Perturbation Correction of a Cylindrical Thimble - type Chamber in a Graphite
نویسنده
چکیده
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 rays, as well as an appropriate transfer instrtunent.
منابع مشابه
Ionization chamber-based reference dosimetry of intensity modulated radiation beams.
The present paper addresses reference dose measurements using thimble ionization chambers for quality assurance in IMRT fields. In these radiation fields, detector fluence perturbation effects invalidate the application of open-field dosimetry protocol data for the derivation of absorbed dose to water from ionization chamber measurements. We define a correction factor C(Q)IMRT to correct the ab...
متن کاملEffective 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 کاملAngular Dependence of Wall Correction for Cylindrical Cavity Chamber
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...
متن کاملIonization Chamber Dosimetry for Conventional and Laser-Driven Clinical Hadron Beams
The practice of using the direct ionization radiation (electrons, protons, antiprotons, pions, ions, etc) or of the indirect ionization radiation (photons, neutrons, etc) in economy and social life has led to the introduction of the absorbed dose magnitude (ICRU 1953) defined as the energy absorbed per mass unit of the irradiated substance. This is a fundamental magnitude valid for any type of ...
متن کاملFabrication of Free Air Well Type Ionization Chamber and Calculational Assessment and Measurement of Its Operational Characteristics
Introduction: Well type ionization chamber is a measuring device which is used to determine the activity of brachytherapy sources. The chamber has a cylindrical volume in which a cylindrical tube is mounted in the middle of the chamber. For the measurements, the brachytherapy sources are transferred to the middle of the tube. Materials and Methods: For designing the well type chamber, the measu...
متن کامل