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

本研究利用多光电二极管与超大型积体电路芯片，研制出一种低功耗的多量程读出系统。【读出系统的开发】为了测量BGO晶体闪烁体中的能量存款，开发了一种使用多个光电二极管和前端电路（包括模拟ASIC、16位ADC和FPGA）的读出系统，其动态范围为1 MIP（最小电离粒子）至10^6 MIP。1 MIP的输出信号用宇宙线μ子进行了刻度。宇宙线μ子对BGO光产额的ADC计数约为10.8fC。在1 MIP ~ 2400 MIP的范围内，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。【VA32_HDR14.2的开发】新开发了输入信号为正极性的VA32_HDR14.2，以优化光电二极管的读出电路。我们采用了0.35μ m工艺，该芯片的抗辐射性和噪声性能得到了显著改善。[抗辐射性试验]进行用于调查VLSI芯片的抗辐射性的光束试验。在VA 32 HDR 14（0.8μ m工艺）和VA32HDR14.2（0.35μ m工艺）中照射氦束，并且通过测试脉冲测量由总剂量效应引起的噪声水平以及增益的变化。尽管VA32_HD14和VA32HDR14.2的硬辐射分别为1.6Mrad和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.