Thermal neutron flux evaluation by a single crystal CVD diamond detector in LHD deuterium experiment

The single crystal CVD diamond detector (SDD) was installed in the torus hall of the Large Helical Device (LHD) to measure neutrons with high time resolution and neutron energy resolution. The LiF foil with 95.62 % of 6Li isotope enrichment pasted on the detector was used as the thermal neutron convertor as the energetic ions of 2.0 MeV alpha and 2.7 MeV triton particles generated in LiF foil and deposited the energy into SDD. SDD were exposed to the neutron field in the torus hall of the LHD during the 2nd campaign of the deuterium experiment. The total pulse height in SDD was linearly propotional to the neutron yield in a plasma operation in LHD over 4 orders of magnitude. The energetic alpha and triton were separately measured by SDD with LiF with the thickness of 1.9 μm, although SDD with LiF with the thickness of 350 μm showed a broadened peak due to the large energy loss of energetic particles generated in the bulk of LiF. The modeling with MCNP and PHITS codes well interpreted the pulse height spectra for SDD with LiF with different thicknesses. The results above demonstrated the sufficient time resolution and energy discrimination of SDD used in this work

Effects of loading a magnetic field longitudinal to the linear particle-beam track on yields of reactive oxygen species in water

The effects of a magnetic field longitudinal to the ion beam track on the generation of hydroxyl radicals (•OH) and hydrogen peroxide (H2O2) in water were investigated. A longitudinal magnetic field was reported to enhance the biological effects of the ion beam. However, the mechanism of the increased cell death by a longitudinal magnetic field has not been clarified. The local density of •OH generation was estimated by a method based on the EPR spin-trapping. A series of reaction mixtures containing varying concentrations (0.76‒2278 mM) of DMPO was irradiated by 16 Gy of carbon- or iron-ion beams at the Heavy-Ion Medical Accelerator in Chiba (HIMAC, NIRS/QST, Chiba, Japan) with or without a longitudinal magnetic field (0.0, 0.3, or 0.6 T). The DMPO-OH yield in the sample solutions was measured by X-band EPR and plotted versus DMPO density. O2-dependent and O2-independent H2O2 yields were measured. An aliquot of ultra-pure water was irradiated by carbon-ion beams with or without a longitudinal magnetic field. Irradiation experiments were performed under air or hypoxic conditions. H2O2 generation in irradiated water samples was quantified by an EPR spin-trapping, which measures •OH synthesized from H2O2 by UVB irradiation. Relatively sparse •OH generation caused by particle beams in water were not affected by loading a magnetic field on the beam track. O2-dependent H2O2 generation decreased and oxygen-independent H2O2 generation increased after loading a magnetic field parallel to the beam track. Loading a magnetic field to the beam track made •OH generation denser or made dense •OH more reactive

Evaluation of a Graphite Calorimeter for Measuring Absorbed Dose in Heavy-Ion Beams

World Congress on Medical Physics and Biomedical Engineering 200

Graphite Calorimetry for Absorbed Dose Measurements in Heavy-Ion Beams

Committee on Space Research 36th COSPAR Scientific Assembl

Determination of the absorbed dose using a graphite calorimeter

日韓医学物理学術大

Evaluation of the W values for Ionization Chamber Dosimetry in Therapeutic Carbon Beams

The 5th KOREA-JAPAN Joint Meeting on Medical Physic

Comparisons of calorimetric and ionometric measurements in heavy-ion beams

Workshop on “Absorbed Dose and Air Kerma Primary Standards

An evaluation method of clinical impact with setup, range, and radiosensitivity uncertainties in fractionated carbon-ion therapy

In light ion therapy, the dose concentration is highly sensitive to setup and range errors. Herewe propose a method for evaluating the effects of these errors by using the correlation betweenfractions on tumour control probability (TCP) in carbon-ion therapy. This method incorporates theconcept of equivalent stochastic dose (Cranmer-Sargison and Zavgorodni 2005 Phys. Med. Biol. 504097–109), which was defined as a dose that gives the mean expected survival fraction (SF) for thestochastically variable dose. The mean expected SFs were calculated while considering the correlationbetween fractions for setup and range errors. By using this SF, equivalent stochastic clinical doses(ESCD), which are weighted by relative biological effectiveness, of lung and prostate cases withvarying errors were derived. To account for spatial dose heterogeneity, equivalent uniform stochasticclinical doses (EUSCD) were obtained by using the mean expected SF in the volume of interest.TCP curves were calculated for each assumed error considering inter-patient sensitivity variationwith a fractionation effect. ESCD distributions, EUSCD, and TCP curves were affected by the interfractioncorrelation and the contribution of setup and range errors. Irradiated areas that could beaffected by these errors can be visualized quantitatively by using the ESCD distribution. TCP curvesfor the errors of various conditions converged around the TCP curve in nominal conditions by usingthe EUSCD. EUSCD correlated well with TCP in setup and range errors when the errors were notlarge and was comparatively stably insensitive to uncertain biological parameters. The proposedevaluation method with EUSCD and TCP calculations will be useful to indicate tumour doses toimprove realistic dose distributions in carbon-ion therapy

Experimental evaluation of detailed electrometer performance for heavy ion dosimetry

In the ionization chamber dosimetry, electrometers are used to measure the ionized charge in air. Electrometers have various specifications and must be used with performance suitable for treatment. However, the electrometer has been calibrated only for the DC component and has not been tested against pulsed radiation. In this study, the performance of electrometers was examined in detail against the pulsed carbon ion beams using various ionization chambers. As a result, with one electrometer, it depended heavily on sensitive volume, pulse density and beam intensity. Users need to test and confirm the performance of the electrometer against the radiation actually used.8th Japan-Korea Joint Meeting on Medical Physics (JKMP2017) (第114回日本医学物理学会学術大会