Methodical Issues of the Use of Detectors for Dosimetry in Beams of the Carbon Nuclei of the Accelerator U-70 A.G.Alexeev, E.V.Altuhova, I.I.Degtarev, - презентация

1 Methodical Issues of the Use of Detectors for Dosimetry in Beams of the Carbon Nuclei of the Accelerator U-70 A.G.Alexeev, E.V.Altuhova, I.I.Degtarev, O.V.Kiruhin (MSU, Moscow), V.A.Pikalov, O.V.Sumaneev, A.A.Yanovich, F.N.Novoskoltsev Introduction In the SRC Kurchatov Institute-IHEP are working on the project Center for Ion Radiation Therapy. At present, the first stage of this project has been implemented is the creation of the Center Use Radiobiological Stand on Carbon Beam of U-70 (RSU) RSU is used for radiobiological experiments. The research and testing of systems for radiotherapy by a carbon ions beam are tested at RSU. In this paper the result of methodologilal issue of the use of thermoluminescent detectors (TLD) and radiochromic films for dosimetry in a beam of carbon ions are present. Fig.2 Absorbed dose ( secondary charged particles contributions) in the water phantom. The calculation is carried out by FLUKA. Carbon ions energy is 400 MeV/ nucleon. Fig.3 Absorber dose in the water phantom. FLUKA – filled circles; the measurements are not filled circles. Fig.4. The average LET in water phantom. FLUKA calculation. Fig.5. Neutron flux (thermal neutrons (TH ) и total energy range (TOTAL) in the water phantom. MCNPX and FLUKA were used for calculations. Estimation of contribution of thermal neutrons to the indication of DTG-4 ( after the Bragg peak) is not more then 1,5% TLD method for measuring dose The TLD dose measurement methodology includes the following: Annealing order of TLD (temperature and annealing time for each type of TLD in accordance with the manufactures recommendations); Individual calibration of each detector on a calibration source ( performed in each measurement cycle); calibration of the detectors is performed before each accelerator ran; measuring (heating) mode is performed in accordance with the manufacturer recommendation; The time interval between annealing and exposure does not exceed 10 days* ; The time interval between exposure and measurement does not exceed 4 days* ; The dependence of the sensitivity of the TLD in the dose value is taken into account (for each type there is a dependence); The correction for the dependence of MMT-7 sensitivity on LET is done using the HTR-method. *O.I.Batuhtina –private communication/ Report on the study of parameters of DTG-4. Angarsk branch of LLC URALPRIBOR. Angarsk Conclusion The method for measuring the absorber dose of carbon ions by TLD for the purposes of dosemeasurement support of radiobiological research at RBS. The procedure includes all the main factors affecting the accuracy of the measurement. This makes it possible to measure the absorbed dose with an error of not more then 5%. Fig.6. Dependence of HTR parameter for ММТ-7 from LET. Fig.7. LET correction factor for DTG-4, MMT-7, EBT3. RUPAK-18 3 Ocb. 2018г. Used TLD DTG-4 single-crystal TLD, produced by the Angarsk branch of URALPRIBOR ( ММТ-7 polycrystalline, manufactured by RADCARD Poland (LiF) ( ). These TLD are specially desingned for dosimetry for ions beam with large LET. All measurements were performed in a water phantom. Inside the water phantom the air chamber (caisson) was fixed. Detectors and dosimeters were placed in the caisson. Fig.1. Scheme of measurement. Calculation of the Bragg curve and evaluation of the contribution of thermal neutrons to DTG-4 reading