Optical Radiation Measurements Radiometric Standards in the Far Ultraviolet Technical Contact:
Robert Vest
Tel: 301/975-3992
E-mail: robert.vest@nist.gov Do not ship instruments or standards to the mailing address listed below. Contact the technical staff for the shipping address. Mailing Address:
National Institute of Standards and Technology
100 Bureau Drive, Stop 8411
Gaithersburg, MD 20899-8411 Service ID
Number | Description of Services | Fee ($) | | 40510C | Detector Standard, Windowless Photodiode (5 nm to 122 nm) | 4309 | | 40511C | Recalibration of Detector Standard (5 nm to 122 nm) | 3904 | | 40520C | Detector Standard, Windowless Photodiode (18 nm to 122 nm) | 3083 | | 40521C | Recalibration of Detector Standard (18 nm to 122 nm) | 2679 | | 40530C | Detector Standard, Windowless Photodiode (52 nm to 122 nm) | 1857 | | 40531C | Recalibration of Detector Standard (52 nm to 122 nm) | 1453 | | 40540C | Uncalibrated Windowless Photodiode | 791 | | 40560C | Detector Standard, Windowed Photodiode (116 nm to 254 nm) | 12472 | | 40561C | Recalibration of Detector Standard (116 nm to 254 nm) | 1453 | | 40599S | Special Tests on Detectors from the Ultraviolet (254 nm) to the Soft X-Ray Region (5 nm) | At Cost | Fees are subject to change without notice. back to top | back to index of optical radiation measurements Calibrated transfer standard detectors for the far ultraviolet are available from NIST to cover the spectral region 5 nm to 254 nm. Users are furnished with the quantum efficiency as a function of wavelength; quantum efficiency is defined as the average number of photoelectrons per incident photon. Three detector types are available to cover this range: (1) a windowless silicon semiconductor photodiode for the wavelength region 5 nm to 254 nm (available under Service ID No. 40599S); (2) a windowless photoemissive diode with an Al2O3 photocathode for the wavelength region 5 nm to 122 nm; and (3) a MgF2 -windowed photodiode with a semi-transparent CsTe photocathode for the wavelength region 116 nm to 254 nm. The detectors have been extensively studied regarding radiometrically important parameters such as photocathode spatial uniformity and temporal stability of conversion efficiency. It should be noted that the silicon photodiode is not solar blind, while the windowless photoemissive diode is. Stray light considerations should be evaluated before making a choice for the 5 nm to 122 nm region. The relative expanded uncertainties in the measured quantum efficiencies are 7 % to 22 % in the 5 nm to
122 nm windowless photodiode region, and 9 % to 10 % in the 116 nm to 254 nm windowed photodiode region. NIST working standard calibrations are based on the rare gas ionization chamber in the 5 nm to 92 nm region, and on the calculable synchrotron flux from the NIST electron storage ring, SURF II, at wavelengths longer than 110 nm. Two facilities at SURF II are used in these calibrations, one in the 5 nm to 50 nm region and a second in the 116 nm to 254 nm region. A separate laboratory facility is used for the 50 nm to 92 nm calibration of working standards. Outgoing detectors are calibrated by direct intercomparison with precalibrated working standards that are periodically recalibrated. Windowless Al2O3 photodiodes are fabricated in-house; the windowless Si photodiodes and the windowed CsTe photodiodes are procured commercially and tested for stability and spatial homogeneity. Only those photodiodes meeting stringent NIST quality specifications are selected as transfer standards. The calibration costs include the cost of the detector and screening services unless a recalibration of previously used detectors is requested. Special detectors that do not lend themselves to convenient on-site cross-calibration may also be calibrated at NIST if the detectors merit radiometric application and if the NIST calibration facilities are suitable and available for the particular device. back to top | back to index of optical radiation measurements
References-Detector Calibrations in the Ultraviolet Stable Silicon Photodiodes for Absolute Intensity Measurements in the VUV and Soft X-Ray Regions , E. M. Gullikson, R. Korde, L. R. Canfield, and R. E. Vest, J. Electron Spectrosc. Relat. Phenon., 80, 313 (1996). Far Ultraviolet Detector Standards , L. R. Canfield and N. Swanson, J. Res. Natl. Bur. Stand. (U.S.), 92 (2), 97-112 (1987). NBS Measurement Services: Far Ultraviolet Detector Standards , L. R. Canfield and N. Swanson, Natl. Bur. Stand. (U.S.), Spec. Publ. 250-2 (June 1987). Time response of NBS windowless XUV radiometric transfer detectors , E. B. Saloman, Appl. Opt. 14, 1764 (1975). back to top | back to index of optical radiation measurements Date created: 06/30/1999
Last updated: 01/15/2009 | 