Fabrication, Interfacing and Performance of the High Voltage Bias Supply Modules for ICAL RPCs

The Iron-CALorimeter detector of the 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 [1]. Each RPC requires a variable High Voltage (HV) bias supply of up to 12 kV for generation of the operating electric field in the RPC’s gas medium. Considering the large number of supplies needed for the ICAL detector, an indigenously designed, programmable ± 6kV HV supply module, capable of providing 2 $$\upmu $$ A current per channel, has been developed [2]. After initial prototyping and thorough testing of the module, a limited number of modules were fabricated and installed in the RPCs of the mini-ICAL detector, which is operational at IICHEP, Madurai [4]. The modules were interfaced using the SPI interface with the digital front-end (RPCDAQ) [3], which is part of the data acquisition electronics of the mini-ICAL detector. The RPCDAQ sends commands to the HV module to control and monitor the voltage, current and ramp rate. The RPCDAQ has an Ethernet link to the back-end servers and uses TCP/IP for control and data communication. A PyQt4-based software was developed to control and monitor the HV module remotely via the RPCDAQ. This software can control HV of multiple RPCs simultaneously. The software can also display and log the periodic monitoring data of the HV modules, like measured output voltage, current, etc. In this paper, we will discuss the fabrication, interfacing and performance of the HV bias supply in the mini-ICAL detector.