The ProtoDUNE-SP cold electronics and photon detection systems passed their readout integration tests on APA #1 in the CERN cold box in November.
According to Matt Worcester of BNL, the cold electronics L3 manager for ProtoDUNE-SP, it is important to treat the entire TPC readout system of the APA, the cold electronics readout, Faraday cage and feedthrough, and the warm interface and local diagnostics as an integrated whole, and install it as such. Following this guideline, the process started in August with the installation of the photon detection system on this first APA. In early September the cold electronics team installed and tested the front-end motherboards (FEMBs), with great success. In October, once the photon detector readout system was installed and after the APA was inserted into the cold box, but not yet cooled, the cold electronics team worked closely with the photon detector and CERN detector control teams to test their systems in parallel in order to achieve minimal noise from both readouts.
In November, the cold electronics team returned to CERN for the cold test in gaseous nitrogen. Before cooling down, the FEMBs showed noise consistent with connection to the APA wires. During and after the cool-down process all 2560 electronics channels checked out as alive and well – from room temperature all the way to 183K. The average noise levels at 183K remained well below the preliminary Equivalent Noise Charge (ENC) design goal of less than 1100 electrons (e-) – measurements yielded 430 e- for the collection wires and 530 e- for the induction wires.
However, at this temperature, the team found three open connections between the FEMBs and the APA wires. The connections came back to life on their own during warm-up, and currently the CERN, APA, and CE teams are investigating these channels. Data analysis, while promising, is still ongoing.
Regarding the photon detector system, Zelimir Djurcic, the integration manager for this system, reported that the tests showed the full system, from photo sensors to cables to readout-boards, worked and that it was able to communicate remotely with the ProtoDUNE DAQ system.
“The tests helped us understand cabling and grounding issues and how to remove any noise from the system,” he added.