| 1. |
- Ersmark, Tore, et al.
(författare)
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Geant4 Monte Carlo Simulations of the belt proton radiation environment on board the international space Station/Columbus
- 2007
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Ingår i: IEEE Transactions on Nuclear Science. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9499 .- 1558-1578. ; 54:No 4, s. 1444-1453
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Tidskriftsartikel (refereegranskat)abstract
- A detailed characterization of the trapped-proton-induced radiation environment on board Columbus and the International Space Station (ISS) has been carried out using the Geant4 Monte Carlo particle transport toolkit. Dose and dose equivalent rates, as well as penetrating particle spectra are presented. These results are based on detailed Geant4 geometry models of Columbus and ISS, comprising a total of about 1000 geometry volumes. Simulated trapped-proton dose rates are found to be strongly dependent on ISS altitude. Dose rates for different locations inside the Columbus cabin are presented, as well as for different models of the incident trapped-proton flux. Dose rates resulting from incident anisotropic trapped protons are found to be lower than, or equal to, those of omnidirectional models. The anisotropy induced by the asymmetric shielding distribution of Columbus/ISS is also studied. The simulated trapped-proton dose (equivalent) rates, averaged over different locations inside Columbus, are 120 mu Gy/d (154 mu Sv/d) and 79 mu Gy/d (102 mu Sv/d) for solar minimum and maximum conditions according to AP8 incident proton spectra and an ISS orbit of 380 km. The solar maximum dose rates are found to be of the same order as measurements in other modules in the present ISS.
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| 2. |
- Ersmark, Tore, et al.
(författare)
-
Geant4 Monte Carlo simulations of the galactic cosmic ray radiation environment on-board the international space station/columbus
- 2007
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Ingår i: IEEE Transactions on Nuclear Science. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9499 .- 1558-1578. ; 54:No 5, s. 1854-1862
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Tidskriftsartikel (refereegranskat)abstract
- A characterization of the Galactic Cosmic Ray (GCR) induced radiation environment on-board Columbus and the Inter-national Space Station (ISS) has been carried out using the Geant4 Monte Carlo particle transport toolkit and detailed geometry models of Columbus and ISS. Dose and dose equivalent rates, as well as penetrating particle spectra are presented. Simulation results indicate that the major part of the dose rates due to GCR protons are associated with secondary particles produced in the hull of ISS. Neutrons contribute about 15% of the GCR proton dose equivalent rate and mesons about 10%. More than 40% of the simulated GCR proton dose and dose equivalent rates are due to protons in the energy range above 10 GeV. Protons in the energy range above 50 GeV contribute only 5% to the dose rates. The total simulated dose and dose equivalent rates at solar maximum are 63 mu Gy/d and 123 mu Sv/d, respectively. The dose equivalent rate underestimates measurements made during the 2001 solar maximum. The discrepancy can be attributed to deficiencies in hadronic ion-nuclei interaction models for heavy ions and to the lack of such models above 10 GeV/N in Geant4.
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| 3. |
- Ersmark, Tore, 1977-
(författare)
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Geant4 Monte Carlo Simulations of the International Space Station Radiation Environment
- 2006
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- A detailed characterization of the proton and neutron induced radiation environment onboard Columbus and the International Space Station (ISS) has been carried out using the Geant4 Monte Carlo particle transport toolkit. Dose and dose equivalent rates, as well as penetrating particle spectra corresponding to incident trapped protons, GCR protons, SPE protons and cosmic ray albedo neutrons are presented. These results are based on detailed Geant4 geometry models of Columbus and ISS, comprising a total of about 750 and 350 geometry volumes, respectively. Additionally, the physics models of Geant4 have been validated with respect to space radiation shielding applications. Geant4 physics configurations based on the “Binary Cascade” and “Bertini Cascade” models of hadronic reactions were found to adequately model the particle interactions of the relevant space radiation fields. Other studied Geant4 models of hadronic reactions were found to be unsatisfactory for this application. Calculated trapped proton dose rates are found to be strongly dependent on ISS altitude. Dose rates for different locations inside the Columbus cabin are presented, as well as for different models of the incident space radiation flux. Dose rates resulting from incident anisotropic trapped protons are found to be lower, or equal to, those of omnidirectional models. The anisotropy induced by the asymmetric shielding distribution of Columbus/ISS is also studied. GCR proton dose rates are presented, and it is demonstrated that the presence of thick shielding may increase the dose rate. A possible problem using Geant4 for future studies of effects induced by high-energy GCR ions is discussed. The dose rate due to cosmic ray albedo neutrons is demonstrated to be negligible. The calculated trapped proton dose rates are 120 μGy/d and 79 μGy/d for solar minimum and maximum conditions, respectively. GCR dose rates are estimated based on calculated GCR proton dose rates to 161 μGy/d and 114 μGy/d, respectively. These dose rates are found to be compatible with experimental measurements.
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| 4. |
- Ersmark, Tore, et al.
(författare)
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Status of the DESIRE project : Geant4 physics validation studies and first results from columbus/ISS radiation simulations
- 2004
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Ingår i: IEEE NUCLEAR SCIENCE SYMPOSIUM, CONFERENCE RECORD. ; , s. 1540-1544
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The DESIRE (Dose Estimation by Simulation of the ISS Radiation Environment) project aimes to accurately calculate radiation fluxes and doses to astronauts inside the European Columbus module of the International Space Station using Geant4. Firstly physics benchmark studies have been performed and comparisons made to experimental data and other particle transport programs. This will be followed by a detailed evaluation of the incident radiation fields on the ISS and culminate with the geometry modelling and full-scale flux and dose simulations for the Columbus. Geant4 validation studies are presented here. These concern the angle and energy distribution of particles leaving irradiated targets and of energy depositions in the targets. Comparisons are made between simulations using different Geant4 physics models, experimental data and other particle transport programs. Geant4 using the "Binary Cascade" model for inelastic nucleon reactions performs very well in these comparisons but some issues with other models remain to be resolved if these models are to be used for space radiation shielding applications. Results of Geant4 simulations of the transport of relevant radiation field components through the hull of the Columbus/ISS are also presented.
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| 5. |
- Ersmark, Tore, et al.
(författare)
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Status of the DESIRE project : Geant4 physics validation studies and first results from columbus/ISS radiation simulations
- 2004
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Ingår i: IEEE Transactions on Nuclear Science. - 0018-9499 .- 1558-1578. ; 51:4, s. 1378-1384
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Tidskriftsartikel (refereegranskat)abstract
- The Dose Estimation by Simulation of the ISS Radiation Environment (DESIRE) project aims to accurately calculate radiation fluxes and doses to astronauts inside the European Columbus module of the International Space Station using Geant4. Since Geant4 has not been previously used for this type of application it needs to be validated. This will be followed by a detailed evaluation of the incident radiation fields on ISS and culminate with the geometry modeling and full-scale flux and dose simulations for Columbus. Geant4 validation studies and comparisons to other tools are presented. These concern the angle and energy distributions of particles leaving irradiated targets and of energy depositions in the targets. Comparisons are made between simulations using different Geant4 physics models, experimental data, and other particle transport programs. Geant4 using the Binary Cascade model for inelastic nucleon reactions performs very well in these comparisons, but some issues with other models remain to be resolved if they are to be used for space radiation shielding applications. Results of Geant4 simulations of the transport of some relevant radiation field components through the hull of a simplified model of Columbus are also presented.
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| 6. |
- Karjalainen, Eeva-Liisa, 1980-, et al.
(författare)
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Optimization of Model Parameters for Describing the Amide I Spectrum of a Large Set of Proteins
- 2012
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Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207. ; 116:16, s. 4831-4842
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Tidskriftsartikel (refereegranskat)abstract
- A new simulation protocol for the prediction of the infrared absorption of the amide I vibration of proteins was developed. The method incorporates known effects on the intrinsic frequencies (backbone conformation, interpeptide and peptide-solvent hydrogen bonding) and couplings (nearest neighbor coupling, transition dipole coupling) of amide I oscillators in a parametrized manner. Model parameters for the simulation of amide I spectra were determined through fitting and optimization of simulated spectra to experimentally measured infrared spectra of 44 proteins that represent maximum structural variation in terms of different folds and secondary structure contents. Prediction of protein spectra using the optimized parameters resulted in good agreement with experimental spectra and in a considerable improvement compared to a description involving only transition dipole coupling.
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