Modern Physics > Quantum Effects > X-Ray and Electron Diffraction

DCS# 7A60.10

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ELECTRON DIFFRACTION

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APPARATUS

electron diffraction tube	201A
power supply	201A
video camera	202-09-C4

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DESCRIPTION

Show the diffraction patterns produced by an electron beam passing through the three different targets.  When displaying the patterns with a camera, place a small polarizer or piece of electrical tape on the central bright spot so its intensity doesn't blow out the image.

The Bragg equation can be used to calculate the separation between lattice planes from measurements of the pattern spacing on the screen.

NOTES

Set-up:

 

 

Intensity and voltage should be turned all the way down before the power supply is turned on.  Allow a few minutes for tube filament to warm up, then set anode voltage to about 6 kV but do not exceed 7 kV. Turn intensity up to about 6.5.  Current should be less than 100 uA.

 

Use horizontal and vertical controls to steer beam and locate targets.

 

The following images are taken from the Welch Scientific Company Instructions for the Electron Diffraction Tube:

two-dimensional hexagonal pyrolitic graphite	polycrystalline aluminum	polycrystalline hexagonal p-graphite