Heike R2010-11 R64

RUN NOVEMBER 2010

First Run with Cu-Stage!

Summary

• 11.29. : Cryo closed
• 11.30. : Start filling LN (13:30)
• 12.01. : Start filling LHe (12:40), Start conditions: T_Si=166K, T_Mag,TOP=155K, T_Dewar=110K.
• 12.01. : After 400l of LHe (11:40) dewar is filled and T_Si=4.2K.
• 12.17. : MIX OUT

Tests

We did a lot of test with our new build in devices and connected heat-switches.

• Thermometry:
  • Test Si-Diode (Model: DT-470-CU): Works great down to approximately 1.1K There is only a small deviation of 0.1K at 4.2K. So we should do some small corrections of the calibration curve.
  • Test PdFe- Susceptibility Thermometer: Doesn't work!
  • Test ET- Susceptibility Thermometer: Works! :)
  • Test Pt-NMR: Works so far. Frozen in a persistent current of 1.5A, but we weren't able to read out the NMR quit well since we didn't know whether the Cu-stage was cold or not.
  • FPD: Read-out doesn't work with the digital Lock-In amplifier ITHACO 3961B due to its too high noise on the analog signal output. Therefore we changed to a analog Lock-In amplifier (ITHACO 393). With this device we are now able to detect all five T_C's.

• Persistent Current Switch:
  • Test PCS of Pt-NMR: Works! (1.5Amp)
  • Test Heat-Switch of Cu-Stage: Doesn't work! :( Seems like the superconducting wire has a small ohmic resistance of a few m${\Omega }$. This leads to small heating of some mW and causes the shunting via the 4K-flange!

TO DO

• Get rid of ground loops.
• Fixing the superconducting PCS of the thermal link connecting the Cu-stage.
• Suppress magnetic noise
• Remove filters in NMR-line.
• ...