An in-line ionization chamber has been developed for the real-time measurement of the absolute intensity of the pulsed parametric X-ray (PXR) beam during irradiation experiments. The quasi-monochromatic PXR generating system was developed at the Laboratory for Electron Beam Research and Application (LEBRA) in Nihon University. In contrast to typical narrow X-ray beams in synchrotron radiation f...

A pencil-type ionization chamber, developed at Instituto de Pesquisas Energéticas e Nucleares (IPEN), was characterized with the objective to verify the possibility of its application in radiation field mapping procedures. The characterization tests were evaluated, and the results were satisfactory. The results obtained for the X radiation field mapping with the homemade chamber were compared w...

This work quantified differences between recommendations of the TG-51 and TG-51 addendum reference dosimetry protocols. Reference dosimetry was performed for flattened photon beams with nominal energies of 6, 10, 15, and 23 MV, as well as flattening-filter free (FFF) beam energies of 6 and 10 MV, following the recommendations of both the TG-51 and TG-51 addendum protocols using both a Farmer® i...

The characteristics of the pressure ionization chamber at t he National Bureau of Standards have been studied for the gamma radiation from a cesium-137 sou rce (0.6614 Mev) and from a cobalt-60 source (1.1715 and 1.3316 Mev). The dosage rates produced in air by these sources were measured with this chamber with an accuracy of about 2 percent. Dosage rates obtained with an extrapolation chamber ...

PURPOSE The purpose of the study is to investigate the characteristics of a two-dimensional (2D) liquid-filled ion chamber detector array, which is used for the verification of radiotherapy treatment plans that use small field sizes of up to 10 × 10 cm. METHODS The device used in this study was Octavius 1000 SRS model (PTW, Freiburg, Germany). Its 2D array of detectors consists of 977 liquid-...

PURPOSE The finite extension of an ionization chamber gives rise to a spatial averaging effect, known as the "volume effect". In order to provide the appropriate corrections, the response functions along its lateral and longitudinal directions are characterized using Gaussian distributions, whose standard deviations slat and slong have been determined for a large set of clinical dosimeters. M...

Background: We have validated the monitor unit calculations from a commercially available treatment planning system (TPS) for three intensity modulated radiotherapy (IMRT) planning techniques for tangential breast irradiation by using ionization chamber measurements. Materials and Methods: Treatment plans were generated for forty-two breast patients by a forward planned field in field ...

2014 Human contact between ground and the metal parts of a vacuum chamber can be dangerous if the metal is not grounded, and if an ionization gauge is operating in the chamber at pressures of 0.1 pascal (7 x 10-4 torr) or higher. Lethal electrical shock can possibly occur if all of these conditions are present. Common grounding of the metal parts of the vacuum chamber and of the ionization gaug...

Ionization chambers are frequently moved from one environment to another, sometimes with significant differences in temperature between the chamber and measurement phantom. To obtain reliable ionization data, the temperature of the air in the chamber must be allowed to equilibrate with the measuring phantom. The air temperature inside a thimble of a Farmer-type ion chamber was measured as a fun...

A device is described for use in confirming the energy constancy of clinical electron beams. A wedge shaped absorber is placed over an ionization chamber leading to an energy dependent response. A measurement under the energy filter is divided by a measurement in air to correct for the inherent energy dependence of the chamber. A nearly linear response is demonstrated.