Proposal for a Wire Chamber-Based CsI Photocathode for a B-Factory RICH

A design is considered for a CsI photocathode incorporating a proportional wire anode plane. This would have the advantage over the previously considered mesh anode or near wire anode that the anode wires could be moved further away from the cathode pads, allowing position to be determined using interpolation of imaged charge. This would enable comparable or superior position resolution with larger pads, ultimately reducing the channel count. Another advantage would be that the larger gap would simplify the mechanical design and reduce the risk of electrical breakdown, particularly when compared to the mesh-anode design, which behaves as a parallel plate chamber. This note discusses the optimum design parameters (spacing, gas-gain, etc) and estimated performance for such a scheme.