Development of a VLSI-read-out system of crystal calorimeter for space experiment

本研究采用多光电二极管和VLSI芯片，开发了一种低功耗的多量程读出系统。【读出系统的开发】采用多光电二极管和前端电路，包括模拟ASIC、16位ADC和FPGA，开发了一种读出系统，用于测量BGO晶体闪烁体的能量沉积，动态范围从1MIP（最小电离粒子）到10^6MIPs。用宇宙射线μ子标定了1 MIP的输出信号。宇宙射线μ子对BGO光产率的ADC计数约为10.8fC。采用LED脉冲发生器和重离子束对读出系统的动态范围进行了测试，测试范围为1MIP ~约2400 mip。[VA32_HDR14.2的开发]为了优化光电二极管读出电路中具有正极性输入信号的VA32_HDR14.2。采用了0.35μm工艺，大大提高了芯片的抗辐射性能和噪声性能。[辐射硬度测试]对VLSI芯片的辐射硬度进行了波束测试。在VA32HDR14 （0.8μm-process）和VA32HDR14.2 （0.35μm-process）中辐照氦气束，通过测试脉冲测量了总剂量效应引起的噪声级和增益变化。尽管VA32_HD14的硬辐射为1.6Mrad, VA32HDR14.2的硬辐射为74 kRad，但两种芯片均未发现严重损坏。

A multiple range read-out system was developed with the low consumption electric power in which a multi-photo diode and a VLSI chip were used by this research. [Development of read-out system] A read-out system using multi-photo diode and a front-end circuit including analog ASIC, 16 bit ADC and FPGA was developed to measure the energy deposit with the dynamic range from 1MIP (Minimum Ionization Particle) up to 10^6MIPs in a BGO crystal scintillator. The output signal of 1 MIP was calibrated by cosmic ray muon. The ADC count of light yield of BGO by cosmic ray muons was 10.8fC approximately. The dynamic range of the read-out system was tested with both LED pulser and heavy ions beam in the range from 1MIP to about 2400 MIPs. [Development of VA32_HDR14.2] VA32_HDR14.2 which has positive polarity of the input signal was developed newly to optimize it in the read-out circuit of the photo diode. We adapted 0.35μm-technology, and a radiation resistance and noise performance are improved drastically with this chip. [Radiation-hardness test] The beam test to investigate radiation-hardness of the VLSI chip was done. Helium beam was irradiated in VA32HDR14 (0.8μm-process) and VA32HDR14.2 (0.35μm-process), and a noise level by total-dose effect as well as a change in gain were measured by the test pulse. In spite of hard radiation of 1.6Mrad in case of VA32_HD14 and 74 kRad in case of VA32HDR14.2, there was no serious damage found in both chips.