low-temperature primary thermometry development at nrc
DESCRIPTION
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 - PowerPoint PPT PresentationTRANSCRIPT
Low-temperature primary thermometry development at NRC
Dr. Patrick M.C. RourkeMeasurement 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 - T
90 (m
K)
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 [Re
(S21
) or I
m(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) o
r Im
(S21
)]
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)
7
Electrical conductivity
0 50 100 150 200 250 3000
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,Cu
Cu (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, p
rese
nt s
tudy
- 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]
