2016/05/09 (Monday)
| Setup: HV mode, DIB1/2/3 → -/-/Phonon reroute board → cables → 3.2MHz Filters → HV board → HV1/HV2 → DCRC55/50, DCRCs off overnight | |
| Tower temperature stable overnight | |
| 0830 | Tower/MC/Coldplate = 46.6/45.0/266 mK, Still = 1.05 K / 0.080 mbar, G1/G2 = 115/115 mbar, 1K Pot = 1.53 K / 2.0 mbar, Main Bath = 49.8% |
| 0835 | Fill LN2 cold trap partially, Dewar ran dry |
| 0835 | Tweak 1K Pot needle valve open a few more degrees. Settles around 1.66 K / 7.5 mbar |
| 0857 | Continuing search for HV leakage. |
| Bias [V] | Leakage [mV] | Tower Temp (mK) |
|---|---|---|
| DIB2 PB SQUID bias/FB, Feedback coil/ret lines connected. All others floating. | ||
| 0 | 0 | 41 |
| 5 | 8 → 0 | 41 |
| 10 | 10 → 5 | 41 |
| 15 | 12 → 5 | 41 |
| 20 | 10 → 6 | 41 |
| 25 | 13 → 8 | 41 |
| 30 | 13 → 7 | 41 |
| Last week we saw that only biasing PB QET bias/ret lines gave the full leakage current and increased base temp at around HV = 20V. The above is further proof that our leakage is occurring in the QET bias/ret, but only on this DIB. Check DIB2 PA QET bias/ret to confirm. |
| Bias [V] | Leakage [mV] | Tower Temp (mK) |
|---|---|---|
| DIB2 PA QET bias, QET return lines connected. All others floating. | ||
| 0 | 0 | 41 |
| 5 | 7 → 4 | 41 |
| 10 | 10 | 41 |
| 15 | 19→21 | 41 |
| 20 | 30 | 41 |
| 25 | 41 | 41 |
| 30 | 51 → 55 | 41 |
| 35 | 60→63 | 41 |
| 40 | 74 | 41 |
| Interesting, so PA QET bias/return shows high leakage, but tower temp is unaffected. It seems the only thing that elevates tower temp is PB QET bias/return which also happens to be the HV biased phonon channel with the highest Tc. Let's double check that DIBs 1,3 are not doing anything like this. |
| Bias [V] | Leakage [mV] | Tower Temp (mK) |
|---|---|---|
| DIB1, DIB3 w/diverter connected. DIB2 floating | ||
| 10 | 16 → 5 | 41 |
| 20 | 18 | 41→43 |
| 25 | 30 | 43→45 |
| 0 | 0 | 41 |
| DIB3 w/diverter connected. DIBs 1/2 floating. | ||
| 5 | 5 | 41 |
| 10 | 12→6 | 41 |
| 15 | 14→10 | 41→42 |
| 20 | 20 | 42→44 |
| 25 | 30 | 44→45 |
| 0 | 0 | 41 |
| DIB1 connected. DIBs 2/3 floating. | ||
| 10 | 10 | 42 |
| 20 | 20 | 41 |
| 30 | 25 | 42 |
| Note: These suggest higher leakage than previously seen on DIBs 1 & 3, but in these measurements not much time was given to allow it to decay. |
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| Okay, so DIB3 causes heating too. Must have missed that last week… | |
| 1034 | Let's try to cobble together a data-taking mode. We'll just rely on the biased charge channels and shut off the problem Phonon channels. Thus: DIB1 connected, DIB2 connected with switchboard and PA,PB QET bias/ret disconnected, DIB3 disconnected entirely. |
| 1200 | After powering DCRCs 1&3, and zapping SQUIDs, HV1 pA, pB, and pC are alive (pC even shows small pulses), but HV2 pB, pC, and pD are railed. (pB is blocked, but pC & pD should be showing something). Adjusting HV2 pD's driver offset to an extreme value (~4.4V) finally unrails the channel, but it shows just a bunch of jagged noise. Unpower DCRC3(HV2) and wait a bit before repowering it. |
| 1245 | Still can only get jagged noise on HV2 pC & pD. Turn on FET heater for ~60s, but to no effect. Unpower both HV1 & HV2. |
| 1330 | Temperature has dropped to 40.5mK. Repower both DCRCs, zap SQUIDs. |
| 1340 | Same issue still present: HV2 pC & pD only unrail at extreme Driver Offset values and even then only show jagged noise. |
| Unpower DCRCs, remove re-router board from DIB2 at EBox, so cable goes directly from EBox to back of HV board. Repower DCRCs. | |
| 1355 | HV2 pC & pD are back. |
| 1410 | While studying the re-router board, try applying HV to the detector to see if it's possible, or if the leakage is still present. Applying 30V HV to the board produces 53.1mV of leakage, which is as before. Unpower DCRCs so we're ready once we've figured out the issue with the re-router board. |
| NOTE: | Discovered that the re-router board switches, intended to turn off HV to DIB2's biased phonon channels, were set wrong. So above observations are irrelevant. |
| 1535 | Commence LHe transfer (37.8%). |
| 1555 | After adjusting the switches on the re-router board, re attach to EBox on DIB2 and repower DCRCs. Zap SQUIDs. |
| 1605 | HV2 pC & pD are alive and showing pulses. |
| 1615 | Cease LHe transfer (93.2%). |
| 1635 | Release pressure in Main Bath. |
| 1645 | Testing HV with new rerouter board attached shows minimal leakage current, however when taking HV up to 10V, the pulses on HV2 pC & pD go away and do not return after ~10 minutes. Details below: |
| HV (V) | Leakage (mV) Measured After ~2min | pC Baseline (V) | pD Baseline |
|---|---|---|---|
| -0.001 | -6.3 | - | - |
| 5.000 | 1.1 | - | - |
| 10.00 | 1.0 | -.312 | -.011 |
| 12.04 | 2.2 | -.308 | -.013 |
| 9.27* | 0.6 | -.311 | -.018 |
| 4.998 | -1.8? | -.412 | -.380 |
| -0.005 | 0.1 | -.465 | -.385 |
| *Note: | Hints of pulses can be seen again. No effect on temperature seen. |
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| 1655 | Fill LN2 cold trap full. |
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