GAS GAIN STABILITY OF MSGCS OPERATING AT HIGH-RATE

Micro Strip Gas Counters (MSGCs) with coated and uncoated borosilicate glass substrates have been investigated on their high rate capability and long-term gas gain stability. It is shown that the gain remains a lmost constant at count rates up to 10(5) mm(-2) s(-1) when a semicond uctive layer of S8900 glass or polydiamond is applied under or over th e strips. The application of such a coating also favours the gain stab ility at long-term operation. However, the maximum attainable gas gain for coated substrates is 4-10 times smaller than for bare borosilicat e glass supports. For the latter substrate type, we observe less agein g when the strips are made of nickel instead of aluminium or copper.