Standard Daughter Board
The detector board accommodates two ASIC chips to read detector signals, a temperature sensor placed close to the chips and the fewest additional components. A 5V supply level is sent from the mother board. This supply level is regulated by two LDO (Low Drop Out) linear regulators for obtaining the dc supply levels required by the readout chips (2.5 V) and the buffer stage (3.3 V). The detector high voltage power supply is supplied directly to the detector board. This supply level is decoupled prior to the detector.
For this system the ASIC chip analogue output onto one port is used. In this case the analogue front-end pulse signal is sampled into the pipeline with the frequency of the ASIC chip clock (40 MHz). The peak voltage of the front-end pulse signal is proportional to the collected charge at the detector channel, the peak time of this signal is about 25 ns (depending on the load capacitance among other parameters) and the remainder of the peak voltage after 25 ns is below 30% (i.e. the ratio between the signal voltage 25 ns after the peak and the peak voltage). Therefore, a 65–70 ns pulse length is considered in order to reconstruct the pulse. For reading out a particular position of the pipeline, a pulse of 25 ns (TRIGGER) is generated by the mother board. This pulse is sampled with the falling edge of the readout chip clock (CLK). The analogue pipeline latency has been fixed to 128 clock cycles, so this TRIGGER pulse is generated 128 CLK cycles after a particular front-end signal point has been sampled and stored in the pipeline. For the laser setup, the TRIGGER pulse is generated for each event (i.e. laser pulse) with a delay programmed by the user regarding the event occurrence. For the radioactive source setup, the TRIGGER pulse is generated with a fixed delay regarding the event occurrence (i.e. a particle crossing the detector) and a time stamp for each event is obtained with a TDC in the mother board. Therefore, just one sample of the analogue pipeline is required per event in both setups. The pulse shape can be reconstructed by acquiring enough number of events.
The Standard Daughter Board is shippped with:
- 1 populated Daughter Board with fanins
- 2 detector boards
- 6 extra fanins