Optimus - Model TKD - Detector Head
Bruker’s high performance e-Flash EBSD detector series can be equipped with a special detector head designed for optimal geometric conditions in performing Transmission Kikuchi Diffraction analysis (TKD) in a SEM. It is interchangeable with the standard detector head of any e-Flash EBSD detector, supporting EBSD and TKD using the same detector.
The unique OPTIMUS TKD detector head has a horizontal phosphor screen that can be positioned under an electron transparent sample to acquire the diffracted electron signal where it is strongest. Additionally to acquiring Kikuchi patterns with unmatched sensitivity, the OPTIMUS TKD detector head also virtually transforms a SEM into a TEM by giving access to SAED (Selected Area Electron Diffraction) like patterns as well as to dark and bright field imaging capabilities.
Placing the phosphor screen directly beneath the sample has two major advantages compared to a standard EBSD detector with vertical screen:
- much stronger signal
- lowest possible gnomonic projection distortions
The first advantage results either in data acquisition that is either faster or can be performed with lower beam current and/or acceleration voltage. Apart from an improved lateral spatial resolution a low beam current also minimizes carbon contamination of the sample. A low acceleration voltage is useful for the analysis of very thin samples, as the probability of interaction with the sample crystal lattice (diffraction) is increased.
Distortions caused by gnomonic projection are a common issue in EBSD and particularly affect TKD using a vertical screen. The OPTIMUS™ TKD detector head allows screen positioning so that the pattern center is in the center of the screen, providing even better geometric conditions than those for EBSD. This insures that the Kikuchi patterns will have minimum distortions further improving band detection and subsequent indexing accuracy.
OPTIMUS™ is equipped with theARGUS™ imaging system. Dark field and bright field imaging in this configuration is also benefitted by the excellent geometric conditions, resulting in brilliant images containing details down to the nanometer scale. ARGUS™ can for instance be used to display individual dislocations and networks of dislocation walls in deformed materials. It is even possible to produce dark field images showing detail like 3D information on boundary plane inclination.
Owing to a universal, flexible design all new and existing e-Flash detectors can be fitted with the OPTIMUS TKD detector head. The exchange can be easily done in less than 20 minutes by a trained user. This allows the switch between EBSD and TKD setup easily and whenever needed. Same as the standard detector head OPTIMUS TKD also features an advanced collision protection system. In the unlikely event of a collision the detector will immediately retract at a speed of 10 mm/s. The OPTIMUS TKD detector head also combines seamlessly with the TKD sample holder and the XFlash EDS detector series.