Development of a 128-Channel Readout System for a Multistrip Ionization Chamber in PREF

A new 128-channel readout system is designed for a multistrip ionization chamber (MSIC) of the Proton radiation effects facility (PREF) end station. This system consists of 128 ultralow noise analog front-ends (AFEs), 16 eight-channel 60 Msps simultaneous sampling analog-to-digital converters (ADCs), 8 Kintex-7 field-programmable gate arrays (FPGA), and a Zynq FPGA. It is capable of monitoring weak current signals of 25 pA-1.8 mu A with an analog bandwidth of 1 kHz. The Kintex-7 FPGA is an intermediate buffer stage, designed to decode the ADC's serial output data and to perform digital signal processing algorithms. Finally, the Zynq FPGA performs data aggregation, beam profile fitting, and data interaction with the host computer. During offline tests, the effective number of bits (ENOB) is 12 bits at an AFE gain of 500 k Omega, and the nonlinearity of the full-scale is less than 0.12%. Finally, the system is deployed for the beam profile measurement with an MSIC at the Cooling Storage Ring of the Heavy Ion Research Facility in Lanzhou (HIRFL-CSR) and the PREF. This readout system not only performs an accurate beam profile measurement, but also can monitor the beam flatness, symmetry, and scanning uniformity. In a word, this system plays an important role in the fields of extremely weak beam profile measurements.