title: LET distributions from CR-39 plates on Space Shuttle missions STS-84 and STS-91 and a comparison of the results of the CR-39 plates with those of RRMD-II and RRMD-III telescopes.
abstract: The LET distributions during the Space Shuttle missions STS-84 (altitude 270-412 km, average 375 km; inclination angle, 51.6 degrees) and STS-91 (altitude 328-397 km, average 373 km; inclination angle, 51.6 degrees) were measured using CR-39 plastic nuclear track detectors. A correction for the dip-angle dependence of the track-formation sensitivity of the CR-39 plates was applied to the data analysis. The absorbed doses and the dose equivalents around RRMD Detector Units, estimated from the LET distributions in the LET region of 4-200 keV/micrometers, fluctuated with standard deviations of +/- 21% to +/- 35% in both flight experiments. The LET distributions obtained from the CR-39 plates agreed well with that obtained from RRMD-II in STS-91. However, the particle fluxes obtained from RRMD-III in STS-84 and STS-91 were two or three times higher than those obtained from RRMD-II and the CR-39 plates. It was concluded that the LET distributions obtained from RRMD-II and the CR-39 plates in the present flight experiments did not include the contribution of target-fragmented secondary heavy particles produced by low-LET particles, such as relativistic or semi-relativistic protons and helium ions, whereas RRMD-III was able to detect these secondary particles because of its low triggering level.
authors.affiliation: High Energy Accelerator Research Organization, Radiation Science Center, Oho 1-1, Tsukuba-shi, Ibaraki 305-0801, Japan. hiroko.tawara@kek.jp
authors.forename: H
authors.initials: H
authors.lastname: Tawara
authors.forename: T
authors.initials: T
authors.lastname: Doke
authors.forename: T
authors.initials: T
authors.lastname: Hayashi
authors.forename: J
authors.initials: J
authors.lastname: Kikuchi
authors.forename: A
authors.initials: A
authors.lastname: Kyan
authors.forename: S
authors.initials: S
authors.lastname: Nagaoka
authors.forename: T
authors.initials: T
authors.lastname: Nakano
authors.forename: S
authors.initials: S
authors.lastname: Takahashi
authors.forename: K
authors.initials: K
authors.lastname: Terasawa
authors.forename: E
authors.initials: E
authors.lastname: Yoshihira
mesh_terms: D003359:Cosmic Radiation; D020450:Heavy Ions; D006371:Helium; D018499:Linear Energy Transfer; D011092:Polyethylene Glycols; D011522:Protons; D011829:Radiation Dosage; D011834:Radiation Monitoring / Q000295:instrumentation*; D011835:Radiation Protection; D011874:Radiometry; D013026:Space Flight / Q000295:instrumentation*; D014893:Weightlessness
chemical_list: D011522:Protons; D006371:Helium; C028827:CR 39; D011092:Polyethylene Glycols