2015/09/03 (Thursday)
| Current setup: DIB1/2/3 → cables → 3.2 MHz filters → HV1/2 → DCRC50/55. Currently the unused LED on the HV board has been grounded - previously it just floated | |
| Overnight, Cf source in shield activating detector, detector baking with two LEDs available through HV board | |
| 0935 | Remove Cf-252 source from fridge. Fill LN2 cold trap full. |
| 0940 | Tower temperature at 183 mK. Stop baking detector, and temperature begins to drop. |
| 1008 | Tower cools to 32 mK after 28 minutes |
| 1035 | Tower/MC(H35)/MC sensor/Cold Plate = 30.9/24.7/40.4/152 mK, Still = 1.33 K / 0.080 mbar, G1/G2 = 155 mbar, 1K Pot = 1.72 K / 22 mbar, Main bath = 63.1%. |
| italicized temperatures from Fridge Out 1 cable are still elevated for some reason | |
| Main bath boiloff rates have been relatively high since Aug 28. About 1.8%/hour when the bath is at 50%, normal seems to be closer to 1.6% | |
| 1050 | ~180Hz sine wave in most phonon channels. Temperature elevated. Also see spike pattern in charge channels. |
| 1053 | Power cycle DCRCs. |
| 1105 | Apply SQUID and QET settings. Noise still present on phonon channels. Unpower DCRCs and wait for fridge to cool all the way to base this time. |
| Temperature excursions after turning off the DCRCs |
|---|
 |
The first drop is right after powering down. The later excursions are not unusual occurrences after powering down the DCRCs after a “bad state”.
| 1230 | Temperature has dropped below 31mK and it's relatively stable in its decline. |
|---|---|
| 1245 | Change to Mixing Chamber. More stable at 24.2mK. |
| 1252 | Tower temperature more stable now: 30.5±.25mK. Power up DCRCs. |
| 1320 | Pulses are back and the only noise we see is the usual 5mVpp ~150Hz. |
| 1324 | Never mind, the bad state is back, but it went away after ~30s, though. This brief bad state wasn't accompanied by any temperature rise. |
| 1327 | Bad state is back. ~20mVpp on HV1 and ~30mVpp on HV2. |
| 1330 | Noise gradually decreases to nothing. |
| 1500 | Applying HV with smaller supply. Monitor HV1pA baseline: |
| HV board with all three DIBs, filters | ||
|---|---|---|
| HV (V) | Ileak (nA) | Baseline Elevation (mV) |
| 5.00 | 8.8 | 0 |
| 10.0 | 17.7 | 0 |
| 15.0 | 26.1 | 0 |
| 15.7 | 26.6 | 0 |
| 16.0 | 27.0 | +30 |
| 16.2 | 27.5 | +40 |
| 16.5 | 28.0 | +100 |
| 16.9 | 28.6 | +190 |
| 17.4 | 29.6 | +270 (phonon pulses disappearing) |
| 17.7 | 30.3 | +270 (phonon pulses dead) |
| slope is 1.71 nA/V (0.587 GΩ) | ||
| Phonon baseline rises then comes back down after measuring Ileak. 180Hz sine wave comes and goes. | |
| 1515 | Bring HV to 0. Spiky noise back on charge channels. Power cycle DCRCs. Unplug |
| 1520 | Repower DCRCs |
| 1535 | Set up DCRC50 (HV1), see 60Hz sine wave on Qi, Qo, but not on phonon channels. ~10mVpp. |
| 1545 | Realize that I unplugged DIB3 when I meant to unplug DIB2. Power off DCRCs, plug in DIB3. Unplug DIB2. This will mean that both Side 2 charge channels and 2/6 Side 2 phonon channels won't be biased (including Side2pA, the outer channel) |
| 1610 | After loading all of the settings, HV1 channels look good. HV2pB is only HV2 channel that should show pulses, but it's just railed. |
| 1615 | All of a sudden, 50KHz, 150mVpp noise seen on HV2pB. 20mVpp noise also on HV1Qi and Qo. |
| 1616 | Apply HV, monitor HV1pA baseline: |
|---|
| HV board with DIBs 1 and 3 only, filters | ||
|---|---|---|
| HV(V) | Ileak (nA) | Baseline Elevation (mV) |
| 5.00 | 5.9 | 0 |
| 6.00 | 5.3 | 0 |
| 7.0 | 6.5 | +215 |
| 7.5 | 7.1 | +275, phonon pulses disappear |
| 15 | 22.0 | +275 (Tower Temp 30.8 → 31.7mK) |
| -5.00 | -8.2 | 0 |
| -6.00 | -8.6 | 0 |
| -7.0 | -9.4 | +200 |
| -7.5 | -9.0 | +280 (phonon pulses gone) |
| slope is 1.28 nA/V (0.779 GΩ) | ||
| 1648 | Unpower DCRCs. Unplug DIB3. Only DIB1 plugged in. This means only one phonon channel biased on Side 2, all other phonon and charge channels floating. |
|---|---|
| 1647 | Power up HV1 (DCRC50). Before zapping, notice ~60Hz 100mVpp sine wave in Qi, Qo. Power cycle. |
| 1659 | Noise still there. By touching shield of cables to top of fridge and bottom of EBox, noise disappears. |
| 1708 | Apply HV, monitor HV1pA baseline: |
| HV board with DIB 1 only, filters | ||
|---|---|---|
| HV(V) | Ileak(nA) | Baseline(mV) |
| 5.0 | 3.5 | 65 |
| 6.0 | 3.5 | 65 |
| 8.0 | 5.9 | 65 |
| 9.5 | 4.0 | 340 (pulses gone) |
| 8.0 | 3.6 (drifts upward) | 72 (measuring Ileak drops it back to 65mV) |
| 9.0 | 3.9 | 68 |
| 9.5 | 3.3 | 340 (pulses gone) |
| slope is 0.486 nA/V (2.06 GΩ) | ||
If we calculate Vcrystal as Vbias - Ileak * 0.43 GΩ, we find that for 3 DIBs and 2 DIBs pulses disappear at around Vcrystal = 4.5 V, as before, but in the 1 DIB case we seem to be able to bias it to 7.3 V.
| 1726 | Unpower DCRC50. Plug in DIBs 2&3. Repower DCRCs. |
|---|---|
| 1743 | Boards all set up. Bake overnight. |
| 1750 | Fill LN2 cold trap full. |