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2016/05/17 (Tuesday)

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Status: Fridge warming. All valves closed and pumps off. All mixture has been pumped to dump. LN2 traps at room temperature and pumped out.
0910 Tower (Cernox) = 248 K. Rising at about 1K / hour
0915 Start bleeding N2 gas into main bath using LN fill tube. Took the stopper off the other port for exhaust.
1125 Cernox thermometer at 251K. P2 at 2.0mbar. Open Gate and Condenser Line speedivalve to see if there's anything still in the fridge. P2 remains at 2.0mbar. Open V14 to let warm mixture from dump into the fridge.
1530 Perform mu-metal shield magnetometer tests as a function of height inside the mu-metal shield.
  1. Tape magnetometer to bottom of dewar inside mu-metal shield (7cm above bottom edge of mu-metal shield).
    1. X-direction: West wall of lab
    2. Y-direction: Upwards
    3. Z-direction: North wall of lab
  2. Distance from floor to magnetometer: 53cm. Will call this Δh = 0.
  3. Distance from floor to center of tape on outside of mu-metal shield to denote detector detector height: 104cm.
  4. Distance between magnetometer's placement and detector height: 51cm.
  5. Distance from magnetometer to top of mu-metal shield: 117cm.
  6. Place piece of tape on steel cable at bottom of cable spool. Will measure to this piece of tape when measuring Δheight.
  7. By lowering mu-metal shield, we increase Δh (i.e. the height of the magnetometer inside the mu-metal shield).
Δh (cm) B-x (V) B-y (V) B-z (V)
0 0.051 -4.184 -0.924
10 -0.025 -1.972 -0.682
20 -0.002 -0.890 -0.397
30 0.001 -0.413 -0.233
40 -0.006 -0.231 -0.161
50* -0.010 -0.166 -0.124
60 -0.012 -0.170 -0.098
70 -0.013 -0.246 -0.058
80 -0.010 -0.465 0.029
90 -0.002 -0.972 0.217
100 0.022 -2.166 0.574
110 0.061 -4.451 0.957
120‡ 0.085 -6.88 0.751
*Note: Roughly detector height.
‡Note: Magnetometer above mu-metal shield at this height.
Uncertainty: ~0.002V
As mentioned on 2016/04/19, the conversion factor for this magnetometer is 1V = 10 μT. The field computes out to:
Δh (cm) B-x (μT) B-y (μT) B-z (μT)
0 0.51 -41.84 -9.24
10 -0.25 -19.72 -6.82
20 -0.02 -8.90 -3.97
30 0.01 -4.13 -2.33
40 -0.06 -2.31 -1.61
50* -0.10 -1.66 -1.24
60 -0.12 -1.70 -0.98
70 -0.13 -2.46 -0.58
80 -0.10 -4.65 0.29
90 -0.02 -9.72 2.17
100 0.22 -21.66 5.74
110 0.61 -44.51 9.57
120‡ 0.85 -68.8 7.51
*Note: Roughly detector height.
‡Note: Magnetometer above mu-metal shield at this height.
Uncertainty: ~0.02μT

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