On 22/11/2018 in the afternoon:
We increased the ADC thresholds to 40 (previously 8).
For an alpha source with pulser connected, the event multiplicity dropped from ~63 to ~10. Dead time ~ 7%
Checking the timing signals for the near S2:
- RAL X channels 0 - 5 bad, 6 and 7 good -> disconnected timing
- RAL U, XII, XIII, R, and S good
- RAL W channels 0 - 5 good, 6 and 7 bad
- RAL Q all bad -> disconnected timing
Started alpha source run with pulser (same pulser settings as run before)
After run the Far S2 RAL thresholds set to 10mV, the close S2 thresholds set to 50mV
Started alpha source run, no pulser
Stopped run due to poor alpha rate -> ECL-Nim ribbon cable disconnected.
Checking bias:
- Far S2 bias = -130V, leak I = 1.91uA
- Close S2 bias = -129.9V, leak I = 13.11uA
- diode bias = -70V, leak I = 0uA
Vented chamber and checked 12um mylar foil in front of close S2 - no visual damage. LEft
Close detector changed: S2 2623-26 (505um) replaced with S2 2623-18 (508um). Mounted new S2 in close position with 12um mylar
Removed alpha source - needed by other experiment. Otherwise target ladder configuration is same as eLog entry #47
Checked grounding cables going from preamps to ICU boxes were tightly connected
Attempted to bias close S2 -> no leak current! Left lab for the day.
The next morning (23/11/2018):
We found the BNC - SMC bulkhead connector attached to the near S2 preamp box is missing a pin. We dismounted the near S2.
We observed ~50kHz noise on Far S2, this is removed when we lifted the preamp - ICU box ribbon cables away from the chamber vacuum gauges. |