2021/06/17 (Thursday)
- Lab in-personnel: Matt, Derek
| Status | Run 74 in progress. First cooldown after IVC rebuild. Started circulation last week. |
|---|---|
| Tower thermometer is reading high, probably this is a thermometer problem and the actual temperature is much lower. High noise in some of the charge channels. | |
| Setup: DIB1/2+acc → SL 41/43 → 3.2 MHz filters → cables 2/3 → nothing/Source_mover_board+HV_diverter_board → DCRC50(3)/55(1). Kepco 40V supplye → HV BNC. No lead/poly shield. | |
| 1140 | Tower/MC/Coldplate = 204/31.3/178 mK, Still = 1.37 K / 0.085 mbar / 0 mW, G1/G2= 158/152 mbar, 1K Pot = 1.65 K / 26±2 mbar. MB = 25.0% |
| 1141 | Fill LN2 cold trap bath. |
| 1150 | At 10kHz noise in DCRC3qI/qO/DCRC1qI/qO = 40/6.4/24/68 e-6. This is q3/q1/q4/q2 At 3kHz (peak) noise in DCRC3qI/qO/DCRC1qI/qO = 2900/290/210/3400 e-6 |
| these are mostly slightly better than yesterday. Although q4 is actually a bit worse. | |
| 1445 | Begin LHe transfer @ MB = 20.2% |
| Note: the recovery system is down so we are using a Praxair Dewar. In the past, ice in these Dewars have caused 1K Pot failures. We marked the transfer line extender to indicate where the bottom of the Dewar is - we'll try to avoid going down low, hopefully avoiding the ice. | |
| 1540 | End LHe transfer @ MB = 93.5% |
| 1610 | At 10kHz noise in DCRC3qI/qO/DCRC1qI/qO = 11/1.8/27/14 e-6. This is q3/q1/q4/q2 At 3kHz (peak) noise in DCRC3qI/qO/DCRC1qI/qO = 390/40/50/550 e-6 |
| The 3kHz noise is a lot lower now. Sadly the noise at 10kHz in q4 is higher now than earlier today. | |
| 1615 | Adjust cable connections for DCRC1 - can get DCRC1qI noise to drop dramatically. |
| 1615 | At 10kHz noise in DCRC3qI/qO/DCRC1qI/qO = 6.2/1.3/2.7/19 e-6. This is q3/q1/q4/q2 At 3kHz (peak) noise in DCRC3qI/qO/DCRC1qI/qO = 250/40/20/700 e-6 |
| 1627 | Start 15min series of 0V/-15V data (bias applied after 1 min) (bias reduced during series, see below), with 1000 beginning randoms, trigger threshold none/none/160/none on DCRC3qI/qO/DCRC1qI/qO, 5Hz in-run randoms, with 1.6384 ms pulses (8192 length) and 400 us prepulse (500 length). Start sequence with Start button. |
| 1630 | MC temperature rises after bias is applied, 32→38 mK and still rising… |
| 1635 | Traces looked OK early in the series but now there's ugly noise - breakdown? |
| 1636 | Reduce bias -15 → -10 V. Breakdown noise improves a little maybe. Causes MC temperature to suddenly start falling (peaked at 44.1 mK) |
| 1639 | Reduce bias -10 → -5 V. Maybe more improvement in waveforms, but not seeing many pulses now. |
| 1641 | Reduce bias to zero. End series. |
| 1650 | Experimenting with rebiasing the detector, watching pulseviewer and temperature. At the start traces look fine, temperature low at 33 mK. At around -8V start seeing traces. At around -10V temperature started to rise a little. As I increased bias temperature kept increasing, but never saw any problems in the traces, no breakdown noise. At -20V MC → 48 mK but traces still OK. |
| 1655 | Brought bias as high as -30V, then back to 0V. Temperature peaked at 61 mK, starts falling after bringing bias to zero. |
| 1700 | Tried plugging in test BNC on the HV diverter board to monitor the current draw, but attaching a cable causes ugly noise in DCRC1qI. |
| 1705 | Flash detector for 30 seconds |