09:00

Came in to see the bias for DSSD4 which has been fluctuating for the past few days had tripped during the night. From the gnuplot it looks like it was fluctuating all night and just after midnight it went above 20uA and tripped.

Other leakage currents are around the value they have been recently, day night cycle still observed. Again perhaps the leakage current of DSSD1 and DSSD3 is slowly decreasing and reaching a lower minimum value. Reset the module, DSSD4 does bias back up and is currently around 10uA. See attachments 1+2.

I have also noticed a small spike in current when starting up the FEE power, see the small spikes in attachment 2.

Continuing with different ground configurations from yesterday.

Ground config 5: I have now removed the grounding cables between non-bias FEE modules. So grounding cable goes between pn and nn bias FEEs and then one grounding cable to the coolant pipe. No grounding on any other FEEs. (attachments 3-8). Effect on pulser widths is hard to discern, some widths have decreased i.e 5 and 6 wheras others have increased such as 11. One interesting note is that the rates on aida03 have decreased by just over a factor 2 so now read ~100k. Whether this is the result of different grounding or maybe similar to what was seen for DSSD3 where rates decreased on there own over time? Attachment 8 shows the rates for each ASIC and most have now reached similar level to the other FEEs (note log scale).

Ground config 6: Have kept grounds to only pn or nn bias FEEs. Have now also included a ground cable from the body of the FEE module into the grounding connection. The ADC data items rate increase from 100k to 150k in aida03, no other impact on rates. Pulser widths remain largely unchanged, although some widths saw increases in the pulser widths. (attachments 9-13)

Ground config 7: Wanted to check impact of having no grounds at all. No impact on leakage currents. Rates look pretty similar for all FEEs, aida03 and aida04 200k and 350k respectively. Pulser widths and waveforms significantly worse than grounded case. See attachments 14-18

Ground config 8: Have reattached all ground cables (back to config1). In addition I have added a ground cable from the coolant pipe to effectively the CARME chamber. Rates appear pretty unchanged. Pulser widths better than no grounding but worse than original configuration. Attachments 19-23

Note since after lunch DSSD4 leakage current no longer fluctuating. Nothing has been changed. As I write that currents start fluctuating again. Maybe some ongoing work in the cave is affecting this?

Removed groud cable going to the chamber.

I wanted to rule out any affect from the test inputs. Have removed all test inputs. Only input is directly from pulser to DSSD3 as this previously had best pulser widths. All other cables removed. See attachments 24-26. Still see very high rates in aida03 and aida04 (250k and 350k). Pulser widths in DSSD3 seem worse now for some reason? While pulser detattched decided to lower slow comparator to 0x32 (500keV) and 0x24 (360 keV) to see rates in all FEEs. Rates still look pretty good, other than aida03 and 04. See attachments 27,29. Putting test inputs back.

Test inputs all back. Ground configuration back to configuration 1. Pulser tests, widths are best so far - will upload them later from all tests.Rates good in all except aida03 and aida04 still.

FEEs off, bias on and monitoring. Have put pins back in motors.

20:50

Bias has tripped again on DSSD4. It had remiained stable with noi fluctuations ~20 mins before leaving.