2017/02/10 (Friday)
| Setup: DIB1/3/4 → 3.2 MHz filters 3/2/1 → cable 3/2/1 →gender changer 3/2/1 → DCRC55(1)/33(2)/50(3) (on/on/off) | |
| 1010 | Fill LN2 cold trap bath. |
| 1132 | Performing 6“ Si charge readout bench test. This test will include a flexible side coax, tower, SQUET, stripline, diverter board, and DCRC all operating at room temperature. Using stripline 41 from Soudan. Confirmed charge related lines on stripline 41 are functioning. Using ZC-68 (used in 6” fridge run), and DCRC 32 (which is somewhat broken already) We will drive the flexible side coax with a square wave from the function generator and look at the output signal on a DCRC. |
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| 1143 | Notice that FET chassis is isolated from MC stage chassis via the tower. When installed, these would both connect to the fridge and thus the star ground at the e-box. For the purpose of this test, we'll short these stages together with a wire. |
| 1210 | With bench test setup, power on DCRC32 from jiajin. |
| 1215 | Can communicate with DCRC32 via telnet. Started up MIDAS DCRC programs and pulse viewer. Could see noise traces on some phonon lines, but both charge channels are railed. After a minute or so, pulse viewer freezes, but DCRC still seems active and functioning in telnet session. |
| 1220 | Restarting pulse viewer doesn't help. It freezes immediately. |
| 1225 | Only recourse was to shut down DCRC programs and power cycle DCRC. |
| 1232 | Upon restart, phonon channels had noise, but charge channels were railed. Phonon pointer address was incrementing, but charge pointer address (0x0E) was not. Setting DCRC5/General/ChargeADCreset to y briefly changed the output from ADC railed to stuck at an intermediate value, but changing it back to n ADC railed the charge output. Then, changing this setting had no further effect. |
| 1233 | Pulse viewer freezes, shut 'er down. |
| 1251 | Restart DCRC32. Find that phonon traces are still good and charge traces are railed. However, triggering on charge seems to work. It's just that the traces are not displayed. |
| 1253 | Pulse viewer freezes… Turn off programs and power down DCRC32. |
| 1445 | Fridge failure of some sort, happened at about 13:55… The pump power failed, both 3He and 4He pumps were off. Pressed Power Main and Reset buttons to restart them. |
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| Fridge failure timeline: | |
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| 1358 | 1K Pot pressure rises, 28 → max(1000) mbar. 1K Pot temperature rises steadily reaching ~4 K in 30 minutes Still pressure rises reaching max(1000) after 20 minutes Circulation pressures fall from 180 mbar, flattening to about 40 mbar over 30 minutes tower temperature rises, reaching 650 mK by 14:40 |
| 1402 | G3 (1K Pot pressure) starts to read an overpressure, reaches 70 mbar above 1 atm |
| 1440 | Failure discovered |
| 1445 | Pumps turned back on, fridge seems to be recovering. |
| 1505 | Tower = 200 mK. |
| 1514 | Tower/MC/Coldplate = 56.0 (and falling)/45.2/195 mK, Still = 1.28 K / 0.130 mbar, G1/G2 = 212/212 mbar, 1K Pot = 1.685 K / 26 mbar, Main bath = 64.4%. Boil off rate: faster than slow mode. |
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| 1534 | Attempt 6“ Si charge readout bench test again. This time, DCRC32 showed noise on charge channels after startup. Applied between 1mV and 1V square waves to QO and QI pins on detector end of side coax, but saw no change in signal. Ensured that 15V power was enabled via ODB. Using switchboard, disabled Qo bias. Still no signal. After a few minutes, pulse viewer freezes. |
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| 1556 | Perform electrical check on charge lines from Dsub end of stripline. Both Qi/QO look healthy. Realize, however, that the Dsub pin numbering is messed up. Usually, the stripline connects to the DCRC through the ebox, which, being male-male straight through, transposes the pin numbering scheme for each row of pins. (1 ↔ 17, 2 ↔ 16, 18 ↔ 33, etc. ) |
| 1619 | Connect only QO pins from stripline to DCRC using wires. |
| 1632 | With 50mVpp input square wave from the signal generator, able to see pulses! The noise level is quite high (as expected, but there appears to be no noticable ringing. Programs freeze. |
| 1643 | After restarting and power cycling, can still see pulses. Changing trigger settings causes programs to crash AGAIN! |
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| 1647 | Upon restart, no pulses seen. Just similar noise to that observed when wiring was incorrect earlier. Jiggling the janky wiring brings back the pulses, but the pulse viewer dies as soon as I try to change the charge offset. |
| 1718 | Fill LN2 cold trap full. |