Development of an ASIC for Si/CdTe detectors in a radioactive substance visualizing system

• Published in: Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment Vol. 765; pp. 223 - 226
• Main Authors: Harayama, Atsushi, Takeda, Shin׳ichiro, Sato, Goro, Ikeda, Hirokazu, Watanabe, Shin, Takahashi, Tadayuki
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 21.11.2014
• Subjects: Analog front-end; ASIC; Cadmium tellurides; Channels; Chips; Detectors; Dynamical systems; Dynamics; Gamma ray; Imaging; Si/CdTe; Silicon; ASIC; Analog front-end; Gamma ray; Si/CdTe
• ISSN: 0168-9002; 1872-9576
• DOI: 10.1016/j.nima.2014.05.030

We report on the recent development of a 64-channel analog front-end ASIC for a new gamma-ray imaging system designed to visualize radioactive substances. The imaging system employs a novel Compton camera which consists of silicon (Si) and cadmium telluride (CdTe) detectors. The ASIC is intended for the readout of pixel/pad detectors utilizing Si/CdTe as detector materials, and covers a dynamic range up to 1.4MeV. The readout chip consists of 64 identical signal channels and was implemented with X-FAB 0.35μm CMOS technology. Each channel contains a charge-sensitive amplifier, a pole-zero cancellation circuit, a low-pass filter, a comparator, and a sample-hold circuit, along with a Wilkinson-type A-to-D converter. We observed an equivalent noise charge of ~500 e− and a noise slope of ~5 e−/pF (r.m.s.) with a power consumption of 2.1mW per channel. The chip works well when connected to Schottky CdTe diodes, and delivers spectra with good energy resolution, such as ~12keV (FWHM) at 662keV and ~24keV (FWHM) at 1.33MeV.