Experimental determination of the recombination correction factor kS for SNC 125c, SNC 350p and SNC 600c ionization chambers in pulsed photon beams

Abstract

Accurate ionization chamber measurements of the absorbed dose to water require the correction of incomplete collection of charges created within the chamber volume. According to current dosimetry protocols such as the TRS-398 or the DIN 6800-2, incomplete charge collection is accounted for by the correction factor ks, which can be determined numerically or experimentally. The method proposed by Burns & McEwen (Phys. Med. Biol., 1998) was used in this study to determine the coefficients γ and δ used for the calculation of the correction factor ks of three ionization chambers, the SNC 125c, the SNC 600c and the SNC 350p (all Sun Nuclear Corp., Melbourne, Florida) for an absorbed dose to water range of 0.2mGy to 1.6mGy per pulse in pulsed photon beams. The shift of the effective point of measurement from the reference point Δz and the correction factor kr were determined for the SNC 350p according to the draft DIN 6800-2:2019-07.