3B SCIENTIFIC® PHYSICS
1
Electron Diffraction Tube D
U19171
Instruction sheet
08/08 ALF
1 4-mm sockets for connecting
heater supply
2 2-mm socket for connecting
cathode
3 Internal
resistor
4 Filament
5 Cathode
6 Anode
7 4-mm plug for connecting
anode
8 Focussing
electrode
9 Polycrystalline graphite grating
10 Boss
11 Fluorescent screen
1. Safety instructions
Hot cathode tubes are thin-walled, highly evacu-
ated glass tubes. Treat them carefully as there is a
risk of implosion.
•
Do not subject the tube to mechanical stresses.
•
Do not subject the connection leads to any
tension.
•
The tube may only be used with tube holder D
(U19100).
If voltage or current is too high or the cathode is at
the wrong temperature, it can lead to the tube
becoming destroyed.
•
Do not exceed the stated operating parame-
ters.
•
Only change circuit with power supply equip-
ment switched off.
•
Only exchange tubes with power supply
equipment switched off.
When the tube is in operation, the stock of the tube
may get hot.
•
If necessary, allow the tube to cool before
dismantling.
The compliance with the EC directive on electro-
magnetic compatibility is only guaranteed when
using the recommended power supplies.
2. Description
The electron diffraction tube illustrates the wave
nature of electrons by allowing observation of
interference caused by a beam of electrons passing
through a polycrystalline graphite target on a fluo-
rescent screen (Debye-Scherrer diffraction). The
wavelength of the electrons can be calculated for
various anode voltages from the radius of the dif-
fracted rings and the distance between the crystal
layers in the graphite. The tube also confirms the
de Broglie hypothesis.
The electron diffraction tube is a highly evacuated
tube with an electron gun consisting of a pure
tungsten heater filament and a cylindrical anode
all contained in a clear glass bulb. The electrons
emitted by the heated cathode are constrained to a
narrow beam by an aperture and are then focussed
by means of an electron-optical system. The result-
ing tight, monochromatic beam then passes
