M. Nakazawa

A 12-channel CMOS preamplifier-shaper-discriminator ASIC for APD and gas counters

A 12-Channel (Ch) CMOS Preamplifier-Shaper-Discriminator ASIC designed for avalanche photodiode (APD) and gas counter readout has been fabricated on a 2.4 mmtimes2.4 mm die area using ROHM 0.35-muCMOS technology. This mixed signal ASIC consists of both analog and digital components and a window type discriminator is easily implemented through the use of a digital encoder to encode outputs from two comparators. The charge sensitive preamplifier is based on gain-boosted (regulated) cascode topology. The gain (voltage output to charge input) is 0.9 mV/fC and has been tested to have a low optimum Equivalent Noise Charge (ENC) of about 370 e-+30 e-/pF rms at a shaping time of 0.5 mus. The gain of the shaper is about 2.5 mV/fC and its peaking time can be varied from about 0.3 mus to 0.8 mus via an external pin. This chip is capable of sensing bipolar signals and is linear at least up to 320 fC for negative charge and 150 fC for positive charge. The average ENC of each channel has been calculated to be about 640 e -+30 e-/pF. The power consumption of the chip is approximately 0.13 W

Multichannel CMOS ASIC preamplifiers for avalanche photodiode and microstrip gas chamber readouts

A 10-channel (Ch) and a 16-Ch application specific integrated circuit (ASIC) preamplifier chip with telescopic-cascode topology and gain-boosted (regulated) cascode topology respectively has been designed for avalanche photodiode (APD) and microstrip gas chamber (MSGC) readouts. These highly integrated and reliable chips can be used for individual readouts from many channels to improve the spatial resolution and counting rate of such detectors over light sharing or charge division schemes. These chips were fabricated on a 2.4 times2.4 mm die area using ROHM 0.35-mu CMOS technology. The chips were tested to have a low optimum equivalent noise charge (ENC) of about 880 e

Development of a multi-channel waveform-sampling front-end ASIC and DOI detector for APD based animal PET

at a shaping time of 0.5 mus. The voltage output to charge input gains of the 10-Ch and 16-Ch preamplifiers are 0.71/pf and 0.91/pf while the rise times (10%-90%) are 15 and 13 ns, respectively. The 16-Ch chip was used to readout a GSO-APD detector and an optimum energy resolution of 11.3% (511 Kev peak of Na-22) was obtained while the coincidence time resolution with two such detectors is about 12.5 ns. The energy resolution of the 5.9 keV peak from a Fe-55 source obtained with a 3 times3 cm MSGC plate was about 20.5%

Clustering method to process signals from compound semiconductor detectors

A new multi-channel waveform sampling front-end (WSFE) application specific integrated circuit (ASIC) for positron emission tomography (I5ET) has been developed to digitize signals from scintillating crystals at an early stage to suppress noise while facilitating signal processing. Each channel of the chip consists of a preamplifier, a variable gain amplifier (VGA) and a fast analog to digital converter (ADC). This multi-channel chip will be used to readout each pixel of a phoswich detector based on GSO scintillators coupled individually to a multi-array avalanche photodiode (APD). Two WSFE ASIC have been developed together with some low noise preamplifiers in a separate chip.

Development of front end electronics for M-MSGC using individual-readout ASIC with resistive strip output

The application of compound semiconductor detectors is limited by the poor mobility of holes and internal ununiformity. To improve their performance we developed new digital signal processing technique, a clustering method which derives typical patterns containing information on the real situation inside detector from measured signals and is used combining with the pattern matching method. The effectiveness of this method was verified with a CdZnTe detector of 2 mm thick and several gamma ray sources. The obtained energy resolution for Cs-137 was improved to about 8 keV (FWHM). Because the clustering method is only related to the measured waveforms, it can be applied to any type and size of detectors and is compatible with any filtering method.

Multi-channel CMOS ASIC preamplifiers for APD and MSGC readouts

A multi-grid-type microstrip gas chamber (M-MSGC) is being developed for the new spallation neutron source in Japan. The objective of this study is to provide a new position readout electronics for two-dimensional M-MSGC which can reduce the number of interconnections through a gas vessel by using a new encoding readout scheme based on ASIC technology. In order to test an ASIC based individual readout method, an ASIC chip, which has typically 16 individual input channels, has been designed and fabricated using a ROHM 0.35µ;m CMOS process and the chip was connected to a developed encoding circuit. The main results of the performance test indicated that the front-end electronics was able to encode 1500 pixels of the input position with 4.4% of position non-linearity. The results of this work confirm that the developed circuit would be appropriate for the front-end electronics of He-3 two-dimensional M-MSGC.

Development of a High Resolution APD sased Animal PET and Multi-Channel Waveform Sampling Front-End ASIC

A 10-channel (Ch) and a 16-Ch application specific integrated circuit (ASIC) preamplifier chip with telescopic-cascode topology and gain-boosted folded-cascode topology respectively has been designed for avalanche photodiode (APD) and microstrip gas chamber (MSGC) readouts. These highly integrated and reliable chips can be used for individual readout from many channels to improve the spatial resolution and counting rate of such detectors over light sharing or charge division schemes. These chips were fabricated on a 2.4 mm times 2.4 mm die area using ROHM 0.35 mu CMOS technology. The chips were tested to have a low optimum equivalent noise charge (ENC) of about 880 e-. The gains of the 10-Ch and 16-Ch preamplifiers are (1.4-pF)-1 and (1.1-pF)-1 while the rise times are 15 s and 13 s respectively. The 16-Ch chip was used to readout GSO-APD detectors and an optimum energy resolution of 11.3% (551 keV peak of Na-22) was obtained while the coincidence time resolution with a BaF2 detector is about 11.5 ns. The energy resolution of Fe-55 with a 3 times 3 cm MSGC plate is about 20.5%.