Shielded focused ion beam field emission scanning electron microscope (FIB-FE-SEM). Evaluation, technical modification and implementation

Scanning electron microscopy (SEM) and energy dispersive X-ray spectrometry (EDS) are important analyses techniques in the PSI Hot-laboratory to characterize nuclear materials. Since 1992 the PSI Hot-laboratory operates the SEM DSM962 on low active irradiated materials, but with the raising operation time the maintenance of the electronic spare parts becomes more and more difficult and therefore the acquirement of a new instrument was indispensable. On the other hand the PSI research division of nuclear materials has the request of materials characterization in the atomic scale, which is possible at synchrotron beam lines. Due to statutory specified limited activity values at these facilities the production of tiny specimens is essential. To combine the requests the new shielded analytical tool should be equipped with a focused Ion beam (FIB) gun and a micromanipulator for in-situ sample preparation combined with an analytical system consisting of Energy Dispersive X-ray Spectrometry (EDS), Wavelength Dispersive X-ray Spectrometry (WDS) and Electron Back Scatter Diffraction (EBSD). The instrument should allow to handle highly radioactive samples like irradiated fuel and cladding. To protect human health and life and the sensitive parts of the instrument modifications have to be performed on the conventional purchasable instrument and detectors. The best offered instrument combined with the favorable conditions was a Zeiss Crossbeam 540 Zeiss is represented in Switzerland by the company Gloor Instruments AG. The device in the final stage will be equipped with the following system: GEMINI II field emission electron optic, Capella FIB column with liquid Ga ion source, micro manipulator highly precise 'Oxford Omniprobe Autoprobe 200.2', Everhart-Thornley-type chamber detector (SE), in-lens SE-detector, a YAG-detector for Back-Scattered Electrons (BSE), in-lens EsB, Energy Dispersive X-ray Spectrometry (EDS), with 3D analysis, Wavelength Dispersive X-ray Spectrometry (WDS), Electron Back Scatter Diffraction (EBSD) with high resolution 'DigiView 5' camera, with 3D analysis. Since there is a limitation of floor loading in the laboratory, the construction of the hot cell was challenging. The dimensions of the lead shielding had to be large enough for a small glove box and the instrument attached with all the detectors, but also small enough not to exceed the maximum floor loading allowed. In order to fulfill these requests the instrument is installed in a cabin with a wall thickness of 10 cm lead, detectors are protected with shutters and the remote controlled loading system is realized with manipulators through an attached glove box, which allows safe handling of highly alpha/gamma radioactive and/or contaminated samples. With this new installation it is planned to prepare tiny specimens for further analyses on various PSI-internal as well on PSI-external beam lines. The complex analysis system of the FIB/SEM itself allows qualitative and semi-quantitative elemental and crystallographic analyses of in-situ prepared surfaces and ion cut and polished open laid structures of any bulk material. (author)