High voltage generator for the power supply of photomultipliers in the time of flight system of Alpha Magnetic Spectrometer-2 experiment

In this report, the behaviour of the first prototype high voltage generator (HVG) that might be used in the time of flight (TOF) system for the AMS-2 experiment is described. The system receives a positive continuous voltage about 100–120 V as input, and it provides a programmable negative continuous voltage from −1600 to −2400 V as output, versus a total load of 50 MΩ. The most important aspect is the absence of a transformer which usually is used in the step-up DC–DC converters. In the TOF system of alpha magnetic spectrometer (AMS)-2 experiment there is a big magnetic field, higher than 2 kG, that does not allow to use a transformer, therefore this prompted us to use the Cockroft–Walton system. The power consumption is about 300 mW and the peak-to-peak high frequency ripple is lower than 0.3% of the output high voltage. We also estimated the reliability of the HVG and we obtained a failure probability lower than 0.5% after three years of continuous functioning. Besides, in this report, much importance was given to the calculation of a simple model of the system to estimate the stability margins.