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Electron Gun

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Lab Activities

Using a homemade electron gun, students do the following:

a. measurement of the mean free path of an electron vs the pressure in the gun; by plotting the data the students confirm that P is proportional to 1/L and from the slope of the line the ra-dius of an air molecule can be computed;

b. qualitative observation of the motion of an electron in an electric field;

c. qualitative observation of the magnetic focusing of a divergent electron beam in a uniform magnetic field when the beam is directed parallel to the direction of the magnetic flux lines; measurement of the electron velocity and the cyclotron frequency;

d. measurement of the charge to mass ratio for the electron; and

e. qualitative observation of a plasma.

All quantitative results are of order of magnitude agreement only.

Course Level


Student Handouts


Number of set-ups available: 1

Per lab station:

1 vacuum pump/hose
1 main power supply
1 light/e-gun platform
1 ruler
1 flashlight
1 circle template
1 black backdrop
1 high voltage power supply
1 36" red banana lead
1 black electrical deflection lead
1 right angle copper tubing/thermocouple
1 set of Helmholtz coils/leads
1 Helmholtz coil power supply
1 C-clamp
1 electron gun/filament shield

Per class:

1 vernier caliper
1 accelerating anode from an e-gun
1 dead gun rack



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Site contact: largent@Dartmouth.EDU

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