Symmetry: EBSD Detector

Optimised phosphor screen

Symmetry utilises a -performance phosphor screen, ideal for -speed analyses yet maintaining superb sensitivity for applications requiring beam currents and beam energies. All systems can be fitted with an in-built infrared filter, enabling the acquisition of uncompromised data during in-situ heating experiments.

Integrated forescatter detector system

Symmetry is fitted with 5 discrete forescatter (FSD) diodes, providing flexible imaging independent of the EBSD . All diodes are angled towards the sample for maximum signal detection:

Backscatter position - 2 diodes above screen for optimised atomic number contrast imaging

Forescatter position - 3 diodes below screen for optimised orientation contrast imaging (with false-colour imaging) and topographic contrast. In addition, these diodes provide transmitted darkfield images of electron transparent samples mounted for transmission Kikuchi diffraction (TKD).

Speed - adjustable exposure time providing quality imaging at more than 10⁶ points per second

Fast and precise mechanical positioning

With both software and handset control, Symmetry has fully motorised insertion and retraction, enabling fast and quiet positioning of the phosphor screen to any position with 0.1 mm precision. The AZtec software automatically calibrates the EBSD collection geometry, whatever the insertion position, providing the user with absolute flexibility and confidence in the system performance.

Advanced, high-efficiency optics

The within the Symmetry are designed to ensure maximum efficiency with minimal distortion. This guarantees quality patterns at electron doses, enabling spatial resolution analyses at beam currents and energies, thus making the ideal for detailed analyses and HR-EBSD.

Bellows SEM interface

Symmetry uses a bellows to the SEM, ensuring the microscope’s vacuum integrity for the lifetime of the . The bellows mechanism is specifically designed to enable large insertion distances, ensuring that Symmetry is compatible with large chamber SEMs.

Software-controlled tilting interface

Variable tilting of the EBSD allows the elevation of the phosphor screen to be optimised, delivering the best results over the widest range of working distances. The tilting mechanism is fully motorised and is both controlled and monitored through the AZtec software, making geometry optimisation a simple and intuitive process for every application.

In-software auto-calibration routines automatically read and compensate for the tilt and insertion values, guaranteeing flawless indexing every time.

Seamless EDS integration

Symmetry has been designed to work in synergy with the complete range of Instruments EDS detectors. Symmetry’s nose has a tapered , allowing the phosphor screen to be positioned close to the sample for maximum collection solid angle, yet permitting simultaneous X-ray analysis without shadowing. Even at the fastest collection speeds of over 3000 pps, simultaneous chemical mapping is possible with no penalty on speed.

Complete flexibility

Symmetry is designed to work both in conventional, backscattered EBSD mode and in transmission mode (transmission Kikuchi diffraction). The flexibility in screen positioning, the sensitivity and the extreme speed of Symmetry ensure that you always get the best results, whatever the sample.

One for all scales of analysis. Left – large area orientation map of a welded duplex steel, of view 4.75mm; right – TKD orientation map of a nanocrystalline Ni sample, of view 500 nm.

Low accelerating voltage operation

Symmetry’s superior sensitivity permits fast and effective analyses, even at accelerating voltages below 5 kV. This makes it the ideal when spatial resolution is a key factor, when mapping heavily deformed structures or when analysing beam-sensitive samples that preclude the use of higher beam energies.

Pattern quality map and corresponding IPF orientation map of a martensitic steel sample, analysed at 500 pps using a 12 kV accelerating voltage and with a measurement step size of 30 nm

Contactless collision sensor

Symmetry has a unique proximity sensor, designed to help avoid colliding with other systems within the SEM chamber. Collisions may be detected before they occur, reducing the potential for costly system down-time and repair.

Intuitive camera configurations

Symmetry can operate in a number of different modes: these are set-up to maximise ease-of-use, allowing a seamless switch between pattern resolutions and speeds. With no need to worry about detailed camera settings or calibration, the user can focus on what’s most important: their results.

High pattern resolution at all speeds

The CMOS-based Symmetry does not need to use pixel binning in order to attain speed data collection. CCD technology requires the pattern resolution to be binned down to 40 x 30 pixels to achieve the fastest speed whereas with Symmetry, even at over 3000 pps, the pattern resolution is an impressive 156 x 128 pixels. This equates to 16 x more pixels than with the fastest CCD-based detectors.

In addition, for those applications needing exquisite pattern detail such as HR-EBSD, Symmetry delivers distortion-free 1244 x 1024 pixel diffraction patterns. This is truly one to fit all applications.

Diffraction patterns collected from a duplex steel sample with ∼10 nA beam current: left at 3000 pps, 156 x 128 resolution and right at 100 pps, 1244 x 1024 resolution