Schematic of electron diffraction tube

(Click figure to enlarge)

Schematic of electron beam diffraction from a crystal film

(Click figure to enlarge)

Clear and sharp diffraction rings

## LEAI-62 Electron Diffraction Experimental Apparatus

Features

• More than 8 distinct and sharp diffraction rings enabling quantitative measurements

• Well isolated high-voltage and low-voltage by using a pulse-coupled transformer

• Fully sealed CRT and high-voltage connectors for student safety

Introduction

In the early 20th century, it was known that light has a property of wave-particle duality. In 1924, French physicist de Broglie presented a hypothesis that all micro particles have wave-particle duality. In 1927, American physicists Davisson and Germer conducted an electron reflection diffraction experiment with a crystalline nickel target. This experiment verified the de Broglie hypothesis and demonstrated the wave-particle duality of electrons. Later, a similar experiment was conducted by British physicist Thomson by letting electrons pass through a crystalline film to measure the de Broglie wavelength. Now, electron diffraction approach has become an advanced technology to study solid thin films and the surface layer of a crystal structure.

This LEAI-62 electron diffraction apparatus is equipped with a specially designed diffraction tube, whose structure can be observed through a transparent window on the side panel of the apparatus. The electron gun is designed to withstand high voltage with a long lifetime. The polycrystalline gold foil target is placed between the electron gun and the screen. Electron beam is accelerated by high voltage up to 20 kV to bombard the thin metallic target and hence a diffraction phenomenon is generated. The diffraction pattern is very bright and clear on the screen, enabling quantitative measurements.

Using this apparatus, the following experiments can be conducted:

1. Acquire the wavelength of a moving electron to verify the de Broglie equation.

2. Measure the lattice constant of a gold crystalline material.

3. Measure the Miller indices of corresponding diffraction rings.

4. Calculate the Planck's constant.

Specifications

 Description Specifications DC high voltage 0 ~ 20 kV adjustable; current 0.8 mA Filament voltage 6.5 V Screen diameter of diffraction tube 130 mm Diffraction target polycrystalline gold foil; diameter 15 mm Dimensions 360 mm × 200 mm × 520 mm

Part List

 Description Qty Main unit 1 CRT 1 Grounding cable 1 Mini plastic ruler 1 Power cord 1 Instructional manual 1

Schematic of electron diffraction tube

(Click figure to enlarge)

Schematic of electron beam diffraction from a crystal film

(Click figure to enlarge)

Clear and sharp diffraction rings