A tandem ionization chamber, developed at the Instituto de Pesquisas Energéticas e Nucleares (IPEN), for X radiation beams, radiotherapy level, was applied into a quality control program of the Calibration Laboratory of IPEN. This ionization chamber is composed by two ionization chambers, with a volume of 0.6 cm each one. Its inner plane-parallel electrodes and guard rings are made of different...

Introduction: Due to its simplicity, fast response and high reliability, ion chamber detectors are one of the most suitable dosimetry instruments for X and gamma rays. The dosimeter    of photon beams, which used in radiotherapy centers, requires high accuracy and should pass requirements of IEC 60731 standards. About 80 percent of the IEC 60731 standard tests such as stabil...

We study the quantitative effects of excitation, ionization, radiation energy and pressure, on the jump conditions in hypersonic shocks in a real gas. The ionization structure and excitation energies are calculated from the local temperature and density, using the Screened Hydrogenic Model. We assume an optically thick medium and no radiation flux through the shock front. We investigate the jum...

New methods of dosimetry in computed tomography (CT) X-ray fields require the use of high-resolution detectors instead of pencil-type ionization chambers typically used for CT dose index (CTDI) measurements. This paper presents a study on the suitability of a wide range of ionization chambers, diodes, and a two-dimensional detector array, used primarily in radiation therapy, for CT and cone-bea...

The kerma-area product (PKA) is a useful quantity to establish the reference levels in diagnosis of conventional X ray examinations. A KAP meter can be calibrated in laboratory or in situ, where it is used. The patient dose calibrator (PDC) is a new equipment from Radcal that measures PKA. It was manufactured following the IEC 60580 recommendations. The aim of this study was to calibrate the PD...

As the chemical structures of radiation damaged molecules may differ greatly from their undamaged counterparts, investigation and description of radiation damaged structures is commonly biased by the researcher. Radical formation from ionizing radiation in crystalline α-l-rhamnose monohydrate has been investigated using a new method where the selection of radical structures is unbiased by the r...

The remarkable similarity between emission spectra of narrow line regions (NLR) in Seyfert Galaxies has long presented a mystery. In photoionization models, this similarity implies that the ionization parameter is nearly always the same, about U ∼ 0.01. Here we present dusty, radiation-pressure dominated photoionization models that can provide natural physical insight into this problem. In thes...