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We measured specific activities of the long‐lived cosmogenic radionuclides 60Fe in 28 iron meteorites and 53Mn in 41 iron meteorites. Accelerator mass spectrometry was applied at the 14 MV Heavy Ion Accelerator Facility at ANU Canberra for all samples except for two which were measured at the Maier‐Leibnitz Laboratory, Munich. For the large iron meteorite Twannberg (IIG), we measured six samples for 53Mn. This work doubles the number of existing individual 60Fe data and quadruples the number of iron meteorites studied for 60Fe. We also significantly extended the entire 53Mn database for iron meteorites. The 53Mn data for the iron meteorite Twannberg vary by more than a factor of 30, indicating a significant shielding dependency. In addition, we performed new model calculations for the production of 60Fe and 53Mn in iron meteorites. While the new model is based on the same particle spectra as the earlier model, we no longer use experimental cross sections but instead use cross sections that were calculated using the latest version of the nuclear model code INCL. The new model predictions differ substantially from results obtained with the previous model. Predictions for the 60Fe activity concentrations are about a factor of 2 higher, for 53Mn, they are ~30% lower, compared to the earlier model, which gives now a better agreement with the experimental data. [ABSTRACT FROM AUTHOR]

We present results of a systematic study of the morphology of etched ion tracks in amorphous SiO 2 using a combination of small angle X-ray scattering (SAXS) and scanning electron microscopy. We focus on the analysis of SAXS data obtained in grazing incidence (GISAXS) configuration from conical etched channels with a base radius of less than 50 nm. Swift heavy ion irradiation of 2 μm thick thermally grown SiO 2 layers with 185 MeV Au ions was conducted at the ANU Heavy Ion Accelerator Facility in Canberra, Australia. Low irradiation fluences of 109 ions per cm2 were chosen to minimize overlap of the etched structures. Irradiated samples were etched in aqueous hydrofluoric acid (HF) with concentrations of 5%, for etching times between 30 and 90 s. In grazing incidence configuration, we obtain good data quality from the very small cones, since the X-ray beam interacts with a greater proportion of the sample at the very low incidence angle compared with normal transmission mode. [ABSTRACT FROM AUTHOR]

Small angle x-ray scattering was used to study the morphology of conical structures formed in thin films of amorphous SiO2. Samples were irradiated with 1.1 GeV Au ions at the GSI UNILAC in Darmstadt, Germany, and with 185, 89 and 54 MeV Au ions at the Heavy Ion Accelerator Facility at ANU in Canberra, Australia. The irradiated material was subsequently etched in HF using two different etchant concentrations over a series of etch times to reveal conically shaped etched channels of various sizes. Synchrotron based SAXS measurements were used to characterize both the radial and axial ion track etch rates with unprecedented precision. The results show that the ion energy has a significant effect on the morphology of the etched channels, and that at short etch times resulting in very small cones, the increased etching rate of the damaged region in the radial direction with respect to the ion trajectory is significant. [ABSTRACT FROM AUTHOR]