2021/09/01 (Wednesday)
- Lab in-personnel: Matt and Giulia
| Status | Run 74 in progress. First cooldown after IVC rebuild. |
|---|---|
| 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. Lead shield erected, 4 walls. Currently both DCRCs are on. | |
| Position of Am source: y = 0.0 mm | |
| 0851 | Tower/MC/Coldplate = 138.7/34.0/191.3 mK, Still = 1.38 K / 0.070 mbar / 0 mW, G1/G2= 287/262 mbar, 1K Pot = 1.58 K / 10±1 mbar. MB = 40.0%. |
| 0859 | Fill LN2 cold trap bath. |
| 0942 | At 10kHz noise in DCRC3qI/qO/DCRC1qI/qO = 22/4.3/2.8/80 8e-6. This is q3/q1/q4/q2 At 3kHz (peak) noise in DCRC3qI/qO/DCRC1qI/qO = 490/46/52/1100 e-6 |
| Noise is pretty much the same @10kHz, but is considerably higher @3kHz than yesterday. | |
| 1115 | Ugly noise in all channels, showed up all of the sudden while adjusting trigger thresholds, around 1e-4 at 10kHz so about 2 orders of magnitude higher than normal. Tried flashing, didn't seem to help. |
| 1115 | Try messing with connections at HV and DCRC Dsubs, no improvement |
| 1120 | Turn off the three DAQ programs and power-cycle the DCRCs. |
| 1120 | Noise is still bad after powercycling |
| 1125 | Try powering down DCRC55(1) and looking at data with only DCRC50(3) powered and enabled. Noise in DCRC3 channels looks different than the sorta breakdown-looking noise before - strong 2-3kHz noise in both channels (usually it's not strong in qO) and pretty strong high-frequency noise making the waveform “fuzzy” (300-ish kHz peak at 1e-4 in both channels). |
| 1125 | Noticed that the e-box purge was not connected. Maybe humidity at the e-box is causing problems? Reconnected the e-box N2 purge. |
| 1130 | With DCRC3 on and DCRC1 still off, try unplugging cable to DCRC1 (actually from the source mover board). No change in DCRC3 noise. |
| 1135 | Connect and power DCRC1 again. Now noise is back to ugly “breakdown” appearance. The high-frequency peak is still present - basically this is just additional noise that looks like 1/f over pretty much the full frequency range. Between around 1e-4 and 4e-4 at 10kHz in all channels. |
| 1140 | Try removing source-mover board from behind DCRC1. No improvement in noise. |
| 1150 | Try removing DCRC1 then using DCRC3 on Cable 3 (plus HV board). This basically eliminates the 1/f “breakdown” noise. So that seems to be a DCRC1 problem. Noise is almost normal for these channels, but rather high - strong oscillations in qO, much weaker oscillations in qI, but qI has a ~320kHz peak making baseline quite fuzzy. Noise is reading 2 or 3 times higher than this morning. |
| 1200 | Try blowing dust off DCRC1, then reconnecting it in the normal place. 1/f “breakdown” noise is gone! Though other noise is still present and pretty high. |
| 1205 | Try reconnecting both DCRCs. Now breakdown noise is back. Well that's annoying. |
| 1205 | Unplug power from DCRCs for now. We'll let them rest and try again later. |
| 1330 | Repower DCRCs. Still seeing high 1/f “breakdown” noise. |
| 1345 | Finally discovered that DCRC1 had its charge biases set to 10V. How did that happen?? DCRC3 was at 0V. So with both connected, there would be a 10V difference between channels which would cause breakdown. OK, try setting up again… Talking with Giulia, she had actually tried using the sequencer to start data. She stopped the sequencer because she saw overtriggering, and even though she stopped it before it should have applied the bias, apparently it got as far as setting DCRC1 biases before it actually stopped. |
| 1350 | Reconnect both DCRCs, back to normal (except source-mover board removed). Look at pulses - now they look normal, although the oscillations are bad today (but not out of the ordinary range). OK, we need to flash since the detector has been partially biased. |
| 1355 | Flash DCRC1&3 LEDs for 2 minutes |
| 1450 | At 10kHz noise in DCRC3qI/qO/DCRC1qI/qO = 25/5.1/5.5/130 8e-6. This is q3/q1/q4/q2 At 3kHz (peak) noise in DCRC3qI/qO/DCRC1qI/qO = 760/50/76/1400 e-6 |
| Noise is slightly higher than this morning. | |
| 1600 | Start 45 min series of +10V/0V (bias applied after 60 sec), with 1000 beginning randoms, trigger threshold 130/60/40/400 on DCRC3qI/qO/DCRC1qI/qO, 5Hz in-run randoms, with 1.6384 ms pulses (8192 length) and 400 us prepulse (500 length). Use Sequencer script r74_takeandflash_dcrcbias.msl. This flashes for 30 seconds at end of series. |
| 1657 | Begin LHe transfer @ MB = 28.5% |
| 1538 | End LHe transfer @ MB = 93.1% |
| Stepper Motor Tests | |
|---|---|
| We want to test the room temperature stepper motor with a load. We got a rod of steel diam 1.91 cm, length 11.01 cm, so mass around 250 g. We drilled a hole near the middle for the motor shaft and a perpendicular threaded hole to mount to the shaft with a 2-56 screw. | |
| We used the capacitor filters that are used in the cold case. | |
| Initially we set dwell = 40 ms, power = 6.8 V. It seemed to be missing steps. Increasing power to 8.5 V helped. But more importantly, increasing the dwell helps. At 8.5 V and dwell = 80 ms, seems to move properly. Tried as high as dwell = 320 ms - in that case it moves in a sort of bouncy way, moves a bit and wobbles, then moves the next bit. But seems to reliably end up where it should. | |
| Trying to do moves of less than 4 steps does not seem to work. Behavior is erratic. Removing the capacitor filters or increasing the power (we tried 10 V) didn't improve things. Scott thinks this is an issue with the driver board rather than the motor itself. | |