Today, the foil was opened, the pins on the bottom right detector were checked and looked fine, the right-hand arm was moved a bit in and then out, and the foil was tightly closed again. The negative bias voltage was applied from 0 to 50 V in steps of 10 V. During the measurement, the lights in the cave were switched off to ensure no leakage current from the light*. The results are shown in Attachment 1. To condition the detector, it was left at a negative bias voltage of 50 V for ~ 3 hours with lights on. No increase in current was seen (see Attachment 2), indicating the chamber was nicely covered with foil. Then the negative voltage was increased from 60 V to 150 V in steps of 10 V. No large current readings, like yesterday, were seen today (see Attachment 3). The detector was then left at -150 V for ~ 30 minutes with the current to be nearly stable with fluctuations in the range of 70-100 nA. The foil was then taken off to check if there are any dust particles on the detector surface. As can be seen in Attachment 6, some dust particle was found at the bias/multi-guard ring (MGR) boundary structures of the DSSSD. The area was then nicely cleaned with isopropanol + lab tissue wipe (see Attachment 7) and the chamber was covered with aluminum foil again. The negative bias voltage was applied from 0 to 150 V in steps of 10 V again and the results can be seen in attachment 5, indicating the response of the detector to be normal, unlike yesterday. Before calling the day off, the detector was left at -150 V overnight.

* Every time, before switching off the lights, it was checked that no one else was in the cave.