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1.
  • Ambrozova, I., et al. (author)
  • Measurement of target fragments produced by 160 MeV proton beam in aluminum and polyethylene with CR-39 plastic nuclear track detectors
  • 2014
  • In: Radiation Measurements. - : Elsevier BV. - 1350-4487. ; 64, s. 29-34
  • Journal article (peer-reviewed)abstract
    • Production of target fragments from reactions of 160 MeV proton beams in aluminum and polyethylene was measured with CR-39 plastic nuclear track detectors (PNTD). Due to the detection limit of PNTD, primary protons cannot be detected; only low-energy short-range target fragments are registered. As a feasibility study, a so called "two step etching method" was employed to get the linear energy transfer (LET) spectra, absorbed dose, and dose equivalent. This method is discussed in this paper, together with the measured results. (C) 2014 Elsevier Ltd. All rights reserved.
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2.
  • El-Jaby, S., et al. (author)
  • ISSCREM: International Space Station cosmic radiation exposure model
  • 2013
  • In: IEEE Aerospace Conference Proceedings. - 1095-323X. - 9781467318112
  • Conference paper (peer-reviewed)abstract
    • A semi-empirical model is derived from operational data collected aboard the International Space Station (ISS) with the U.S. tissue equivalent proportional counter (TEPC). The model provides daily and cumulative mission predictions of the operational dose equivalent that space-crew may receive from galactic cosmic radiation (GCR) and trapped radiation (TR) sources as a function of the ISS orbit. The parametric model for GCR exposure correlates the TEPC dose equivalent rate to the cutoff rigidity at ISS altitudes while the TR parametric model relates this quantity to the mean atmospheric density at the crossing of the South Atlantic Anomaly (SAA). The influences of solar activity, flux asymmetry inside the SAA, detector orientation, and position aboard the ISS on the dose equivalent have been examined. The model has been successfully benchmarked against measured data for GCR and TR exposures to within ±10% and ±20%, respectively, over periods of time ranging from a single day to a full mission. In addition, preliminary estimates of the protection quantity of effective dose equivalent have been simulated using the PHITS Monte Carlo transport code. These simulations indicate that the TEPC dose equivalent is a conservative estimate of the effective dose equivalent.
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3.
  • El-Jaby, S., et al. (author)
  • Method for the prediction of the effective dose equivalent to the crew of the International Space Station
  • 2014
  • In: Advances in Space Research. - : Elsevier BV. - 1879-1948 .- 0273-1177. ; 53:5, s. 810-817
  • Journal article (peer-reviewed)abstract
    • This paper describes a methodology for assessing the pre-mission exposure of space crew aboard the International Space Station (ISS) in terms of an effective dose equivalent. In this approach, the PHITS Monte Carlo code was used to assess the particle transport of galactic cosmic radiation (GCR) and trapped radiation for solar maximum and minimum conditions through an aluminum shield thickness. From these predicted spectra, and using fluence-to-dose conversion factors, a scaling ratio of the effective dose equivalent rate to the ICRU ambient dose equivalent rate at a 10 mm depth was determined. Only contributions from secondary neutrons, protons, and alpha particles were considered in this analysis. Measurements made with a tissue equivalent proportional counter (TEPC) located at Service Module panel 327, as captured through a semi-empirical correlation in the ISSCREM code, where then scaled using this conversion factor for prediction of the effective dose equivalent. This analysis shows that at this location within the service module, the total effective dose equivalent is 10-30% less than the total TEPC dose equivalent. Approximately 75-85% of the effective dose equivalent is derived from the OCR. This methodology provides an opportunity for pre-flight predictions of the effective dose equivalent and therefore offers a means to assess the health risks of radiation exposure on ISS flight crew. Crown copyright (C) 2014 Published by Elsevier Ltd. on behalf of COSPAR. All rights reserved.
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4.
  • Golovchenko, A. N., et al. (author)
  • Fragmentation of 370 MeV/n Ne-20 and 470 MeV/n Mg-24 in light targets
  • 2010
  • In: Radiation Measurements. - : Elsevier BV. - 1350-4487. ; 45:7, s. 856-860
  • Journal article (peer-reviewed)abstract
    • Total charge-changing cross sections and cross sections for the production of projectile-like fragments were determined for fragmentation reactions induced by 370 MeV/n Ne-20 ions in water and lucite, and 490 MeV/n Mg-24 ions in polyethylene, carbon and aluminum targets sandwiched with CR-39 plastic nuclear track detectors. An automated microscope system and a track-to-track matching algorithm were used to count and recognize the primary and secondary particles. The measured cross sections were then compared with published cross sections and predictions of different models. Two models and the three-dimensional Monte Carlo Particle Heavy Ion Transport Code System (PHITS) were used to calculate total charge-changing cross sections. Both models agreed within a few percent for the system Mg-24 + CH2, however a deviation up to 20% was observed for the systems Ne-20 + H2O and C5H8O2, when using one of the models. For all the studied systems, PHITS systematically underestimated the total charge-changing cross section. It was also found that the partial fragmentation cross sections for Mg-24 + CH2 measured in present and earlier works deviated up to 20% for Z = 6-11. Measured cross sections for the production of fragments (Z = 4-9) for Ne-20 + H2O and C5H8O2 were compared with predictions of three different semi-empirical models and JQMD which is used in the PHITS code. The calculated cross sections differed from the measured data by 10-90% depending on which fragment and charge was studied, and which model was used. (C) 2010 Elsevier Ltd. All rights reserved.
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5.
  • Gustafsson, Katarina, 1980, et al. (author)
  • PHITS simulations of the Matroshka experiment
  • 2010
  • In: Advances in Space Research. - : Elsevier BV. - 1879-1948 .- 0273-1177. ; 46:10, s. 1266-1272
  • Journal article (peer-reviewed)abstract
    • The radiation environment in space is very different from the one encountered on Earth. In addition to the sparsely ionizing radiation, there are particles of different Z with energies ranging from keV up to hundreds of GeV which can cause severe damage to both electronics and humans. It is therefore important to understand the interactions of these highly ionizing particles with different materials such as the hull of space vehicles, human organs and electronics. We have used the Particle and Heavy-Ion Transport code System (PHITS), which is a three-dimensional Monte Carlo code able to calculate interactions and transport of particles and heavy ions with energies up to 100 GeV/nucleon in most matter. PHITS is developed and maintained by a collaboration between RIST (Research Organization for Information Science & Technology), JAEA (Japan Atomic Energy Agency), KEK (High Energy Accelerator Research Organization), Japan and Chalmers University of Technology, Sweden. For the purpose of examining the applicability of PHITS to the shielding design we have simulated the ESA facility Matroshka (MTR) designed and lead by the German Aerospace Center (DLR). Preliminary results are presented and discussed in this paper.
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6.
  • Hayatsu, K., et al. (author)
  • Lunar radiation dose due to cosmic rays and their secondary particles
  • 2010
  • In: 61st International Astronautical Congress 2010, IAC 2010.Prague, 27 September-1 October 2010. - 9781617823688 ; 5, s. 4084-4088
  • Conference paper (peer-reviewed)abstract
    • To be able to safely perform human activities on the lunar surface, it is very important to assess the radiation environment, including the dose from galactic cosmic Rays (GCRs) and large Solar Energetic Particles (SEPs). Especially, large SPEs are highly hazardous to lunar habitants. In this paper, several SPEs have been evaluated in order to estimate the effective dose equivalent on the lunar surface. Several events give more than 1 Sv without any shield.
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7.
  • Koliskova, Z., et al. (author)
  • Simulations of absorbed dose on the phantom surface of MATROSHKA-R experiment at the ISS
  • 2012
  • In: Advances in Space Research. - : Elsevier BV. - 1879-1948 .- 0273-1177. ; 49:2, s. 230-236
  • Journal article (peer-reviewed)abstract
    • The health risks associated with exposure to various components of space radiation are of great concern when planning manned long-term interplanetary missions, such as future missions to Mars. Since it is not possible to measure the radiation environment inside of human organs in deep space, simulations based on radiation transport/interaction codes coupled to phantoms of tissue equivalent materials are used. However, the calculated results depend on the models used in the codes, and it is therefore necessary to verify their validity by comparison with measured data. The goal of this paper is to compare absorbed doses obtained in the MATROSHKA-R experiment performed at the International Space Station (ISS) with simulations performed with the three-dimensional Monte Carlo Particle and Heavy-Ion Transport code System (PHITS). The absorbed dose was measured using passive detectors (packages of thermoluminescent and plastic nuclear track detectors) placed on the surface of the spherical tissue equivalent phantom MATROSHKA-R, which was exposed aboard the ISS in the Service Zvezda Module from December 2005 to September 2006. The data calculated by PHITS assuming an ISS shielding of 3 g/cm(2) and 5 g/cm(2) aluminum mass thickness were in good agreement with the measurements. Using a simplified geometrical model of the ISS, the influence of variations in altitude and wall mass thickness of the ISS on the calculated absorbed dose was estimated. The uncertainties of the calculated data are also discussed; the relative expanded uncertainty of absorbed dose in phantom was estimated to be 44% at a 95% confidence level.
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8.
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9.
  • Larsson, Irina, 1975, et al. (author)
  • Factors influencing helium measurements for detection of control rod failures in BWR
  • 2012
  • In: International Conference on the Physics of Reactors 2012: Advances in Reactor Physics (PHYSOR 2012), Knoxville, TN;15- 20 April 2012. - 9781622763894 ; 4, s. 3092-3099
  • Conference paper (peer-reviewed)abstract
    • Much effort has been made to minimize the number and consequences of fuel failures at nuclear power plants. The consequences of control rod failures have also gained an increased attention. In this paper we introduce a system for on-line surveillance of control rod integrity which has several advantages comparing to the surveillance methods available today in boiling water reactors (BWRs). This system measures the helium released from failed control rods containing boron carbide (B4C). However, there are a number of factors that might influence measurements, which have to be taken into consideration when evaluating the measured data. These factors can be separated into two groups: 1) local adjustments, made on the sampling line connecting the detector to the off-gas system, and 2) plant operational parameters. The adjustments of the sample line conditions include variation of gas flow rate and gas pressure in the line. Plant operational factors that may influence helium measurements can vary from plant to plant. The factors studied at Leibstadt nuclear power plant (KKL) were helium impurities in injected hydrogen gas, variation of the total off-gas flow and regular water refill. In this paper we discuss these factors and their significance and present experimental results of measurements at KKL.
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10.
  • Larsson, Irina, 1975, et al. (author)
  • Improvements of fuel failure detection in boiling water reactors using helium measurements
  • 2012
  • In: International Congress on Advances in Nuclear Power Plants 2012, ICAPP 2012. - 9781622762101 ; 4, s. 2401-2406
  • Conference paper (peer-reviewed)abstract
    • To certify a continuous and safe operation of a boiling water reactor, careful surveillance of fuel integrity is of high importance. The detection of fuel failures can be performed by off-line gamma spectroscopy of off-gas samples and/or by on-line nuclide specific monitoring of gamma emitting noble gases. To establish the location of a leaking fuel rod, power suppression testing can be used. The accuracy of power suppression testing is dependent on the information of the delay time and the spreading of the released fission gases through the systems before reaching the sampling point. This paper presents a method to improve the accuracy of power suppression testing by determining the delay time and gas spreading profile. To estimate the delay time and examine the spreading of the gas in case of a fuel failure, helium was injected in the feed water system at Forsmark 3 nuclear power plant. The measurements were performed by using a helium detector system based on a mass spectrometer installed in the off-gas system. The helium detection system and the results of the experiment are presented in this paper.
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11.
  • Larsson, Irina, 1975, et al. (author)
  • On-line monitoring of control rod integrity in BWRs using a mass spectrometer
  • 2013
  • In: Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. - : Elsevier BV. - 0168-9002. ; 698, s. 249-256
  • Journal article (peer-reviewed)abstract
    • Surveillance of fuel and control rod integrity in the core of a boiling water reactor is essential for maintaining a safe and reliable operation. Control rods of a boiling water reactor are mainly filled with boron carbide as a neutron absorber. Due to the irradiation of boron with neutrons, a continuous production of lithium and helium will occur inside a control rod. Most of the created helium will be retained in the boron carbide lattice; however a small part will escape into the void volume of the control blade. Therefore the integrity of control rods during operation can efficiently be followed by on-line measurements of helium concentration in the reactor off-gas system using a mass spectrometer. Since helium is a fill gas in fuel rods, the same method is a useful early warning system for primary fuel failures. In this paper, we introduce an on-line helium detector system which is installed at the nuclear power plant in Leibstadt. Furthermore the measuring experiences of control rod failure detection at the plant are presented. Different causes of increased helium levels in the off-gas system have been distinguished. There are spontaneous helium releases as well as helium releases caused by changed conditions in the reactor (power reduction, control rod movement, etc.). Helium peaks can also be characterized according to the released amount of helium, the peak shape and the duration of the release, which leads to different interpretations of the release mechanisms. In addition, the measured amount of released helium from a 50 days period (280 l) is also compared to the calculated amount of produced helium from the washed out boron during the same time period (190 l). © 2012 Elsevier B.V.
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12.
  • Larsson, Irina, 1975, et al. (author)
  • Qualification of helium measurement system for detection of fuel failures in a BWR
  • 2014
  • In: Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. - : Elsevier BV. - 0168-9002. ; 745, s. 24-37
  • Journal article (peer-reviewed)abstract
    • There are several methods for surveillance of fuel integrity during the operation of a boiling water reactor (BWR). The detection of fuel failures is usually performed by analysis of grab samples of off-gas and coolant activities, where a measured increased level of ionizing radiation serves as an indication of new failure or degradation of an already existing one. At some nuclear power plants the detection of fuel failures is performed by on-line nuclide specific measurements of the released fission gases in the off-gas system. However, it can be difficult to distinguish primary fuel failures from degradation of already existing failures. In this paper, a helium measuring system installed in connection to a nuclide specific measuring system to support detection of fuel failures and separate primary fuel failures from secondary ones is presented. Helium measurements provide valuable additional information to measurements of the gamma emitting fission gases for detection of primary fuel failures, since helium is used as a fill gas in the fuel rods during fabrication. The ability to detect fuel failures using helium measurements was studied by injection of helium into the feed water systems at the Forsmark nuclear power plant (NPP) in Sweden and at the nuclear power plant Leibstadt (M(L) in Switzerland. In addition, the influence of an off-gas delay line on the helium measurements was examined at KM. by injecting helium into the off-gas system. By using different injection rates, several types of fuel failures with different helium release rates were simulated. From these measurements, it was confirmed that the helium released by a failed fuel can be detected. It was also shown that the helium measurements for the detection of fuel failures should be performed at a sampling point located before any delay system. Hence, these studies showed that helium measurements can be useful to support detection of fuel failures. However, not all fuel failures which occurred at Forsmark NPP during the test period were detected; neither with the helium measurement system nor with the system for the measuring the gamma emitting noble fission gases. Possible reasons for that are discussed in the paper. The experiences with helium measurements for detection of fuel failures are still limited since the helium detector has only been in operation for two years at Forsmark NPP and for four years at Leibstadt nuclear power plants. Further studies are therefore needed to optimize these systems. (C) 2014 Elsevier B.V. All rights reserved.
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13.
  • Li, Q. A., et al. (author)
  • Therapeutic techniques applied in the heavy-ion therapy at IMP
  • 2011
  • In: Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms. - : Elsevier BV. - 0168-583X. ; 269:7, s. 664-670
  • Journal article (peer-reviewed)abstract
    • Superficially-placed tumors have been treated with carbon ions at the Institute of Modern Physics (IMP), Chinese Academy of Sciences (CAS), since November 2006. Up to now, 103 patients have been irradiated in the therapy terminal of the heavy ion research facility in Lanzhou (HIRFL) at IMP, where carbon-ion beams with energies up to 100 MeV/u can be supplied and a passive beam delivery system has been developed and commissioned. A number of therapeutic and clinical experiences concerning heavy-ion therapy have been acquired at IMP. To extend the heavy-ion therapy project to deep-seated tumor treatment, a horizontal beam line dedicated to this has been constructed in the cooling storage ring (CSR), which is a synchrotron connected to the HIRFL as an injector, and is now in operation. Therapeutic high-energy carbon-ion beams, extracted from the HIRFL-CSR through slow extraction techniques, have been supplied in the deep-seated tumor therapy terminal. After the beam delivery, shaping and monitoring devices installed in the therapy terminal at HIRFL-CSR were validated through therapeutic beam tests, deep-seated tumor treatment with high-energy carbon ions started in March 2009. The therapeutic techniques in terms of beam delivery system, conformal irradiation method and treatment planning used at IMP are introduced in this paper.
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14.
  • Maeyama, T., et al. (author)
  • Production of a fluorescence probe in ion-beam radiolysis of aqueous coumarin-3-carboxylic acid solution-2: Effects of nuclear fragmentation and its simulation with PHITS
  • 2011
  • In: Radiation Physics and Chemistry. - : Elsevier BV. - 1879-0895 .- 0969-806X. ; 80:12, s. 1352-1357
  • Journal article (peer-reviewed)abstract
    • The G(OH) values in aqueous coumarin-3-carboxylic-acid (3-CCA) solutions irradiated with (12)C(6+) beams having the energies of 135, 290 and 400 MeV/u were measured by a fluorescent method around the Bragg peak, with 0.6 mm intervals, and quartz cells of 1 cm optical lengths, at the Heavy Ion Medical Accelerator in Chiba, National Institute of Radiological Sciences (NIRS). For each ion, the G(OH) has been calculated as a function of dose average LET and position. The calculated results have been compared to measurements, and the results, reproducibility and reliability of the calculations are discussed in the paper.
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15.
  • Nakajima, Y., et al. (author)
  • Approach to 3D dose verification by utilizing autoactivation
  • 2011
  • In: Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. - : Elsevier BV. - 0168-9002. ; 648 (Supplement 1):SUPPL. 1, s. S119-S121
  • Journal article (peer-reviewed)abstract
    • To evaluate the deposited dose distribution in a target, we have proposed to utilize the annihilation gamma-rays emitted from the positron emitters distributed in the target irradiated with stable heavy-ion beams. Verification of the one dimensional (1-D) dose distributions along and perpendicular to a beam axis was achieved through our previous works. The purpose of this work is to verify 3-D dose distributions. As the first attempt uniform PMMA targets were irradiated in simple rectangular parallelepiped shapes, and the annihilation gamma-rays were detected with a PET scanner. By comparing the detected annihilation gamma-ray distributions with the calculated ones the dose distributions were estimated. As a result the estimated positions of the distal edges of the dose distributions were in agreement with the measured ones within 1 mm. However, the estimated positions of the proximal edges were different from the measured ones by 5-9 mm depending on the thickness of the irradiation filed.
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16.
  • Nakajima, Y., et al. (author)
  • Dosimetry by means of in-beam PET with RI beam irradiation
  • 2013
  • In: IEEE Nuclear Science Symposium Conference Record. - 1095-7863.
  • Conference paper (peer-reviewed)abstract
    • In situ visualization of deposited dose distribution is necessary to exploit the advantages of Carbon-ion therapy. Therefore we are developing the world's first, open-type PET 'OpenPET' to verify the field irradiated. In addition, a method of utilizing activity measurement in the target irradiated with the beam with positron-emitting radioisotopes (RI) such as 11C and 10C has been proposed. This method has advantage in the amount of activity as well as direct visualization of primary particles themselves, compared with the irradiation with stable nuclei 12C beam. With the RI beam, however, the profile of the dose was still different from that of the activity. Therefore interpretation from activity distribution to dose distribution is necessary to confirm the irradiation field precisely. In this paper, we developed a method of estimating the dose distribution from PET measurements. To utilize the activity measurement of the target, we used the code which calculated the activation distribution and dose distribution taking initial beam energy as a free parameter. Then the maximum likelihood parameter of the initial energy was determined by comparing the measured and the calculated distributions. By using the parameter determined, the dose distribution in the target was calculated as the estimated distribution for the actual one. The uniform PMMA target was irradiated with 11C beam for 10 s. The target was measured from the time beam irradiation started and to 60 s after finishing the irradiation by using a small single-ring OpenPET prototype developed for a proof-of-concept of the in-beam monitoring for charged particle therapy. As a result, the dose distribution, which was originally different from primary particles distribution, was successfully estimated. The peak depth of the estimated dose distribution was in good agreement with the measured dose peak. © 2013 IEEE.
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17.
  • Niita, K., et al. (author)
  • Applicability of the PHITS Code to Heavy Ion Accelerator Facilities
  • 2011
  • In: Journal of the Korean Physical Society. - : Korean Physical Society. - 0374-4884. ; 59:2, s. 1640-1643
  • Journal article (peer-reviewed)abstract
    • PHITS, a general-purpose Particle and Heavy Ion Transport code System, has been used for various research fields such as radiation science, accelerator and its shielding design, space research, medical application and material research. In this paper, we present an overview of the PHITS code, particularly the heavy ion reaction model included in the code and the capability of the transport of charged particles and heavy ions under magnetic field and discuss the applicability of the PHITS code to heavy ion accelerator facilities by showing some examples of the analysis.
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18.
  • Niita, K., et al. (author)
  • Event Generator Models in the Particle and Heavy Ion Transport Code System; PHITS
  • 2011
  • In: Journal of the Korean Physical Society. - : Korean Physical Society. - 0374-4884. ; 59:2, s. 827-832
  • Journal article (peer-reviewed)abstract
    • We present the event generator rnodels incorporated in the particle and heavy ion transport code system PHITS. For the high energy nuclear reactions, we discuss the QMD model and the INC model followed by the statistical decay model. For low energy neutron transport by using the nuclear data, we propose a new model, in which we combine the evaluated nuclear data and the reaction models so as to describe all ejectiles of collision keeping the energy and momentum conservation. By this new model, we can estimate new quantities which are related to the higher order correlations beyond one-body observable, for an example, the deposit energy distribution in a cell, which cannot be obtained by the transport calculation based on the Boltzmann equation with the evaluated nuclear data.
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19.
  • Ota, S., et al. (author)
  • Charge resolution of CR-39 plastic nuclear track detectors for intermediate energy heavy ions
  • 2011
  • In: Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms. - : Elsevier BV. - 0168-583X. ; 269:12, s. 1382-1388
  • Journal article (peer-reviewed)abstract
    • The charge resolution (delta Z) for heavy ions (nuclear charge: Z = 60 mu m (30 h etching), saturation occurs and there is no further improvement in delta Z. Analysis of the correlations between projectile Z, energy, detector response, and fluctuation of the response make it possible to develop a model to predict the delta Z for projectiles of given Z and energy. The predicted and measured values of delta Z show good agreement within 10%. We conclude that 4
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20.
  • Ota, S., et al. (author)
  • Depth dependency of neutron density produced by cosmic rays in the lunar subsurface
  • 2014
  • In: Advances in Space Research. - : Elsevier BV. - 1879-1948 .- 0273-1177. ; 54:10, s. 2114-2121
  • Journal article (peer-reviewed)abstract
    • Depth dependency of neutrons produced by cosmic rays (CRs) in the lunar subsurface was estimated using the three-dimensional Monte Carlo particle and heavy ion transport simulation code, PHITS, incorporating the latest high energy nuclear data, JENDL/HE-2007. The PHITS simulations of equilibrium neutron density profiles in the lunar subsurface were compared with the measurement by Apollo 17 Lunar Neutron Probe Experiment (LNPE). Our calculations reproduced the LNPE data except for the 350-400 mg/cm(2) region under the improved condition using the CR spectra model based on the latest observations, well-tested nuclear interaction models with systematic cross section data, and JENDL/HE-2007.
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21.
  • Ota, S., et al. (author)
  • Improvement of charge resolution for trans-iron nuclei (Z≥30) in CR-39 plastic nuclear track detectors using trajectory tracing technique
  • 2011
  • In: Astrophysics and Space Sciences Transactions. - : Copernicus GmbH. - 1810-6528 .- 1810-6536. ; 7:4, s. 495-500
  • Journal article (peer-reviewed)abstract
    • Charge identification of trans-iron nuclei (nuclear charge: Z≥ 30) using CR-39 plastic nuclear track detector (PNTD) is essential as a part of an effort to our future measurements of the projectile charge changing cross sections for galactic cosmic ray nuclei, but extremely hard. Therefore, an improvement method of the charge resolution (δZ) for 350 MeV/n Ge in CR-39 PNTD using the trajectory tracing technique with averaging the signals of nuclear tracks for each ion was studied. Eight sheets of CR-39 PNTDs were aligned and exposed to Ge beam behind a graphite target to produce projectile fragments. Average of the nuclear track data was taken over 16 detector surfaces for each ion, then the δZ of Ge was successfully improved from 0.31 charge unit on single surface to 0.15 charge unit in rms, which is good enough for making the precise cross section measurements and no other experiments using CR-39 PNTDs or the other passive detectors have achieved such a good δZ for the trans-iron nuclei with ≥Z 50 (β: relativistic velocity). This method will be very important for our future cross section measurements toward the study of galactic cosmic ray origin. © 2011 Author(s).
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22.
  • Ota, S., et al. (author)
  • Neutron production in the lunar subsurface from alpha particles in galactic cosmic rays
  • 2011
  • In: Earth, Planets and Space. - : Springer Science and Business Media LLC. - 1880-5981 .- 1343-8832. ; 63:1, s. 25-35
  • Journal article (peer-reviewed)abstract
    • The neutron production from alpha particles in galactic cosmic rays (GCR) in the lunar subsurface has not been estimated with reliable precision despite its importance for lunar nuclear spectroscopy and space dosimetry. Here, we report our estimation of neutron production from GCR nuclei (protons and alpha particles) with the Particle and Heavy Ion Transport code System (PHITS), which includes several heavy ion interaction models. PHITS simulations of the equilibrium neutron density profiles in the lunar subsurface are compared with experimental data obtained in the Apollo 17 Lunar Neutron Probe Experiment. Our calculations successfully reproduced the data within an experimental error of 15%. Our estimation of neutron production from GCR nuclei, estimated by scaling that from protons by a factor of 1.27, is in good agreement within an error of 1% with the calculations using two different alpha particle interaction models in PHITS during a period of average activity of the solar cycle. However, we show that the factor depends on the incident GCR spectrum model used in the simulation. Therefore, we conclude that the use of heavy ion interaction models is important for estimating neutron production in the lunar subsurface.
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23.
  • Pachnerova Brabcová, Katerina, 1978, et al. (author)
  • Clustered DNA damage on subcellular level: effect of scavengers
  • 2014
  • In: Radiation and Environmental Biophysics. - : Springer Science and Business Media LLC. - 1432-2099 .- 0301-634X. ; 53:4, s. 705-712
  • Journal article (peer-reviewed)abstract
    • Clustered DNA damages are induced by ionizing radiation, particularly of high linear energy transfer (LET). Compared to isolated DNA damage sites, their biological effects can be more severe. We investigated a clustered DNA damage induced by high LET radiation (C 290 MeV u(-1) and Fe 500 MeV u(-1)) in pBR322 plasmid DNA. The plasmid is dissolved in pure water or in aqueous solution of one of the three scavengers (coumarin-3-carboxylic acid, dimethylsulfoxide, and glycylglycine). The yield of double strand breaks (DSB) induced in the DNA plasmid-scavenger system by heavy ion radiation was found to decrease with increasing scavenging capacity due to reaction with hydroxyl radical, linearly with high correlation coefficients. The yield of non-DSB clusters was found to occur twice as much as the DSB. Their decrease with increasing scavenging capacity had lower linear correlation coefficients. This indicates that the yield of non-DSB clusters depends on more factors, which are likely connected to the chemical properties of individual scavengers.
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24.
  • Pachnerova Brabcová, Katerina, 1978, et al. (author)
  • Dose Distribution Outside the Target Volume for 170-Mev Proton Beam
  • 2014
  • In: Radiation Protection Dosimetry. - : Oxford University Press (OUP). - 0144-8420 .- 1742-3406. ; 161:1-4, s. 410-416
  • Journal article (peer-reviewed)abstract
    • Dose delivered outside the proton field during radiotherapy can potentially lead to secondary cancer development. Measurements with a 170-MeV proton beam were performed with passive detectors (track etched detectors and thermoluminescence dose-meters) in three different depths along the Bragg curve. The measurement showed an uneven decrease of the dose outside of the beam field with local enhancements. The major contribution to the delivered dose is due to high-energy protons with linear energy transfer (LET) up to 10 keV mu m(-1). However, both measurement and preliminary Monte Carlo calculation also confirmed the presence of particles with higher LET.
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25.
  • Ploc, Ondrej, 1979, et al. (author)
  • PHITS simulations of the Protective curtain experiment onboard the Service module of ISS: Comparison with absorbed doses measured with TLDs
  • 2013
  • In: Advances in Space Research. - : Elsevier BV. - 1879-1948 .- 0273-1177. ; 52:11, s. 1911-1918
  • Journal article (peer-reviewed)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.
  •  
26.
  • Ploc, Ondrej, et al. (author)
  • Poster session 11: Space dosimetry and environment dosimetry measurements using timepix in mixed radiation fields induced by heavy ions; comparison with standard dosimetry methods
  • 2014
  • In: Journal of Radiation Research. - : Oxford University Press (OUP). - 0449-3060 .- 1349-9157. ; 55, s. i141-i142
  • Journal article (peer-reviewed)abstract
    • Objective of our research was to explore capabilities of Timepix for its use as a single dosemeter and LET spectrometer in mixed radiation fields created by heavy ions. We exposed it to radiation field (i) at heavy ion beams at HIMAC, Chiba, Japan, (ii) in the CERN's high-energy reference field (CERF) facility at Geneva, France/Switzerland, (iii) in the exposure room of the proton therapy laboratory at JINR, Dubna, Russia, and (iv) onboard aircraft. We compared the absolute values of dosimetric quantities obtained with Timepix and with other dosemeters and spectrometers like tissue-equivalent proportional counter (TEPC) Hawk, silicon detector Liulin, and track-etched detectors (TEDs). © The Author 2014. Published by Oxford University Press on behalf of The Japan Radiation Research Society and Japanese Society for Therapeutic Radiology and Oncology.
  •  
27.
  • Puchalska, Monika, 1977, et al. (author)
  • Simulations of MATROSHKA experiment outside the ISS using PHITS
  • 2012
  • In: Advances in Space Research. - : Elsevier BV. - 1879-1948 .- 0273-1177. ; 50:4, s. 489-495
  • Journal article (peer-reviewed)abstract
    • The radiation environment at the altitude of the International Space Station (ISS) is substantially different than anything typically encountered on Earth in both the character of the radiation field and the significantly higher dose rates. Concerns about the biological effects on humans of this highly complex natural radiation field are increasing due to higher amount of astronauts performing long-duration missions onboard the ISS and especially if looking into planned future manned missions to Mars. In order to begin the process of predicting the dose levels seen by the organs of an astronaut, being the prerequisite for radiation risk calculations, it is necessary to understand the character of the radiation environment both in- and outside of the ISS as well as the relevant contributions from the radiation field to the organ doses. In this paper the three-dimensional Monte Carlo Particle and Heavy Ion Transport code System (PHITS) and a voxel-based numerical human model NUNDO (Numerical RANDO) were used to estimate the radiation load of human organs during a long term activity outside the ISS. The baseline measured data was generated with the MATROSHKA-1 (MTR-1) experiment taking place from February 2004 up to October 2005 outside the Russian Zvezda module of the ISS, thereby simulating a long term extravehicular activity (EVA) of an astronaut. The organ absorbed dose values calculated by PHITS for the inner organs are in a good agreement with the experimental data. However, a rather large disagreement was observed for the most outer organs. This disagreement appears to be due to the strong dependence that the thickness of the applied carbon fiber container, acting as the EVA suit of the astronaut, has on the effects caused by the trapped electron (TE) component. The organ dose equivalent values for the deeper organs are a factor of two lower than the experimental data. The detailed reason behind this is still under investigation.
  •  
28.
  • Reed, R. A., et al. (author)
  • Anthology of the Development of Radiation Transport Tools as Applied to Single Event Effects
  • 2013
  • In: IEEE Transactions on Nuclear Science. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9499 .- 1558-1578. ; 60:3, s. 1876-1911
  • Journal article (peer-reviewed)abstract
    • This anthology contains contributions from eleven different groups, each developing and/or applying Monte Carlo-based radiation transport tools to simulate a variety of effects that result from energy transferred to a semiconductor material by a single particle event. The topics span from basic mechanisms for single-particle induced failures to applied tasks like developing websites to predict on-orbit single event failure rates using Monte Carlo radiation transport tools.
  •  
29.
  • Rohling, Heide, et al. (author)
  • Comparison of PHITS, GEANT4, and HIBRAC simulations of depth-dependent yields of beta(+)-emitting nuclei during therapeutic particle irradiation to measured data
  • 2013
  • In: Physics in Medicine and Biology. - : IOP Publishing. - 0031-9155 .- 1361-6560. ; 58:18, s. 6355-6368
  • Journal article (peer-reviewed)abstract
    • For quality assurance in particle therapy, a non-invasive, in vivo range verification is highly desired. Particle therapy positron-emission-tomography (PT-PET) is the only clinically proven method up to now for this purpose. It makes use of the beta(+)-activity produced during the irradiation by the nuclear fragmentation processes between the therapeutic beam and the irradiated tissue. Since a direct comparison of beta(+)-activity and dose is not feasible, a simulation of the expected beta(+)-activity distribution is required. For this reason it is essential to have a quantitatively reliable code for the simulation of the yields of the beta(+)-emitting nuclei at every position of the beam path. In this paper results of the three-dimensional Monte-Carlo simulation codes PHITS, GEANT4, and the one-dimensional deterministic simulation code HIBRAC are compared to measurements of the yields of the most abundant beta(+)-emitting nuclei for carbon, lithium, helium, and proton beams. In general, PHITS underestimates the yields of positron-emitters. With GEANT4 the overall most accurate results are obtained. HIBRAC and GEANT4 provide comparable results for carbon and proton beams. HIBRAC is considered as a good candidate for the implementation to clinical routine PT-PET.
  •  
30.
  • Sato, T., et al. (author)
  • Applications of the microdosimetric function implemented in the macroscopic particle transport simulation code PHITS
  • 2012
  • In: International Journal of Radiation Biology. - : Informa UK Limited. - 0955-3002 .- 1362-3095. ; 88:1-2, s. 143-150
  • Journal article (peer-reviewed)abstract
    • Purpose: Microdosimetric quantities such as lineal energy are generally considered to be better indices than linear energy transfer (LET) for expressing the relative biological effectiveness (RBE) of high charge and energy particles. To calculate their probability densities (PD) in macroscopic matter, it is necessary to integrate microdosimetric tools such as track-structure simulation codes with macroscopic particle transport simulation codes. Methods: As an integration approach, the mathematical model for calculating the PD of microdosimetric quantities developed based on track-structure simulations was incorporated into the macroscopic particle transport simulation code PHITS (Particle and Heavy Ion Transport code System). The improved PHITS enables the PD in macroscopic matter to be calculated within a reasonable computation time, while taking their stochastic nature into account. Applications: The microdosimetric function of PHITS was applied to biological dose estimation for charged-particle therapy and risk estimation for astronauts. The former application was performed in combination with the microdosimetric kinetic model, while the latter employed the radiation quality factor expressed as a function of lineal energy. Conclusion: Owing to the unique features of the microdosimetric function, the improved PHITS has the potential to establish more sophisticated systems for radiological protection in space as well as for the treatment planning of charged-particle therapy.
  •  
31.
  • Sato, Tatsuhiko, et al. (author)
  • Applications of the microdosimetric function implemented in the macroscopic particle transport simulation code PHITS
  • 2012
  • In: International Journal of Radiation Biology. - : Informa UK Limited. - 0955-3002 .- 1362-3095. ; 88:1-2, s. 143-150
  • Journal article (peer-reviewed)abstract
    • Purpose: Microdosimetric quantities such as lineal energy are generally considered to be better indices than linear energy transfer (LET) for expressing the relative biological effectiveness (RBE) of high charge and energy particles. To calculate their probability densities (PD) in macroscopic matter, it is necessary to integrate microdosimetric tools such as track-structure simulation codes with macroscopic particle transport simulation codes. Methods: As an integration approach, the mathematical model for calculating the PD of microdosimetric quantities developed based on track-structure simulations was incorporated into the macroscopic particle transport simulation code PHITS (Particle and Heavy Ion Transport code System). The improved PHITS enables the PD in macroscopic matter to be calculated within a reasonable computation time, while taking their stochastic nature into account. Applications: The microdosimetric function of PHITS was applied to biological dose estimation for charged-particle therapy and risk estimation for astronauts. The former application was performed in combination with the microdosimetric kinetic model, while the latter employed the radiation quality factor expressed as a function of lineal energy. Conclusion: Owing to the unique features of the microdosimetric function, the improved PHITS has the potential to establish more sophisticated systems for radiological protection in space as well as for the treatment planning of charged-particle therapy.
  •  
32.
  • Sato, T., et al. (author)
  • Dose estimation for astronauts using dose conversion coefficients calculated with the PHITS code and the ICRP/ICRU adult reference computational phantoms
  • 2011
  • In: Radiation and Environmental Biophysics. - : Springer Science and Business Media LLC. - 1432-2099 .- 0301-634X. ; 50:1, s. 115-123
  • Journal article (peer-reviewed)abstract
    • Absorbed-dose and dose-equivalent rates for astronauts were estimated by multiplying fluence-to-dose conversion coefficients in the units of Gy.cm(2) and Sv.cm(2), respectively, and cosmic-ray fluxes around spacecrafts in the unit of cm(-2) s(-1). The dose conversion coefficients employed in the calculation were evaluated using the general-purpose particle and heavy ion transport code system PHITS coupled to the male and female adult reference computational phantoms, which were released as a common ICRP/ICRU publication. The cosmic-ray fluxes inside and near to spacecrafts were also calculated by PHITS, using simplified geometries. The accuracy of the obtained absorbed-dose and dose-equivalent rates was verified by various experimental data measured both inside and outside spacecrafts. The calculations quantitatively show that the effective doses for astronauts are significantly greater than their corresponding effective dose equivalents, because of the numerical incompatibility between the radiation quality factors and the radiation weighting factors. These results demonstrate the usefulness of dose conversion coefficients in space dosimetry.
  •  
33.
  • Sato, T., et al. (author)
  • Evaluation of dose rate reduction in a spacecraft compartment due to additional water shield
  • 2011
  • In: Cosmic Research (English translation of Kosimicheskie Issledovaniya). - 0010-9525 .- 1608-3075. ; 49:4, s. 319-324
  • Journal article (peer-reviewed)abstract
    • The dose reduction rates brought about by the installation of additional water shielding in a spacecraft are calculated in the paper using the particles and heavy ion transport code system PHITS, which can deal with transport of all kinds of hadrons and heavy ions with energies up to 100 GeV/n in three-dimensional phase spaces. In the PHITS simulation, an imaginary spacecraft was irradiated isotropically by cosmic rays with charges up to 28 and energies up to 100 GeV/n, and the dose reduction rates due to water shielding were evaluated for 5 types of doses: the dose equivalents obtained from the LET and linear energy spectra, the dose equivalents to skin and red bone marrow, and the effective dose equivalent. The results of the simulation indicate that the dose reduction rates differ according to the type of dose evaluated. For example, 5 g/cm(2) water shielding reduces the effective dose equivalent and the LET dose equivalent by approximately 14% and 32%, respectively. Such degrees of dose reduction can be regarded to make water shielding worth the efforts required to install it.
  •  
34.
  • Sato, T., et al. (author)
  • Overview of Particle and Heavy Ion Transport Code System PHITS
  • 2014
  • In: Sna + Mc 2013 - Joint International Conference on Supercomputing in Nuclear Applications + Monte Carlo. - Les Ulis, France : EDP Sciences. ; , s. article no 06018-
  • Conference paper (peer-reviewed)abstract
    • A general purpose Monte Carlo Particle and Heavy Ion Transport code System, PHITS, is being developed through the collaboration of several institutes in Japan and Europe. The Japan Atomic Energy Agency is responsible for managing the entire project. PHITS can deal with the transport of nearly all particles, including neutrons, protons, heavy ions, photons, and electrons, over wide energy ranges using various nuclear reaction models and data libraries. It is written in Fortran language and can be executed on almost all computers. All components of PHITS such as its source, executable and data-library files are assembled in one package and then distributed to many countries via the Research organization for Information Science and Technology, the Data Bank of the Organization for Economic Co-operation and Development's Nuclear Energy Agency, and the Radiation Safety Information Computational Center. More than 1,000 researchers have been registered as PHITS users, and they apply the code to various research and development fields such as nuclear technology, accelerator design, medical physics, and cosmic-ray research. This paper briefly summarizes the physics models implemented in PHITS, and introduces some important functions useful for specific applications, such as an event generator mode and beam transport functions.
  •  
35.
  • Sato, T., et al. (author)
  • Particle and Heavy Ion Transport code System, PHITS, version 2.52
  • 2013
  • In: Journal of Nuclear Science and Technology. - : Informa UK Limited. - 0022-3131 .- 1881-1248. ; 50:9, s. 913-923
  • Journal article (peer-reviewed)abstract
    • An upgraded version of the Particle and Heavy Ion Transport code System, PHITS2.52, was developed and released to the public. The new version has been greatly improved from the previously released version, PHITS2.24, in terms of not only the code itself but also the contents of its package, such as the attached data libraries. In the new version, a higher accuracy of simulation was achieved by implementing several latest nuclear reaction models. The reliability of the simulation was improved by modifying both the algorithms for the electron-, positron-, and photon-transport simulations and the procedure for calculating the statistical uncertainties of the tally results. Estimation of the time evolution of radioactivity became feasible by incorporating the activation calculation program DCHAIN-SP into the new package. The efficiency of the simulation was also improved as a result of the implementation of shared-memory parallelization and the optimization of several time-consuming algorithms. Furthermore, a number of new user-support tools and functions that help users to intuitively and effectively perform PHITS simulations were developed and incorporated. Due to these improvements, PHITS is now a more powerful tool for particle transport simulation applicable to various research and development fields, such as nuclear technology, accelerator design, medical physics, and cosmic-ray research.
  •  
36.
  • Sihver, Lembit, 1962, et al. (author)
  • A comparison of total reaction cross section models used in FLUKA, GEANT4 and PHITS
  • 2012
  • In: Aerospace Conference, 2012 IEEE. ; , s. 1-10, s. 1 - 10
  • Conference paper (peer-reviewed)abstract
    • Understanding the interactions and propagations of high energy protons and heavy ions are essential when trying to estimate the biological effects of Galactic Cosmic Rays (GCR) and Solar Particle Events (SPE) on personnel on interplanetary missions, and when preparing the construction of a lunar base. To be able to calculate the secondary particles, including neutrons, and to estimate shielding properties of different materials and radiation risks inside complex geometries, particle and heavy ion transport codes are needed. The interactions of the GCR and SPE with matter include many complex properties and many factors influence the calculated results. In all particle and heavy ion transport codes, the probability function that a projectile particle will collide with a nucleus within a certain distance x in the matter depends on the total reaction cross sections, which also scale the calculated partial fragmentation cross sections. It is therefore crucial that accurate total reaction cross section models are used in the transport calculations. FLUKA, GEANT4 and PHITS are three major multi-purpose three-dimensional Monte Carlo particle and heavy ion transport codes widely used for fundamental research, radioprotection, radiotherapy, and space dosimetry. In this paper, a systematic comparison of the total reaction cross section models used as default in these three codes is performed for a variety of systems of importance for space dosimetry, and the need for future improvements and benchmarking against experimental results is discussed. The need for benchmarking and improvements of the partial nuclear reaction and evaporation models, as well as how impact parameter functions, switching time between the dynamical/pre-equilibrium and the de-excitation/evaporation stages, low energy data libraries, etc., influence the final results, is also briefly be discussed.
  •  
37.
  • Sihver, Lembit, 1962, et al. (author)
  • A comparison of total reaction cross section models used in particle and heavy ion transport codes
  • 2010
  • In: Aerospace Conference, 2010 IEEE. - IEEE. ; , s. 1-9:Issue Date: 6-13 March 2010, s. 1 - 9
  • Conference paper (peer-reviewed)abstract
    • To be able to calculate the nucleon-nucleon and nucleon-nucleus total reaction cross sections with precision is very important for studies of basic nuclear properties, e.g. nuclear structure. This is also of importance for particle and heavy ion transport calculations since in all particle and heavy ion transport codes, the probability function that a projectile particle will collide within a certain distance x in the matter depends on the total reaction cross sections. This will also scale the calculated partial fragmentation cross sections. It is therefore crucial that accurate total reaction cross section models are used in the transport calculations. In this paper, different models for calculating nucleon-nucleus and nucleus-nucleus total reaction cross sections are compared.
  •  
38.
  • Sihver, Lembit, 1962, et al. (author)
  • A comparison of total reaction cross section models used in particle and heavy ion transport codes
  • 2012
  • In: Advances in Space Research. - : Elsevier BV. - 1879-1948 .- 0273-1177. ; 49:4, s. 812-819
  • Journal article (peer-reviewed)abstract
    • Understanding the interactions and propagations of high energy protons and heavy ions are essential when trying to estimate the biological effects of Galactic Cosmic Rays (GCR) and Solar Particle Events (SPE) on personnel in space. To be able to calculate the shielding properties of different materials and radiation risks, particle and heavy ion transport codes are needed. In all particle and heavy ion transport codes, the probability function that a projectile particle will collide within a certain distance x in the matter depends on the total reaction cross sections, and the calculated partial fragmentation cross sections scale with the total reaction cross sections. It is therefore crucial that accurate total reaction cross section models are used in the transport calculations. In this paper, different models for calculating nucleon-nucleus and nucleus-nucleus total reaction cross sections are compared with each other and with measurements. The uncertainties in the calculations with the different models are discussed, as well as their overall performances with respect to the available experimental data. Finally, a new compilation of experimental data is briefly presented.
  •  
39.
  • Sihver, Lembit, 1962, et al. (author)
  • A study of total reaction cross section models used in particle and heavy ion transport codes
  • 2011
  • In: IEEE Aerospace Conference Proceedings. - : IEEE conference proceedings. - 1095-323X. - 9781424473502
  • Conference paper (peer-reviewed)abstract
    • Understanding the interactions and propagations of high energy protons and heavy ions are essential when trying to estimate the biological effects of Galactic Cosmic Rays (GCR) and Solar Particle Events (SPE) on personnel in space. 12 To be able to calculate the shielding properties of different materials and radiation risks, particle and heavy ion transport codes are needed. In all particle and heavy ion transport codes, the probability function that a projectile particle will collide within a certain distance x in the matter depends on the total reaction cross sections, which also scale the calculated partial fragmentation cross sections. It is therefore crucial that accurate total reaction cross section models are used in the transport calculations. In this paper, different models for calculating nucleon-nucleus and nucleus-nucleus total reaction cross sections are compared with each other and with measurements. The uncertainties in the calculations with the different models are discussed, as well as their overall performances with respect to the available experimental data. Finally, a new compilation of experimental data is presented and new measurements to improve the current models are suggested.
  •  
40.
  • Sihver, Lembit, 1962, et al. (author)
  • An update about recent developments of the PHITS code
  • 2010
  • In: Advances in Space Research. - : Elsevier BV. - 1879-1948 .- 0273-1177. ; 45:7, s. 892-899
  • Journal article (peer-reviewed)abstract
    • PHITS (Particle and Heavy-Ion Transport code System) is a general-purpose three-dimensional Monte Carlo code, developed and maintained by RIST, JAEA and KEK in Japan together with Sihver et al. at Chalmers in Sweden. PHITS can deal with the transports of all varieties of hadrons and heavy ions with energies up to around 100 GeV/nucleon, and in this paper the current status of PHITS is presented. We introduce a relativistically covariant version of JQMD, called R-JQMD, that features an improved ground state initialization algorithm, and we will present the introduction of electron and photon transport in PHITS using EGS5, which have increased the energy region for the photon and energy transport from up to around 3 GeV to up to several hundred GeV depending on the atomic number of the target. We show how the accuracy in dose and fluence calculations can be improved by using tabulated cross sections. Benchmarking of shielding and irradiation effects of high energy protons in different materials relevant for shielding of accelerator facilities is also presented. In particular, we show that PHITS can be used for estimating the dose received by aircrews and personnel in space. In recent years, many countries have issued regulations or recommendations to set annual dose limitations for aircrews. Since estimation of cosmic-ray spectra in the atmosphere is an essential issue for the evaluation of aviation doses, we have calculated these spectra using PHITS. The accuracy of the atmospheric propagation simulation of cosmic-ray performed by PHITS has been well verified by experimental cosmic-ray spectra taken under various conditions. Based on a comprehensive analysis of the simulation results, an analytical model called "PARMA" has been proposed for instantaneously estimating the atmospheric cosmic-ray spectra below the altitude of 20 km. We have also performed preliminary simulations of long-term dose distribution measurements at the ISS performed with the joint ESA-FSA experiment MATROSHKA-R (MTR-R) led by the Russian Federation Institute of Biomedical Problems (IMBP) and the ESA supported experiment MATROSHKA (MTR), led by the German Aerospace Center (DLR). For the purpose of examining the applicability of PHITS to the shielding design in space, the absorbed doses in a tissue equivalent water phantom inside an imaginary space vessel has been estimated for different shielding materials of different thicknesses. The results confirm previous results which indicate that PHITS is a suitable tool when performing shielding design studies of spacecrafts. (C) 2010 COSPAR. Published by Elsevier Ltd. All rights reserved.
  •  
41.
  • Sihver, Lembit, 1962, et al. (author)
  • Current status of the "Hybrid Kurotama model" for total reaction cross sections
  • 2014
  • In: Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms. - : Elsevier BV. - 0168-583X. ; 334, s. 34-39
  • Journal article (peer-reviewed)abstract
    • To be able to calculate the nucleon + nucleus and nucleus + nucleus total reaction cross sections with precision is of great importance for studies of fundamental nuclear properties, e.g., the nuclear structure. This is also very important for particle and heavy ion transport calculations since in all particle and heavy ion transport codes, the probability function according to which a projectile particle will collide within a certain distance in a matter depends on the total reaction cross sections. This will also scale the calculated partial fragmentation cross sections. It is therefore crucial that accurate total reaction cross section models are used in the transport calculations. In this paper, a new general purpose total reaction cross section model/subroutine called "Hybrid Kurotama" is presented. The model has been tested against available p + He, p + nucleus, and nucleus + nucleus total reaction cross sections and an overall better agreement has been found than for earlier published models. This model is therefore very suitable to be used in any deterministic or Monte Carlo particle and heavy ion transport code.
  •  
42.
  • Sihver, Lembit, 1962, et al. (author)
  • Improved parametrization of the transparency parameter in Kox and Shen models of total reaction cross sections
  • 2014
  • In: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X .- 2469-9985 .- 2469-9993. ; 89:6, s. 067602-
  • Journal article (peer-reviewed)abstract
    • The total reaction cross section is an essential quantity in particle and heavy-ion transport codes when determining the mean free path of a transported particle. Many transport codes determine the distance a particle is transported before it collides with the target or is stopped in the target material, with the Monte Carlo (MC) method using semiempirical parametrization models for the total reaction cross sections. In order to improve the well-known Kox and Shen models of total reaction cross sections and allow the models to be used at energies below 30 MeV/nucleon, we propose a modified parametrization of the transparency parameter. We also report that the Kox and Shen models have a projectile-target asymmetry and should be used so that the lighter nucleus is always treated as the projectile.
  •  
43.
  • Sihver, Lembit, 1962, et al. (author)
  • Monte Carlo simulations of MATROSHKA experiment outside ISS
  • 2011
  • In: IEEE Aerospace Conference Proceedings. Big Sky, 5-12 Mars 2011. - 1095-323X. - 9781424473502
  • Conference paper (peer-reviewed)abstract
    • Concerns about the biological effects of space radiation are increasing rapidly due to the perspective of long-duration manned missions, both in relation to the International Space Station (ISS) and to manned interplanetary missions to Mars in the future. As a preparation for these long duration space missions it is important to ensure an excellent capability to evaluate the impact of space radiation on human health in order to secure the safety of the astronauts/cosmonauts and minimize their risks. It is therefore necessary to measure the radiation load on the personnel both inside and outside the space vehicles and to certify that organ and tissue equivalent doses can be simulated as accurate as possible. In this paper we will present simulations using the three-dimensional Monte Carlo Particle and Heavy Ion Transport code System (PHITS) of long term dose measurements performed with the ESA supported experiment MATROSHKA (MTR), which is an anthropomorphic phantom containing over 6000 radiation detectors, mimicking a human head and torso. The MTR experiment, led by the German Aerospace Center (DLR), was launched in January 2004 and has measured the absorbed dose from space radiation both inside and outside the ISS. In this paper comparisons of measured and calculated dose and organ doses in the MTR located outside the ISS will be presented and uncertainties of the simulations will be discussed. This project was funded by the European Commission in the frame of the FP7 HAMLET project (Project # 218817).
  •  
44.
  • Sihver, Lembit, 1962, et al. (author)
  • PHITS - Applications to radiation biology and radiotherapy
  • 2013
  • In: 13th International Varenna Conference on Nuclear Reaction Mechanisms, NRM 2012. - 2078-8835. - 9789290833826 ; , s. 497-502
  • Conference paper (peer-reviewed)abstract
    • PHITS is a 3-dimensional general-purpose Monte Carlo code, which can transport of all varieties of hadrons and heavy ions with energies up to around 100 GeV/nucleon. To be able to estimate the biological damage from neutrons with PUTTS, a feature has been included to treat low energy neutron collisions as "events" which means that the energy and momentum is conserved in each event and makes it possible to extract the kinetic energy distributions of all the residual nuclei without using any local approximation. To estimate the direct biological effects of radiation, mathematical functions, for calculating the microdosmetric probability densities in macroscopic material, have been incorporated in PUTTS. This makes it possible to instantaneously calculate the probability densities of lineal and specific energies around the trajectories of high energetic charged particle tracks. A method for estimating the biological dose has also been established by using the improved PUTTS coupled to a microdosimetric kinetic model.
  •  
45.
  • Sihver, Lembit, 1962, et al. (author)
  • Projectile fragment emission angles in fragmentation reactions of light heavy ions in the energy region
  • 2013
  • In: Radiation Measurements. - : Elsevier BV. - 1350-4487. ; 48:1, s. 73-81
  • Journal article (peer-reviewed)abstract
    • Measurements of fragment emission angles for 57 and 93 MeV/nucleon C-12 and 95 MeV/nucleon O-16 projectiles in graphite, Plexiglas and polyethylene targets were performed using trajectory tracing technique with CR-39 detectors. The results were compared with calculations with the fragment emission angle model (FRANG). The angular resolution of the measurements was achieved to be
  •  
46.
  • Sihver, Lembit, 1962, et al. (author)
  • Simulations of MATROSHKA experiments at ISS using PHITS
  • 2010
  • In: 12th International Conference on Nuclear Reaction Mechanisms, NRM 2009; Varenna; Italy; 15 June 2009 through 19 June 2009. - 2078-8835. - 9789290833413 ; 2, s. 553-560
  • Conference paper (peer-reviewed)abstract
    • Concerns about the biological effects of space radiation are increasing rapidly due to the perspective of long-duration manned missions, both in relation to the International Space Station (ISS) and to manned interplanetary missions to Moon and Mars in the future. As a preparation for these long duration space missions it is important to ensure an excellent capability to evaluate the impact of space radiation on human health in order to secure the safety of the astronauts/cosmonauts and minimize their risks. It is therefore necessary to measure the radiation load on the personnel both inside and outside the space vehicles and certify that organ and tissue equivalent doses can be simulated as accurate as possible. In this paper we will present simulations using the three-dimensional Monte Carlo Particle and Heavy Ion Transport code System (PHITS) of long term dose measurements performed with the ESA supported experiment MATROSHKA (MTR), which is an anthropomorphic phantom containing over 6000 radiation detectors, mimicking a human head and torso. The MTR experiment, led by the German Aerospace Center (DLR), was launched in January 2004 and has measured the absorbed dose from space radiation both inside and outside the ISS. In this paper preliminary comparisons of measurements outside the ISS will be presented. The results confirm previous calculations and measurements which indicate that PHITS is a suitable tool for estimations of dose received from cosmic radiation and when performing shielding design studies of spacecraft.
  •  
47.
  • Sihver, Lembit, 1962, et al. (author)
  • Simulations of the MATROSHKA experiment at the international space station using PHITS
  • 2010
  • In: Radiation and Environmental Biophysics. - : Springer Science and Business Media LLC. - 1432-2099 .- 0301-634X. ; 49:3, s. 351-357
  • Journal article (peer-reviewed)abstract
    • Concerns about the biological effects of space radiation are increasing rapidly due to the perspective of long-duration manned missions, both in relation to the International Space Station (ISS) and to manned interplanetary missions to Moon and Mars in the future. As a preparation for these long-duration space missions, it is important to ensure an excellent capability to evaluate the impact of space radiation on human health, in order to secure the safety of the astronauts/cosmonauts and minimize their risks. It is therefore necessary to measure the radiation load on the personnel both inside and outside the space vehicles and certify that organ- and tissue-equivalent doses can be simulated as accurate as possible. In this paper, simulations are presented using the three-dimensional Monte Carlo Particle and Heavy-Ion Transport code System (PHITS) (Iwase et al. in J Nucl Sci Tech 39(11):1142-1151, 2002) of long-term dose measurements performed with the European Space Agency-supported MATROSHKA (MTR) experiment (Reitz and Berger in Radiat Prot Dosim 120:442-445, 2006). MATROSHKA is an anthropomorphic phantom containing over 6,000 radiation detectors, mimicking a human head and torso. The MTR experiment, led by the German Aerospace Center (DLR), was launched in January 2004 and has measured the absorbed doses from space radiation both inside and outside the ISS. Comparisons of simulations with measurements outside the ISS are presented. The results indicate that PHITS is a suitable tool for estimation of doses received from cosmic radiation and for study of the shielding of spacecraft against cosmic radiation.
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48.
  • Sihver, Lembit, 1962 (author)
  • Transport calculations and accelerator experiments needed for radiation risk assessment in space
  • 2010
  • In: Neural Computation and Particle Accelerators: Research, Technology and Applications. - 9781607412809 ; , s. 89-104
  • Book chapter (other academic/artistic)abstract
    • It is well known that one of the largest obstacles to be solved to enable safe future humanactivities on the lunar surface, building of a lunar base, and performing interplanetary spacemissions, is how to protect the personnel from cosmic and solar radiation. To do so, theradiobiological effects of the radiation inside and outside a spacecraft must be well understoodand countermeasures developed. The major uncertainties on space radiation risk estimates inhumans are associated to the poor knowledge of the biological effects of low and high LETradiation, with a smaller contribution coming from the characterization of space radiation fieldand its primary interactions with the shielding and the human body. However, to decrease theuncertainties on the biological effects and increase the accuracy of the risk coefficients forcharged particles radiation, the initial charged-particle spectra from the Galactic Cosmic Rays(GCRs) and the Solar Particle Events (SPEs), and the radiation transport through the shieldingmaterial of the space vehicle and the human body, must be well characterized. Since it ispractically impossible to measure all primary and secondary particles from all possibleposition-projectile-target-energy combinations needed for a correct risk assessment in space,accurate particle and heavy ion transport codes must be used. These codes are also neededwhen estimating the risk for radiation induced failures in advanced microelectronics, such assingle-event effects, etc., and the efficiency of different shielding materials. It is thereforeimportant that the models and transport codes will be carefully benchmarked and validated tomake sure they fulfill preset accuracy criteria, e.g. to be able to predict particle fluence, doseand energy distributions within a certain accuracy. When validating the accuracy of thetransport codes, well defined ground based accelerator as well as space experiments areneeded. In this paper, accelerator experiments needed for testing and validating particle andheavy ion transport codes, and shielding materials, are presented. Advantages anddisadvantages with deterministic one dimensional and stochastic three dimensional transport codes are discussed, together with different concepts of shielding and protection from cosmicradiation.
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49.
  • Sihver, Lembit, 1962, et al. (author)
  • Voxel model of individual cells and its implementation in microdosimetric calculations using GEANT4
  • 2014
  • In: Radiation and Environmental Biophysics. - : Springer Science and Business Media LLC. - 1432-2099 .- 0301-634X. ; 53:3, s. 571-579
  • Journal article (peer-reviewed)abstract
    • Accurate dosimetric calculations at cellular and sub-cellular levels are crucial to obtain an increased understanding of the interactions of ionizing radiation with a cell and its nucleus and cytoplasm. Ion microbeams provide a superior opportunity to irradiate small biological samples, e.g., DNA, cells, and to compare their response to computer simulations. However, the phantoms used to simulate small biological samples at cellular levels are often simplified as simple volumes filled with water. As a first step to improve the situation in comparing measurements of cell response to ionizing radiation with model calculations, a realistic voxel model of a KB cell was constructed and used together with an already constructed geometry and tracking 4 (GEANT4) model of the horizontal microbeam line of the Centre d'Etudes Nucl,aires de Bordeaux-Gradignan (CENBG) 3.5 MV Van de Graaf accelerator at the CENBG, France. The microbeam model was then implemented into GEANT4 for simulations of the average number of particles hitting an irradiated cell when a specified number of particles are produced in the beam line. The result shows that when irradiating the developed voxel model of a KB cell with 200 alpha particles, with a nominal energy of 3 MeV in the beam line and 2.34 MeV at the cell entrance, 100 particles hit the cell on average. The mean specific energy is 0.209 +/- A 0.019 Gy in the nucleus and 0.044 +/- A 0.001 Gy in the cytoplasm. These results are in agreement with previously published data, which indicates that this model could act as a reference model for dosimetric calculations of radiobiological experiments, and that the proposed method could be applied to build a cell model database.
  •  
50.
  • Zeitlin, C., et al. (author)
  • Nuclear fragmentation database for GCR transport code development
  • 2010
  • In: Advances in Space Research. - : Elsevier BV. - 1879-1948 .- 0273-1177. ; 46:6, s. 728-734
  • Journal article (peer-reviewed)abstract
    • A critical need for NASA is the ability to accurately model the transport of heavy ions in the Galactic Cosmic Rays (GCR) through matter, including spacecraft walls, equipment racks, etc. Nuclear interactions are of great importance in the GCR transport problem, as they can cause fragmentation of the incoming ion into lighter ions. Since the radiation dose delivered by a particle is proportional to the square of (charge/velocity), fragmentation reduces the dose delivered by incident ions. The other mechanism by which dose can be reduced is ionization energy loss, which can lead to some particles stopping in the shielding. This is the conventional notion of shielding, but it is not applicable to human spaceflight since the particles in the GCR tend to be too energetic to be stopped in the relatively thin shielding that is possible within payload mass constraints. Our group has measured a large number of fragmentation cross sections, intended to be used as input to, or for validation of, NASA's radiation transport models. A database containing over 200 charge-changing cross sections and over 2000 fragment production cross sections has been compiled. In this report, we examine in detail the contrast between fragment measurements at large acceptance and small acceptance. We use output from the PHITS Monte Carlo code to test our assumptions using as an example Ar-40 data (and simulated data) at a beam energy of 650 MeV/nucleon. We also present preliminary analysis in which isotopic resolution was attained for beryllium fragments produced by beams of B-10 and B-11. Future work on the experimental data set will focus on extracting and interpreting production cross sections for light fragments. (C) 2010 COSPAR. Published by Elsevier Ltd. All rights reserved.
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