FUTURE PERSPECTIVES OF THERMOMETRY AND GAS … · 2019-01-02 · Outline Future perspectives of...
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FUTURE PERSPECTIVES OF THERMOMETRY AND GAS METROLOGY Roberto M. Gavioso
Transcript of FUTURE PERSPECTIVES OF THERMOMETRY AND GAS … · 2019-01-02 · Outline Future perspectives of...
FUTURE PERSPECTIVES OF THERMOMETRY AND GAS METROLOGY
Roberto M. Gavioso
Outline Future perspectives of thermometry and gas metrology
Current activities in primary thermometry
• extending the range of primary methods (AGT, RIGT, DCGT)• simplifying primary methods
Calculating thermodynamics for gas metrology
• ab-initio calculation of thermodynamic properties • improving primary gas-based thermometry• improving other gas-based metrology: pressure, humidity, ..
Novel proposed temperature sensors (& standards)
• photonic thermometry• optomechanic thermometry • whispering gallery thermometry• free electron gas thermometry
methods used for the experimental determination of the Boltzmann constant k or the thermodynamic temperature T
u02
acoustic gas thermometry (AGT)
u02 = 0 kT NA /M
p
+_
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C(p)
p
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C(p)
dielectric constant gas thermometry (DCGT)
p =kT 0 (r - 1)/0
<V 2> = 4 kT R
Johnson noise thermometry
(JNT)
100 150 200 250 300 350 400-10
-8
-6
-4
-2
0
2
4
6
8
10
NPL - AGT 2015 NPL - AGT 2016 INRiM - AGT 2016 VNIIFTRI - AGT 2017 NIM - AGT 2017 LNE - AGT 2015
(T-T
90) /
mK
Temperature / K
2012 - 2017 AGT data
AGTDCGT
AGT
2015
refractive index gas thermometry (RIGT)
2
A
1 (3 3 ) ..pn A AN kT
2
2 vacuum
pressure
f gn
f g
extending the temperature range of Acoustic Gas Thermometry up to the Al (~ 930 K) or even up to Cu fixed point (~ 1350 K)
Inconel pressure vessel 1 MPa @ 1000 K
NPL High-Temperature Cylindrical Resbonator
2 00
RTuM
expected temperature uniformity at 800 K
A) External Vacuum chamber: diameter and length 650 mm, withfeedthroughs for two acoustic waveguides, two high T microwave cables, 4long-stem SPRTS (which can be inserted and withdrawn from ambient)
B) Internal OFHC copper shell with Macor insulators is illuminated by 8main heaters (IR lamps) plus 8 secondary low voltage heaters.All the heaters are independently supplied with variable voltages allowingactive reactioned control to enhance temperature uniformity
C) Internal copper vessel: it replies feedthroughs for acoustic andmicrowave waveguides and SPRTs; vacuum- and pressure-tight up to 2.5MPa
extending the temperature range of Acoustic Gas Thermometry up to 1000 K
2 00
TMRu
Benefits
• 2-stage pulse-tube cryostat no liq He• minimum temperature < 4 K• same calorimeter for T and T90 realization• houses a larger number of CSPRTs• provides good stability especially
in ranges 30 K – 77 K and 150 K – 234 K
Risks and drawbacks
• vibrations may limit measurement precision• complex design, long realization time
2016 -2019 EMRP Research Project Implementing the new kelvin 2 - InK2 -coordinator G. Machin
extending the temperature range of Acoustic Gas Thermometry down to 4 K and below
prototype spherical resonator
AGT at T < 4 K
INRiM 12 June 2018 Page 9
extending the temperature range of DCGT up to ambient
10 100-10
-8
-6
-4
-2
0
2
(T-T90)DCGT 2014 (He)
(T-T90)DCGT 2014 (mean C1-C2-He-Ne)
(T-T90)DCGT 2010 corrected
(T-T90)AGT NPL 2016
(T-T90)AGT LNE/NIST 2006
(T-T90)AGT INRIM 2016
(T-T90)CCT 2010
(T-T
90) (
mK
)
T(K)
C. Gaiser, B. Fellmuth, N. Haft, Metrologia 54 141 (2017)u (T )/ T = 7 ppm at 84 K
C. Gaiser, B. Fellmuth, N. Haft, Metrologia 54 141 (2017)u (T )/ T = 7 ppm at 84 K
developing refractive index gas thermometry (RIGT)
2
A
1 (3 3 ) ..pn A AN kT
11
looking for alternatives for dissemination: simplification of primary methods
SPRT insert
LNE apparatus for the calibration of SPRTs
Copper vessel
Liquid bath
Vacuum
Thermal shield
SPRT
2 2 20 1 2, , ( ) ( ) ..u p T u p T A T p A T p
8 cm
16 cm
22 c
m
termination of acoustic and microwave waveguides
measured calculable for He
looking for alternatives for dissemination: simplification of primary methods
• material: copper; • shape: triaxial ellipsoid; • interrnal radius: 4 cm; • interrnal volume: 260 cm3; • thick wall to minimize shell coupling; • cavity designed to be vacuum- and pressure tight• excitation of acoustic and microwave resonances
by waveguides• embedded thermometer wells for cSPRTs and
long-stem SPRTs• working gas: helium (calculable properties) purity
maintained by a getter• temperature range of initial tests: 230 K to 430 K;• aimed accuracy: ± 5 ppm
ab initio calculation of thermodynamic properties
For helium, the accuracy of calculated transport properties and virial coefficients based on an accurate ab initio potential now exceeds that of the best measurements.
The ab initio results should be used to calibrate measuring apparatus
two atoms: calculation of interaction energy (r)
experimentally measured
density,speed of sound,
viscosity
He
calculated standards
temperaturepressureviscosity
stated uncertainty
ab initio calculation of thermodynamic propertiestwo and three He atoms calculation of interaction energies (r), (r,)
2012
2007
1998
2017
viscosity (T)thermalconductivity (T)
density virial coeffs B(T), C(T), ..
21 ...Bp R T CT T
from theoryfrom experiment
2 2( )1 ...( )a apT TRTuM
p
acoustic virial coeffs (T), (T), ..
,u u p T
using the calculated viscosity of He as a reference standard led to most ever accurate viscosity (ratio) measurements with Ar, Xe, H2, CH4
,p T
00
He 3 -10.517 254 13 (6) cm molA 2016
0 electric dipole polarizability a fundamental property of one He atom ab initio calculation of thermodynamic properties
refractive index gas thermometry (RIGT)
2
02r r 1 3T
p
fn k p
f
p
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+
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+
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+
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+
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+_+ _
C(p)
p
+_
+_
+
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+
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+_
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+_+ _+ _
C(p)
dielectric constant gas thermometry (DCGT)
p =kT 0 (r - 1)/0
0r 1 3T
p
Ck p
C
2
2
12
An
An
an electrical measurement of gas density is possible
r
r
12
A
dielectric virial coeffs. b(T), c(T), ..
21 3 ..r A b c
how does the capability to calculate all these properties represent an improvement and a simplification for thermometry ?
example: acoustic gas thermometry
2 2( ) ( )1 ...a aRTu p pTM
T
202
w 0 w
u TTT u T
20
MT uR
absolute relative
0 200 400 600 800
947500
950000
952500
u2 He(p
,T) /
m2 s
-2
pressure / kPa
extrapolation to zero pressure
corrected ab initio
boundary layer thermal correction requires knowledge of the thermal conductivity (T)
acoustic temperature
acoustic pressure
current capabilities of theory and experiment to accurately determine the electromagnetic and thermophysical properties of different substances
EXPERIMENT
THEORY
helium
©
For He the uncertainty of the calculated properties is well below their experimental determinations, already making possible
primary standards of pressure, temperature and viscosity.
THEORY EXPERIMENT
neon
argon
NEED ‐ The current imperfect knowledge of these properties for other gases represents a fundamental
limit to the uncertainty and the useful working range of calculated thermophysical standards.
krypton
waterTHEORY
water
EXPERIMENT
xenon
what could we do if we knew - ab initio - argon as well as we know helium?
for DCGT & RIGT thermometry the sensitivity of capacitance or frequency changes in the apparatus to changes in density would be 8 times larger
Ar He8A A
for AGT, DCGT & RIGT thermometry we would be much more less sensitive to impurities
sensitivity of AGT to impurities
Component Certificate Gas (ppb)
Specification Getter (ppb)
SpecificationAdsorber (ppb)
H2 < 30 < 10 < 0.1H2O < 50 < 10 < 0.1O2 < 30 < 10 < 0.1CO < 30 < 10 < 0.1CO2 < 30 < 10 < 0.1N2 < 10Hydro-carbons < 1 < 10 < 0.1Noble gases
99.99999% Helium (Linde AG)
Gas purifier (adsorber)(Micro Torr SP70, SAES Pure Gase, Inc.)
Helium purifier (getter)(HP2, Valco Instruments, Co. Inc.)
Mass‐spectrometry measurements
sensitivity of DCGT and RIGT to impurities
helium
©
argon
©
Helium
©
Neon
©
Argon
©
HeNeA A
HeArA A
what else can we realize for gas metrology using ab initio calculated properties?
novel primary pressure standards 2 1 3nRTp A A
what's wrong with traditional gas pressure standards & sensors?
piston gauge aka pressure balanceHg ultrasonic manometer
drawbacks : slowness, bulkyness, sensitivity to vibration, limited range, cost $$$
what else can we realize for gas metrology using ab initio calculated properties?
novel primary pressure standards 2 1 3p AnRT
what else can we realize for gas metrology using ab initio calculated properties?
novel primary pressure standards 2 1 3p AnRT
Fixed ‐ length optical cavity (FLOC)
calibration with UIMshows good repatability
Variable ‐ length optical cavity (VLOC)
drawback: He is absorbed in glass and changes the length of the appparatus, ... it would be good to use Ar instead
superconducting microwave cavity pressure standard in the range 200 Pa to 20 kPa
niobium coating thickness 3 m
2
2 vacuum
pressure
f gn
f g
virial coefficients of unlike interactions
what's next for gas metrology from ab initio calculations?
primary humidity standards at high p, T, RH
composition of mixtures
calculation/measurement of electromagnetic and thermophysical properties of:water vapor; gaseous mixtures: dry air; humid air; air constituents
dry AIR humid
AIR
example application: how much H2 in a tank ?
example application: how much CO2 out of a
smokestack ?
novel measurement methods
novel temperature sensors (thermometers)
Water Triple Point Cell
novel - photonic/optomechanical thermometer• Combined standard & sensor• No need of calibration• Zero-chain traceability• Deployable
• Artifact based standard• Requires expensive (time & money) ITS90 calibration• 150 years old• Extremely fragile
traditional - Standard Platinum Resistance ThermometerSPRT
Fiber Bragg grating
A fiber Bragg grating (FBG) is a type of distributed Braggreflector constructed in a short segment of optical fiberthat reflects particular wavelengths of light and transmitsall others. This is achieved by creating a periodic variationin the refractive index of the fiber core, which generatesa wavelength‐specific dielectric mirror.
Photonic thermometryrefers to the use of light-matter interaction in guided media to probe temperature induced changes in the refractive indexChanges in refractive index transduce large change in device resonance frequency which can be read out using standardfrequency metrology techniques
B eff2n B = Bragg wavelegnth = grating periodneff = effective refractive index
2 2T n T n T
waveguide Bragg gratings
slot waveguide Bragg gratings
silicon nanobeam photonic crystal cavity
2018
primary standard-built-in-the-sensor design
The act of position measurement alters the motion of an object being measured. This quantum measurement backaction is typically much smaller than the thermal motion of a room-temperature object and thus difficult to observe. By shining laser light through a nanomechanical beam, we measure the beam’s thermally driven vibrations and perturb its motion with optical force fluctuations at a level dictated by the Heisenberg measurement disturbance uncertainty relation. We demonstrate a cross-correlation technique to distinguish optically driven motion from thermally driven motion, observing this quantum backaction signature up to room temperature.We use the scale of the quantum correlations, which is determined by fundamental constants, to gauge the size of thermal motion, demonstrating a path toward absolute thermometry with quantum mechanically calibrated ticks
harmonically bound mirror forming one end of an optical cavity.
mthT n
k
optical resonance at 980 nm
breathing mechanical mode at 4 GHz
photonic thermometrysimplification
& cost reduction
sensitivity comparable to (or even better than) a platinum resistance thermometer (PRT)
extremely good stability and repeatability
novel temperature sensors whispering gallery
the WGM thermometer can achieve a measurement uncertainty
better than 4 mK over the temperature range from−40 ◦C to 85 ◦C.
electron gas thermometry
[..] under particular bias conditions, collector current constitutes a true probe of the energy distribution of the emitter free charge carrier gas which depends on temperature.
0( , ) ( )EBqV
kTC EB CI V T I T e
