Michael G. Mitch
Please contact the technical staff before shipping instruments or standards to the address listed below.
Dosimeters are provided twice a year to users requesting assistance with absorbed-dose measurements in high-energy electron beams. The user irradiates the two furnished dosimeters to between 50 Gy and 80 Gy (5000 rad and 8000 rad) to water at electron energies between 5 MeV and 50 MeV, employing the irradiation geometry (field size, phantom, position of dosimeter in phantom) given in the "Protocol for Dosimetry of High-Energy Electrons," Physics in Medicine and Biology 11, 505 (1966). After irradiation, the dosimeters are returned to NIST for evaluation terms of absorbed dose in the phantom, using appropriate methods. These dose interpretations ignore certain corrections for the effects of spectral perturbations, and so represent a measurement quality assurance service rather than a calibration service. Measurements with Fricke dosimeters are no longer supported. The measurement procedure will be adapted for use with alanine dosimeters and is not presently available.
The following dosimetry services are for individual users of intense radiation fields, in particular large gamma-ray sources and electron accelerators up to approximately 10 MeV. These services include the administering of known absorbed doses of photons to customer-supplied dosimeters; supplying calibrated transfer standard dosimeters to customers for irradiation and subsequent NIST readout and dose interpretation; and special measurement services such as the administration of absorbed doses to a customer-defined, non-standard irradiation geometry.
Certified irradiations are available for customer-supplied dosimeters or test samples that conform to calibrated NIST irradiation geometries that provide electron-equilibrium conditions. The dosimeters and samples are irradiated in the NIST 60Co irradiation facility to specific agreed-upon absorbed dose values in the nominal range of 10 Gy to 105 Gy, and irradiation temperatures from -77 °C to +70 °C. The dosimeters are then sent back to the customer for analysis and evaluation. Dosimeters must fit within NIST calibrated geometries (radiochromic film, alanine pellets, 2 mL ampoules, and red perspex). Certifications of the absorbed dose in water delivered to the dosimeter has an expanded uncertainty of approximately* 1.3 %. Upon request, certifications can be made in terms of absorbed dose in silicon; here the expanded uncertainty is approximately* 4.1 %.
NIST provides services for the measurement of calibrated alanine transfer dosimeters irradiated by the customer to nominal agreed-upon absorbed dose levels in a prescribed geometrical arrangement.
Through service codes 49020C-49022C, NIST provides sets of calibrated alanine transfer dosimeters to the customer for irradiation to nominal agreed-upon absorbed dose levels in a prescribed geometrical arrangement. The unopened polystyrene-packaged dosimeters are then returned to NIST to be measured and the results certified. The absorbed dose range for the transfer dosimeters is 0.5 kGy to 100 kGy. The alanine transfer dosimeter certifications have an expanded uncertainty of approximately* 1.8 % for absorbed dose in water. Upon request, the certification can be made in terms of absorbed dose in silicon; here the expanded uncertainty is approximately* 4.1%.
Through service codes 49030C-49032C, NIST administers calibrated alanine transfer dosimeters from prescribed commercial dosimeter lots that the customer has irradiated to nominal agreed-upon absorbed dose levels in a prescribed geometrical arrangement. The dosimeters are then sent to NIST to be measured and the cumulative results are certified for a period of up to 90 days. The absorbed dose range for the transfer dosimeters is 20 Gy to 50 Gy. The alanine transfer dosimeter certifications have an expanded uncertainty of approximately* 3.0 % for absorbed dose in water.
*For current uncertainty values see High-Dose Dosimetry Uncertainty Tables.
Tests of dosimeter response, such as temperature dependence, dose rate dependence, and dose distributions in specific irradiation geometries, can be provided as special measurement services. These dose distribution measurements can include dose profiles in heterogenous absorbers and at interfaces of different materials.
References-Dosimetry of High-Energy Electron Beams
NBS Measurement Services: Fricke Dosimetry in High-Energy Electron Beams, C. G. Soares, E. L. Bright, and M. Ehrlich, Natl. Bur. Stand. (U.S.), Spec. Publ. 250-4 (1987).
Radiation Dosimetry: Electron Beams with Energies between 1 and 50 MeV, Report 35, International Commission on Radiation Units and Measurements, Bethesda, MD (1984).
Uniformity of High-Energy Electron-Beam Calibrations, M. Ehrlich and P. J. Lamperti, Phys. Med. Biol. 14, 305 (1969).
Proposed National Bureau of Standards Program for the Calibration of Instruments Used in High-Energy Electron and X-Ray Beams, M. Ehrlich, Ann. N.Y. Acad. Sci. 161, 139 (1969).
Dosimetry Systems for Radiation Processing, W. L. McLaughlin and M. F. Desrosiers, Radiat. Phys. Chem. 46, 1163 (1995).
ESR-Based Analysis in Radiation Processing, W. L. McLaughlin, M. F. Desrosiers and M. C. Saylor, Sterilization of Medical Products, Vol. VI (R. F. Morrissey, Ed.), Polyscience Publications, Inc. Marin Heights, Canada, p. 213 (1993).
ESR Dosimetry, W. L. McLaughlin, Radial. Prot. Dosim. 47, 255 (1993).
NBS Measurement Services: Dosimetry for High-Dose Applications, J. C. Humphreys, D. Hocken, and W. L. McLaughlin, Natl. Bur. Stand. (U.S.) Spec. Publ. 250-11 (Mar. 1988).
Dosimetry for Industrial Radiation Processing, W. L. McLaughlin, J. C. Humphreys, and A. Miller, Natl. Bur. Stand. (U.S.) Spec. Publ. 609 (1982).
A National Standardization Programme for High-Dose Measurements, W. L. McLaughlin, Technical Report No. 205, Intl. Atomic Energy Agency, Vienna, p. 17 (1981).
Dye Film Dosimetry for Radiation Processing, J. C. Humphreys and W. L. McLaughlin, IEEE Trans. Nucl. Sci. NS-28 (2), 1797 (1981).
The Measurement of Absorbed Dose and Dose Gradients, W. L. McLaughlin, Radial. Phy. Chem. 15, 9 (1980).
Dosimetry Standards for Industrial Radiation Processing, W. L. McLaughlin, National and International Standardization of Radiation Dosimetry, Intl. Atomic Energy Agency, Vienna, p. 1 (1978).Calibrations
Phone: 301-975-2200, Fax: 301-975-2950
NIST, 100 Bureau Drive, Stop 8363, Gaithersburg, MD 20899-8363