training for advanced research


Glossary terms about Chamber

The space in which the sample is housed in a scanning electron microscope.

17 pages mention Chamber

Beam Adjustment
Check that you have enough room around your sample before tilting so as not to bump into anything in the chamber
Electromagnetic lenses, apertures and beam size
Environmental scanning electron microscope (ESEM)
Sample temperature and specimen chamber vapour pressure can both be controlled, allowing samples to be heated, cooled, wetted or dried. 
Generating an image
These are termed "SE2" Interaction of the beam with the sample chamber, pole piece etc. 
High vacuum mode and pump system
Because backscattered electrons and characteristic X-rays are generally of higher energy than secondary electrons, their detection is not critically dependant on a high vacuum being maintained in the specimen chamber
Image Capture
Turn the beam off and let air into the chamber
Main control panel
Used to indicate that the progress of bringing the specimen chamber and column to atmospheric pressure (lamp is blinking) and when venting is complete (lamp lights up). 
Principles of SEM operation
A scanning electron microscope is a machine comprised of an electron generating component called the gun, a column through which the electron beam travels, a series of lenses to shape the electron beam, the sample chamber at the base, and a series of pumps to keep the system under vacuum. 
Risk assessment example: using a SEM
Design features contain ionizing radiation when produced (eg shielding) and prevent generation of an electron beam if chamber is open (electronic safety controls). 
Role of sample height
Within the sample chamber the sample stage can be wound up closer to the end of the column (a short working distance) or dropped down lower (a long working distance). 
Sample insertion and beam activation
To use the SEM you must first place a sample in the sample chamber
Sample preparation
Specimen chamber
Troubleshooting: edge effect, charging, sample damage
This can ruin a sample (as well as contaminate the SEM chamber). 
Variable Pressure or Low Vacuum scanning electron microscopy (LVSEM)
This type of machine is basically like a conventional SEM but has the advantage in low vacuum (LV) mode that the pressure can be adjusted in the sample chamber until the artefact of "electron charging" is removed from images. 
What is an SEM (Parts of the machine)?
the computer that drives the microscope, with the additional bench controls ancillary equipment that, for example, analyses composition. 
What the SEM can't do
This requires two images that have been tilted relative to one another to create a 3D image, and specialised processing software. Generally, SEMs are not used for experiments involving liquids, chemical reactions, and air-gas systems although some specialised machines and sample chambers do allow for these experiments.