Design of a general purpose data collection module for the NuTel telescope

We have developed a Data Collection Module (DCM) to digitize, store and select data from the NuTel telescope, which observes Cherenkov photons from near horizontal air showers. Multi-anode photo-multiplier tubes (MAPMT) are used as photon-sensitive devices. DCM processes 32 input signals from the charge-sensitive pre-amplifiers located close to the MAPMT. The module design uses 40-MHz 10-bit pipeline ADCs and medium-size FPGAs. A programmable gain/attenuation control ×0.5-2 is applied to each channel before the ADC providing a comfortable operation with a multi-channel system using MAPMT as photon-sensitive device because the gain of MAPMT fluctuates from channel to channel as 1:3. DCM has a flexible on-board trigger inside FPGA firmware. The system design is made in 32-bit 33-MHz cPCI. Thirty-two DCMs housed in two crates process signals from the two telescopes of 512 channels each looking to the same direction for coincidence.