Experimental determination ofk(Q)factors for two types of ionization chambers in scanned proton beams.

Objective.Experimental determination of beam qualitykQfactors for two types of Farmer ionization chambers, NE2571 and IBA FC65-G, in a scanned proton beam for three nominal energies (140 MeV, 180 MeV and 220 MeV) based on water calorimetry.Approach.Beam quality correction factors were determined comparing the results obtained with water calorimetry and ionometry. Water calorimetry was performed to determine the absorbed dose at a depth of measurement in water of 5 g cm-2, limited by the extension of the calorimeter glass vessel used. For the ionometry, two chambers of each type were included in the study. The ionization chambers were calibrated in terms of absorbed dose to water in60Co at the Swedish Secondary Standard Dosimetry Laboratory, directly traceable to the BIPM, and were used according to the IAEA TRS-398 Code of Practice.Main results. ThekQvalues determined in the present work have been compared with the values tabulated in TRS-398 and its forthcoming update and also with those obtained in previous water calorimetric measurements and Monte Carlo calculations. All results were found to agree within the combined uncertainties of the different data.Significance. It is expected that the present work will serve as an experimental contribution tokQ-factors for the two chamber types and three scanned proton beam qualities used.

Medin J ，Andreo P ，Palmans H 《-》

Implementation of water calorimetry in a 180 MeV scanned pulsed proton beam including an experimental determination of kQ for a Farmer chamber.

Medin J 《-》

Experimental comparison of cylindrical and plane parallel ionization chambers for reference dosimetry in continuous and pulsed scanned proton beams.

Objective. In this experimental work we compared the determination of absorbed dose to water using four ionization chambers (ICs), a PTW-34045 Advanced Markus, a PTW-34001 Roos, an IBA-PPC05 and a PTW-30012 Farmer, irradiated under the same conditions in one continuous- and in two pulsed-scanned proton beams.Approach. The ICs were positioned at 2 cm depth in a water phantom in four square-field single-energy scanned-proton beams with nominal energies between 80 and 220 MeV and in the middle of 10 × 10 × 10 cm3dose cubes centered at 10 cm or 12.5 cm depth in water. The water-equivalent thickness (WET) of the entrance window and the effective point of measurement was considered when positioning the plane parallel (PP) ICs and the cylindrical ICs, respectively. To reduce uncertainties, all ICs were calibrated at the same primary standards laboratory. We used the beam quality (kQ) correction factors for the ICs under investigation from IAEA TRS-398, the newly calculated Monte Carlo (MC) values and the anticipated IAEA TRS-398 updated recommendations.Main results. Dose differences among the four ICs ranged between 1.5% and 3.7% using both the TRS-398 and the newly recommendedkQvalues. The spread among the chambers is reduced with the newlykQvalues. The largest differences were observed between the rest of the ICs and the IBA-PPC05 IC, obtaining lower dose with the IBA-PPC05.Significance. We provide experimental data comparing different types of chambers in different proton beam qualities. The observed dose differences between the ICs appear to be related to inconsistencies in the determination of thekQvalues. For PP ICs, MC studies account for the physical thickness of the entrance window rather than the WET. The additional energy loss that the wall material invokes is not negligible for the IBA-PPC05 and might partially explain the lowkQvalues determined for this IC. To resolve this inconsistency and to benchmark MC values,kQvalues measured using calorimetry are needed.

Vilches-Freixas G ，Bosmans G ，Douralis A ，Martens J ，Meijers A ，Rinaldi I ，Salvo K ，Thomas R ，Palmans H ，Lourenço A ... -  《-》

Experimental determination of beam quality factors, kQ, for two types of Farmer chamber in a 10 MV photon and a 175 MeV proton beam.

Medin J ，Ross CK ，Klassen NV ，Palmans H ，Grusell E ，Grindborg JE ... -  《PHYSICS IN MEDICINE AND BIOLOGY》

Dosimetry using plane-parallel ionization chambers in a 75 MeV clinical proton beam.

Palmans H ，Verhaegen F ，Denis JM ，Vynckier S ... -  《PHYSICS IN MEDICINE AND BIOLOGY》