low-temperature primary thermometry development at nrc dr. patrick m.c. rourke measurement science...
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Low-temperature primary thermometry development at NRC
Dr. Patrick M.C. Rourke
Measurement Science and Standards (MSS)
National Research Council Canada (NRC)
CAP Congress, Sudbury, 19 June 2014
Thermometry
• Primary thermometer• Directly measure “real” thermodynamic temperature T• Complicated, large, difficult to use not many in existence
• Secondary thermometer• Needs calibration in order to set scale• Almost all thermometers are secondary
• International Temperature Scale of 1990 (ITS-90)• Used for secondary thermometer calibrations worldwide between
0.65 K and 1357.77 K• Based on best thermodynamic data from primary thermometers
available up to 1990• Newer measurements suggest the scale should be improved
2
ITS-90 scale deviates from thermodynamic temperature
0 50 100 150 200 250 300
-12
-10
-8
-6
-4
-2
0
2
4
Gas Thermometers
Constant Volume(CVGT)
Kemp 1986 Steur 1986 Astrov rev.
1995/96
Acoustic(AGT)
Moldover 1999 Ewing 2000 Benedetto 2004 Pitre 2006
Dielectric Constant(DCGT)
Gaiser 2008 Gaiser 2010
T -
T9
0 (
mK
)
Temperature (K)
3
Adapted from CCT-WG4 report (2008), Fischer et al., Int. J. Thermophys. 32, 12 (2011),Astrov et al., Metrologia 32, 393 (1995/96) and Gaiser et al., Int. J. Thermophys. 31, 1428 (2010)
• Microwave resonances in a gas-filled conducting cavity• Fixed temperature & gas pressure
• Resonance frequency f gas refractive index n• c0: speed of light in vacuum
• ξ: electromagnetic eigenvalue for microwave resonance
• a: radius of spherical cavity
• Thermal expansion coefficient αL and isothermal compressibility κT important
• Calculate thermodynamic temperature T from n using virial equations• Helium gas: quantum mechanics
• Similarities to other techniques• Acoustic gas thermometry (AGT)• Dielectric constant gas thermometry (DCGT)• Resolve differences between them?
Refractive index gas thermometry (RIGT) in principal
4
RIGT in practice
2.612 2.613 2.614 2.615 2.616 2.617 2.618 2.6190
5
10
15
20
25
30
35
40
45
2.621 2.622 2.623 2.624 2.625 2.626 2.627 2.628
0
5
10
15
20
25
30
35
40
45
Frequency (GHz) at T = 5 K
TM11 mode at 297 K and 5 K, in vacuum
g3
g2
g1
f3
f2
peak 3 ("z")
peak 2 ("x")
106|S
21|
Frequency (GHz) at T = 297 K
peak 1 ("y")
f1
• Quasi-spherical resonator• Controllably lift resonance
degeneracy
• Finite electrical conductivity• microwaves penetrate into skin
layer• resonances broadened &
shifted
• Eigenvalue corrections• Shape effects• Disturbances due to waveguides
5
Experimental details
• Motivation: RIGT to measure T - T90: 5 K – 300 K• Initially, characterize resonator in vacuum• Microwave resonances resonator size, shape,
conductivity
• Prototype copper resonator
• Copper pressure vessel• Resistive thermometers (ITS-90) on copper coupling rod
• Two-stage pulse-tube cryocooler• Home-made thermal control system
6
Microwave fitting
2.612 2.613 2.614 2.615 2.616 2.617 2.618 2.619
-10
-8
-6
-4
-2
0
2
4
6
8
10
10
6 [R
e(S
21) or
Im(S
21)]
Frequency (GHz)
TM11 mode at 297 K, in vacuum
2.621 2.622 2.623 2.624 2.625 2.626 2.627 2.628
-15
-10
-5
0
5
10
15
20
25
30
35
40
106 [
Re(S
21) or
Im(S
21)]
Frequency (GHz)
TM11 mode at 5 K, in vacuum
• Measure microwave resonances using 2-port Portable Network Analyzer
• Complex 3-Lozentzian + polynomial background fitting routine
• Peak frequencies and half-widths
• Several microwave modes measured
• Optimized spectral fitting background terms, 1st- & 2nd-order shape corrections, and waveguide corrections
• Room temperature results agree with those done at NIST May et al., Rev. Sci. Instrum. 75, 3307 (2004)
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Electrical conductivity
0 50 100 150 200 250 300
0
1x108
2x108
3x108
4x108
5x108
6x108
7x108
8x108
9x108
1x109
Present study
OFHC Cu from Simon et al. 1992 / Hust & Lankford 1984
+/- 15% of Simon et al. 1992 / Hust & Lankford 1984 curve
r,C
u C
u (
S·m
-1)
Temperature (K)
Copper conductivity, TM11 peak 1 half-width • Temperature dependence of resonator conductivity (from peak width)
• Stable, fixed temperatures over entire temperature range
• Agrees with literature within literature curve’s 15% uncertainty Simon et al., NIST Monograph 177, 1992
• Free parameter σ(T = 0) ≡ 1/ρ0 set to present experimental data at 5 K
8
Thermal expansion coefficient αL
0 50 100 150 200 250 300
0.0
2.0x10-6
4.0x10-6
6.0x10-6
8.0x10-6
1.0x10-5
1.2x10-5
1.4x10-5
1.6x10-5
Present study, TM11 mode Present study, TE11 mode Present study, TM12 mode
OFHC Cu from Simon et al. 1992 / NIST CMPD 2010
+/- 1.4 × 10-7 K-1 standard deviation of Simon et al. 1992
L (K
-1)
Temperature (K)
Copper thermal expansion coefficient• Experimental data
from 3 microwave modes• Good consistency
• Literature curve – no free parameters!• Simon et al., NIST
Monograph 177, 1992• NIST Cryogenic
Materials Properties Database (2010 revision)
• Excellent agreement with literature values over entire temperature range
9
Thermal expansion coefficient αL
0 50 100 150 200 250 300
-2.0x10-7
-1.0x10-7
0.0
1.0x10-7
2.0x10-7
Present study, TM11 mode Present study, TE11 mode Present study, TM12 mode
+/- 1.4 × 10-7 K-1 standard deviation of Simon et al. 1992
L,
pre
sen
t st
ud
y -
L,
lite
ratu
re(K
-1)
Temperature (K)
Copper thermal expansion coefficientwith Simon et al. 1992 / NIST CMPD 2010 curve subtracted
• Present data is within 1 st. dev. of literature curve at all temperatures measured
10
Conclusions & future directions
Conclusions
• International Temperature Scale of 1990 deviates from thermodynamic temperature• More measurements needed to resolve issues before replacement scale created• NRC developing microwave RIGT for Canadian thermodynamic temperature measurement capability
• Microwave resonances measured in quasi-spherical copper resonator• Vacuum, 5 K – 300 K
• Comparison to literature properties of copper measured with other methods• Excellent agreement over wide temperature range• Increased confidence in our microwave implementation
Next steps
• Measure triaxial ellipsoid resonator• Better shape, reduced background effects
• Gas in resonator• Refractive Index Gas Thermometry
11
We’re looking for a few good physicists: do you have what it takes?
THE PROJECT
• Electrical resistivity and Seebeck voltage of platinum-group metals (and other metals and alloys) – considerable interest to thermometry• Solid-state theory and experimental measurements to understand the
temperature dependencies of these properties• Electronic band structure, electron-phonon scattering, electron-electron (s-d)
scattering, oxidation, recrystallization, and scattering from vacancies and dislocations
• Suitability of various phase transformations as reference temperatures• Typically liquid/solid and solid/liquid transformations of pure elements or
eutectics• Various metal-carbon eutectics and peritectics are of current interest at high
temperatures
KEY SPECIFICATIONS• Ph.D. in Physics (experimental solid state / condensed matter physics preferred)
• Ability to design, construct, and operate experimental equipment with a minimum of technical assistance
• Innovative “hands on” approach towards the solution and attainment of high accuracy in a variety of measurement problems
• Attention to detail commensurate with the operation of a primary standards facility
• Ability to work effectively within a small group devoted to the research, development, and dissemination of temperature standards
Get in touch for more information: [email protected]
