SOI readout ASIC of pair monitor for International Linear Collider

The pair monitor extracts information on the beam profile at the interaction point of the International Linear Collider. It utilizes the electron and positron number density distribution in the plane perpendicular to the beam direction. The pairs of electrons and positrons are detected by pixel detectors placed close to the beam on both sides of the interaction point, and a readout ASIC that meets the stringent requirements has been developed. In order to measure the beam profile as a function of location within a train and to deal with the high hit rate, the pixel detector is read out in 16 time-slices per bunch train. We develop the prototype ASIC using a 0.2 μ m fully depleted SOI (FD-SOI) CMOS process (OKI Semiconductor Co., Ltd). In this paper, we describe the design of the readout circuit and present the results of the performance tests.