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The REM-2 tissue-equivalent recombination chamber was used for dosimetry measurements performed in monoenergetic neutron reference fields at National Physical Laboratory, UK for the neutron energy range from 144 keV to 5 MeV. Measurement data were used for the determination of the recombination index of radiation quality, ambient dose, and finally ambient dose equivalent, H*(10). Results justify the relevance of the application of this measuring method in mixed radiation fields with dominant neutron component, which are present, for example, at photon and proton radiotherapy facilities. The relative response of the chamber in terms of H*(10) in the investigated neutron energy range, resulted in the correction factor at the maximum level of 1.25. Analysis of the saturation curves and use of the recombination microdosimetric method, RMM resulted in the determination of dose distribution at a nanometric level in terms of restricted linear energy transfer, L Δ. Monte Carlo simulations performed with the FLUKA code allowed to obtain double-differential distributions of L which were compared with those obtained during measurements. Comparison between measured and simulated data showed that RMM is a reliable method for microdosimetric investigations in mixed neutron-gamma fields present around medical radiotherapeutic units. • Dose distributions in restricted L were compared with simulated L spectra. • Correction factor for the REM-2 chamber for monoenergetic neutrons was up to 1.25 • LET distributions for 144 keV to 5 MeV neutrons were measured and calculated. • REM-2 chamber has wide, flat energy dependence in terms of H*(10) for mixed n-γ fields. [ABSTRACT FROM AUTHOR]

Abstract: The paper presents an overview of the applications of recombination chambers for dosimetric measurements at radiotherapy facilities. The chambers were used at electron, proton and heavy ion accelerators, in the beam and in the vicinity of the accelerators at very different dose rates. The examples of measurements discussed in the paper include: the determination of the absorbed dose and radiation quality parameters of a 170 MeV proton beam and BNCT (boron neutron capture therapy) beam, neutron dose measurements at a phantom surface outside the beam of a 15 MV electron medical accelerator, determination of ambient dose equivalent, H∗ (10) outside the irradiated phantom in the proton therapy treatment room at JINR (Dubna, Russia), and at working places outside the shielding of the heavy ion therapy facility at GSI (Darmstadt, Germany). [ABSTRACT FROM AUTHOR]

Abstract: The proposed method involves determination of ratio of absorbed doses in a mixed radiation field due to radiations from two different sources, provided that both radiations are of different LET, hence of a different quality factor. A detector used in the method is a tissue-equivalent recombination chamber. Shape of saturation curve of such a chamber depends on LET (on radiation quality). If the shapes of saturation curves are known for the radiations from two sources or for both components of a two-component radiation, then the actual ratio of absorbed dose components created simultaneously by these radiations in the mixed radiation field can be determined, performing relatively simple measurements of the ionization current at two different polarizing voltages applied to the chamber. [ABSTRACT FROM AUTHOR]