Electron Diffraction (7A60.10)


Photo by Tel-Atomic Inc.

Description:

Electrons are diffracted through a thin polycrystalline graphite mesh (Debye-Scherrer diffraction) and hit a fluorescent screen. The diffraction pattern consists of a central bright spot of undeflected electrons and two concentric rings. The diameters of the rings can be changed by altering the accelerating voltage of the electrons. Increasing the electron's energy decreases the de Broglie wavelength and decreases the diameter of the diffraction pattern rings.

Procedure or Operation Notes:

Turn on the power supply and wait a few seconds for the filament to heat up. Adjust the accelerating potential to produce the diffraction pattern.

Filament voltage: 6.3 VAC
Acceleration potential: 0 - 5 kV
Lattice constants of graphite: d10 = 0.213nm, d11 = 0.123nm

You may need to adjust both the aperture and the focus of the lens to get a good display of the diffraction pattern. A wider, open aperture works well at low potentials but higher potentials will saturate or wash-out the camera sensor. Close down the aperture and readjust the lens focus.


Figures from Tel-Atomic Inc.

References, Comments, or Footnotes:

1) More information about the TEL-Atomic Electron Diffraction System. The tube is part number TEL-555.

2) Wikipedia articles about powder diffraction and the Scherrer equation.