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E Usadi, NPL
Low TemperatureBlackbody for CAVIAR:Characterisation & Calibration
Eric Usadi
Thanks to
Chris PriceTheo Theocharous
Title
E Usadi 02Jun08
E Usadi, NPL
• blackbody description
• traceability chain
• calibration & validation
plan
E Usadi 02Jun08
E Usadi, NPL
• blackbody description
• traceability chain
• calibration & validation
Blackbody short description
E Usadi 02Jun08
E Usadi, NPL
UniquenessUNIQUE CALIBRATION TOOLS
CAVIAR blackbody• in-air (i.e. non-vacuum)• temperature range• time response• aperture size• emissivity• calibrated & characterised
IR filter radiometer• world leading infrared FR• enables traceability
E Usadi 02Jun08
E Usadi, NPLCAVIAR blackbody
Blackbody schematic (not to scale)
ethanol in
LN2
insulation
PRT s
fluid heater/chiller
& circulator
(sealed system)
-60o C to +30o C
heat
exchanger
E Usadi 02Jun08
E Usadi, NPL
Copper parts
E Usadi 02Jun08
E Usadi, NPL
Copper parts
E Usadi 02Jun08
E Usadi, NPL
• blackbody description
• traceability chain
• calibration & validation
Traceability chain
E Usadi 02Jun08
E Usadi, NPL
Traceability schematic
Cryogenic radiometer
High emissivity BB (@ Ga fixed point)
CBB
TAFTS Aries
IR filter radiometer
IR filter
Transmittance scale
E Usadi 02Jun08
E Usadi, NPL
Traceability schematic 2
Cryogenic radiometer
High emissivity BB (@ Ga fixed point)
CBB
TAFTS Aries
IR filter radiometer
IR filter
Transmittance scale
E Usadi 02Jun08
E Usadi, NPL
Calibration schematicHigh emissivity blackbody@ Gallium Melting Point (29.76 deg C)
IR filter radiometer(4.7 m, et al)
Low temperature blackbody
E Usadi 02Jun08
E Usadi, NPLR
adia
nce
@ 4
.7
m
Temperature (K)
Planck function
Res
pons
ivity
Unc
erta
inty
(%
)
(microns)
Planck function Filter RadiometerResponsivity
E Usadi 02Jun08
Wavelength (m)
Ra
dia
nce
10 20 30 40
2 . ´ 10 6
4 . ´ 10 6
6 . ´ 10 6
8 . ´ 10 6
1 . ´ 10 7
303 K
258 K
213 K
Wavelength (m)
Ra
dia
nce
10 20 30 40
2 . ´ 10 6
4 . ´ 10 6
6 . ´ 10 6
8 . ´ 10 6
1 . ´ 10 7
303 K
258 K
213 K
10 20 30 40
2 . ´ 10 6
4 . ´ 10 6
6 . ´ 10 6
8 . ´ 10 6
1 . ´ 10 7
303 K
258 K
213 K2 .5 3 .0 3 .5 4 .0 4 .5 5 .0 5 .5
1 00
1 00 0
1 04
1 05
1 06
2 .0 2 .5 3 .0 3 .5 4 .0 4 .5 5 .0 5 .5
1 .0
0 .5
2 .0
0 .2
5 .0
1 0 .0
240 260 280 300
500 000
1 . ´ 10 6
1 .5 ´ 10 6
2 . ´ 10 6
E Usadi, NPL
Spectral Radiance slope
E Usadi 02Jun08
0
1
2
3
4
5
6
7
-70 -60 -50 -40 -30 -20 -10 0 10 20 30 40
T (deg C)
% s
lope
of S
pect
ral R
adia
nce 4.7 microns
10 microns
20 microns
30 microns
40 microns
50 microns
% s
lope
of S
pect
ral R
adi
ance
0
1
2
3
4
5
6
7
-70 -60 -50 -40 -30 -20 -10 0 10 20 30 40
T (deg C)
% s
lope
of S
pect
ral R
adia
nce 4.7 microns
10 microns
20 microns
30 microns
40 microns
50 microns
% s
lope
of S
pect
ral R
adi
ance
E Usadi, NPL
• blackbody description
• traceability chain
• calibration & validation
Calibration & validation
E Usadi 02Jun08
E Usadi, NPL
E Usadi 02Jun08
measure BB temperature
measure BB radiance @ 4.7 microns
calculate BB radiance
uncertainty of calculation
uncertainty of measurement
difference between measurement & calculation
difference < uncertainty ?
measure BB temperature
measure BB radiance @ 4.7 microns
calculate BB radiance
uncertainty of calculation
uncertainty of measurement
difference between measurement & calculation
difference < uncertainty ?
E Usadi, NPL
-40
-30
-20
-10
0
10
20
30
0 2 4 6 8 10
Time (hours)
Tem
p (d
eg C
) AMBER
Ch 2
Ch 5
Ch 1
22May08 data
Blackbody thermometer readings
AMBER radiometerreading of referenceblackbody (arb units)
AMBER radiometerreading of low-tempblackbody
E Usadi 02Jun08
E Usadi, NPL
E Usadi 02Jun08
-40
-30
-20
-10
0
10
20
30
0 2 4 6 8 10
Time (hours)
Tem
p (d
eg C
) AMBER
Ch 2
Ch 5
Ch 1
22May08 data
-2 mK0.007%
-16 mK0.06%
-25 mK0.1%
-13 mK0.05%
-53 mK0.24%
-78 mK0.38%
-112 mK0.59%
-62 mK0.29%
-31 mK0.13%
-11 mK0.04%
3 mK
0.01%
Difference between end platethermometer readings
Resultant radiance difference
AMBER radiometerreading of referenceblackbody (arb units)
AMBER radiometerreading of low-tempblackbody
-40
-30
-20
-10
0
10
20
30
0 2 4 6 8 10
Time (hours)
Tem
p (d
eg C
) AMBER
Ch 2
Ch 5
Ch 1
22May08 data
-2 mK0.007%
-16 mK0.06%
-25 mK0.1%
-13 mK0.05%
-53 mK0.24%
-78 mK0.38%
-112 mK0.59%
-62 mK0.29%
-31 mK0.13%
-11 mK0.04%
3 mK
0.01%
Difference between end platethermometer readings
Resultant radiance difference
AMBER radiometerreading of referenceblackbody (arb units)
AMBER radiometerreading of low-tempblackbody
E Usadi, NPL
Equation 6
E Usadi 02Jun08
E Usadi, NPL
Equation 6 detailPlanck function
Filter radiometer responsivity
measured at discrete ’s
Signal from
reference blackbody
at Gallium Point
Emissivities known by
design & modelling
Signal from
CAVIAR blackbody
1) MEASURED
2) CALCULATED
E Usadi 02Jun08
E Usadi, NPL
E Usadi 02Jun08
0.25
0.75
1.25
1.75
2.25
2.75
3.25
3.75
2 3 4 5 6 7 8
Time (hours)
Radia
nce
(arb
unit
s)
AMBER
Ch 2
Ch 5
Ch 1
0.05%
-0.10%
0.12%
0.03%
-0.33%
0.08%
0.25%
0.30%
0.31%
0.09%
-0.69%
Difference betweenmeasured & calculatedradiance
22May08 data
-0.13%
Radiometer uncertainty : 0.22% Calculated spectral radiance uncertainty: 0.2% @ T = 303K
0.9% @ T = 233K
0.25
0.75
1.25
1.75
2.25
2.75
3.25
3.75
2 3 4 5 6 7 8
Time (hours)
Radia
nce
(arb
unit
s)
AMBER
Ch 2
Ch 5
Ch 1
0.05%
-0.10%
0.12%
0.03%
-0.33%
0.08%
0.25%
0.30%
0.31%
0.09%
-0.69%
Difference betweenmeasured & calculatedradiance
22May08 data
-0.13%
Radiometer uncertainty : 0.22% Calculated spectral radiance uncertainty: 0.2% @ T = 303K
0.9% @ T = 233K
E Usadi, NPL
Uncertainty budget
E Usadi 02Jun08
CAVIAR BB Uncertainty Budget
PRT calibrationPRT measurement by Agilent DMMGradient across paint due to convective heat tansferNextel reflectanceeffective emissivityuniformitynumerical integration of ratioIntegration: filter radiometer calibration uncertaintiesIntegration: temperature uncertaintiesReflection of ambientTemp gradient along cylinder
E Usadi, NPL
Combined uncertainty
E Usadi 02Jun08
Tbb=303K, Tbgnd=293K
0
2000000
4000000
6000000
8000000
10000000
12000000
2 3 4 5 6 7 8 9 10 12 14 16 18 20 25 30 35 40 45 50
wavelength (microns)
0
0.05
0.1
0.15
0.2
0.25
0.3
Spectral Radiance (arb units)
Combined standard uncertainty (%)
T b b = 2 3 3 K , T b g n d = 2 7 3 K
0
5 0 0 0 0 0
1 0 0 0 0 0 0
1 5 0 0 0 0 0
2 0 0 0 0 0 0
2 5 0 0 0 0 0
3 0 0 0 0 0 0
2 3 4 5 6 7 8 9 1 0 1 2 1 4 1 6 1 8 2 0 2 5 3 0 3 5 4 0 4 5 5 0
w a v e le n g th (m ic ro n s)
0
0 .2
0 .4
0 .6
0 .8
1
1 .2
1 .4
1 .6
1 .8
2
S p e c t ra l R a d ia n c e (a rb u n it s )
C o m b in e d s ta n d a rd u n c e rt a in t y (% )
E Usadi, NPL
Conclusion
E Usadi 02Jun08
Conclusions
• blackbody tested -60 to +30 deg C
• performance CALIBRATED & VALIDATED
• full uncertainty analysis
• unique characterisation of low-temp blackbody
• ready for ARIES & TAFTS……
