CMS HCAL Photodetector's Power Supply System

In CMS HCAL subdetector proximity focused hybrid photo diodes (HPDs) are used, capable of operating in high magnetic field. For normal operation HPDs need two supply voltages - one high voltage (HV) about 10 kV and one bias voltage (BV) - about 100 V. The total number of HPDs in entire HCAL subdetector is around 500. The appropriate power supply system of about 500 HV and 500 BV channels is described in the article. The basic unit of the system is a 6U Eurocrate, containing 6 HPD power supply modules. There is in each module 4 HV and 4 BV channels. The whole system is controlled by a host computer, using standard RS485 interface between it and all crates, and custom protocol inside the crate. To provide the control and monitoring of the Power Supply System a program package has been developed. The package is built according to the Client/Server architecture. As interface the Distributed Information Manager (DIM) is used.