| | The last flash was at 7:23. The last 7 series were all at elevated temperatures (0.5 to 1 K). |
| 0825 | Tower = 1.25 K, temperature rising since 1:41. (Temperature spikes from flashes still visible, data taking continuing.) Still = “1000 mbar”. 1K Pot = 5.6 K / “1000 mbar”. G3 (pot overpressure) = 103 mbar. |
| 0840 | Close V6 and open V14 to release still pressure into dump |
| 0840 | On pump power switchbox press MAINS ON, then DC FAIL light goes on. Press RESET then DC FAIL light goes off. |
| 0845 | Start 1K Pot pump with valve closed, then open valves. Pot quickly returns to 1.52 K / 4.5 mbar. |
| 0846 | Close V14, start 3He pump. |
| 0848 | Open V6 to 12% |
| 0850 | Fill LN2 cold trap bath |
| 0853 | G1/G2 = 60 mbar |
| 0855 | Open V6 to 13.5%. Circulation pressure rises. Will begin opening V6 in steps. |
| 0900 | V6 = 14.0%. Still pressure (P1) falls into readable range. Tower temperature falling. |
| 0905 | MC/Tower/Coldplate = 0.94/0.99/1.29 K, Still = 1.31 K / 8.5 mbar, 1K Pot = 1.55 K / 5.5 mbar, MB = 71.1% |
| 0915 | Remove Ba source from fridge, return to safe. |
| 0915 | V6 = 16%, Still = 1.11 K / 0.60 mbar, Tower = 0.75 K |
| 0935 | V6 = 30%, Still = 0.18 mbar, Tower = 144 mK, G1/G2 = 175/170 mbar |
| 0950 | G1/G2 at ~125mbar each, and P1 reads 0.100 mbar. Open V14 to let remaining mixture from dump back into circulation. P1 increases to 60.0 mbar before falling again. G1/G2 rises to 200/194 mbar and begins falling again. |
| 1300 | P1: 0.12mbar and steady for a while. Close V14 to isolate dump and continue normal circulation. Tower temperature at 45mK. |
| 1355 | Unpower DCRC1, attach (newly grounded) HV board and repower. Apply +/+4V. Pulses look amahzing and no sign of 60Hz noise! |
| | Attach Coax cable from unpowered HV supply to HV board. 60Hz noise comes back. Connect the multiple ground planes of HV Box (1 for each DIB) together with a wire. The 60Hz noise disappears. |
| | It makes sense that we should have to ground together the unused DIBs with the used DIB on the HV board since normally, all three DIBs would be attached to Star GND at the EBox. |
| 1430 | After soldering the shells of the DSUB connectors together for all 3 DIBs, reattach and power DCRC1. |
| 1440 | Powering on the Variac causes spikes to appear every 7.5ms (~133Hz). This makes triggering difficult since the majority of triggered events will be due to these spikes rather than pulses. Switch to random triggers to watch for pulses while increasing the HV to look for charge breakdown. |
| 1500 | Increasing HV up to 25V causes no visible signs of breakdown. Measure the leakage at 55 mV and find that (using the Vcrystal formula) we're really only sending <5V across the crystal. |
| | During cooldown, we noticed that DIB1 & DIB2 both showed low resistances from pD Feedback Coil & Feedback Return to chassis. This may be the source of the leakage. Power off DCRC1 and attach switchboard between cable and EBox. Phonon D Feedback Coil & Feedback return lines are switched off. |
| 1530 | Apply 10V from 0-40V HV supply. Read leakage at about 1.5 mV, corresponding to 9.3 V at the detector. Much better. |
| 1535 | Apply 17.27V. Breakdown witnessed on DCRC1 Qo. Leakage measured at 6.7±.1 mV, and fairly stable. (Calculates out to ~14.4V across the detector). Despite displaying signs of breakdown, DIB1 Qo occasionally shows good pulses or rails. By lowering HV to 15.59V (and leakage of 4.3mV → 13.7Vcrystal), breakdown signs disappear. |
| 1545 | Lower HV to 0V and flash detector for 60s. |
| 1640 | Reapply HV. At 15V, leakage is 3.0mV → ~13.7Vcrystal. No signs of breakdown yet. |
| 1645 | Applying 17.55V, leakage is 5.4mV → 15.18Vcrystal. Breakdown is happening in waves, similar to the periodic behavior we were seeing earlier. |
| 1650 | Scale back to 15.38V, leakage is 1.4mV → 14.76Vcrystal. Breakdown is gone. |
| 1700 | Fill LN2 cold trap full. |
| 1710 | Applying a negative bias now: HV set to -10.00V, leakage is -5.1mV → -7.75Vcrystal. No signs of breakdown. |
| 1720 | Raise HV to -15.01, leakage is -4.0mV → -13.25Vcrystal. No signs of breakdown. |
| 1721 | Raise HV to -20.01V, leakage is -4.8mV → -17.90Vcrystal. No signs of breakdown yet. |
| 1722 | Almost immediately after writing that last sentence, breakdown happens with a vengeance. I barely touched the HV knob, and it increased the HV to -20.03V, leakage increased to -10.4mV → -15.45Vcrystal, which means that Vcrystal actually decreased when/after breakdown occurred. |
| 1725 | Decreasing HV to 16.43V, leakage is -3.6mV → -14.85Vcrystal. Breakdown disappears at this voltage. |
| | Set HV back to 0V. I've realized that we won't be able to take overnight data at HV since we won't be able to zero the Qbias while we flash. So we'll do that tomorrow. For now we'll just flash for 60s. |