L. Di Fino

Heavy-Ion Anisotropy Measured by ALTEA in the International Space Station

The uneven shielding of the International Space Station from the vessel hull, racks and experiments produces a modulation of the internal radiation environment. A detailed knowledge of this environment, and therefore of the Stations shielding effectiveness, is mandatory for an accurate assessment of radiation risk. We present here the first 3D measurements of the Stations radiation environment, discriminating particle trajectories and LET, made possible using the detection capability of the ALTEA-space detector. We provide evidence for a strong (factor ≈ 3) anisotropy in the inner integral LET for high-LET particles (LET > 50 keV/µm) showing a minimum along the longitudinal station axis (most shielded) and a maximum normal to it. Integrating over all measured LETs, the anisotropy is strongly reduced, showing that unstopped light ions plus the fragments produced by heavier ions approximately maintain flux/LET isotropy. This suggests that, while changing the quality of radiation, the extra shielding along the station main axis is not producing a benefit in terms of total LET. These features should be taken into account (1) when measuring radiation with detectors that cannot distinguish the direction of the impinging radiation or that are unidirectional, (2) when planning radiation biology experiments on the ISS, and (3) when simulating the space radiation environment for experiments on the ground. A novel analysis technique that fully exploits the ability to retrieve the angular distribution of the radiation is also presented as well as the angular particle flux and LET characteristic of three geomagnetic zones measured during 2009 by the ALTEA-space detector. This technique is applied to the ALTEA-space detector, but a wider applicability to other detectors is suggested.

Measurements of heavy-ion anisotropy and dose rates in the Russian section of the International Space Station with the Sileye-3/Alteino detector

In this work we present data on linear energy transfer (LET), dose and dose equivalent rates from different locations of the Russian part of the International Space Station (ISS) measured by the Sileye-3/Alteino detector. Data were taken as part of the ESA ALTCRISS project from late 2005 through 2007. The LET rate data shows a heavy-ion (LET keV/?m) anisotropy. From the heavy-ion LET rate in the Zvezda service module we find ISS (Starboard) and (Nadir) to be about 10?15 times higher than in (Forward). The situation is similar for dose and dose equivalent rates, ranging from 25?40 ?Gy d?1 in to about 75 ?Gy d?1 in , whereas for the dose equivalent the rate peaks in with around 470 ?Sv d?1. The heavy-ion anisotropy confirms what has been reported by the ALTEA collaboration. Measurements using two sets of passive detectors, DLR-TLDs and PADLES (TLD+CR-39), have also been performed in conjunction with Alteino measurements, both shielded and unshielded. The passive detectors register a dose rate about 3?5 times as high as Alteino, 260?280 ?Gy d?1 for PADLES and 200?260 ?Gy d?1 for DLR-TLDs. For the dose equivalent PADLES measurements ranges from 560?740 ?Sv d?1.

Relative nuclear abundance from C to Fe and integrated flux inside the Russian part of the ISS with the Sileye-3/Alteino experiment

In this work we present data from the Sileye-3/Alteino detector on board the International Space Station (ISS), which was gathered following a recalibration after several years in orbit. We also measure the relative nuclei abundance and integratedflux,whichwerenormalizedtothesolarmodulationvaluesofAugust 2007. The measurements were made at different locations of the Russian part of the ISS. The relative nuclear abundances of C to Fe in relation to C, in an energyrangeabove � 60MeV/n,showshighlevelsofoddZparticlesinsidethe ISS and an under-abundance of C and O compared with the galactic spectrum, as presented by Simpson in 1983. In addition, the values of the integrated flux varies primarily according to location and detector orientation. An additional polyethylene shield also reduces the flux, although in a lower amount than changes in the orientation of the telescope. Data were taken as part of the ESA ALTCRISS project from late 2005 through to 2007.