| 1. |
- Ambrozova, I., et al.
(författare)
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Microdosimetry for a carbon ion beam using track-etched detectors
- 2015
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Ingår i: Radiation Protection Dosimetry. - : Oxford University Press (OUP). - 0144-8420 .- 1742-3406. ; 166:1-4, s. 247-252
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Tidskriftsartikel (refereegranskat)abstract
- Track-etched detectors (TED) have been used as linear energy transfer (LET) spectrometers in heavy ion beams for many years. LET spectra and depth-dose distribution of a carbon ion beam were measured behind polymethylmethacrylate degraders at Heavy Ion Medical Accelerator in Chiba, Japan. The measurements were performed along monoenergetic beam with energy 290 MeV u-1 in different positions: (1) at beam extraction area, (2) at beginning, (3) maximum and (4) behind the Bragg peak region (0, 117, 147 and 151 mm of water-equivalent depth, respectively). The LET spectra inside and outside of the primary ion beam have been evaluated. TED record only heavy charged particles with LET above 8-10 keV μm-1, while electrons and ions with lower LET are not detected. The Geant4 simulation toolkit version 4.9.6.P01 has been used to estimate the contribution of non-detected particles to absorbed dose. Presented results demonstrate the applicability of TED for microdosimetry measurements in therapeutic carbon ion beams.
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| 2. |
- Ploc, Ondrej, 1979, et al.
(författare)
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PHITS simulations of the Protective curtain experiment onboard the Service module of ISS: Comparison with absorbed doses measured with TLDs
- 2013
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Ingår i: Advances in Space Research. - : Elsevier BV. - 1879-1948 .- 0273-1177. ; 52:11, s. 1911-1918
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Tidskriftsartikel (refereegranskat)abstract
- "Protective curtain" was the physical experiment onboard the International Space Station (ISS) aimed on radiation measurement of the dose - reducing effect of the additional shielding made of hygienic water-soaked wipes and towels placed on the wall in the crew cabin of the Service module Zvezda. The measurements were performed with 12 detector packages composed of thermoluminescent detectors (TLDs) and plastic nuclear track detectors (PNTDs) placed at the Protective curtain, so that they created pairs of shielded and unshielded detectors. We simulated the experiment by the general purpose 3D Monte Carlo Particle and Heavy Ion Transport code System (PHITS), as 10 cm-thick water-filled panels housed in a model of the Zvezda module. External radiation environment was modeled using the AP8MIN and ISO-15390 standard models for the trapped proton (TP) and galactic cosmic ray (GCR) spectra, respectively. The absorbed doses were calculated for all detector packages used in the experiment. Comparison of calculated results with experimental data (TLDs) showed good agreement for the total (TP+GCR) absorbed doses. Further, we analyzed the systematic uncertainty introduced by differences in the detector thicknesses used in the simulations from the ones used in the measurements. The reducing effect of the Protective curtain was studied by comparing the calculated absorbed doses in shielded and unshielded detectors separately for the TPs and GCRs. In case of TPs, the reducing effect was larger than 60% and 40% for pairs of detectors located at aluminum wall and at crew cabin window, respectively. In case of GCRs, small shielding effect was observed for detectors located behind the window but for those located behind the aluminum wall, the effect was even opposite: the absorbed doses in the unshielded detectors were about 10% lower than in the shielded ones. This result was confirmed by the depth-dose analysis using rectangular source emitting broad parallel incident particles impinging on the simple geometry composed of aluminum/glass box and water box of variable thickness simulating the spacecraft wall/window and Protective curtain, respectively. The additional dose in the shielded detectors is related to the secondary fragments known as the "wall effect". However, since GCR contributes by about 30% and 15% only to the total dose in water in shielded and unshielded detectors, respectively, the total shielding effect is high and the Protective curtain is very efficient when it is applied on a spacecraft at low-Earth orbits.
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| 3. |
- Ploc, Ondrej, 1979, et al.
(författare)
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Publicly available database of measurements with the silicon spectrometer Liulin onboard aircraft
- 2013
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Ingår i: Radiation Measurements. - : Elsevier BV. - 1350-4487. ; 58, s. 107-112
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Tidskriftsartikel (refereegranskat)abstract
- Aircrew members are exposed to ionizing radiation due to their work onboard aircraft. ICRP recommended the monitoring of their effective doses because they regularly exceed the limit of 1 mSv per year for the public exposure. The effective doses are routinely calculated by computer codes that take into account flight parameters like altitude, geographic position, and solar activity. This approach was preferred against personal dosimeters method because the effective dose cannot be evaluated experimentally. However, it is generally accepted, that these calculations should be periodically verified by measurements of H*(10) which is frequently used as a surrogate for effective dose. This report refers about the database (available online http://hroch.ujf.cas.cz/ similar to aircraft/) of long-term measurements with the silicon spectrometer Liulin onboard aircraft. The measurements have been performed since March 2001; so up to date, the database covers a period of 11-years (with a few interruptions) which is usually the duration of the whole solar cycle. The database comprises more than 10(5) individual records of energy deposition spectra, absorbed dose rates, and ambient dose equivalent rates. Each record contains also the information on all flight parameters needed for calculation of dosimetric quantities by the computer codes, and thus the database represent an useful tool for verification of the routine dosimetry of aircraft crews. (C) 2013 Elsevier Ltd. All rights reserved.
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| 4. |
- Sihver, Lembit, 1962, et al.
(författare)
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Radiation Environment at Aviation Altitudes and in Space
- 2015
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Ingår i: Radiation Protection Dosimetry. - : Oxford University Press (OUP). - 0144-8420 .- 1742-3406. ; 164:4, s. 477-483
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Tidskriftsartikel (refereegranskat)abstract
- On the Earth, protection from cosmic radiation is provided by the magnetosphere and the atmosphere, but the radiation exposure increases with increasing altitude. Aircrew and especially space crew members are therefore exposed to an increased level of ionising radiation. Dosimetry onboard aircraft and spacecraft is however complicated by the presence of neutrons and high linear energy transfer particles. Film and thermoluminescent dosimeters, routinely used for ground-based personnel, do not reliably cover the range of particle types and energies found in cosmic radiation. Further, the radiation field onboard aircraft and spacecraft is not constant; its intensity and composition change mainly with altitude, geomagnetic position and solar activity (marginally also with the aircraft/spacecraft type, number of people aboard, amount of fuel etc.). The European Union Council directive 96/29/Euroatom of 1996 specifies that aircrews that could receive dose of >1 mSv y(-1) must be evaluated. The dose evaluation is routinely performed by computer programs, e.g. CARI-6, EPCARD, SIEVERT, PCAire, JISCARD and AVIDOS. Such calculations should however be carefully verified and validated. Measurements of the radiation field in aircraft are thus of a great importance. A promising option is the long-term deployment of active detectors, e.g. silicon spectrometer Liulin, TEPC Hawk and pixel detector Timepix. Outside the Earth's protective atmosphere and magnetosphere, the environment is much harsher than at aviation altitudes. In addition to the exposure to high energetic ionising cosmic radiation, there are microgravity, lack of atmosphere, psychological and psychosocial components etc. The milieu is therefore very unfriendly for any living organism. In case of solar flares, exposures of spacecraft crews may even be lethal. In this paper, long-term measurements of the radiation environment onboard Czech aircraft performed with the Liulin since 2001, as well as measurements and simulations of dose rates on and outside the International Space Station were presented. The measured and simulated results are discussed in the context of health impact.
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| 5. |
- Sommer, Marek, et al.
(författare)
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Monte Carlo simulation of semiconductor-based detector in mixed radiation field in the atmosphere
- 2022
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Ingår i: Life Sciences in Space Research. - : Elsevier BV. - 2214-5532 .- 2214-5524. ; 34, s. 30-36
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Tidskriftsartikel (refereegranskat)abstract
- Calculation of radiation protection quantities in tissue equivalent material from measurements using semiconductor detectors requires correction factors for conversion of the measured values in the semiconductor material to the tissue equivalent material. This approach has been used many times in aircraft and for space dosimetry. In this paper, we present the results of Monte Carlo simulations which reveal the need to take into account both the radiation field and the detector material when performing the conversion of measured values to radiation protection quantities. It is shown that for low Z target material, most of the dose equivalent at aviation altitudes comes from neutrons originating from nuclear reactions, while in high Z targets most of the dose equivalent comes from photons, originating from electromagnetic reactions.
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