Since the incident air kerma
to be measured is generally only slightly higher than background levels, the standards and guidance documents in Table 1 generally recommend, for sensitivity, using a largevolume, free-air (thin-walled) ionization chamber (IC) with a high-quality electrometer with 0.
Units must produce at least 21 mGy air kerma
(2400 mR) within a 3-second period to meet the amended final requirement.
Both FACs are proven national-standard instruments deemed suitable for the realization of air kerma
for these sources.
7) The final result is a linear but inverse relationship between the S-value and the average air kerma
or exposure of the region of interest.
The results reveal the degree to which the participating calibration facility can demonstrate proficiency in transferring air kerma
calibrations under the conditions of the said facility at the time of the measurements.
primary standards for air kerma
(formerly exposure) for x rays generated at potentials in the range from 10 kVp to 300 kVp using a series of free-air ionization chambers.
national primary standard for air kerma
(and exposure) for gamma rays from [.
Relative standard uncertainties (in %) associated with the calibration of the transfer ionization chambers NIST BIPM Source of Type A Type B Type A Type B uncertainty Air kerma
mr or mr per unit time (now termed mR or mR per unit time), have been converted to air kerma
rate units, i.
This Unit is not in general use, and the quantity exposure will probably be replaced by the quantity air kerma
Erratum: Comparison of the NIST and NPL Air Kerma
Standards Used for X-Ray Measurements Between 10 kV and 80 kV
A direct comparison was made between the air kerma
primary standards used for the measurements of low-energy x rays at the National Institute of Standards and Technology (NIST) and the National Physical Laboratory (NPL).