title: Effect of the diaphragm of free-air ionisation chamber for X-ray air-kerma measurements.
abstract: Free-air ionisation chambers are widely used at standards laboratories as primary standards for absolute measurements of air kerma in X-ray fields. The area of the diaphragm aperture of a free-air ionisation chambers is an important factor for absolute measurements because it defines the size of the X-ray beam incident on the free-air chamber. In this study, correction factors for the contribution of X rays transmitted through the diaphragm of a free-air ionisation chamber and those scattered from the surface of the diaphragm aperture are obtained by Monte Carlo simulation for two different sized free-air ionisation chambers and for various diaphragm aperture sizes, X-ray energies and source-to-chamber distances.
authors.affiliation: National Metrology Institute of Japan, National Institute of Advanced Industrial Science and Technology, 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568, Japan. tadahiro-kurosawa@aist.go.jp
authors.forename: Tadahiro
authors.initials: T
authors.lastname: Kurosawa
authors.forename: Nobuhisa
authors.initials: N
authors.lastname: Takata
authors.forename: Norio
authors.initials: N
authors.lastname: Saito
mesh_terms: D000390:Air Ionization; D003198:Computer Simulation; D009010:Monte Carlo Method; D011874:Radiometry / Q000295:instrumentation* / Q000592:standards*; D012542:Scattering, Radiation; D014965:X-Rays