Development of the readout system for the K2K SciBar detector

Readout electronics for the scintillation bar tracking detector (SciBar) in the K2K neutrino oscillation experiment has been newly developed. Its purpose is to make a readout system for multi-anode photo-multiplier (MAPMT) be compact. A combination of ASICs (VA32HDR11 and TA32CG) is employee to multiplex pulse-height information from each anode of a 64-channel MAPMT and to make a fast triggering signal. A frontend circuit board to be attached to MAPMT is designed to generate biases for ASICs and to relay control signals. A backend electronics module is also newly developed. It is implemented using programmable logic devices and analog devices to generate control signals and digitize multiplexed signals. The system has enough low noise, less than 0.3 photo-electrons and good linearity up to 300 photo-electrons for MAPMTs at the gain of 5×10⁵.