Programmable power supply system for SiPM bias

NEXT is a double beta decay experiment that will be operated in Canfranc Underground Laboratory (Spain). The goal of the NEXT Collaboration is to search for ββ0ν decays of the 136Xe isotope. This challenge can be met with a 100 kg High Pressure enriched Xenon TPC. One key issue of such a TPC will be an excellent energy resolution, which can only be achieved if the TPC is operated in electroluminescent mode. This mode provides two different signals: primary scintillation (weak and fast) and electroluminescence light (strong and slow). The tracking system will be done with TPB coated SiPMs sensitive to ultraviolet light. A prototype of TPC called NEXT1-IFIC is equipped with about 250 SiPMs that require stable bias supply voltage. Within this context, a programmable microcontroller-based power supply board has been developed in order to monitor and program the bias voltages to the required values with convenient accuracy. The system is based on an ATMEL microcontroller, which can be controlled via USB. The system is equipped with high resolution ADCs and DACs to obtain resolutions of the order of decants of milivolts.