HighPressure Johnson Noise Thermometry Absolute Pressure and Temperature Calibration

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High-Pressure Johnson Noise Thermometry(Absolute
Pressure and Temperature Calibration)

• Yanbin Wang, Mark Rivers, Ivan Getting

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Pressure Effects on TCs

• True Pressure Effect 0 5 ??
• Shear Stress resulting in plastic deformation.
  ???
• Re-crystallization. ???
• Chemical reactions. Possibly very significant.
  Time and temperature dependent.
• Electric shunting/coupling. Significant at
  higher temperatures.
• Relative combined standard uncertainty could be
  as large as 10 , but remains remarkably
  unknown and is likely to vary dramatically.

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Johnson Noise Thermometry

• Immune to the deleterious effects on TCs, except
  that electrical integrity must be maintained.
• Type A relative standard uncertainty 0.2 in
  10 s, better w/ more readings. Tests to 0.02
  on the bench to date.
• Calibrated wrt TC at very low pressure.
• Provides TC calibration at all higher pressure
  conditions.
• Each cell need be characterized only once.

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Design and construction of JNT, 2002-2005 (I.
Getting and J. Hall)
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5 mm Diameter Resistor for JNT Temperature
Measurements

• Titanium and Platinum layers vapor-deposited on a
  polished Lucalox substrate to form a mechanically
  robust and thermally tolerant resistor.
• Mechanical/electrical contact with the four
  thermoelement leads on the pads at the ends of
  the serpentine filament.

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First High-P Test (w/o JNT) resolving signal
contamination issues
June, 2005
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Second High-P Test JNT amplification problems

• TC DC signal saturated JNT preamp
• Added filter for preamp (John Hall)
• Bench test JNT okay

Jan, 2006
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JNT Migrate to GSECARS

• Large spikes occurred on JNT power spectrum from
  harmonics of the quasi-sinusoidal heater power
  supply.
• Ground loops associated with weak definition of
  the press body potential gave rise to other
  corrupting components in JNT signal.
• Inadequate shielding in the leads emanating from
  the cell led to additional pick-up.

March, 2006
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JNT signal contamination from electronic
environment
Connected to high-P cell
JNT signal not connected to high-P cell
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Future directions

• Identifying an APS electronic engineer to solve
  noise problems
• Post-doc identified, projected starting date
  Sept. 1 (COMPRES support 50)
• First high-P JNT test
• Software improvement
• Developing smaller resistor probes for higher
  pressures