1. Spatial distribution and high LET component of absorbed dose measured by passive radiation monitors in ISS Russian segment N. Yasuda, H. Kawashima, M. Kurano, Y. Uchihori, H. Kitamura (NIRS) Yu. Akatov, V. Shurshakov (IMBP) I. Jadrnickova, F. Spurny (NPI) I. Kobayashi (Nagase Landauer, Ltd.) H. Ohguchi, Y. Koguchi (Chiyoda Technol Corporation)

2. BRADOS experiment We conducted an intercomparison experiment for passive radiation dosimeters, Space Intercomparison/BRADOS, aboard the International Space Station (Russian Service Module ). Phase-2 - Spatial distributions of dose (rate) at 5 locations - Intercomparison for dosimeters of NIRS and IBMP - Exposure duration: 268.5 days This experiment was performed in the frame work of ICCHIBAN project.

3. Passive dosimeter (NIRS) TLD layer Luminescence detectors: low LET CR-39: high LET ≥ 5 keV/  m

4. Locations of BRADOS boxes and exposed durations Box # (Panel #) LocationExposure duration (days) A46 (P#443) Starboard side91.5 A41 (P#445) Starboard side268.5 A42 (P#240) Port side268.5 A43 (P#111) Floor, Starboard side 268.5 A44 (P#445) Starboard side268.5 A45 (P#326) Ceiling near the R-16, port side 268.5

5. Shielding functions in the Service Module model Service Module Less Shielded Most Shielded

6. Results 1 Spatial distributions ~31g/cm 2 ~40g/cm 2

7. Dose quantities are depending on local shielding environment.

8. Combination of short and long etch

9. Comparison RRMD and CR-39 Tawara, Doke et al., RM35(2002)119. Both results are in good agreement when they pick up only cone-shaped etch pits.

10. Track Taxonomy: Representative Sample Cone-shaped Track Well-behaved Track Well-behaved Stopper Track Over-Etched Stopper Track

11. Estimation of dose contribution of short range particles  AFM Short bulk etch ~ 1  m  Different types of CR-39 detectors Different detection threshold (HARZLAS TD-1 for >5 keV/mm) (BARYOTRAK for higher LET particles)

12. Calibration curves for different types of CR-39 LET Threshold ~ 5 keV/  m LET Threshold ~ 50 keV/  m Pure CR-39 + anti-oxidant 200eV

13. HARZLAS TD-1 B=18  m

14. BARYOTRAK B=19  m

15. LET spectra (cone shape track only)

16. BARYOTRAK B=19  m

17. How to estimate For results of BARYOTRAK, The component of cone shape track is in good agreement with TD-1 detector. Assumption: - all the shallow track (green) has LET = 50 keV/  m (Threshold LET: minimum case)

18. Results Top layer of A41 stackTD-1 only TD-1 + shallow track in BARYOTRAK Method (combination)CR-39/Glass CR-39 /TLD-100 CR-39/Glass CR-39 /TLD-100 TLD Dose Rate (  Gy/day)206±18228±17206±18228±17 Dose Rate >= 5 keV/  m (  Gy/day) 28 ± 148 ± 2 Total Dose Rate (  Gy/day)234 ± 14207 ± 8243 ± 14216 ± 8 Dose Equivalent Rate >= 5 keV/  m (  Sv/day) 324 ± 27812 ± 45 Total Dose Equivalent Rate (  Sv/day) 530 ± 30503 ± 281007 ± 47979 ± 45 Averaged Quality Factor2.3 ± 0.22.4 ± 0.24.1 ± 0.34.5 ± 0.3 QF: x 1.8 (at least) Dose: x 1.7 (at least) Dose eq: x 2.5 (at least)

19. Conclusions  Dose quantities seem to be depending on local shielding environment.  Contribution of short range tracks was estimated with assumption (all shallow tracks = 50 keV/  m). to dose (x 1.7) to dose eq (x 2.5) to averaged QF (x 1.8) (at least)  Contribution of short range tracks seems to be significant for dose and dose eq. - need further systematic study coupled with accelerator exp. (ICCHIBAN) - need some clear definitions/guide line to verify dose amounts by CR-39 - need model calculations

20. Interval of measurements (dd.mm.yyyy) Exposure duration, day Absorbed dose, mGy Pille-ISS *) R-16 А0305А0306D1D2D2 14.01.2004- 09.02.2004 263.693.553.053.00 09.02.2004- 11.03.2004 314.134.513.754.35 11.03.2004- 24.04.2004 445.676.115.155.90 24.04.2004- 14.05.2004 202.762.672.402.90 14.05.2004- 18.06.2004 354.584.894.054.90 18.06.2004- 20.07.2004 324.244.593.703.85 20.07.2004- 19.08.2004 304.554.343.854.65 19.08.2004- 24.09.2004 365.595.344.065.24 24.09.2004- 14.10.2004 203.002.842.272.65 14.10.2004- 08.11.2004 253.583.87-- Factor ~ 1.2

21. R-16 detector 0.5 g/cm 2 3.5 g/cm 2 SI1 This exp. Autumn 2005 MATROSHKA-1

22. Detectors  R-16 (1 location) with Pille-ISS  DB-8 (4 locations)  BRADOS BOX (5 locations) from IBMP - TLD LiF:Mg,Ti from NIRS - TLD LiF:Mg,Ti - Luxel OSL - Glass detector - CR-39 (HARZLAS TD-1, BARYOTRAK) *One box was located near the R-16 detector. *Two Pilles were located on the R-16 detector.

23. Overview of presentation  Spatial dose distribution (5 locations in Russian Service Module)  Comparison of luminescence detector and on board monitors (R-16, DB-8 and Pille- ISS)  Contribution of short range particle to dose and dose equivalent

24. Results Box # (Panel #) LocationExposure duration (days) TLD-100 (LiF)  Gy/day Glass  Gy/day R-16  Gy/day A46 (P#443) Starboard side91.5222±4205±2117 (3.5g/cm 2 ) 145 (0.5g/cm 2 ) A41 (P#445) Starboard side268.5206±18228±17 A42 (P#240) Port side268.5208±12221±3 A43 (P#111) Floor, Starboard side268.5204±11219±8 A44 (P#445) Starboard side268.5157±7172±2 A45 (P#326) Ceiling near the R-16, port side 268.5169±14180±10119 (3.5g/cm 2 ) 146 (0.5g/cm 2 ) * DB-8 monitors: 264, 208, 219, 146  Gy/day ~±20%Difference ~20% ~±30%

25. Relevant Facts concerning Galactic Cosmic Radiation  GCR consists of 87% protons, 11% helium nuclei (a-particles) and 1% heavy ions (Z  3).  While heavy ions are only 1% of flux, they make a significant (>25%) contribution to total dose equivalent.  Intensity of GCR is inversely proportional to level of solar activity throughout the 11 year Solar Cycle.  GCR is omnidirectional and isotropic.  Much of the GCR component is too energetic to practically shield (e.g. surrounding the spacecraft with polyethylene).  Leads to constant (chronic), low dose rate. - GCR produce secondary nuclei by nuclear reactions with shielding materials / inside body. - Short range and higher LET component will not be appeared in the active detector devices.