arranged in two stations, each composed of two planes with 18 RPCs per plane. The detectors are operated in maxi-avalanche mode using a mixture of 89.7% C₂H₂F₄, 10% i-C₄H₁₀ and 0.3% SF₆. A number of detector performance indicators, such as efficiency and dark current, have been monitored over time throughout the LHC Run2 (2015–18). While the efficiency showed very good stability, a steady increase in the absorbed dark current was observed.

Since the end of 2018, the LHC has entered a phase of long shutdown, during which the ALICE experiment will be upgraded to cope with the next phase of data taking, expected in 2021. The MTR is undergoing a major upgrade of the front-end and readout electronics, and will change its functionalities, becoming a Muon Identifier[1]. Only the replacement of the most irradiated RPCs is planned during the upgrade. It is therefore important to perform dedicated studies to gain further insights into the status of the detector. In particular, two RPCs were flushed with pure Ar gas for a prolonged period of time and a plasma was created by fully ionizing the gas. The output gas was analyzed using a Gas Chromatograph combined with a Mass Spectrometer and the possible presence of fluorinated compounds originating from the interaction of the plasma with the detector inner surfaces has been assessed using an Ion-Selective Electrode station.

This contribution will include a detailed review of the ALICE muon RPC performance at the LHC; the procedure and results of the argon plasma test, described above, are also discussed.

ALICE 介子触发 (MTR) 系统由 72 个电阻板室 (RPC) 探测器组成，这些探测器布置在两个站中，每个站由两个平面组成，每个平面有 18 个 RPC。_{探测器使用 89.7% C 2} H ₂ F ₄、10% iC ₄ H ₁₀和 0.3% SF ₆的混合物以最大雪崩模式运行。在整个 LHC Run2（2015-18 年）期间，随着时间的推移监测了许多探测器性能指标，例如效率和暗电流。虽然效率显示出非常好的稳定性，但观察到吸收的暗电流稳定增加。

2018年底以来，大型强子对撞机进入长期停运阶段，期间将升级ALICE实验以应对预计在2021年进行的下一阶段数据采集。港铁正在对前端进行重大升级和读出电子设备，并将改变其功能，成为介子标识符[1]。升级期间仅计划更换辐照最多的 RPC。因此，进行专门的研究以进一步了解探测器的状态非常重要。特别是，用纯 Ar 气体长时间冲洗两个 RPC，并通过完全电离气体产生等离子体。

该贡献将包括对 LHC 的 ALICE muon RPC 性能的详细审查；也讨论了上述氩等离子体测试的程序和结果。