Heike R2012-09 R67

NEW

• Renewed and improved noise thermometer.
• The wiring for four Double-Channel-Squids is installed.
• Two more stainless steel Coax-Cables are installed with their own port at room-temperature. The are numbered #5 and #6. Up to now they end at the mixing chamber and are connected to each other.
• Two semi-rigid coax-cables were installed, too.
• Filter-boxes I, II and VI were improved by adding a second coil at the input (cryo-end) of the filter circuit. The coils were manufactured by Würth Electronik, Part No. 744221, 2000$\mu$H; 600mA; 0.42${\Omega }$

TEST

• 07.09.2012 : Degauss FPD, see log-book at page 234.
• Testing new noise thermometer ...
• 18.09.2012 : NEW RECORD! Due to the new filter-box design we reached a new record! The crabon thermometer mounted on the mixing chamber reached the highest resistance so far: R_MC,CT5=14.1k${\Omega }$. Referred to the old Bayreuth-Calibration this is about 9 mK, corresponding to a our new calibration table (see log book p.139) this is about ~6 mK. Nevertheless even this temperature seems to be too high since the RuOx-thermometer already shows a temperature below 5.9mK (lowest limit of its calibration) at ~11k${\Omega }$ of the crabon thermometer. It is also remarkable that we reached this high resistance while we used the LR-700 multiplexer. Prior to this using the multiplexer always showed up ugly disturbance of the read out resistance values.

TIME TABLE

• 30.08.2012: FIRST DAY - CLOSING, CLEANING & PRE-COOLING
  • Closing cryostat and dewar. Cleaning/pumping lines.
  • Exchange gas p_VC~3mbar.
  • 17:57 : Pre-cooling with 50l LN.

• 31.08.2012: SECOND DAY - LIQUID HELIUM
  • 09:00 : Status = T_Dewar=155K, T_Magn,l=152K, p_VC=0.78mbar
  • 10:00 : Start filling LHe
  • 15:10 : During 3rd can (after ~ 230 LHe in total): T_RuOx=4.6K, p_VC=3.3*10^-3mbar
  • 15:58 : Pump VC
  • 17:15 : He 100%, LHe in total ~318l
  • 18:45 : Stop pumping VC, p_VC=4.7*10^-5mbar

• 07.09.2012: THIRD DAY - MIX IN
  • 09:25 : Status = p_VC=2.9*10^-5mbar, T_MC,RuOx=4.08, T_MC.Si=4.17K
  • 09:40 : Start condensing mix. T₁=683mbar, T₂=695mbar, T₃=0mbar, p₄=973mbar.
  • 12:30 : Close Heat-Switch (I_PCS#4=1.5A, I_H=0.5mA) @ T_RuOx=600mK
  • 12:40 : I_Still=3.0mA, T_RuOx=580mK
  • 14:30 : All mix is in, all pumps are running.

TO DO

• Disconnect RuOx from BOX VI:X2! Connect to BOX I: X7 since using BOX VI seems to cause parasitic heating based on coupling 4.5kHz frequency into the cryostat.