The work reports the results on 71 Ga and 27 Al NMR investigation of the gallium and aluminum ions distribution over tetrahedral and octahedral positions in the Y 3 Al 5−x Ga x O 12 :Ce single crystals and Lu 3 Al 5−x Ga x O 12 :Ce single-crystalline epitaxial films. The gallium content x varies between 0 and 5 in crystals and between 0.3 and 2 in films.. We find that in both the Y-and Lu-based solid solutions the larger gallium ions are preferably located at the tetrahedral position while the smaller aluminum ions prefer the octahedral position of the garnet host. Based on NMR data, the dependence of fractional occupation parameters of the tetrahedral site of Ga and Al ions on the Ga content is determined. In particular, in the Y 3 Al 2 Ga 3 O 12 :Ce crystal only 28% of Ga ions occupy octahedral sites, whereas 72% occupy tetrahedral ones. NMR investigations suggest that observed nonmonotonic dependences of electron trap depths monitored by thermally stimulated luminescence of Y 3 Al 5−x Ga x O 12 :Ce complex garnets on the Ga content are related to preferential localization of the Ga and Al ions over the tetrahedral and octahedral positions of the garnet lattice, respectively. Our data confirm that the tetrahedral site preference (over the octahedral site) for the Ga occupation is an intrinsic property of the mixed Y 3 (Lu 3 )Al 5−x Ga x O 12 garnets.

We report for the first time the optimized content and excellent scintillation properties of single crystalline film (SCF) scintillators of multicomponent Gd3–xLux Al5–yGay O12:Ce garnet compounds grown by liquid phase epitaxy (LPE) method. The Gd1.5Lu1.5Al2.75Ga2.25O12:Ce and Gd3Al2.75–2Ga2.25–3O12:Ce SCF show the light yield (LY) comparable with that of high‐quality bulk crystal analogues of these garnets but faster scintillation decay and very low thermoluminescence in the above room temperature range. To our knowledge, these SCF possess the highest LY values ever obtained in LPE grown garnet SCF scintillators exceeding by at least 1.5–1.6 times the values previously reported for SCF scintillators. Left figure: image of Gd1.5Lu1.5Al2.75Ga2.25O12:Ce (PbO) (inset, left) and Gd3Al2.35Ga2.65O12:Ce (BaO) (inset, right) SCF scintillators, grown by LPE method onto Gd3Al2.5Ga2.5O12 (GAGG) substrate; in the middle, green–yellow light emitting by Gd1.5Lu1.5Al2.75Ga2.25O12:Ce (BaO) SCF under 350 nm laser illumination. Right figure: XRD pattern of (1200) planes of the Gd1.5Lu1.5Al2.75Ga2.25O12:Ce (PbO) (black) and Gd3Al2.75Ga2.25O12:Ce (BaO) (red) SCFs, grown onto GAGG substrates. The film/substrate lattice misfit is –0.73% and –0.3%, respectively. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)

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The radiation environment encountered in space differs in nature from that on Earth, consisting mostly of highly energetic ions from protons up to iron, resulting in radiation levels far exceeding the ones present on Earth for occupational radiation workers. Since the beginning of the space era, the radiation exposure during space missions has been monitored with various active and passive radiation instruments. Also onboard the International Space Station (ISS), a number of area monitoring devices provide data related to the spatial and temporal variation of the radiation field in and outside the ISS. The aim of the DOSIS (2009DOSIS ( -2011 and the DOSIS 3D (2012-ongoing) experiments was and is to measure the radiation environment within the European Columbus Laboratory of the ISS. These measurements are, on the one hand, performed with passive radiation detectors mounted at 11 locations within Columbus for the determination of the spatial distribution of the radiation field parameters and, on the other, with two active radiation detectors mounted at a fixed position inside Columbus for the determination of the temporal variation of the radiation field parameters. Data measured with passive radiation detectors showed that the absorbed dose values inside the Columbus Laboratory follow a pattern, based on the local shielding configuration of the radiation detectors, with minimum dose values observed in the year 2010 of 195-270 lGy/day and maximum values observed in the year 2012 with values ranging from 260 to 360 lGy/day. The absorbed dose is modulated by (a) the variation in solar activity and (b) the changes in ISS altitude.

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