A gas avalanche light detector for multi-kiloton liquid argon TPC

We are developing a photodetector sensitive to liquid noble gas scintillation light which is able to operate down to liquid nitrogen temperature (77 K). It has to be able to produce fast signals for timing and triggering purposes in multi-kiloton liquid argon time projection chambers. We studied the possibility to couple a standard photocathode to a suitable electron multiplication system in gas. In the first part of the programme the gas avalanche multiplication at cryogenic temperature and low pressure was studied. The second part of the programme foresees the production of a photocathode able to operate at low temperature. A complete detector prototype is going to be set up. It will consist of a simple CsSb photocathode and a multiplication stage made of 100μ m stainless steel wires. We present the results of the evaluation of the gain attainable with different gas mixtures.