Heike R2012-02 R66

NEW

• Pt-NMR read-out via two s.s. mini-coax. Signal Coil is connected with port #1 and #3.
• Different capacitances two improve the NMR tank-circuit.

TEST

• Testing Pt-NMR. Coax #1 and #3 is connected with a special box. Inside this box the inner conductor of coax #1 is grounded and the inner conductor of #3 is feed through. For details see Pt-NMR Log-Book page 20. At first glance it seems like the device works at Curie-Mode.

• In spite of many attempts with different setups it isn't possible to measure in the Korringa-Mode with the PLM-4 so far.

• Heating by RF-Signal causes a significant parasitic heat input on the mixing chamber and on the Cu-Stage. Several tests were done to prove this. See e.g. logbook: 16.03. or 22.03.2012.

• NEW LOWEST TEMPERATURE ACHIEVED: T_NMR ~ 85 $\mu$K (14.03.)

• New Filter-Design for some Boxes.

TIME TABLE

Icy transfer tube with a sub-prime vacuum :)

• 28.02.2012: FIRST DAY - CLOSING, CLEANING & PRECOOLING
  • Closing cyrostat and dewar. Cleaning/pumping lines.
  • Precooling with 50l LN.

• 29.02.2012: SECOND DAY - LIQUID HELIUM
  • 07:50 : Status = T_Dewar=207K, T_MC,Si=216K, T_Magn,l=217K, p_VC=2.15mbar
  • 09:55 : Start filling LHe
  • 17:00 : Status after two cans (188.8l LHe) =T_MC,Si=80K, T_Magn,u=50K, p_VC=0.45mbar

• 01.03.2012: THIRD DAY - MIX IN
  • 08:00 : Status = T_Dewar=78K, T_MC,Si=80K, T_Magn,u=81K, p_VC=0.67mbar, connect 3^rd can LHe
  • 11:45 : T_MC,Si=4K, start pumping vacuum vessel.
  • 14:00 : Start condensing mix. T₁=688mbar, T₂=700mbar, T₃=0mbar, p₄=774mbar.
  • 14:10 : 100% He-Level. Total consumption to reach this level: 428.2 litres (Five cans) .
  • 16:20 : Close Heat-Switch (I_PCS#4=1.5A, I_H=0.5mA) @ T_RuOx=700mK
  • 17:20 : All mix is in, all pumps are running. I_STILL=3.0mA, T_RuOx=90mK

• 02.03.2012: 4^th DAY
  • Testing FPD
  • Connecting and Testing Pt-NMR

• 05.03.2012: 1^st RAMP MAGNET
  • Satus : Heat switch is closed.
  • 12:40 : I_M= 40 A, heat switch closed (1,5 A)

• 07.03.2012: 1^st DEMAG
  • 11:04 : Open HS, T_i= 19.6 mK (corresponding to Noise Thermometer), B_i= 3.96 T
  • 19:06 : I_M= 0.6 A, T_NMR ~ 389 uK, NT was disturbed by additional noise contribution in the frequency spectrum.

PLM-4 display shows temperature after demag (Curie-Mode)(14.03.12).

• 08.03.2012: 2^nd RAMP MAGNET
  • 12:00 : I_M= 40 A, heat switch closed (1,5 A)

• 14.03.2012: 2^nd DEMAG
  • ! Changed setup of PLM-4! See NMR-textbook page 23
  • 11:04 : Open HS, T_i= 14.95 mK (corresponding to Noise Thermometer), B_i= 3.96 T
  • 19:06 : I_M= 0.1 A, T_NT ~ 300uK ( caused by disturbances !!! ), T_NMR ~ 85 $\mu$K (!!!) in Curie Mode.

• 17.03.2012: 3^rd RAMP MAGNET
  • 13:05 : Closing heat switch.
  • 13:38 : I_M= 40 A, heat switch closed (1,5 A)

• 21.03.2012: 3^rd DEMAG
  • 10:43 : Open HS, T_i= 19.23 mK (corresponding to Noise Thermometer), T_NMR= 19.045 mK, B_i= 3.96 T
  • 10:59 : Start Demag: T_NT= 17.80 mK
  • 16:16 : Stop Noise-Thermometer read-out due to massive external distributions by additional noise (SQUID-Radio Moscow :) ).
  • 18:50 : I_M= 0.3 A, T_NMR ~ 240 $\mu$Kin Curie Mode.

TO DO

• Find correct setup of the PLM-4 Korringa-Mode.
• Improve Filter-Design!
• Reduce parasitic heating by rf-signals.
• Get rid of SQUID-Radio Moscow :)