Development of a ±6 kV Bias Supply for ICAL Detectors of INO

Abstract

The Iron-CALorimeter detector of India-based Neutrino Observatory is designed to use 28,800 single gap Resistive Plate Chambers (RPCs) of 2 m \(\times \) 2 m size as its active detector elements. Each RPC requires a variable High Voltage (HV) supply of up to 12 kV for generation of the operating electric field in the detector gas medium. Considering the large number of supplies needed for the ICAL detector, the location of HV supplies has significant importance in system design in terms of overall cost and space requirement. External generation of HV and its distribution to so many RPC has the disadvantage of requiring bulky HV connectors and cables. In order to avoid HV distribution problem, an indigenous development of a programmable, ± 6 kV HV supply has been carried out. The supply has been developed in a very compact form factor as the space available for it is very limited inside the RPC. In order to achieve low switching noise, the HV inverters have been designed with quasi-sinusoidal waveforms. The developed supply has HV output voltage and current read back facility with two control ports (SPI and RS-232) for remote programming and monitoring purposes. This paper will discuss salient design features, performances and test results of the developed prototype.