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SkyScan µ-CT

Site last updated 06 Jun 2008
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Detectors for Energy Dispersive Spectrometry (EDS) on Scanning Electron Microscopes (SEM).

e2v scientific instruments has a wealth of experience in the design and manufacture of detectors used for EDS on Scanning Electron Microscopes. EDS is an invaluable technique providing elemental composition information in direct relation to the SEM image.

Applications
SEM

The EDX (Energy Dispersive X-Ray) detector is mounted on a suitable vacuum port on the SEM chamber, and is used to detect the characteristic fluorescence x-rays emitted from the sample as a result of excitation by the imaging electron beam. Crucial design parameters are correct mechanical geometry, high collection efficiency, good low energy response and immunity to scattered electrons, without affecting the primary imaging function of the electron beam.

e2v scientific instruments provides a range of detectors to suit all commercial SEMs. The parameters that determine the mounting of an EDX detector on an SEM are as follows (the microscope manufacturer will normally recommend operating parameters for a particular SEM when performing EDS analysis):

Working Distance (WD). Defined as the distance between the base of the pole piece (last element in the electron optics) and the sample. The EDX detector is designed to view samples at this fixed working distance.

Take Off Angle (TOA). Defines the angle between the EDX detector crystal axis and the plane of the sample. The available TOA range is limited by the position of the EDX port on the SEM. The detector is designed to work at a fixed TOA (though users can sometimes vary the angle of emission of x-rays by tilting the sample stage). For light element analysis a larger TOA is desirable to minimise the effects of absorption by the topography of the sample.

The Sirius SEM range of Si(Li) detectors has been developed to give state of the art performance for today's range of analytical SEMs, incorporating e2v scientific instruments' own crystal processing technology providing:

High energy resolution.
Exceptional peak to background figures.
Excellent light element sensitivity.

NB. Light element performance is also a function of the detector entrance window and the pulse processor.

Typical Light Element spectrum (Sirius 10mm² on SEM)

In addition, e2v scientific instruments Sirius detectors for SEMs also include specific hardware features:

Electron trap for deflection of scattered electrons.
Slide mounting for easy advance and retraction of the detector snout from the sample area.
UHV features for Field Emission SEM's.
Angled crystal assemblies for increased take off angle where appropriate.