Very fast front end ASIC associated with multi-anode PMTs for a scintillating-fibre beam hodoscope

Abstract

For developing a scintillating-fibre beam monitor, wehave designed a front-end 16-Channel readout chip (version 2) to beassociated with Multi-anode photomultipliers Ma-PMTs (Hamamatsu H8500) in a0.35 μm BiCMOS process. Each channel of the ASIC consists of one inputcurrent conveyor driving separately a current comparator for signal eventdetection and a charge-sensitive amplifier (CSA) for signal chargemeasurement. The ASIC has brought significant improvements compared to itsprevious version: larger input dynamic range (53 dB against 33 dB), lowerpower consumption (11 mW/channel instead of 22 mW/channel under a 3.3-Vsupply), lower noise (4 fC versus 19 fC in Equivalent input Noise Charge, orENC) and a better phase margin for optimizing stability and speed. Thisdedicated chip had been used in a beam test at HIT (Heidelberg Ion-BeamTherapy Center). System testing has shown achievements of 1 mm spatialresolution (size of the scintillating fibers) and a 4 MHz count rate. Themain limitation comes from the Ma-PMTs which saturates at such a frequency.The ASIC operates normally with satisfied performances.