The sample is placed in a small chamber that is at a vacuum. Argon gas and an electric field cause an electron to be removed from the argon, making the atoms positively charged. The argon ions then become attracted to a negatively charged gold foil. The argon ions knock gold atoms from the surface of the gold foil. These gold atoms fall and settle onto the surface of the sample producing a thin gold coating. The radiation safety concerns are related to the electrons that are backscattered from the sample, as well as X-rays produced in the process.
Most SEMs are extremely well shielded and do not produce exposure rates greater than background. However, scanning electron microscopes are radiation-generating devices and should be at least inventoried. It is also important that the integrity of the shielding is maintained, that all existing interlocks are functioning, and that workers are aware of radiation safety considerations.
Purdue Police Phone: Purdue Fire Phone: Sign up for Emergency Text Messages. Quick Links. Radiological and Environmental Management. How does a SEM work? How is a sample prepared? What are the radiation safety concerns? Allows the electrical properties of samples to be related to the microstructure - e. Heating holder. Gatan Double tilt heating holder.
Allows samples to be heated up to degrees in the TEM column. Bright field STEM detector. HADDF detector. MEMS Heating holder. DENSsolutions Wildfire S3 capable of analyses up to o C with millisecond heat and quench speed, and nanoscale sample drift with step changes of hundreds of degrees.
Tomography compustage for tomographic characterisation. Cryo-stage for low temperature observation of temperature dependent or hydrated samples. Ideal for low-contrast, beam-sensitive biological specimens, or other soft materials such as polymers.
LaB 6 or tungsten filament electron gun. Low background double-tilt sample holder and single-tilt sample holder for 2 samples. This image can be then studied directly within the TEM or photographed. Figure 1 shows a diagram of a TEM and its basic parts. Drawing by Graham Colm, courtesy of Wikimedia Commons.
Although TEMs and light microscopes operate on the same basic principles, there are several differences between the two. The main difference is that TEMs use electrons rather than light in order to magnify images. The power of the light microscope is limited by the wavelength of light and can magnify something up to 2, times. Electron microscopes, on the other hand, can produce much more highly magnified images because the beam of electrons has a smaller wavelength which creates images of higher resolution.
Resolution is the degree of sharpness of an image. Figure 2 compares the magnification of a light microscope to that of a TEM. Light microscope x Photo by K.
Photo by J. Specimens must be very thin so that electrons are able to pass through the tissue.
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