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BMDO Transfer Radiometer (BXR)
 
The LBIR facility routinely calibrates small-aperture blackbodies for BMDO test facilities. In several cases, these blackbodies are used in the BMDO chambers as the input of collimating optics that provide large beams of highly collimated and spectrally filtered infrared radiation for testing infrared arrays and systems. Because the throughput of the collimating optics is not often known to a satisfactory uncertainty, simply knowing the input radiance is sometimes not enough to establish adequate NIST traceability of the output irradiance. Thus NIST developed a radiometer for measuring the output irradiance in such beams, known as the BMDO Transfer Radiometer (BXR). The BXR is a portable filter radiometer designed to measure low-level irradiance in highly collimated beams in a low-background environment. It uses an arsenic-doped silicon blocked-impurity band (BIB) detector behind a rotating filter wheel.
Schematic of BXR Chamber and Cryoshroud

BXR Chamber and Cryoshroud
Photograph of BXR Optics Plate Left Side

BXR Optics Plate Left Side; Front View

 Photograph of BXR Optics Plate Right Side

BXR Optics Plate Right Side; Front View

Photograph of BXR During Calibration

BXR During Calibration

The BIB detector operates at temperatures near 12 K and is cooled by a flow of liquid helium. All other elements of the radiometer are cooled to temperatures below 20 K to reduce background. The BXR bolts onto the host chamber and requires liquid helium and liquid nitrogen. It has a built in reference source as a stability monitor. The BXR is capable of detecting irradiance levels as low as 10-15 W/cm2 over the spectral range from 2 µm to 30 µm. The standard uncertainty goal is 5% for irradiance levels up to 10-9 W/cm2.

The BXR is tested and calibrated at the NIST LBIR facility against a collimated source developed specially for this purpose. The collimated source is calibrated in a separate step against the ACR in the same facility.

BXR Capabilities

  • Transfer standard to NIST absolute cryogenic radiometer (ACR)
  • Measure collimated beam with irradiance input levels between 10-15 W/cm2 and 10-9 W/cm2
  • Spectrally resolve beams over IR wavelengths from 2 µm to 30 µm with 2%-6% bandpass
  • Evaluate linear polarization of collimated beam
  • Easily transported with support equipment
  • Self contained vacuum and cryogenic systems for operation external to test chamber being evaluated
Return to Low Background Infrared Radiometry   -   Novel Detectors and Transfer Standards
For technical information or questions, call:
Adriaan Carter   Timothy Jung   Allan Smith
Phone: 301-975-4765   Phone: 301-975-2330   Phone: 301-975-8536
Fax: 301-840-8551   Fax: 301 869-5700   Fax: 301 869-5700
E-mail: adriaan.carter@nist.gov   Email: timothy.jung@nist.gov   Email: allan.smith@nist.gov
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Online: November 2006