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Figure 2. Layout of the measurement setup. The system can be triggered either by actively triggering the flash or by the signal of a photocell. References Espinar, B., Blanke, J., Ramírez, L., Bolós, M., Rodríguez, J.A., Blanco, M., Measurement of the spectral distribution of globar solar radiation and its components by the SPECTRO 320D Scanning Spectrometer, Measurement and modeling of Solar Radiation & Day-light Conference, Edinburgh, September 2003. 272
A normal broadband irradiance (Heat Flux) calibration facility M. Ballico and E. Atkinson National Measurement Institute of Australia, Lindfield Australia Abstract. The existing heat flux scale in Australia is based on a set of thermopile and Gardon type sensors, calibrated against a room temperature ESR using an 800 o C blackbody filtered by crown glass. NMIA has recently set up a new calibration system based on heat-pipe blackbodies with temperatures measured on the ITS-90, calibrated apertures and careful control of the ambient infra-red radiances. As measurements are made in air, corrections based on LOWTRAN data are made to the data, and the accuracy of this correction has been assessed using inert purging of part of the optical path. The facility is used to allow confirmation of the spectral flatness of heat-flux sensors into the thermal IR. Introduction Heat flux sensors are often calibrated under total hemispherical irradiance conditions by inserting the sensor fully into the mouth of a large blackbody source at a known temperature and using Planck’s law to calculate the irradiance [1]. This technique places significant thermal load on the detector, requiring water cooling, but avoids problems of atmospheric absorption, since the gas in the blackbody is at essentially the same temperature as the radiation field. The present standard used in Australia [2] calibrates heat flux sensors using an 800 o C blackbody filtered by crown glass (and reported as such). Whilst giving reproducible calibration results, these sensors are usually used to measure surface irradiance due to thermal sources as low 600 o C. In such cases, a substantial fraction of the radiation is above the 1-2 µm radiation source against which they were calibrated, and spectral blackness of detector is essential for the calibration to be meaningful. Accordingly, NMIA has developed a facility to measure the total normal irradiance responsivity to a range of blackbody source spectra. Experimental apparatus The facility is based on the blackbody sources and pyrometers from the NMIA radiation thermometry calibration facility [3]. For 400-1100 o C Cs and Na heatpipes are used whilst for 1000-2900 o C, a Thermogage blackbody is used. Temperature gradients have been measured and emissivities both measured and calculated [3,4,5], and are included as uncertainties. Temperature measurements are made using NMIA’s 850 nm and 650 nm pyrometers (MTSP and HTSP) calibrated on the ITS-90 give uncertainties from 0.2 o C over 400 o C-1100 o C rising to 0.5 o C at 1700 o C. The measurement is essentially trivial: the blackbody temperature is measured, and an aperture of known area in front of the blackbody provides a calculable irradiance in the measurement plane. However, at low source temperatures the irradiance from the surroundings is comparable to that from the aperture. Retro-reflection from the thermopile and its surrounds, ambient reflection and thermal emission from the plane containing the aperture must be controlled. The aperture is mounted in a 300 mm square ribbed anodized panel (Figure 1). Its IR reflectance, is measured [4] at below 0.5%. The aperture itself is covered by a light trap consisting of anodized concentric sharpened annuli, with a reflectance estimated below 0.2%. Over 100 W flux from the blackbody illuminates the aperture assembly, but its temperature rise (and consequent re-radiation to the thermopile) is kept below 0.1 o C by water cooling. Either side of the aperture is clear of an F/1 viewing cone to minimize the risk of stray reflections. The pyrometers, aperture assembly and thermopile are on a translating stage in front of a range of blackbody sources, and a typical measurement sequence consists of measuring the blackbody temperature, then measuring the thermopile signal with the aperture assembly opposite either the blackbody or a light trap at ambient temperature. Atmospheric absorption corrections The commercial computer package LOWTRAN has been used to compute the transmission through a range of atmospheres and paths (Figure 2) It is interesting to note that the integrated absorption predicted by LOWTRAN increases nearly as the square root of the distance (naively, one may expect something like Beer’s law). This results from the strong overlapping of numerous absorption lines. One consequence of this is that the absorption initially decreases very quickly (with distance) however, after 600 mm the rate falls to 5%/m for an 800 o C source. At higher source temperatures, less of the spectrum falls in the major CO 2 and H 2 O bands and the total absorption is lower. The total path length between the aperture of the blackbody and sensor is about 600 mm however the air column in the mouth of the blackbody is not at ambient temperature. Air near the blackbody temperature will radiate equal to its absorption, and may be considered part of the blackbody, but air at temperatures intermediate between the blackbody and ambient will have lower density and hence shorter effective optical thickness, but will also have thermally broadened absorption bands. We have not yet fully studied this effect, and as the insulation in the front of the blackbody is 100 mm in length, it is simply included as a 70 mm uncertainty in the effective atmospheric path. This results in an uncertainty in transmission varying from 0.3% at 600 o C to 0.2% at 1500 o C. Experimental measurements of atmospheric absorption Proceedings NEWRAD, 17-19 October 2005, Davos, Switzerland 273
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NEWRAD PROCEEDINGS OF THE 9 TH INTE
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NEWRAD 2005 Scientific Program Day
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14:50 Hiroshi Shitomi, AIST 5-3 Pho
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NEWRAD 2005 Scientific Program-Post
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33. Drift in the absolute responsiv
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Session 6 Novel Techniques 64. The
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Session 9 Realisation of scales 94.
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Absolute Accuracy of Total Solar Ir
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Low-uncertainty absolute radiometri
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NIST Reference Cryogenic Radiometer
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Measurement of the absorptance of a
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Grooves for Emissivity and Absorpti
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New apparatus for the spectral radi
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VUV and Soft X-ray metrology statio
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The metrology line on the SOLEIL sy
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Cryogenic radiometer developments a
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measured with BiTe thermopiles. Exp
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variations of the spectral sensitiv
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aperture area by I = π·L·F·A, w
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Table 1 Ratio of radiometric power
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Consistency of radiometric temperat
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Project of absolute measuring instr
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Session 2 UV, Vis, and IR Radiometr
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Table 1: Summary of the quality ass
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wavelength / nm U180 @ MLS band wid
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ight half is uncoated. Measurements
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Change [%] 2 1 0 -1 -2 -3 -4 PTFE d
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had been accommodated to industrial
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Relative Uncertainty 0.4% 0.3% 0.2%
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instrument differences or from diff
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3.00E-08 Nomalized radiant flux 2.5
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frequencies, the chopping frequency
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600 mA for each set. In both cases,
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Detailed and comparative results wi
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measurement to an independent spect
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The stability of silicon n-on-p jun
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applied. Reproducibility of measure
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Mutual comparison Mutual comparison
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A comparison of the performance of
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Stray-light correction of array spe
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Characterizing the performance of U
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Optical Radiation Action Spectra fo
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A newly developed double broadband
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On potential discrepancies between
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Correcting for bandwidth effects in
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Establishment of Fiber Optic Measur
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Detector-based NIST-traceable Valid
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Long-term calibration of a New Zeal
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Drift in the absolute responsivitie
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Radiance source for CCD low-uncerta
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Improved NIR spectral responsivity
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Characterization of a portable, fib
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Synchrotron radiation based irradia
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The Spectral Irradiance and Radianc
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NIST BXR I Calibration A. Smith, T.
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NIST BXR II Infrared Transfer Radio
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Proceedings NEWRAD, 17-19 October 2
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Spectral responsivity interpolation
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Monochromator Based Calibration of
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Study of the Infrared Emissivity of
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Radiometric Stability of a Calibrat
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Session 3 Photolithography and UV P
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NEWRAD 2005: Improvements in EUV re
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Measuring pulse energy with solid s
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Vacuum ultraviolet quantum efficien
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Spatial Anisotropy of the Exciton R
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Comparison of spectral irradiance r
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Session 4 Remote sensing Proceeding
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Solar Radiometry from SORCE G. Kopp
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Inter-comparison Study of Terra and
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The Solar Bolometric Imager - Recen
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On measuring the radiant properties
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A Model of the Spectral Irradiance
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Determination of Aerosol Optical De
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Procedures of absolute calibration
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Using a Blackbody to Determine the
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On the drifts exhibited by cryogeni
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On-orbit Characterization of Terra
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Space solar patrol mission for moni
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Multi-channel ground-based and airb
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Thermal Modelling and Digital Servo
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Calibration of Filter Radiometers f
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Radiometric Calibration of a Coasta
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A Verification of the Ozone Monitor
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Session 5 Photometry and Colorimetr
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Review on new developments in Photo
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Linking Fluorescence Measurements t
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Photoluminescence from White Refere
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A Simple Stray-light Correction Mat
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New robot-based gonioreflectometer
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Rotational radiance invariance of d
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Minimizing Uncertainty for Traceabl
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Development of a total luminous flu
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Determination of the diffuser refer
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DEVELOPMENT OF A LUMINANCE STANDARD
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Measuring photon quantities in the
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Session 6 Novel techniques Proceedi
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Characterization of germanium photo
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Determination of luminous intensity
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ËÒÐ¹ÔÓØÓÒ ×ÓÙÖ ÖÐÒ
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The Measurement of Surface and Volu
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The evaluation of a pyroelectric de
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UV detector calibration based on an
Page 221 and 222: NEWRAD 2005: Non selective thermal
Page 223 and 224: NEWRAD 2005 Calibration of Current-
Page 225 and 226: Simplified diffraction effects for
Page 227 and 228: Widely Tunable Twin-Beam Light Sour
Page 229 and 230: Measurement of quantum efficiency u
Page 231 and 232: Session 7 International Comparisons
Page 233 and 234: The CCPR K1-a Key Comparison of Spe
Page 235 and 236: Comparison of Measurements of Spect
Page 237 and 238: APMP PR-S1 comparison on irradiance
Page 239 and 240: Comparison Measurements of Spectral
Page 241 and 242: Comparison of mid-infrared absorpta
Page 243 and 244: Comparison of photometer calibratio
Page 245 and 246: A Comparison of Re-C, Pt-C, and Co-
Page 247 and 248: Session 8 Radiometric and Photometr
Page 249 and 250: Application of Metal (Carbide)-Carb
Page 251 and 252: On Estimation of Distribution Tempe
Page 253 and 254: Hyperspectral Image Projectors for
Page 255 and 256: Reproducible Metal-Carbon Eutectic
Page 257 and 258: Thermodynamic temperature determina
Page 259 and 260: Spatial Light Modulator-based Advan
Page 261 and 262: Novel subtractive band-pass filters
Page 263 and 264: Analysis of the Uncertainty Propaga
Page 265 and 266: Absolute linearity measurements on
Page 267 and 268: Comparison of two methods for spect
Page 269 and 270: Precision Extended-Area Low Tempera
Page 271: Flash Measurement System for the 25
Page 275 and 276: A laser-based radiance source for c
Page 277 and 278: Furnace for High-Temperature Metal
Page 279 and 280: Investigations of Impurities in TiC
Page 281 and 282: Determining the temperature of a bl
Page 283 and 284: High-temperature fixed-point radiat
Page 285 and 286: Long-term experience in using deute
Page 287 and 288: High-temperature fixed-point radiat
Page 289 and 290: A comparison of Co-C, Pd-C, Pt-C, R
Page 291 and 292: Irradiance measurements of Re-C, Ti
Page 293 and 294: Evaluation and improvement of the p
Page 295 and 296: The Spectrally Tunable LED light So
Page 297 and 298: Session 9 Realisation of scales Pro
Page 299 and 300: The Realization and the Disseminati
Page 301 and 302: The establishment of the NPL infrar
Page 303 and 304: The PTB High-Accuracy Spectral Resp
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Page 307 and 308: An integrated sphere radiometer as
Page 309 and 310: From X-rays to T-rays: Synchrotron
Page 311 and 312: Infrared Radiometry at LNE: charact
Page 313 and 314: Transfer standard pyrometers for ra
Page 315 and 316: Preliminary Realization of a Spectr
Page 317 and 318: New photometric standards developme
Page 319 and 320: Distribution temperature scale real
Page 321 and 322: Gloss standard calibration by spect
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Absolute cryogenic radiometry in th
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Detailed Comparison of Illuminance
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Radiometric Temperature Comparisons
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Characterization of Thermopile for
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Detector Based Traceability Chain E
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Comparison of the PTB Radiometric S
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Spectral Responsivity Scale between
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Realization of the NIST Total Spect
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Goniometric Realisation of Reflecta
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