Fast Readout Electronics

We are building a dedicated electronics & DAQ system around a commercial 12-bit, 4 channel, 80 MHz ADC that continuously digitises the data for the MARS/SoLiD detectors to read out the light from the photo-sensors.

The photo-soensors are Multi-Pixel Photon Counters (MPPCs) from Hamamatsu and are connected to a dedicated front end card (Deimos), which has several functions: it supplies the MPPCs with their individually adjustable voltage, amplifies their signals and drives them to a differential ADC located on the Digital Processing Card DPC (see blow) and also provides a charge injection capability to calibrate the electronics. Deimos is a largely passive card connected to 32 MPPCs. 2 or 1 Deimos card are connected to a DPC.

The DPC is the hard of the system, it continuously digitises the data from the MPPCs, using its on-board ADCs. The ADCs are controlled and send their data to a SPARTAN 6 Field Programmable Gate Array (FPGA) from Virtex. This FPGA is the heart of the system. It zero suppresses the data, putting all significant hits into a ring buffer, which should be able to hold data for several hundred \musec. At the same time as the data it is stored it can identify neutron and neutrino signatures, which are distinct several \musec long pulses. Once it found this signature, it will communicate this information (via a token ring) to the other DPCs and all DPCs will write the data in the ring buffer to the DAQ. In the same way one can record pedestal events (using random triggers), calibration triggers and cosmics (looking for a distinct hit pattern in a single card).
The timing of the different cards will be synchronised using a common clock and regular time synchronisation signal. A high level overview of the system can be found in figure below.

MARS Electronics