R & D Study on High Speed and High Precision Frontend Electronics for Electromagnetic Shower Calorimeter.

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It is primarily important for high energy physics studies to have a high precision and high speed electromagnetic shower calorimeter for gamma detection. Radiation hardness is also another importance of it. We have developed the scintillation heavy crystal, PWO (PbWO4, lead tungstate) under the framework of the GAMS collaboration among CERN, IHEP (Protvino) and. KEK-Universities. A high precision and high speed frontend electronics, ADC for PWO is also desired to be developed at the same time to meet the performance of PWO.The specification requested for an ADC system will be better than 10 bits (0.1%) for linearity, 13 bits (10^4) for dynamic range and less than 3 mus for conversion time. Power consumption will also be important for use for a detector system with more than multi-thousands channels.We have developed a full-custom QAC (charge to amplitude converter) circuit for an ADC system of the QAC-ADC combined arrangement. QAC is the most important circuit to be developed to meet t … More he requirements. The specification for QAC might be better than 10 bits of linearity ; 13 bits of dynamic range and 3 mus of conversion time Power consumption can be expected to be less than 180 mW.We accommodate two independent QAC's with different sensitivities of x4 and xl in one chip in order to meet the requirement of wide dynamic range of 10^4. The development of the QAC is performed on the IC engineering of the Harris company. UIIF-l process. it is the new full-custom bipolar process and is known to be hard for radiation damage.The first prototype of the full-custom QAC IC chips (named QAC 100SdM) have been designed on a computer simulation of Microsim and been fabricated by the Harris company . The test results of the chips have shown the excellent performance over the requested specifications, i.e. more than 10 bits for linearity, 1200 Pc for full scale and 2 mus for conversion time. The test results shoes that the conversion time will be expected better than lmus with careful choice of the parameters. The power consumption has been reduced to 140 mW.The QAC 100SdM QAC IC can be used as a standard ADC system for high energy physics studies of planning at present and of coming in future. Less