Study of Deterioration Resistive Plate Chamber

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This research is to investigate deterioration properties of a resistive plate chamber. In particular, we investigate why the chamber gets not to work under the operation of (1) the mixing gas with a little vapor and (2) with large dark current. Up to now, no clear evident was reported for this deterioration of the chamber.One of the reasons why such a study was not performed was that the chamber was made of two resistive glass plates glued by hard bond. This breaks the glass plates when we want to open and see inside the chamber and made it difficult to investigate the deterioration.In this study, we made a new chamber which has two electrodes on the glass plate and can be opened without breaking the glass plates . To build such a chamber was possible by making the gas sealing with silicon grease and bolts. The plan is that the one side of the electrodes is operated with normal HV and the other is operated with destructive HV.When the one operated with destructive HV is dead, we open the chamber and compare both sides of the electrodes.Using the chamber built, we first tested the performance of the chamber with normal operational HV.The chamber worked with high detection efficiencies of 〜90% for both electrodes and the dark current was normal up to HV=4300V.However, the chamber got spark off and could not go up more than 4300V.Because of this trouble, we decided to open up the chamber and to investigate why the chamber sparks off. We will continue to investigate this research after fixing the chamber.