Radiation Thermometry and Emissivity Measurements Under Vacuum at the PTB

Abstract

A new experimental facility was realized at the PTB for reducedbackground radiation thermometry under vacuum. This facility serves three purposes: (i) providing traceable calibration of space-based infrared remote-sensing experiments in terms of radiation temperature from −173 • C to 430 • C and spectral radiance; (ii) meeting the demand of industry to perform radiation thermometric measurements under vacuum conditions; and (iii) performing spectral emissivity measurements in the range from 0 • C to 430 • C without atmospheric interferences. The general concept of the reduced background calibration facility is to connect a source chamber with a detector chamber via a liquid nitrogen-cooled beamline. Translation and alignment units in the source and detector chambers enable the facility to compare and calibrate different sources and detectors under vacuum. In addition to the source chamber, a liquid nitrogen-cooled reference blackbody and an indium fixed-point blackbody radiator are connected to the cooled beamline on the radiation side. The radiation from the various sources is measured with a vacuum infrared standard radiation thermometer (VIRST) and is also imaged on a vacuum Fourier-transform infrared spectrometer (FTIR) to allow for spectrally resolved measurements of blackbodies and emissivity samples. Determination of the directional spectral emissivity will be performed in the temperature range from 0 • C to 430 • C for angles from 0 • to ±70 • with respect to normal incidence in the wavelength range from 1 µm to 1,000 µm.References to commercial products are provided for identification purposes only and constitute neither endorsement nor representation that the item identified is the best available for the stated purpose.

A Vacuum Infrared Standard Radiation Thermometer at the PTB

“…At the Physikalisch-Technische Bundesanstalt (PTB), a reduced-background calibration facility (RBCF) [1][2][3][4] was constructed. The RBCF is intended for the calibration of cryogenic and near-ambient-temperature blackbodies and infrared detector systems under medium vacuum ( p < 10 −2 Pa) or controlled atmosphere conditions and reduced-background radiation (liquid-nitrogencooled radiation shields).…”

Calibration capabilities at PTB for radiation thermometry, quantitative thermography and emissivity

“…The Emissivity Measurement in Air Facility (EMAF) allows measurements in the temperature range from 25 °C to 500 °C and in a wavelength range from 1.5 µm to 50 µm under angles of observation ranging from 0° to 80°. The Reduced Background Calibration Facility (RBCF) [3] is used for radiation thermometry measurements under vacuum in the temperature range from -170 °C to 430 °C and emissivity measurements from -40 °C to 1000 °C. The RBCF (see Figure 5) is the ideal instrument for the calibration of remote sensing applications avoiding any atmospheric interferences [4].…”

“…The spectral distribution of uncertainty has to be calculated for each individual measurement via a Monte-Carlo based method which is described in detail in [3].…”

“…Highly accurate measurements of the directional spectral emissivities of several widely used black coatings, which are often applied in different industrial and scientific applications, were recently performed at PTB and presented in detail in [3].…”

A Facility for Spectral Emissivity Measurement under Vacuum for Industrial and Remote Sensing Applications

“…Using a newly developed facility for radiation thermometry under vacuum at PTB [2][3][4] directional spectral emissivity, total directional emissivity and total hemispherical emissivity measurements in a broad wavelength and temperature range can be performed highly accurate under vacuum with traceable uncertainties.…”