A week ago I posted about the Robocold setup in this post. Now I have coded further in the control software for it and it is capable of performing automated beta scans on all the detectors. Using this, I have done a beta scan on each of the (working) detectors that are installed at the moment. Such detectors are, one non irradiated from the CMS ETL Market Survey from the UFSD4 production, and four detectors irradiated all to different fluences from the UFSD3.2 production, which have been annealed at room temperature for “a long time”. It has to be noted that these scans don’t have “a lot” of statistics, at the time I am writing this I am repeating the scans but with more events each.
As seen in the plot above, the collected charge makes sense, at least qualitatively, taking into account the irradiation levels. The time resolution shown below is also consistent, at least qualitatively, with the irradiation levels.
Finally, to understand why the time resolution gets worse when the bias voltage is “very high” even though the charge is bigger we can look at the noise:
As can be seen, the noise increases beyond certain value. This is because the devices go very close to breakdown and fake spikes appear which are not related to beta particles but to thermally induced avalanches.
The IV curves of these devices are shown below.
With the setup in the current status, the required working time to go from the detectors to these results is about one day as it is highly automated.