2015/05/12 (Tuesday)
| 0850 | Fill LN cold trap Dewar |
|---|---|
| 0854 | MC/Tower = 52/68 mK. G1/G2 = 278/256 mbar. Still = 4 mW / 1.09 K / 0.19 mbar. 1K Pot = 1.73 K / 20 mbar. Coldplate = 9.49 kΩ / 307 mK. MC sensor = -39.51 kΩ. |
| 1000 | Commence taking IbIs measurements on DIB1 (Stripline 19, DCRC 33). |
| 1110 | Commence pumping out LHe transfer stick with turbo pump. |
| 1135 | Attach DCRC33 to DIB2 (Stripline 27) and commence zapping SQUIDs before running IbIs measurements. |
| 1330 | IbIs have finished. |
| 1544 | Plug DCRC50 into DIB1, DCRC33 is in DIB2. Zap SQUIDs on both DIBs. |
| 1600 | Trouble with DIB1(DCRC50): interference patterns appear on charge channels, noise on phonon channels, no pulses, and base temperature increases. Turning off the DIB1 FETs (with wr 30 0) eliminates the problem but it returns when they are powered up again (wr 30 0800). |
| 1620 | Swap DCRCs: now DCRC33 on DIB1, DCRC50 on DIB2. This is better: can run with FETs powered on both DIBs. |
| 1630 | Zap SQUIDs on both DIBs. Find lockpoints on DIB2/DCRC50 SQUIDs: |
| DIB2 DCRC50 | SQUID Bias [uA] | Lockpoint [mV] | Modulation Depth [Vpp] |
|---|---|---|---|
| A | -78.12 | -4.38 | .330 |
| B | -70.31 | -2.34 | .320 |
| C | -80.08 | -3.01 | .327 |
| D | -80.08 | -2.24 | .349 |
| 1655 | Interference problem appears again: stopping and restarting the DIB1 FET fixes it. So the problem is definitely associated with DIB1, although it appears to be not as bad using DCRC33. |
|---|---|
| 1705 | Set approximate QET biases on DIB1/DCRC33 by watching phonon channels for pulses: |
| Approx. QET biases for DIB1 (DCRC33) | |
|---|---|
| Channel | QET bias (μA) |
| A | -139 |
| B | -139 |
| C | -119 |
| D | -139 |
| 1715 | Charge breakdown study: watch pulses on DIB1 while increasing the charge biases, symmetrically on DIB1 and DIB2. |
|---|---|
| 1715… | The interference problem frequently reoccurs during tests. It can always be fixed by power cycling the DIB1 FETs. Some times it reappears in as little as 10 seconds - other times it stays OK for a few minutes. It may be worse with higher charge biases but it's difficult to say. |
| Charge breakdown: biases at which DIB1 pulses disappear and only noise seen | |
|---|---|
| note: biases modified in steps of 1 V | |
| Side 1 bias (DCRC33) | Side 2 bias (DCRC 50) |
| +5 V | -5 V |
| -4 V | +4 V |
| 1630 | With external pressure sensor reading 6.3E-6 mbar, isolate LHe transfer stick from turbo pump. |
|---|---|
| 1805 | Fill LN2 cold trap full. |