A 64-Channel Wide Dynamic Range Charge Measurement ASIC for Strip and Pixel Ionization Detectors

In this paper we report a 64-channel application specified integrated circuit (ASIC) for the readout of parallel plate strip and pixel ionization detectors. The detectors measure the intensity and the geometrical characteristics of a hadron beam for hadrontherapy cancer treatments. The ASIC is based on a current to frequency converter followed by a counter. It uses a charge balancing integration technique to obtain a dynamic range in excess of$10^5$with a nonlinearity of less than 1%. The ASIC has been designed in a CMOS 0.8$mu m$technology and it has been used for the readout of both strip ionization detectors for beam calibration and pixel detectors for beam monitoring during treatment. A new version of the chip in CMOS 0.35$mu m$technology which allows bipolar input currents has been designed and is currently under test.