Validation of NIST s Low Temperature Infrared Spectral Radiance Scale

Transcription

1 Validation of NIST s Low Temperature Infrared Spectral Radiance Scale Leonard Hanssen Vladimir Khromchenko Sergey Mekhontsev CALCON Logan, Utah, August 24, 2017

2 Outline I. Introduction II. NIST IR Radiance Temperature (IRT) Calibration Instrumentation III. Derivation of the IR Spectral Radiance T Scale IV. Validation of the IRT Scale

3 Key Instrumentation for Scale Realization Measurement Facilities and Systems 1. AIRI: Advanced Infrared Radiometry and Imaging Facility 2. ISEMS: Infrared Spectral Emittance Measurement System 3. FTIS: Fourier Transform Infrared Spectrophotometry Facility 4. LIR: Laser Infrared Reflectometry Facility** Instrumentation A. TFC: Tunable Filter Comparator (AIRI) B. IRIS: Infrared Reference Integrating Sphere (FTIS) ** C. IGRT: Infrared Gonio Reflectometer-Transmissometer (FTIS) ** D. CHILR: Complete Hemispherical Laser-based Reflectometer (LIR) E. ILGRI: Infrared Laser-based Gonio-Reflectometer Instrument (LIR) ** Blackbody Sources I. GFPBB: Gallium Fixed Point Blackbody (AIRI) II. AHPBB: Ammonia Heat Pipe Blackbody (AIRI & ISEMS) III. WBBB: Water Bath Blackbody (AIRI) IV. LTBBB: Low Temperature Ethanol Bath Blackbody (Customer, ISEMS) ** Not Described in Detail

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5 1. National Primary Standard of Radiance Temperature (below 1100 C ) and IR Spectral Radiance Advanced Infrared Radiometry and Imaging (AIRI) Laboratory: providing national level traceability for measurements of absolute spectral radiance and spectral emissivity of blackbody sources and targets at near-ambient temperatures Fixed Point BB Bench and ambient environments. Variable Temperature/Spectral Bench 5 Scene plate/out-of-field Scatter Tool

6 1. Thermal IR Scales Realization below 250 o C IR Spectral Radiance and Radiance Temperature Scales Realization Fixed Temperature Point (Phase Transition) Reference Sources Temperature: ITS-90 Reference Values Cavity Emissivity: Measured and/or Calculated Mercury FP BB Water FP BB Gallium M C FP BB Indium M C FP BB Tin FP BB M C C C C C C 50 mm opening (target) 50 mm opening (target) 43 mm cavity opening 12 mm cavity opening 12 mm cavity opening Spectral Radiance and Temperature Comparisons NIST TFC Comparator 2.5 to 12.5 mm -50 8C to 250 8C NIST InGaAs Pyrometer 1.5 mm 125 8C to 250 8C NIST InSb Pyrometer 4.9 mm, -50 8C to 150 8C Variable Temperature Reference Sources Temperature: Contact Thermometers Cavity Emissivity: Measured and/or Calculated Ammonia C Water M C Water M C Heat Pipe BB Bath BB Heat Pipe BB - 508C to +50 8C 108C to 75 8C 55 8C to 250 8C 75 mm cavity opening 104 mm cavity opening 63 mm cavity opening T Stabilized aperture plate T Stabilized aperture plate T Stabilized aperture plate Secondary Standard BB 0 to C Spectral Radiance and Temperature Transfer NIST TFC Comparator 2.5 to 12.5 mm C to 250 8C T Stabilized aperture plate T Controlled High Emissivity Background Plate Transfer Standard Blackbodies (Customer)

7 2. Infrared Spectral Emittance Measurement System ISEMS Component Setup Flat Plate BB Blackbody Source With Sample Hardware Removed Flat Plate BB UUT FT Based Based Spectral Radiance Comparator (includes Near IR Sphere) Purge, polarization; λ range: 1 µm to 50 µm; T range: 100 C to 900 C Designed for materials characterization easily modified for blackbody calibration Replace sample holder with T-controlled background Scene Plate -> lower T capability

8 3. Fourier Transform Infrared Spectrophotometry Facility: Reflectance and Transmittance Infrared Gonio Reflectometer Transmissometer (IGRT) Infrared Reference Integrating Sphere (IRIS) 8

9 A. Tunable Filter Comparator TFC (AIRI) [ Vuut ( λ) VA( λ) ] [ V ( λ) V ( λ) ] L uut ( λ) = C A + C A TFC has capacity to consistently measure temperature with standard deviation from 5 mk to 25 mk in the range -50 C to 250 C across spectral regions to 3 µm - 5 µm and 8 µm µm Measured spectra Temperature-Controlled Front Plate Elliptic Relay Mirror Lyot Stop Circular Variable Filter InSb, MCT or sandwich detector (shown rotated at 90 for clarity) [ L ( λ) L ( λ) ] L ( λ) Known Spectral Radiances of Ambient and Variable Temperature Reference BB s Internal BB Reflective Chopper Pointing Laser Reflective Field Stop A Aperture Stop Elliptic Primary Mirror Laser Folding Mirror Absolute Transmittance SSE in radiance, absolute Spectral Resolution Example of CVF Filter Transmittance for several angles. Measured at NIST using FTIR Spectrometer Wavelength, Microns Spatial Scatter 3.7 microns, InSb, relative 12 mm diameter source, source 50 C, background 23 C SSE, signal SSE correction, degrees Source Diameter, mm SSE correction, degrees

10 D. Complete Hemispherical Laser-Based Reflectometer (LIR) Cavity Detector Integrating sphere Sphere rotation & X-Y stage CHILR setup designed especially for cavity emissivity determination Also good for very black samples Can measure spatial variation & angle dependence Entrance port 1/2 angle = 1 CO 2, diode, and OPO tunable laser sources Can measure down to approx (equiv to emissivity ) Y (mm) µm µm 9.2 µm µm X (mm) e e e

11 Spectral Radiance Scale Realization Validation Chain ITS-90 via comparison to Fixed Point Blackbody Source(s), Platinum Resistance Thermometers (PRT) & Planck s Law. Steps: 1. Tunable Filter Comparator at AIRI compares Water Bath BB with Gallium FPBB at TFC & FTIR at AIRI compare Ammonia HPBB with Water Bath BB at 11 to Fourier Transform Spectrometer in ISEMS compares Low Temp Ethanol BBB to Ammonia HPBB from - 45 to 25. Reference PRTs used in all blackbody sources, including many UUTs Effective emissivities from measurements (CHILR) and/or modeling (STEEP3) using measured optical properties of cavity coatings are needed.

12 Blackbody Type Effective Emissivities of Blackbodies Employed Nominal Temperature Range, C Emissivity calculated (10.6 μm) Emissivity measured (10.6 μm) Cavity Coating Cavity Aperture, mm Ammonia Heat Pipe - 45 to Nextel Velvet Black 30 Water Bath 10 to Testers Black 50 Ga Fixed Point Z Measured results from CHILR instrument Calculated results from modeling (STEEP3) using coating reflectance measurements (specular, diffuse, and BRDF) LTBBB cavity geometry and coating specified identical to those of the WBBB Similar comparisons performed on numerous other blackbodies 12

13 I. Ga Fixed Point Blackbody Design

14 III. Water Bath Reference BB O88.7 [O3.490] [4.252] Converted from Oil Bath BB with new cone with a few design improvements CHILR Measurements of effective emissivity Currently serves as Primary Standard at the Temperature Range 10 C to 75 C Stability < 2 mk Reflectance Comparison of integrated (averaged over the radius) reflectance of the freshly painted water bath cone Modified Cavity with Inverted Cone Tip Original Cavity Design Radius (mm)

15 Step 1. TFC Comparison of WBBB and Ga Fixed Point (AIRI) Radiance Temperature,C Gallium Melting Plateau measured with TFC at 10 micron relative water bath BB, ITS-90 value C ITS-90 Ga FP temperature C; ε = => 3 mk :00:00 18:00:00 22:00:00 26:00:00 Time, hh:mm:ss Spectral radiance against WBBB within ±10 mk across range Radiance temperature, C Ga BB: Spectral Radiance Measured with TFC Wavelength, microns

16 II. Ammonia Heat Pipe Blackbody Gas heat Exchanger Blackbody Design Reference PRT Micro-Ohm Meter Refrigerated Circulating Bath, -50 C to +55 C Cavity geometry

17 Step 2A. TFC Comparison of Ammonia HPBB to WBBB (AIRI) Apparent Temperature, degrees C TFC Random Uncertainty Evaluation Using Auto-referencing of Ammonia C and water 11 C Wavelength, microns Apparent Temperature, degrees C Measured Radiance Temperature of the Ammonia BB Reference PRT Reading Wavelength, microns Apparent Temperature, degrees C Measured Radiance Temperature of the Ammonia BB Reference PRT Reading C S1 S2 S3 S4 L Wavelength, microns Temperature, C BB Ammonia Stability, PRT temperature Time, seconds

18 Step 2B. FTIR** Comparison of Ammonia HPBB against 15 C (AIRI) Spectral Trad,Ammmonia HP BB Tprt=15.16 C, InSb Detector Spectral Trad, Ammmonia HP BB, Tprt=15.16C,MCT Detector Trad, C 15 Trad, C Wavelength,µ Wavelength,µ Trad Ammonia BB, Tprt= C, Reference Water Bath BB, T= +15 C, Un-ty confidence level = Difference (Trad-Tprt)C Ammonia BB Tprt= 0.295C, Reference Water Bath BB T= +15 C, **Bruker IFS 66 temporarily installed on AIRI sensor calibration bench Temperature, C Wavelength, µ Temperature, C Trad (8-14 mic)=0.283 C Trad - Tprt = C Wavelength,µ

19 Recent Production of Low Temperature Ethanol Bath Blackbody (LTBBB) Supplied to Air Force Primary Standards Lab (AFPSL) via AFMETCAL funding. Produced by Fluke to NIST specifications and consultation. Followed proven design of NIST water bath BB. Temperature range: - 50 C to + 25 C Designedfor operation in ambient conditions Additional improvements (hardware, software and operating procedures) developed after delivery and testing at NIST. Delivered to AFPSL after calibration Performance equivalent to Ammonia HPBB

20 IV. Large Aperture Fluid Bath BB with Purge for Air Force (AFPSL) Integrated Design Air purge or vacuum(optional) 3 aperture, ε = (Fluke) -60 C to +25 C A Clone of NIST Water Bath BB.

21 IV. Blackbody Detail Dust Cover Outer Insulation Removable Snout Tank Insulation Inner Mounting Flange Internal Aperture Holder Internal Coated Cavity Cooled Dry Air Purge Warm Dry Air Purge

22 Step 3. FTIR Compares Low Temp Ethanol Bath BB against AHPBB at 25 C (ISEMS) 25.3 Calibration 7Bath-32 ( mic.) Tset 25 C, Tref= C 25.2 Calibration 7Bath-32 (8-14 mic.) Tset =25 C, Tref= C Trad ( mic)= C, StDev Average=0.013 C Trad (3.5-5 mic)= C, StDev Average=0.04 C Trad, C Trad, C Trad (8-14mic)= C, StDev Average=0.024 C Wavelength, micron Wavelength, micron LTBBB model name 7Bath-32

23 Step 3. FTIR Compares Low Temp Ethanol Bath BB against AHPBB at - 45 C (ISEMS) Calibration 7Bath-32 Tset -45 C, Tref= C( mic.) Calibration 7Bath-32 Tset -45 C, Tref= C (8-14mic.) Trad, C -45 Trad, C Trad ( mic)= C, -47 StDev Average=0.11 C Trad (3.5-5mic)= C, StDev Average=1.2 C Wavelength, micron Trad (8-14mic)= C, StDev Average=0.22 C Wavelength, micron

24 T set C T reference T rad 8 14 µm Expanded Uncertainty (k=2) Results Summary (for band averages) T T rad µm Expanded Uncertainty (k=2) T T rad µm Expanded Uncertainty (k=2) T λλ 1 λλ 2LL(λλ)dddd λλ 2PPPP = λλ, TT dddd λλ 1 Pl( T, λ) = n 2 5 λ c 1L ( exp( c /( n λ T )) 1) 2

25 Summary & Comments Multiple instruments and systems are used at NIST for defining its scale for infrared spectral radiance and radiance temperature. Overlap between these also provide opportunities for comparisons to evaluate and validating and uncertainty budges Recent calibration of a low temperature ethanol bath blackbody has helped to validate our infrared radiance temperature scale down to -45 C. We will continue to pursue studies of error sources to improve uncertainty budgets.

26 Questions?

27 Example UUT Uncertainty Budget with Ammonia HPBB Reference Uncertainty -15 C 0 C +15 C -15 C 0 C +15 C BB Reference Temperature with Hart Scientific Reference BB Emissivity Reference Long Term Stability Reference BB Measurement Noise Ambient Blackbody Temperature UUT BB PRT Probe Red Out Temperature UUT BB Measurement Noise UUT BB Long Term Stability Combined Standard Uncertainty(k=1) Combined Standard Uncertainty (k = 2)