The NPL Air Kerma Primary Standard Free-Air Chamber for Medium Energy X-rays: Summary of Factors Incorporating ICRU Report 90 Recommendations

The NPL air kerma primary standard free-air ionisation chamber for low energy x-ray qualities was established in 1977. The International Commission for Radiation Measurements and Units Report 90 proposes the introduction of two new correction factors applicable to free air ionisation chambers in this energy range. This report summarises all the factors for the NPL primary standard including the two new factors, and changes to the standard up to the publication date.