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

本研究采用多路光电二极管和VLSI芯片，研制了一种低功耗的多量程读出系统。[读出系统的研制]为了测量BGO晶体闪烁体中能量沉积的动态范围从1MIP(最小电离粒子)到10^6MIP(最小电离粒子)，研制了一套基于多光电二极管和包括模拟ASIC、16位ADC和FPGA的前端电路的读出系统。用宇宙线介子对1MIP输出信号进行了定标。宇宙线介子产生BGO光产额的ADC计数约为10.8fC。在1MIP~2400MIP的范围内，用LED脉冲源和重离子束测试了读出系统的动态范围。[VA32_HDR14.2的发展]VA32_HDR14.2是在光电二极管读出电路中对输入信号具有正极性的VA32_HDR14.2进行了优化。我们采用了0.35μm工艺，该芯片的抗辐射和噪声性能都有了很大的提高。[抗辐射测试]对VLSI芯片进行了束流测试，研究了芯片的抗辐射性能。氦束辐照VA32HDR14(0.8μm工艺)和VA32HDR14.2(0.35μm工艺)，通过测试脉冲测量总剂量效应的噪声水平和增益的变化。尽管VA32_HD14的硬辐射为1.6Mrad，VA32HDR14.2的硬辐射为74krad，但两种芯片都没有发现严重的损伤。

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.