Angular Dependence of Wall Correction for Cylindrical Cavity Chamber
نویسندگان
چکیده
Abstract The cylindrical graphite cavity chambers are used for primary standard of air kerma rate of Co-60 and Cs-137. We measured wall attenuation correction factor (Kat) at several irradiation angles using extrapolation technique because of angular dependence. From these results, it can be seen that it is insufficient technique for evaluation of Kat. The Monte Carlo simulations were also done to estimate wall correction factor (Kwall) and the corrected value by calculations becomes constant at any angle.
منابع مشابه
Effective Point of Measurement in Cylindrical Ion Chamber for Megavoltage Photon Beams
Introduction For dose measurement in Megavoltage (MV) photon beams with ion chambers, the effect of volume occupied by the air cavity is not negligible. Therefore, the result of measurement should be corrected with a displacement perturbation correction factor (Pdis) or using an effective point of measurement (EPOM). The aim of this study is to calculate the EPOM for cylindrical ion chamber and...
متن کاملComputational Study of Radiative and Convective Heat Transfer in a Cylindrical Combustion Chamber
In this paper, the effect of cold air on the fluid flow inside the cylindrical combustion chamber and its wall temperature distribution have been studied computationally, taking into account the effect of radiative heat transfer from hot gases. The results have been compared with the case that radiative heat transfer was neglected. It is observed that the reattachment length increases when incr...
متن کاملOn the wall perturbation correction for a parallel-plate NACP-02 chamber in clinical electron beams.
PURPOSE In recent years, several Monte Carlo studies have been published concerning the perturbation corrections of a parallel-plate chamber in clinical electron beams. In these studies, a strong depth dependence of the relevant correction factors (p(wall) and P(cav)) for depth beyond the reference depth is recognized and it has been shown that the variation with depth is sensitive to the choic...
متن کاملSmall Volume Ionization Chambers Angular Dependence and Its Influence on Point-Dose Measurements
Purpose: Cylindrical ionization chambers as the PinPoint and the CC01 have high-spatial resolution and cylindrical symmetry in relevance to small fields. Dosimetry of newly advanced technologies that include non-coplanar beams, such as in Gamma-Knife, VMAT and IMRT treatment plans, the angular dependence of the ion chamber is essential. Therefore in this study we simulated two common used ion c...
متن کاملPerturbation Correction of a Cylindrical Thimble - type Chamber in a Graphite
An experimental determination has been made of the perturbation correction to be applied to a graphite cylindrical (thimble type) ionization chamber. The results indicate that the magnitude of this correction increases with depth and is closely related to the size of the cavity. This makes possible the use of such a chamber as an' excellent standard of absorbed dose in graphite for 60Co gamma r...
متن کامل