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# Electron Diffraction

## Purpose

1) To demonstrate the wave properties of electrons.
2) Examine the DeBroglie relation $\displaystyle \lambda = \frac {h}{\vec p}$
3) To measure the diffraction planes of graphite.

## Theory

the wavelength of a proton traveling at .5c is on the order of 10^-3 pm! the diameter of an atom is around 60 to 600 pm!

## Equipment

• Tel 2501 Universal stand
• Electron Diffractor 2555 (5Kv .3mA)
• Teltron Limited London England 813 KV Power Unit
• HP 6216B Power Supply
• Wavetek Meterman 85XT multimeter
• Carrera Precision 6" digital caliper alloy

## Safety

1. The main safety concern during this procedure is electrical shock as high voltages(813KeV power supply) will be used. Standard high voltage safety precautions should be taken, including checking all equipment for damage and ensuring the equipment is properly connected.
2. The second concern is the integrity of the equipment. Most importantly, the graphite diffraction tube. As indicated in the lab manual, the graphite is extremely thin and can be easily punctured by current overload. Use the multimeter to ensure the current stays below the maximum allowed current (0.25mA). Additionally, check the target regularly during the experiment for a red glow, indicative of current overload.

## Procedure

The procedure should be followed from the Lab Manual experiment 3, electron diffraction.

The following circuit was set up, with the following modification: The low voltage bias was inverted; a multimeter was put in series between the positive HV source and plug G7 on the mount to measure current. NOTE: the max voltage measurable by the multimeter is 1000V. It is important to only measure current with the multimeter while it is connected to prevent damage to the instrument as up to 5kV will be used in this experiment. Image taken from here

## Raw Data

The rings were very difficult to discern while centered, but with a slight offset, they became easier to measure. The offset will be recorded for each voltage.

Voltage Inner Diameter Outer Diameter Center Offset
5.00kV
4.90kV
4.80kV
4.70kV
4.60kV
4.50kV
4.40kV
4.30kV
4.20kV
4.10kV
4.00kV