Johnson Noise Thermometry
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Transcript of Johnson Noise Thermometry
Johnson Noise Thermometry
GSECARS
Overview• 2004:
– 3rd year of Getting’s P, T Calibration Project) – Preparation for JNT migration from UC Boulder to GSECARS, Chicago– Evaluation of electrical noise in 13-ID-D
• 2005: – Development of high P cell at GSECARS, continued bench test at Boulder (varying
R only)– First high P test at Boulder (July), w/o JNT, for TC noise assessment
• 2006:– Jan - First JNT test at high P, discovered JNT circuitry problems, preamp filters
added– Mar – JNT migrated to GSECARS– Nov – Takeshi Sanehira Joined GSECARS working on JNT
• 2007:– Jan – John Labenski (post-doc prospect) visited GSECARS, and worked with crew
to solve ground loop problems– High P JNT tests throughout the year, with inconsistent results
• 2008:– JNT tests continue, results still inconsistent– Preparation for pyrometry using radiospectrometry– Nov – Takeshi to leave GSECARS
Difficulties in high P JNT tests
• Ground loop issues – eliminated floating voltages at microV level
• Electrical noise from equipment – all unnecessary equipment turned off, shielding, grounding
• Power supply – “clean” transformer, power conditioner to eliminate any frequencies other than 60 Hz
• Contamination in cell assembly – no glue, no acetone, all parts fired at 900C for 1 – 2h.
• Numerical filtering to eliminate 60 Hz harmonics in the JNT signal
• Non-white noise at high temperature persists (usually above 300C)
High P tests results
Varying R only(bench)
Wide variation in slope in various runs, cannot be contributed to electrical noise alone.Overall, slopes appear to become shallower with time (Data legends in order of time: 2006 - 2008.
0
0.4
0.8
1.2
1.6
2
0 10000 20000 30000 40000 50000
Sensor RT, ohm K
JNT
out
put
JNT060JNT069_20TJNT069_25TJNT069_25T-2JNT069_35TD0893_20TD0893_30TD0893_40TD0893_30T-2D0893_60TD0894_15TD0894_30TD0903_20TPoly. (JNT060)
In situVarying T mainly
“Bench test”: varying R onlyBench Test All
-2.000
0.000
2.000
4.000
6.000
8.000
10.000
12.000
14.000
16.000
0 50000 100000 150000 200000 250000 300000 350000 400000
RT
JNT
Sig
nal
JNT 058
JNT 060
JNT 076
JNT 077
JNT 078
JNT 079
JNT 080
JNT 081
Bench tests (varying R only) show no significant change in slope over time
Alternative approach: Pyrometry
PC
WC anvil
Fiber cable
BN guide sleeve
Cell assembly (TEL 10 mm)
Spectrometer
Steel spacer
USB cableOptical window:Single crystalmoissanite
Constant intensity light source test: source direction effects
Const. current light source
Moissanitewindow
Anvil with hole
o. fiber
Ocean Opticsspectrometer
Directional effects
0
10000
20000
30000
40000
-0.8 -0.4 0 0.4 0.8 1.2 1.6
Y, mm
Inte
ns
ity
Y scan, Intensity
0
10000
20000
30000
40000
3 3.5 4 4.5 5 5.5
Z, mm
Inte
ns
ity
Z scan, Intensity
0
20000
40000
60000
2 3 4 5 6 7 8 9
X, mm
Inte
ns
ity
X scan, Intensity x
y
z
anvil
Window crystal4 mm dia., 6 mm long
Light sourceThru 0.1 mm pinhole
Y scan Z scan
X scan
Conclusion: Dominant signals from center of the window tip. Pyrometry feasible in MA cell
Bench-top W-lamp test
Tungsten lamp source
Use radiation at 15 Amp as standard, cross check T at 10.48 Amp by radio-spectroscopy ( both points manufacturer calibrated),
Direct fit to the radiation spectrum yields T10.48A = 2085 KTo be compared with 2000 K given by manufacturer
I (λ, T) = C1ε(λ,T)λ-5 /[exp(C2/λT)-1]
Cell assembly
Pyrophyllite (Soft-Fired)
Graphite
Crushable alumina
BN
SiC lens(Single Cryst.)
14.00 mm
6.50 mm
7.00 mm
4.00 mm
TEL 10 mm, ver. 2( cell assembly for pyrometry calibration)
MgO
Al2O3 with double bore (0.8 mm dia.)& Thermocouple
1.00
4.70
0.80 mm
4.00 mm
5.00 mm6.00 mm
6.60 mm
WC anvil
Optical fiber
1.5 mm
BN guide sleeve(OD: 1.5 mm, ID: 0.4mm)
T.C.
BN window (2.5 mmØ)
Pressure marker (MgO+Au, 10:1 by vol)
1.00
Tungsten lamp calibration before applying pressure
anvil
Moissanite window crystal
Lower DIA guide block
Upper DIA guide block
Examples of grey body (abs) fit – 1 ms data collection
1523 K
973 K 1173 K
1323 K
Relative T determination
Assuming that a reference T0 is known, from Wien’s approximation
The ratio of two observations is a straight line give by the J (λ, T) function (Yagi and Susaki, 1992)
in the J - plot, where ω(λ) = C2/λ. And the slope of the line is -1/T.
J (λ, T) = -(1/T)(λ)+ln[ε(λ,T)/ε(λ, T0)] = ln[I(,T)/I(,T0)] - (1/T0) ω()
I (λ, T) = F() C1ε(λ, T)λ-5 /exp(-C2/λT) I (λ, T0) =F) C1ε(λ, T0)λ-5 /exp(C2/λT0)
“J-function” fit, relative to 1523K
973 K 1173 K
1323 K 1573 K
800
1000
1200
1400
1600
800 900 1000 1100 1200 1300 1400 1500 1600
T (T.C.), K
T (
Py
rom
etr
y),
K
T(pyro_J ), up, 1ms
T(pyro_J ), down, 1ms
One to one line
T(pyro_abs), up, 1ms
T(pyro_abs), down, 1ms
Linear (One to one line)
Comparison of T measurements
Pressures: 0.2 to 0.5 GPa
Noise level too high at 1 ms
Difference plot
-600
-500
-400
-300
-200
-100
0
100
800 1000 1200 1400 1600
T (T.C.), K
T(T
C)-
T(p
yro
), K
T(TC)-T(pyro_J), up
T(TC)-T(pyro_J), down,
T(TC)-T(pyro_abs), up
T(TC)-T(pyro_abs), down
thermal drift recognized in power-temp relation
Outlook
• Obtained optical windows (single-crystal diamond) for DIA cells between 12 and 6 mm edge length (P up to ~8 GPa)
• Tests under way for both W/Re and Pt/Rh thermocouples
• One technical paper currently in prep.
• Expect to obtain data up to 8 GPa and ~1800 K by Nov, 2008, results will be out 2009