MEASUREMENT OF DIFFERENT COMPONENTS OF SECONDARY RADIATION ONBOARD INTERNATIONAL SPACE STATION BY MEANS OF PASSIVE DETECTORS

MEASUREMENT OF DIFFERENT COMPONENTS OF SECONDARY RADIATION ONBOARD INTERNATIONAL SPACE STATION BY... Abstract The evaluation of different components of secondary radiation (charged fragments and neutrons) onboard ISS is described. Solid-state nuclear track detectors CR-39™ were applied for the measurements of short-range nuclear fragments, while the measurements of neutrons were carried out by means of thermo-luminescent dosimeters with various concentrations of 6Li and 7Li. The flux of charged secondaries and the gamma-equivalent neutron dose are presented in function of the low-LET dose in various modules of the Russian segment of ISS. INTRODUCTION Dosimetric measurements made aboard different spacecrafts in low earth orbit (LEO) illustrate the significant contribution made to dose and dose equivalent from secondary radiation(1). Secondaries produced in nuclear interactions caused by high energy primaries can possess a significant radiobiological effectiveness during the space flight. The composition of this fraction of space radiation includes mainly high-LET short-range charged particles and neutrons of different energies. Generation of secondaries is subject to various factors: location onboard, shielding, local mass distribution. That is why their investigation is generally more complicated in comparison with primary fluxes(2). Passive detectors, in particular solid-state nuclear track detectors (SSNTD) and thermo-luminescent dosimeters (TLD) proved to be reliable in continuous space projects(3) for composition, flux and dose measurement in mixed space radiation. Track detector technique is suitable to identify short-range particles originated in the bulk of detector due to nuclear interactions(2). These events can be accounted for secondaries as opposed to ‘primaries’ that reach detector from outside. It is important to mention that composition of these ‘primaries’ contains secondary particles generated in the spacecraft shielding and interior as well. However, it is hardly possible to distinguish these fractions of ‘primaries’ by available instruments. For this reason all of them can be considered as primaries. As for secondaries, they are born in fragmentations of the same light nuclei of Carbon and Oxygen in detector and biological tissue. That’s why it is possible to evaluate the flux of secondaries in tissue-equivalent medium by particle track measurement in CR-39™ detector. The goal of this work is investigation of secondary charged particles and neutrons. All measurements were carried out by several scientific groups onboard International Space Station (ISS) in various periods of time. Moreover, alternative track scanning and data analysis were applied to evaluate the contribution of nuclear fragments in SSNTD. MATERIALS AND METHODS Passive detector sets comprised SSNTDs and TLDs of different types. The Russian research group used CR-39 (Trade name: Tastrak, TASL Ltd., Bristol, UK) and NatLiF:Mg,Ti (Trade name: DTG-4, ROSATOM, Russia). The Hungarian research group applied two types of TLDs: 6LiF:Mg,Ti (Trade name: MTS-6) and 7LiF:Mg,Ti (Trade name: MTS-7) produced by the Institute of Nuclear Physics (IFJ), Krakow, Poland. The Czech research group used CR-39 (Trade name: TD-1 HARZLAS, Nagase Landauer Ltd., Japan) and CaSO4:Dy produced by Laboratories Protecta Ltd. In case of SSNTDs different methods for detector treatment, track scanning and data processing were used. The Russian research group applied one-step etching, and tracks from short-range charged secondaries and long-range primaries were manually scanned with the use of optical microscope Carl Zeiss® AxioScope.A1 with magnification of 100–1000×. In scanning of oblique tracks, the parameter of projected length was measured additionally to the track pit diameters. In the case of over-etched tracks, the bottom sphere radius was evaluated. It gave it possible to determine mean sensitivity value and to estimate the depth of track formation of the bulk of detector. Detailed description of the SSNTD evaluation procedure is given in(4). The Czech research group employed two-step etching. Detector surface was analyzed with the automated microscope system HSP-1000 and track measurement software PitFit from SEIKO® Precision(5). In track scanning minor and major axes were measured only. To distinguish secondaries generated in nuclear interactions, individual track shape evolution was considered at the same positions and different depths in detector(6). All TLDs were red out conventionally, details are given in(7) for the Czech detectors, and in(8) for the Russian and the Hungarian detectors. As for neutron measurement, the technique of 6Li/7Li pair detectors was applied similarly to(9). The 6Li nucleus has high cross section for (n,α) reaction at neutron energy below 200 keV as opposed to the 7Li nucleus. Doses for low-ionizing space radiation component are taken from MTS-7 readings(10) and denoted in the text as DTLD(7Li). The gamma-equivalent neutron doses were obtained as the difference of MTS-6 and MTS-7 readings and denoted as Dn γ-eq.. The difference between MTS-6 and MTS-7 indicate presence of thermal and epithermal neutrons. It is proportional to the flux of neutrons in this energy range. Detailed description of dose evaluation is given in(8). The experimental TLD and SSNTD data were convolved using the procedure described in(11). Eventually, TLD dose DTLD, SSNTD dose DSSNTD and dose equivalent HSSNTD, total absorbed dose Dtotal, total dose equivalent Htotal and low-LET dose Dlow-LET were obtained. Detectors were flown onboard the Russian Segment of the International Space Station between 2014 and 2016: First series of Russian detectors were exposed in the framework of the Matryoshka-R project in Pirs docking module (panel 102); MRM-2 module (panel 102) and SM module (panels 325, 461, 323, 305) for 261 days starting on 1 October 2015. Czech detectors were exposed at the same locations in Pirs and SM modules in an earlier flight (May–October 2009)(12). Second, third, fourth and fifth series of detectors were exposed in the framework of the Phoenix project in Pirs docking module (panel 103); MRM-2 module (panel 103) and SM module (panel 436) for 199, 383, 572 and 653 days starting on November 24, 2014 (see(8, 13) for details). Fluxes of secondaries were measured in all series by SSNTDs. Neutrons were measured in the second, third and fourth series only. RESULTS AND DISCUSSION Figure 1 compares fluxes of short-range and long-range particles measured by the Russian research group onboard ISS in the course of the Phoenix experiment(13). Figure 1. View largeDownload slide Comparison of short-range and long-range particle fluxes measured onboard ISS by CR-39™ SSNTD. Detectors were exposed in the Mini-Research Module 2 (panel 103) for 383 days starting on 24 November 2014 (Phoenix project(13)). Figure 1. View largeDownload slide Comparison of short-range and long-range particle fluxes measured onboard ISS by CR-39™ SSNTD. Detectors were exposed in the Mini-Research Module 2 (panel 103) for 383 days starting on 24 November 2014 (Phoenix project(13)). The fluxes of long-range and short-range particles are comparable at values of 80–200 keV/μm. At higher LET (200–800 keV/μm), the flux of secondaries exceeds the long-range particles flux, the difference amounts 0.5–1.0 orders of magnitude. Similar results were obtained previously(6, 13). Experimental points in Figure 1 show smooth flux decrease in the whole LET range with the exception of the interval between 100 and 200 keV/μm, where a weak local growth can be seen. For long-range particles, it is possibly due to the influence of relativistic Fe nuclei(14). On the other hand, this particular region corresponds to LET values of stopping protons, deuterons and He-group nuclei which are the main part of short-range secondaries(15). Table 1 shows dose values in three ISS compartments obtained by different detectors. Values of Dshort-range and Hshort-range in Table 1 are obtained by track detectors taking into account short-range particles only. Track detector doses DSSNTD and HSSNTD are the sums of long-range and short-range components. Table 1. Dose data measured in three ISS compartments for several timeframes of Phoenix mission. Dose value Pirs MRM-2 SM DTLD, mGy 129 ± 13a 107 ± 8 50 ± 3 209 ± 16b 187 ± 9 100 ± 6 310 ± 28c 273 ± 14 138 ± 18 364 ± 39d 311 ± 21 159 ± 20 DSSNTD, mGy 22 ± 1 6 ± 1 8 ± 1 28 ± 1 14 ± 1 10 ± 1 41 ± 1 17 ± 1 15 ± 1 45 ± 1 24 ± 1 19 ± 1 Dshort-range, mGy 4.8 ± 0.5 2.0 ± 0.3 3.2 ± 0.5 5.7 ± 0.6 5.4 ± 0.6 3.4 ± 0.3 7.9 ± 0.8 5.6 ± 0.4 3.6 ± 0.4 9.3 ± 1.0 6.3 ± 0.5 5.1 ± 0.5 HSSNTD, mSv 204 ± 7 98 ± 6 109 ± 6 331 ± 12 218 ± 7 152 ± 5 530 ± 17 264 ± 9 222 ± 7 538 ± 21 342 ± 10 275 ± 10 Hshort-range, mSv 71 ± 6 34 ± 6 53 ± 7 90 ± 9 100 ± 11 62 ± 4 134 ± 12 103 ± 7 64 ± 5 160 ± 15 115 ± 8 92 ± 8 Dlow-LET, mGy 115 ± 13 103 ± 8 47 ± 3 192 ± 16 180 ± 9 95 ± 6 285 ± 28 264 ± 14 130 ± 18 337 ± 39 298 ± 21 148 ± 20 Dtotal, mGy 136 ± 13 110 ± 8 54 ± 3 220 ± 16 194 ± 9 105 ± 6 326 ± 28 280 ± 14 145 ± 18 381 ± 29 322 ± 21 168 ± 20 Htotal, mSv 319 ± 15 201 ± 10 155 ± 7 523 ± 20 398 ± 12 247 ± 8 815 ± 33 527 ± 17 352 ± 19 869 ± 44 641 ± 23 430 ± 22 Dose value Pirs MRM-2 SM DTLD, mGy 129 ± 13a 107 ± 8 50 ± 3 209 ± 16b 187 ± 9 100 ± 6 310 ± 28c 273 ± 14 138 ± 18 364 ± 39d 311 ± 21 159 ± 20 DSSNTD, mGy 22 ± 1 6 ± 1 8 ± 1 28 ± 1 14 ± 1 10 ± 1 41 ± 1 17 ± 1 15 ± 1 45 ± 1 24 ± 1 19 ± 1 Dshort-range, mGy 4.8 ± 0.5 2.0 ± 0.3 3.2 ± 0.5 5.7 ± 0.6 5.4 ± 0.6 3.4 ± 0.3 7.9 ± 0.8 5.6 ± 0.4 3.6 ± 0.4 9.3 ± 1.0 6.3 ± 0.5 5.1 ± 0.5 HSSNTD, mSv 204 ± 7 98 ± 6 109 ± 6 331 ± 12 218 ± 7 152 ± 5 530 ± 17 264 ± 9 222 ± 7 538 ± 21 342 ± 10 275 ± 10 Hshort-range, mSv 71 ± 6 34 ± 6 53 ± 7 90 ± 9 100 ± 11 62 ± 4 134 ± 12 103 ± 7 64 ± 5 160 ± 15 115 ± 8 92 ± 8 Dlow-LET, mGy 115 ± 13 103 ± 8 47 ± 3 192 ± 16 180 ± 9 95 ± 6 285 ± 28 264 ± 14 130 ± 18 337 ± 39 298 ± 21 148 ± 20 Dtotal, mGy 136 ± 13 110 ± 8 54 ± 3 220 ± 16 194 ± 9 105 ± 6 326 ± 28 280 ± 14 145 ± 18 381 ± 29 322 ± 21 168 ± 20 Htotal, mSv 319 ± 15 201 ± 10 155 ± 7 523 ± 20 398 ± 12 247 ± 8 815 ± 33 527 ± 17 352 ± 19 869 ± 44 641 ± 23 430 ± 22 aThe first line of data in every individual cell corresponds to the 199 days exposure starting on 24 November 2014. These particular data were published earlier in(8) and(13) and given here after the final correction. bThe second line of data in every individual cell corresponds to the 383 days exposure starting on 24 November 2014. cThe third line of data in every individual cell corresponds to the 572 days exposure starting on 24 November 2014. dThe fourth line of data in every individual cell corresponds to the 653 days exposure starting on 24 November 2014. Table 1. Dose data measured in three ISS compartments for several timeframes of Phoenix mission. Dose value Pirs MRM-2 SM DTLD, mGy 129 ± 13a 107 ± 8 50 ± 3 209 ± 16b 187 ± 9 100 ± 6 310 ± 28c 273 ± 14 138 ± 18 364 ± 39d 311 ± 21 159 ± 20 DSSNTD, mGy 22 ± 1 6 ± 1 8 ± 1 28 ± 1 14 ± 1 10 ± 1 41 ± 1 17 ± 1 15 ± 1 45 ± 1 24 ± 1 19 ± 1 Dshort-range, mGy 4.8 ± 0.5 2.0 ± 0.3 3.2 ± 0.5 5.7 ± 0.6 5.4 ± 0.6 3.4 ± 0.3 7.9 ± 0.8 5.6 ± 0.4 3.6 ± 0.4 9.3 ± 1.0 6.3 ± 0.5 5.1 ± 0.5 HSSNTD, mSv 204 ± 7 98 ± 6 109 ± 6 331 ± 12 218 ± 7 152 ± 5 530 ± 17 264 ± 9 222 ± 7 538 ± 21 342 ± 10 275 ± 10 Hshort-range, mSv 71 ± 6 34 ± 6 53 ± 7 90 ± 9 100 ± 11 62 ± 4 134 ± 12 103 ± 7 64 ± 5 160 ± 15 115 ± 8 92 ± 8 Dlow-LET, mGy 115 ± 13 103 ± 8 47 ± 3 192 ± 16 180 ± 9 95 ± 6 285 ± 28 264 ± 14 130 ± 18 337 ± 39 298 ± 21 148 ± 20 Dtotal, mGy 136 ± 13 110 ± 8 54 ± 3 220 ± 16 194 ± 9 105 ± 6 326 ± 28 280 ± 14 145 ± 18 381 ± 29 322 ± 21 168 ± 20 Htotal, mSv 319 ± 15 201 ± 10 155 ± 7 523 ± 20 398 ± 12 247 ± 8 815 ± 33 527 ± 17 352 ± 19 869 ± 44 641 ± 23 430 ± 22 Dose value Pirs MRM-2 SM DTLD, mGy 129 ± 13a 107 ± 8 50 ± 3 209 ± 16b 187 ± 9 100 ± 6 310 ± 28c 273 ± 14 138 ± 18 364 ± 39d 311 ± 21 159 ± 20 DSSNTD, mGy 22 ± 1 6 ± 1 8 ± 1 28 ± 1 14 ± 1 10 ± 1 41 ± 1 17 ± 1 15 ± 1 45 ± 1 24 ± 1 19 ± 1 Dshort-range, mGy 4.8 ± 0.5 2.0 ± 0.3 3.2 ± 0.5 5.7 ± 0.6 5.4 ± 0.6 3.4 ± 0.3 7.9 ± 0.8 5.6 ± 0.4 3.6 ± 0.4 9.3 ± 1.0 6.3 ± 0.5 5.1 ± 0.5 HSSNTD, mSv 204 ± 7 98 ± 6 109 ± 6 331 ± 12 218 ± 7 152 ± 5 530 ± 17 264 ± 9 222 ± 7 538 ± 21 342 ± 10 275 ± 10 Hshort-range, mSv 71 ± 6 34 ± 6 53 ± 7 90 ± 9 100 ± 11 62 ± 4 134 ± 12 103 ± 7 64 ± 5 160 ± 15 115 ± 8 92 ± 8 Dlow-LET, mGy 115 ± 13 103 ± 8 47 ± 3 192 ± 16 180 ± 9 95 ± 6 285 ± 28 264 ± 14 130 ± 18 337 ± 39 298 ± 21 148 ± 20 Dtotal, mGy 136 ± 13 110 ± 8 54 ± 3 220 ± 16 194 ± 9 105 ± 6 326 ± 28 280 ± 14 145 ± 18 381 ± 29 322 ± 21 168 ± 20 Htotal, mSv 319 ± 15 201 ± 10 155 ± 7 523 ± 20 398 ± 12 247 ± 8 815 ± 33 527 ± 17 352 ± 19 869 ± 44 641 ± 23 430 ± 22 aThe first line of data in every individual cell corresponds to the 199 days exposure starting on 24 November 2014. These particular data were published earlier in(8) and(13) and given here after the final correction. bThe second line of data in every individual cell corresponds to the 383 days exposure starting on 24 November 2014. cThe third line of data in every individual cell corresponds to the 572 days exposure starting on 24 November 2014. dThe fourth line of data in every individual cell corresponds to the 653 days exposure starting on 24 November 2014. Data in Table 1 illustrate the accumulation of different dose components during the flight. Mean total dose rates were 582 μGy/day in Pirs, 497 μGy/day in MRM-2 and 259 μGy/day in SM compartments. In Figure 2, short-range particles fluxes measured by SSNTD versus low-LET dose are shown for different ISS modules. Figure 2. View largeDownload slide Comparison of integral fluxes of short-range particles measured at various locations in different missions onboard ISS. Figure 2. View largeDownload slide Comparison of integral fluxes of short-range particles measured at various locations in different missions onboard ISS. It is seen from Figure 2 that the short-range particle flux increases smoothly with Dlow-LET growth for all locations. The highest secondary particle fluxes were obtained in the Pirs module. In SM and MRM-2 modules, they are approximately equal to each other. The flux of secondaries in Pirs differs from similar values in SM and MRM-2 by a factor of ~1.5 at the same dose level. This factor is kept hold for different mission timeframes. The last conclusion can be explained bearing in mind that secondaries are generated by low-ionizing primaries. The flux of primaries in Pirs module is higher due to its relatively low shielding. Mean ratio of dose from secondaries to the low-LET dose was evaluated as 0.026 ± 0.007. This estimation was derived from data in Figure 2. In Figure 3, gamma-equivalent neutron dose Dn γ-eq. versus TLD doses DTLD(7Li) are shown in different ISS compartments for the first three timeframes of the Phoenix mission (consequently: 199, 383, 572 days of exposure starting on 24 November 2014). The particular data for the 199 days of exposure were published earlier in(8) and given here jointly with dose values for the subsequent phases of the ongoing project after the final correction. Figure 3. View largeDownload slide Gamma-equivalent neutron dose Dn γ-eq. versus TLD dose DTLD(7Li) obtained in different compartments for three Phoenix missions. Lines are given for eye guidance only. Figure 3. View largeDownload slide Gamma-equivalent neutron dose Dn γ-eq. versus TLD dose DTLD(7Li) obtained in different compartments for three Phoenix missions. Lines are given for eye guidance only. The highest doses from neutrons were obtained in SM module. In Pirs and MRM-2 modules, they are equal to each other within error bars. Averaged contribution of neutrons to the dose is kept approximately invariable in every location. However, the value of this contribution can be dependent on shielding conditions, compartment total mass and local mass distribution (see Table 2). Table 2. Mean ratio of Dn γ-eq. gamma-equivalent neutron dose to TLD dose DTLD(7Li) in different compartments. ISS compartment Compartment mass, tons Dnγ-eq./ DTLD(7Li) Service module 20.3 0.19 Mini-Research Module No.2 4.4 0.07 Pirs docking module 3.7 0.08 ISS compartment Compartment mass, tons Dnγ-eq./ DTLD(7Li) Service module 20.3 0.19 Mini-Research Module No.2 4.4 0.07 Pirs docking module 3.7 0.08 Table 2. Mean ratio of Dn γ-eq. gamma-equivalent neutron dose to TLD dose DTLD(7Li) in different compartments. ISS compartment Compartment mass, tons Dnγ-eq./ DTLD(7Li) Service module 20.3 0.19 Mini-Research Module No.2 4.4 0.07 Pirs docking module 3.7 0.08 ISS compartment Compartment mass, tons Dnγ-eq./ DTLD(7Li) Service module 20.3 0.19 Mini-Research Module No.2 4.4 0.07 Pirs docking module 3.7 0.08 In Table 3, mean dose rate variations are presented for different periods of the Phoenix mission. The values are calculated for SM module by subsequent subtraction of corresponding doses from Table 1 following the procedure proposed in(16). The results thus obtained were compared with the readings of the onboard Radiation Monitoring System R-16(17) for the relevant timeframes. The ISS orbital parameters at the same time intervals are given in Table 3 for reference. Table 3. Dose variations in SM module as observed in four subsequent sessions of the Phoenix project. Timeframe, DOY starting on 24 November 2014 0–199 200–383 384–572 573–653 Mean total dose rate, μGy/day 271 ± 15 277 ± 22 212 ± 35 284 ± 44 *R-16 mean dose rate, μGy/day 262 ± 38 267 ± 32 278 ± 28 279 ± 25 ISS altitude range: Apogee, km 435–412 425–415 426–415 422–420 Perigee, km 410–395 405–397 406–395 404–401 Timeframe, DOY starting on 24 November 2014 0–199 200–383 384–572 573–653 Mean total dose rate, μGy/day 271 ± 15 277 ± 22 212 ± 35 284 ± 44 *R-16 mean dose rate, μGy/day 262 ± 38 267 ± 32 278 ± 28 279 ± 25 ISS altitude range: Apogee, km 435–412 425–415 426–415 422–420 Perigee, km 410–395 405–397 406–395 404–401 *R-16 mean dose rates are obtained from daily data by method(18). Table 3. Dose variations in SM module as observed in four subsequent sessions of the Phoenix project. Timeframe, DOY starting on 24 November 2014 0–199 200–383 384–572 573–653 Mean total dose rate, μGy/day 271 ± 15 277 ± 22 212 ± 35 284 ± 44 *R-16 mean dose rate, μGy/day 262 ± 38 267 ± 32 278 ± 28 279 ± 25 ISS altitude range: Apogee, km 435–412 425–415 426–415 422–420 Perigee, km 410–395 405–397 406–395 404–401 Timeframe, DOY starting on 24 November 2014 0–199 200–383 384–572 573–653 Mean total dose rate, μGy/day 271 ± 15 277 ± 22 212 ± 35 284 ± 44 *R-16 mean dose rate, μGy/day 262 ± 38 267 ± 32 278 ± 28 279 ± 25 ISS altitude range: Apogee, km 435–412 425–415 426–415 422–420 Perigee, km 410–395 405–397 406–395 404–401 *R-16 mean dose rates are obtained from daily data by method(18). It can be seen from Table 3 that passive detectors’ data are in reasonable agreement with R-16 readings. Besides that, no significant change in the radiation field onboard SM module was observed in the period 24 November 2014–7 September 2016. CONCLUSION The following conclusions can be drawn from the experimental results. Contribution from nuclear fragments to the LET spectrum is the most significant in the range of 100–1000 keV/μm (in H2O), that is in a good agreement with previous findings(1, 2, 4, 6, 13). Presumably, the flux of nuclear fragments correlates with the dose from primary low-LET particles. The character of this correlation varies with shielding conditions. The contribution from fragments to the total absorbed dose varies from 2 to 6 %, and amounts to 16–34 % to the total dose equivalent (see Table 1). Gamma-equivalent dose from neutrons amounts to 7–19 % from TLD (7Li) dose and can be dependent on the shielding conditions and spacecraft mass (see Table 2). Further efforts should be focused on the more detailed characterization of nuclear fragments produced in tissue-equivalent media under the impact of cosmic radiation. ACKNOWLEDGMENTS Authors would like to thank Prof. M.Yu. Karganov and Acad. V.M. Baranov (Research Institute for Space Medicine of the Federal Biomedical Agency of Russia, Moscow, Russia) for kindly provided possibility to participate in the Phoenix space project onboard ISS (under the non-monetary Agreement on Technical and Scientific Cooperation between NRNU MEPhI and Res. Inst. Space Med. FBMA Rus. №3-16, dated on 26 September 2016). K.O.I. expresses his gratitude to Mr. Peter E. Parfenov (NRNU MEPhI, Moscow, Russia) for helpful advices on data processing. ISS ballistic data and R-16 daily dose dataset are kindly provided by Prof. V.V. Tsetlin and Dr. V.A. Bondarenko (IBMP RAS, Moscow, Russia) and highly appreciated. FUNDING This work was partly performed within the framework of the National Research Nuclear University MEPhI (Moscow Engineering Physics Institute) Academic Excellence Project (contract № 02.а03.21.0005). REFERENCES 1 Benton , E. R. , Benton , E. V. and Frank , A. L. Passive dosimetry aboard the Mir Orbital Station: internal measurements . Radiat. Meas. 35 , 439 – 455 ( 2002 ). Google Scholar CrossRef Search ADS PubMed 2 Kushin , V. V. Measurement of LET distribution and absorbed dose from secondary particles onboard the spacecraft . Radiat. Prot. Dosim. 141 , 199 – 204 ( 2010 ). Google Scholar CrossRef Search ADS 3 Benton , E. V. and Benton , E. R. Space radiation dosimetry in low-Earth orbit and beyond . Nucl. Instrum. Methods Phys. Res. B 184 , 255 – 294 ( 2001 ). Google Scholar CrossRef Search ADS PubMed 4 Inozemtsev , K. O. , Kushin , V. V. , Kodaira , S. and Shurshakov , V. A. Observation of fragmentation events caused by space radiation: Contribution to the LET spectrum as measured with CR-39 track detectors . Radiat. Meas. 95 , 37 – 43 ( 2016 ). Google Scholar CrossRef Search ADS 5 Yasuda , N. , Namiki , K. , Honma , Y. , Umeshima , Y. , Marumo , Y. , Ishii , H. and Benton , E. R. Development of a high speed imaging microscope and new software for nuclear track detector analysis . Radiat. Meas. 40 , 311 – 315 ( 2005 ). Google Scholar CrossRef Search ADS 6 Ambrožová , I. , Davídková , M. , Brabcová , K. P. , Tolochek , R. V. and Shurshakov , V. A. Contribution of different particles onboard ISS measured with track etched detectors . Radiat. Prot. Dosim. ( 2017 ). DOI:10.1093/rpd/ncx189 7 Ambrožová , I. , Pachnerová Brabcová , K. , Kubančák , J. , Šlegl , J. , Tolochek , R. V. , Ivanova , O. A. and Shurshakov , V. A. Cosmic radiation monitoring at low-Earth orbit by means of thermoluminescence and plastic nuclear track detectors . Radiat. Meas. 106 , 262 – 266 ( 2017 ). Google Scholar CrossRef Search ADS 8 Strádi , A. , Szabó , J. , Inozemtsev , K. O. , Kushin , V. V. , Tolochek , R. V. , Shurshakov , V. A. , Alchinova , I. B. and Karganov , M. Yu. Comparative radiation measurements in the Russian segment of the International Space Station by applying passive dosimeters . Radiat. Meas. 106 , 267 – 272 ( 2017 ). Google Scholar CrossRef Search ADS 9 Obryk , B. , Bilski , P. , Budzanowski , M. , Fuerstner , M. , Ilgner , C. , Jaquenod , F. , Olko , P. , Puchalska , M. and Vincke , H. The response of different types of TL lithium fluoride detectors to high-energy mixed radiation fields . Radiat. Meas. 43 , 1144 – 1148 ( 2008 ). Google Scholar CrossRef Search ADS 10 Strádi , A. , Pálfalvi , J. K. , Szabó , J. , Pázmándi , T. , Ivanova , O. A. and Shurshakov , V. A. Cosmic radiation measurements on the Foton-M4 satellite by passive detectors . Acta Astronaut. 131 , 110 – 112 ( 2017 ). Google Scholar CrossRef Search ADS 11 Hajek , M. , Berger , T. , Vana , N. , Fugger , M. , Pálfalvi , J. K. , Szabó , J. , Eördöghet , I. , Akatov , Y. A. , Arkhangelsky , V. V. and Shurshakov , V. A. Convolution of TLD and SSNTD measurements during the BRADOS-1 experiment onboard ISS (2001) . Radiat. Meas. 43 , 1231 – 1236 ( 2008 ). Google Scholar CrossRef Search ADS 12 Ambrožová , I. , Brabcová , K. , Spurný , F. , Shurshakov , V. A. , Kartsev , I. S. and Tolochek , R. V. Monitoring onboard spacecraft by means of passive detectors . Radiat. Prot. Dosim. 144 , 605 – 610 ( 2011 ). Google Scholar CrossRef Search ADS 13 Karganov , M. Yu. , Alchinova , I. B. , Yakovenko , E. N. , Kushin , V. V. , Inozemtsev , K. O. , Strádi , A. , Szabó , J. , Shurshakov , V. A. and Tolochek , R. V. The ‘PHOENIX’ space experiment: study of space radiation impact on cells genetic apparatus on board the international space station . J. Phys.: Conf. Ser. 784 , 012024 ( 2017 ). Google Scholar CrossRef Search ADS 14 Doke , T. , Hayashi , T. , Kikuchi , J. , Sakaguchi , T. , Terasawa , K. , Yoshihira , E. , Nagaoka , S. , Nakano , T. and Takahashi , S. Measurements of LET-distribution, dose equivalent and quality factor with the RRMD-III on the Space Shuttle Missions STS-84, -89 and -91 . Radiat. Meas. 33 , 373 – 387 ( 2001 ). Google Scholar CrossRef Search ADS PubMed 15 Pálfalvi , J. K. Fluence and dose of mixed space radiation by SSNTDs achievements and constraints . Radiat. Meas. 44 , 724 – 728 ( 2009 ). Google Scholar CrossRef Search ADS 16 Kodaira , S. et al. . Analysis of radiation dose variations measured by passive dosimeters onboard the International Space Station during the solar quiet period (2007–2008) . Radiat. Meas. 49 , 95 – 102 ( 2013 ). Google Scholar CrossRef Search ADS 17 Tverskaya , L. V. , Panasyuk , M. I. , Reizman , S. Ya. , Sosnovets , E. N. , Teltsov , M. V. and Tsetlin , V. V. The features of radiation dose variations onboard ISS and Mir space station: comparative study . Adv. Space Res. 34 , 1424 – 1428 ( 2004 ). Google Scholar CrossRef Search ADS PubMed 18 Badhwar , G. D. , Shurshakov , V. A. and Tsetlin , V. V. Solar modulation of dose rate onboard the Mir station . IEEE Trans. Nucl. Sci. 44 , 2529 – 2541 ( 1997 ). Google Scholar CrossRef Search ADS PubMed © The Author(s) 2018. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/about_us/legal/notices) http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Radiation Protection Dosimetry Oxford University Press

MEASUREMENT OF DIFFERENT COMPONENTS OF SECONDARY RADIATION ONBOARD INTERNATIONAL SPACE STATION BY MEANS OF PASSIVE DETECTORS

Loading next page...
 
/lp/ou_press/measurement-of-different-components-of-secondary-radiation-onboard-jA0p8005Ut
Publisher
Oxford University Press
Copyright
© The Author(s) 2018. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com
ISSN
0144-8420
eISSN
1742-3406
D.O.I.
10.1093/rpd/ncy043
Publisher site
See Article on Publisher Site

Abstract

Abstract The evaluation of different components of secondary radiation (charged fragments and neutrons) onboard ISS is described. Solid-state nuclear track detectors CR-39™ were applied for the measurements of short-range nuclear fragments, while the measurements of neutrons were carried out by means of thermo-luminescent dosimeters with various concentrations of 6Li and 7Li. The flux of charged secondaries and the gamma-equivalent neutron dose are presented in function of the low-LET dose in various modules of the Russian segment of ISS. INTRODUCTION Dosimetric measurements made aboard different spacecrafts in low earth orbit (LEO) illustrate the significant contribution made to dose and dose equivalent from secondary radiation(1). Secondaries produced in nuclear interactions caused by high energy primaries can possess a significant radiobiological effectiveness during the space flight. The composition of this fraction of space radiation includes mainly high-LET short-range charged particles and neutrons of different energies. Generation of secondaries is subject to various factors: location onboard, shielding, local mass distribution. That is why their investigation is generally more complicated in comparison with primary fluxes(2). Passive detectors, in particular solid-state nuclear track detectors (SSNTD) and thermo-luminescent dosimeters (TLD) proved to be reliable in continuous space projects(3) for composition, flux and dose measurement in mixed space radiation. Track detector technique is suitable to identify short-range particles originated in the bulk of detector due to nuclear interactions(2). These events can be accounted for secondaries as opposed to ‘primaries’ that reach detector from outside. It is important to mention that composition of these ‘primaries’ contains secondary particles generated in the spacecraft shielding and interior as well. However, it is hardly possible to distinguish these fractions of ‘primaries’ by available instruments. For this reason all of them can be considered as primaries. As for secondaries, they are born in fragmentations of the same light nuclei of Carbon and Oxygen in detector and biological tissue. That’s why it is possible to evaluate the flux of secondaries in tissue-equivalent medium by particle track measurement in CR-39™ detector. The goal of this work is investigation of secondary charged particles and neutrons. All measurements were carried out by several scientific groups onboard International Space Station (ISS) in various periods of time. Moreover, alternative track scanning and data analysis were applied to evaluate the contribution of nuclear fragments in SSNTD. MATERIALS AND METHODS Passive detector sets comprised SSNTDs and TLDs of different types. The Russian research group used CR-39 (Trade name: Tastrak, TASL Ltd., Bristol, UK) and NatLiF:Mg,Ti (Trade name: DTG-4, ROSATOM, Russia). The Hungarian research group applied two types of TLDs: 6LiF:Mg,Ti (Trade name: MTS-6) and 7LiF:Mg,Ti (Trade name: MTS-7) produced by the Institute of Nuclear Physics (IFJ), Krakow, Poland. The Czech research group used CR-39 (Trade name: TD-1 HARZLAS, Nagase Landauer Ltd., Japan) and CaSO4:Dy produced by Laboratories Protecta Ltd. In case of SSNTDs different methods for detector treatment, track scanning and data processing were used. The Russian research group applied one-step etching, and tracks from short-range charged secondaries and long-range primaries were manually scanned with the use of optical microscope Carl Zeiss® AxioScope.A1 with magnification of 100–1000×. In scanning of oblique tracks, the parameter of projected length was measured additionally to the track pit diameters. In the case of over-etched tracks, the bottom sphere radius was evaluated. It gave it possible to determine mean sensitivity value and to estimate the depth of track formation of the bulk of detector. Detailed description of the SSNTD evaluation procedure is given in(4). The Czech research group employed two-step etching. Detector surface was analyzed with the automated microscope system HSP-1000 and track measurement software PitFit from SEIKO® Precision(5). In track scanning minor and major axes were measured only. To distinguish secondaries generated in nuclear interactions, individual track shape evolution was considered at the same positions and different depths in detector(6). All TLDs were red out conventionally, details are given in(7) for the Czech detectors, and in(8) for the Russian and the Hungarian detectors. As for neutron measurement, the technique of 6Li/7Li pair detectors was applied similarly to(9). The 6Li nucleus has high cross section for (n,α) reaction at neutron energy below 200 keV as opposed to the 7Li nucleus. Doses for low-ionizing space radiation component are taken from MTS-7 readings(10) and denoted in the text as DTLD(7Li). The gamma-equivalent neutron doses were obtained as the difference of MTS-6 and MTS-7 readings and denoted as Dn γ-eq.. The difference between MTS-6 and MTS-7 indicate presence of thermal and epithermal neutrons. It is proportional to the flux of neutrons in this energy range. Detailed description of dose evaluation is given in(8). The experimental TLD and SSNTD data were convolved using the procedure described in(11). Eventually, TLD dose DTLD, SSNTD dose DSSNTD and dose equivalent HSSNTD, total absorbed dose Dtotal, total dose equivalent Htotal and low-LET dose Dlow-LET were obtained. Detectors were flown onboard the Russian Segment of the International Space Station between 2014 and 2016: First series of Russian detectors were exposed in the framework of the Matryoshka-R project in Pirs docking module (panel 102); MRM-2 module (panel 102) and SM module (panels 325, 461, 323, 305) for 261 days starting on 1 October 2015. Czech detectors were exposed at the same locations in Pirs and SM modules in an earlier flight (May–October 2009)(12). Second, third, fourth and fifth series of detectors were exposed in the framework of the Phoenix project in Pirs docking module (panel 103); MRM-2 module (panel 103) and SM module (panel 436) for 199, 383, 572 and 653 days starting on November 24, 2014 (see(8, 13) for details). Fluxes of secondaries were measured in all series by SSNTDs. Neutrons were measured in the second, third and fourth series only. RESULTS AND DISCUSSION Figure 1 compares fluxes of short-range and long-range particles measured by the Russian research group onboard ISS in the course of the Phoenix experiment(13). Figure 1. View largeDownload slide Comparison of short-range and long-range particle fluxes measured onboard ISS by CR-39™ SSNTD. Detectors were exposed in the Mini-Research Module 2 (panel 103) for 383 days starting on 24 November 2014 (Phoenix project(13)). Figure 1. View largeDownload slide Comparison of short-range and long-range particle fluxes measured onboard ISS by CR-39™ SSNTD. Detectors were exposed in the Mini-Research Module 2 (panel 103) for 383 days starting on 24 November 2014 (Phoenix project(13)). The fluxes of long-range and short-range particles are comparable at values of 80–200 keV/μm. At higher LET (200–800 keV/μm), the flux of secondaries exceeds the long-range particles flux, the difference amounts 0.5–1.0 orders of magnitude. Similar results were obtained previously(6, 13). Experimental points in Figure 1 show smooth flux decrease in the whole LET range with the exception of the interval between 100 and 200 keV/μm, where a weak local growth can be seen. For long-range particles, it is possibly due to the influence of relativistic Fe nuclei(14). On the other hand, this particular region corresponds to LET values of stopping protons, deuterons and He-group nuclei which are the main part of short-range secondaries(15). Table 1 shows dose values in three ISS compartments obtained by different detectors. Values of Dshort-range and Hshort-range in Table 1 are obtained by track detectors taking into account short-range particles only. Track detector doses DSSNTD and HSSNTD are the sums of long-range and short-range components. Table 1. Dose data measured in three ISS compartments for several timeframes of Phoenix mission. Dose value Pirs MRM-2 SM DTLD, mGy 129 ± 13a 107 ± 8 50 ± 3 209 ± 16b 187 ± 9 100 ± 6 310 ± 28c 273 ± 14 138 ± 18 364 ± 39d 311 ± 21 159 ± 20 DSSNTD, mGy 22 ± 1 6 ± 1 8 ± 1 28 ± 1 14 ± 1 10 ± 1 41 ± 1 17 ± 1 15 ± 1 45 ± 1 24 ± 1 19 ± 1 Dshort-range, mGy 4.8 ± 0.5 2.0 ± 0.3 3.2 ± 0.5 5.7 ± 0.6 5.4 ± 0.6 3.4 ± 0.3 7.9 ± 0.8 5.6 ± 0.4 3.6 ± 0.4 9.3 ± 1.0 6.3 ± 0.5 5.1 ± 0.5 HSSNTD, mSv 204 ± 7 98 ± 6 109 ± 6 331 ± 12 218 ± 7 152 ± 5 530 ± 17 264 ± 9 222 ± 7 538 ± 21 342 ± 10 275 ± 10 Hshort-range, mSv 71 ± 6 34 ± 6 53 ± 7 90 ± 9 100 ± 11 62 ± 4 134 ± 12 103 ± 7 64 ± 5 160 ± 15 115 ± 8 92 ± 8 Dlow-LET, mGy 115 ± 13 103 ± 8 47 ± 3 192 ± 16 180 ± 9 95 ± 6 285 ± 28 264 ± 14 130 ± 18 337 ± 39 298 ± 21 148 ± 20 Dtotal, mGy 136 ± 13 110 ± 8 54 ± 3 220 ± 16 194 ± 9 105 ± 6 326 ± 28 280 ± 14 145 ± 18 381 ± 29 322 ± 21 168 ± 20 Htotal, mSv 319 ± 15 201 ± 10 155 ± 7 523 ± 20 398 ± 12 247 ± 8 815 ± 33 527 ± 17 352 ± 19 869 ± 44 641 ± 23 430 ± 22 Dose value Pirs MRM-2 SM DTLD, mGy 129 ± 13a 107 ± 8 50 ± 3 209 ± 16b 187 ± 9 100 ± 6 310 ± 28c 273 ± 14 138 ± 18 364 ± 39d 311 ± 21 159 ± 20 DSSNTD, mGy 22 ± 1 6 ± 1 8 ± 1 28 ± 1 14 ± 1 10 ± 1 41 ± 1 17 ± 1 15 ± 1 45 ± 1 24 ± 1 19 ± 1 Dshort-range, mGy 4.8 ± 0.5 2.0 ± 0.3 3.2 ± 0.5 5.7 ± 0.6 5.4 ± 0.6 3.4 ± 0.3 7.9 ± 0.8 5.6 ± 0.4 3.6 ± 0.4 9.3 ± 1.0 6.3 ± 0.5 5.1 ± 0.5 HSSNTD, mSv 204 ± 7 98 ± 6 109 ± 6 331 ± 12 218 ± 7 152 ± 5 530 ± 17 264 ± 9 222 ± 7 538 ± 21 342 ± 10 275 ± 10 Hshort-range, mSv 71 ± 6 34 ± 6 53 ± 7 90 ± 9 100 ± 11 62 ± 4 134 ± 12 103 ± 7 64 ± 5 160 ± 15 115 ± 8 92 ± 8 Dlow-LET, mGy 115 ± 13 103 ± 8 47 ± 3 192 ± 16 180 ± 9 95 ± 6 285 ± 28 264 ± 14 130 ± 18 337 ± 39 298 ± 21 148 ± 20 Dtotal, mGy 136 ± 13 110 ± 8 54 ± 3 220 ± 16 194 ± 9 105 ± 6 326 ± 28 280 ± 14 145 ± 18 381 ± 29 322 ± 21 168 ± 20 Htotal, mSv 319 ± 15 201 ± 10 155 ± 7 523 ± 20 398 ± 12 247 ± 8 815 ± 33 527 ± 17 352 ± 19 869 ± 44 641 ± 23 430 ± 22 aThe first line of data in every individual cell corresponds to the 199 days exposure starting on 24 November 2014. These particular data were published earlier in(8) and(13) and given here after the final correction. bThe second line of data in every individual cell corresponds to the 383 days exposure starting on 24 November 2014. cThe third line of data in every individual cell corresponds to the 572 days exposure starting on 24 November 2014. dThe fourth line of data in every individual cell corresponds to the 653 days exposure starting on 24 November 2014. Table 1. Dose data measured in three ISS compartments for several timeframes of Phoenix mission. Dose value Pirs MRM-2 SM DTLD, mGy 129 ± 13a 107 ± 8 50 ± 3 209 ± 16b 187 ± 9 100 ± 6 310 ± 28c 273 ± 14 138 ± 18 364 ± 39d 311 ± 21 159 ± 20 DSSNTD, mGy 22 ± 1 6 ± 1 8 ± 1 28 ± 1 14 ± 1 10 ± 1 41 ± 1 17 ± 1 15 ± 1 45 ± 1 24 ± 1 19 ± 1 Dshort-range, mGy 4.8 ± 0.5 2.0 ± 0.3 3.2 ± 0.5 5.7 ± 0.6 5.4 ± 0.6 3.4 ± 0.3 7.9 ± 0.8 5.6 ± 0.4 3.6 ± 0.4 9.3 ± 1.0 6.3 ± 0.5 5.1 ± 0.5 HSSNTD, mSv 204 ± 7 98 ± 6 109 ± 6 331 ± 12 218 ± 7 152 ± 5 530 ± 17 264 ± 9 222 ± 7 538 ± 21 342 ± 10 275 ± 10 Hshort-range, mSv 71 ± 6 34 ± 6 53 ± 7 90 ± 9 100 ± 11 62 ± 4 134 ± 12 103 ± 7 64 ± 5 160 ± 15 115 ± 8 92 ± 8 Dlow-LET, mGy 115 ± 13 103 ± 8 47 ± 3 192 ± 16 180 ± 9 95 ± 6 285 ± 28 264 ± 14 130 ± 18 337 ± 39 298 ± 21 148 ± 20 Dtotal, mGy 136 ± 13 110 ± 8 54 ± 3 220 ± 16 194 ± 9 105 ± 6 326 ± 28 280 ± 14 145 ± 18 381 ± 29 322 ± 21 168 ± 20 Htotal, mSv 319 ± 15 201 ± 10 155 ± 7 523 ± 20 398 ± 12 247 ± 8 815 ± 33 527 ± 17 352 ± 19 869 ± 44 641 ± 23 430 ± 22 Dose value Pirs MRM-2 SM DTLD, mGy 129 ± 13a 107 ± 8 50 ± 3 209 ± 16b 187 ± 9 100 ± 6 310 ± 28c 273 ± 14 138 ± 18 364 ± 39d 311 ± 21 159 ± 20 DSSNTD, mGy 22 ± 1 6 ± 1 8 ± 1 28 ± 1 14 ± 1 10 ± 1 41 ± 1 17 ± 1 15 ± 1 45 ± 1 24 ± 1 19 ± 1 Dshort-range, mGy 4.8 ± 0.5 2.0 ± 0.3 3.2 ± 0.5 5.7 ± 0.6 5.4 ± 0.6 3.4 ± 0.3 7.9 ± 0.8 5.6 ± 0.4 3.6 ± 0.4 9.3 ± 1.0 6.3 ± 0.5 5.1 ± 0.5 HSSNTD, mSv 204 ± 7 98 ± 6 109 ± 6 331 ± 12 218 ± 7 152 ± 5 530 ± 17 264 ± 9 222 ± 7 538 ± 21 342 ± 10 275 ± 10 Hshort-range, mSv 71 ± 6 34 ± 6 53 ± 7 90 ± 9 100 ± 11 62 ± 4 134 ± 12 103 ± 7 64 ± 5 160 ± 15 115 ± 8 92 ± 8 Dlow-LET, mGy 115 ± 13 103 ± 8 47 ± 3 192 ± 16 180 ± 9 95 ± 6 285 ± 28 264 ± 14 130 ± 18 337 ± 39 298 ± 21 148 ± 20 Dtotal, mGy 136 ± 13 110 ± 8 54 ± 3 220 ± 16 194 ± 9 105 ± 6 326 ± 28 280 ± 14 145 ± 18 381 ± 29 322 ± 21 168 ± 20 Htotal, mSv 319 ± 15 201 ± 10 155 ± 7 523 ± 20 398 ± 12 247 ± 8 815 ± 33 527 ± 17 352 ± 19 869 ± 44 641 ± 23 430 ± 22 aThe first line of data in every individual cell corresponds to the 199 days exposure starting on 24 November 2014. These particular data were published earlier in(8) and(13) and given here after the final correction. bThe second line of data in every individual cell corresponds to the 383 days exposure starting on 24 November 2014. cThe third line of data in every individual cell corresponds to the 572 days exposure starting on 24 November 2014. dThe fourth line of data in every individual cell corresponds to the 653 days exposure starting on 24 November 2014. Data in Table 1 illustrate the accumulation of different dose components during the flight. Mean total dose rates were 582 μGy/day in Pirs, 497 μGy/day in MRM-2 and 259 μGy/day in SM compartments. In Figure 2, short-range particles fluxes measured by SSNTD versus low-LET dose are shown for different ISS modules. Figure 2. View largeDownload slide Comparison of integral fluxes of short-range particles measured at various locations in different missions onboard ISS. Figure 2. View largeDownload slide Comparison of integral fluxes of short-range particles measured at various locations in different missions onboard ISS. It is seen from Figure 2 that the short-range particle flux increases smoothly with Dlow-LET growth for all locations. The highest secondary particle fluxes were obtained in the Pirs module. In SM and MRM-2 modules, they are approximately equal to each other. The flux of secondaries in Pirs differs from similar values in SM and MRM-2 by a factor of ~1.5 at the same dose level. This factor is kept hold for different mission timeframes. The last conclusion can be explained bearing in mind that secondaries are generated by low-ionizing primaries. The flux of primaries in Pirs module is higher due to its relatively low shielding. Mean ratio of dose from secondaries to the low-LET dose was evaluated as 0.026 ± 0.007. This estimation was derived from data in Figure 2. In Figure 3, gamma-equivalent neutron dose Dn γ-eq. versus TLD doses DTLD(7Li) are shown in different ISS compartments for the first three timeframes of the Phoenix mission (consequently: 199, 383, 572 days of exposure starting on 24 November 2014). The particular data for the 199 days of exposure were published earlier in(8) and given here jointly with dose values for the subsequent phases of the ongoing project after the final correction. Figure 3. View largeDownload slide Gamma-equivalent neutron dose Dn γ-eq. versus TLD dose DTLD(7Li) obtained in different compartments for three Phoenix missions. Lines are given for eye guidance only. Figure 3. View largeDownload slide Gamma-equivalent neutron dose Dn γ-eq. versus TLD dose DTLD(7Li) obtained in different compartments for three Phoenix missions. Lines are given for eye guidance only. The highest doses from neutrons were obtained in SM module. In Pirs and MRM-2 modules, they are equal to each other within error bars. Averaged contribution of neutrons to the dose is kept approximately invariable in every location. However, the value of this contribution can be dependent on shielding conditions, compartment total mass and local mass distribution (see Table 2). Table 2. Mean ratio of Dn γ-eq. gamma-equivalent neutron dose to TLD dose DTLD(7Li) in different compartments. ISS compartment Compartment mass, tons Dnγ-eq./ DTLD(7Li) Service module 20.3 0.19 Mini-Research Module No.2 4.4 0.07 Pirs docking module 3.7 0.08 ISS compartment Compartment mass, tons Dnγ-eq./ DTLD(7Li) Service module 20.3 0.19 Mini-Research Module No.2 4.4 0.07 Pirs docking module 3.7 0.08 Table 2. Mean ratio of Dn γ-eq. gamma-equivalent neutron dose to TLD dose DTLD(7Li) in different compartments. ISS compartment Compartment mass, tons Dnγ-eq./ DTLD(7Li) Service module 20.3 0.19 Mini-Research Module No.2 4.4 0.07 Pirs docking module 3.7 0.08 ISS compartment Compartment mass, tons Dnγ-eq./ DTLD(7Li) Service module 20.3 0.19 Mini-Research Module No.2 4.4 0.07 Pirs docking module 3.7 0.08 In Table 3, mean dose rate variations are presented for different periods of the Phoenix mission. The values are calculated for SM module by subsequent subtraction of corresponding doses from Table 1 following the procedure proposed in(16). The results thus obtained were compared with the readings of the onboard Radiation Monitoring System R-16(17) for the relevant timeframes. The ISS orbital parameters at the same time intervals are given in Table 3 for reference. Table 3. Dose variations in SM module as observed in four subsequent sessions of the Phoenix project. Timeframe, DOY starting on 24 November 2014 0–199 200–383 384–572 573–653 Mean total dose rate, μGy/day 271 ± 15 277 ± 22 212 ± 35 284 ± 44 *R-16 mean dose rate, μGy/day 262 ± 38 267 ± 32 278 ± 28 279 ± 25 ISS altitude range: Apogee, km 435–412 425–415 426–415 422–420 Perigee, km 410–395 405–397 406–395 404–401 Timeframe, DOY starting on 24 November 2014 0–199 200–383 384–572 573–653 Mean total dose rate, μGy/day 271 ± 15 277 ± 22 212 ± 35 284 ± 44 *R-16 mean dose rate, μGy/day 262 ± 38 267 ± 32 278 ± 28 279 ± 25 ISS altitude range: Apogee, km 435–412 425–415 426–415 422–420 Perigee, km 410–395 405–397 406–395 404–401 *R-16 mean dose rates are obtained from daily data by method(18). Table 3. Dose variations in SM module as observed in four subsequent sessions of the Phoenix project. Timeframe, DOY starting on 24 November 2014 0–199 200–383 384–572 573–653 Mean total dose rate, μGy/day 271 ± 15 277 ± 22 212 ± 35 284 ± 44 *R-16 mean dose rate, μGy/day 262 ± 38 267 ± 32 278 ± 28 279 ± 25 ISS altitude range: Apogee, km 435–412 425–415 426–415 422–420 Perigee, km 410–395 405–397 406–395 404–401 Timeframe, DOY starting on 24 November 2014 0–199 200–383 384–572 573–653 Mean total dose rate, μGy/day 271 ± 15 277 ± 22 212 ± 35 284 ± 44 *R-16 mean dose rate, μGy/day 262 ± 38 267 ± 32 278 ± 28 279 ± 25 ISS altitude range: Apogee, km 435–412 425–415 426–415 422–420 Perigee, km 410–395 405–397 406–395 404–401 *R-16 mean dose rates are obtained from daily data by method(18). It can be seen from Table 3 that passive detectors’ data are in reasonable agreement with R-16 readings. Besides that, no significant change in the radiation field onboard SM module was observed in the period 24 November 2014–7 September 2016. CONCLUSION The following conclusions can be drawn from the experimental results. Contribution from nuclear fragments to the LET spectrum is the most significant in the range of 100–1000 keV/μm (in H2O), that is in a good agreement with previous findings(1, 2, 4, 6, 13). Presumably, the flux of nuclear fragments correlates with the dose from primary low-LET particles. The character of this correlation varies with shielding conditions. The contribution from fragments to the total absorbed dose varies from 2 to 6 %, and amounts to 16–34 % to the total dose equivalent (see Table 1). Gamma-equivalent dose from neutrons amounts to 7–19 % from TLD (7Li) dose and can be dependent on the shielding conditions and spacecraft mass (see Table 2). Further efforts should be focused on the more detailed characterization of nuclear fragments produced in tissue-equivalent media under the impact of cosmic radiation. ACKNOWLEDGMENTS Authors would like to thank Prof. M.Yu. Karganov and Acad. V.M. Baranov (Research Institute for Space Medicine of the Federal Biomedical Agency of Russia, Moscow, Russia) for kindly provided possibility to participate in the Phoenix space project onboard ISS (under the non-monetary Agreement on Technical and Scientific Cooperation between NRNU MEPhI and Res. Inst. Space Med. FBMA Rus. №3-16, dated on 26 September 2016). K.O.I. expresses his gratitude to Mr. Peter E. Parfenov (NRNU MEPhI, Moscow, Russia) for helpful advices on data processing. ISS ballistic data and R-16 daily dose dataset are kindly provided by Prof. V.V. Tsetlin and Dr. V.A. Bondarenko (IBMP RAS, Moscow, Russia) and highly appreciated. FUNDING This work was partly performed within the framework of the National Research Nuclear University MEPhI (Moscow Engineering Physics Institute) Academic Excellence Project (contract № 02.а03.21.0005). REFERENCES 1 Benton , E. R. , Benton , E. V. and Frank , A. L. Passive dosimetry aboard the Mir Orbital Station: internal measurements . Radiat. Meas. 35 , 439 – 455 ( 2002 ). Google Scholar CrossRef Search ADS PubMed 2 Kushin , V. V. Measurement of LET distribution and absorbed dose from secondary particles onboard the spacecraft . Radiat. Prot. Dosim. 141 , 199 – 204 ( 2010 ). Google Scholar CrossRef Search ADS 3 Benton , E. V. and Benton , E. R. Space radiation dosimetry in low-Earth orbit and beyond . Nucl. Instrum. Methods Phys. Res. B 184 , 255 – 294 ( 2001 ). Google Scholar CrossRef Search ADS PubMed 4 Inozemtsev , K. O. , Kushin , V. V. , Kodaira , S. and Shurshakov , V. A. Observation of fragmentation events caused by space radiation: Contribution to the LET spectrum as measured with CR-39 track detectors . Radiat. Meas. 95 , 37 – 43 ( 2016 ). Google Scholar CrossRef Search ADS 5 Yasuda , N. , Namiki , K. , Honma , Y. , Umeshima , Y. , Marumo , Y. , Ishii , H. and Benton , E. R. Development of a high speed imaging microscope and new software for nuclear track detector analysis . Radiat. Meas. 40 , 311 – 315 ( 2005 ). Google Scholar CrossRef Search ADS 6 Ambrožová , I. , Davídková , M. , Brabcová , K. P. , Tolochek , R. V. and Shurshakov , V. A. Contribution of different particles onboard ISS measured with track etched detectors . Radiat. Prot. Dosim. ( 2017 ). DOI:10.1093/rpd/ncx189 7 Ambrožová , I. , Pachnerová Brabcová , K. , Kubančák , J. , Šlegl , J. , Tolochek , R. V. , Ivanova , O. A. and Shurshakov , V. A. Cosmic radiation monitoring at low-Earth orbit by means of thermoluminescence and plastic nuclear track detectors . Radiat. Meas. 106 , 262 – 266 ( 2017 ). Google Scholar CrossRef Search ADS 8 Strádi , A. , Szabó , J. , Inozemtsev , K. O. , Kushin , V. V. , Tolochek , R. V. , Shurshakov , V. A. , Alchinova , I. B. and Karganov , M. Yu. Comparative radiation measurements in the Russian segment of the International Space Station by applying passive dosimeters . Radiat. Meas. 106 , 267 – 272 ( 2017 ). Google Scholar CrossRef Search ADS 9 Obryk , B. , Bilski , P. , Budzanowski , M. , Fuerstner , M. , Ilgner , C. , Jaquenod , F. , Olko , P. , Puchalska , M. and Vincke , H. The response of different types of TL lithium fluoride detectors to high-energy mixed radiation fields . Radiat. Meas. 43 , 1144 – 1148 ( 2008 ). Google Scholar CrossRef Search ADS 10 Strádi , A. , Pálfalvi , J. K. , Szabó , J. , Pázmándi , T. , Ivanova , O. A. and Shurshakov , V. A. Cosmic radiation measurements on the Foton-M4 satellite by passive detectors . Acta Astronaut. 131 , 110 – 112 ( 2017 ). Google Scholar CrossRef Search ADS 11 Hajek , M. , Berger , T. , Vana , N. , Fugger , M. , Pálfalvi , J. K. , Szabó , J. , Eördöghet , I. , Akatov , Y. A. , Arkhangelsky , V. V. and Shurshakov , V. A. Convolution of TLD and SSNTD measurements during the BRADOS-1 experiment onboard ISS (2001) . Radiat. Meas. 43 , 1231 – 1236 ( 2008 ). Google Scholar CrossRef Search ADS 12 Ambrožová , I. , Brabcová , K. , Spurný , F. , Shurshakov , V. A. , Kartsev , I. S. and Tolochek , R. V. Monitoring onboard spacecraft by means of passive detectors . Radiat. Prot. Dosim. 144 , 605 – 610 ( 2011 ). Google Scholar CrossRef Search ADS 13 Karganov , M. Yu. , Alchinova , I. B. , Yakovenko , E. N. , Kushin , V. V. , Inozemtsev , K. O. , Strádi , A. , Szabó , J. , Shurshakov , V. A. and Tolochek , R. V. The ‘PHOENIX’ space experiment: study of space radiation impact on cells genetic apparatus on board the international space station . J. Phys.: Conf. Ser. 784 , 012024 ( 2017 ). Google Scholar CrossRef Search ADS 14 Doke , T. , Hayashi , T. , Kikuchi , J. , Sakaguchi , T. , Terasawa , K. , Yoshihira , E. , Nagaoka , S. , Nakano , T. and Takahashi , S. Measurements of LET-distribution, dose equivalent and quality factor with the RRMD-III on the Space Shuttle Missions STS-84, -89 and -91 . Radiat. Meas. 33 , 373 – 387 ( 2001 ). Google Scholar CrossRef Search ADS PubMed 15 Pálfalvi , J. K. Fluence and dose of mixed space radiation by SSNTDs achievements and constraints . Radiat. Meas. 44 , 724 – 728 ( 2009 ). Google Scholar CrossRef Search ADS 16 Kodaira , S. et al. . Analysis of radiation dose variations measured by passive dosimeters onboard the International Space Station during the solar quiet period (2007–2008) . Radiat. Meas. 49 , 95 – 102 ( 2013 ). Google Scholar CrossRef Search ADS 17 Tverskaya , L. V. , Panasyuk , M. I. , Reizman , S. Ya. , Sosnovets , E. N. , Teltsov , M. V. and Tsetlin , V. V. The features of radiation dose variations onboard ISS and Mir space station: comparative study . Adv. Space Res. 34 , 1424 – 1428 ( 2004 ). Google Scholar CrossRef Search ADS PubMed 18 Badhwar , G. D. , Shurshakov , V. A. and Tsetlin , V. V. Solar modulation of dose rate onboard the Mir station . IEEE Trans. Nucl. Sci. 44 , 2529 – 2541 ( 1997 ). Google Scholar CrossRef Search ADS PubMed © The Author(s) 2018. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/about_us/legal/notices)

Journal

Radiation Protection DosimetryOxford University Press

Published: Mar 16, 2018

There are no references for this article.

You’re reading a free preview. Subscribe to read the entire article.


DeepDyve is your
personal research library

It’s your single place to instantly
discover and read the research
that matters to you.

Enjoy affordable access to
over 18 million articles from more than
15,000 peer-reviewed journals.

All for just $49/month

Explore the DeepDyve Library

Search

Query the DeepDyve database, plus search all of PubMed and Google Scholar seamlessly

Organize

Save any article or search result from DeepDyve, PubMed, and Google Scholar... all in one place.

Access

Get unlimited, online access to over 18 million full-text articles from more than 15,000 scientific journals.

Your journals are on DeepDyve

Read from thousands of the leading scholarly journals from SpringerNature, Elsevier, Wiley-Blackwell, Oxford University Press and more.

All the latest content is available, no embargo periods.

See the journals in your area

DeepDyve

Freelancer

DeepDyve

Pro

Price

FREE

$49/month
$360/year

Save searches from
Google Scholar,
PubMed

Create lists to
organize your research

Export lists, citations

Read DeepDyve articles

Abstract access only

Unlimited access to over
18 million full-text articles

Print

20 pages / month

PDF Discount

20% off