SRMA - Facility
Microscope EM7 (Kratos)
The EM7 High Voltage Electron Microscope (HVEM) located at CEA Saclay has been operated since 1981. In 2008-2010 an upgrading was carried out to ensure reliable operation in future years. This microscope runs from 0.3 to 1.2 MeV and allows to form isolated defect (Frenkel Pairs) in almost all nuclear metals (Steels, Zr alloys). This well-known damage permit to directly compare experiments with simulations. Damage rates between 5.10-5 dpa/s and 5.10-3 dpa/s (in metals) can be reached. Thanks to its new Gatan CCD video camera, the Transmission Electron Microscope enable in-situ monitoring. To prevent oxidation of the samples a very good vacuum is maintained ( 5 10-8 Torr). As others facilities, the EM7 parameters (flux, temperature, dose) can be changed easily allowing parametric studies without any activation of the samples. The samples which can be irradiated in the microscope are mostly conventional TEM thin foils, 3 mm in diameter. Recently a new single tilt heating specimen holder dedicated to Atom Probe tips was designed and fabricated.
The microscope has been mostly used so far as a tool to study irradiation effects in materials (metallic alloys, ceramics, glasses), in particular those of interest for nuclear applications.
Some examples of performed experiments/research topics are as follows :
- void swelling under irradiation and effect of solutes
- irradiation-induced segregation at grain boundaries
- ordering/disordering under irradiation
- formation and growth kinetics of point defect clusters
- growth phenomenon in non-cubic metals, in particular Zr alloys, effect of solutes
- phase precipitation/dissolution under irradiation (precipitation phenomena in ferritic alloys/glasses, dissolution of oxide particles in ODS alloys etc.)
- irradiation effects in neutron-absorbing materials …