Explain the arrangement of the Davisson and Germer experiment.

(N/A) The wave nature of electrons was first experimentally verified by $C.J. Davisson$ and $L.H. Germer$ in $1927$ and $G.P. Thomson$ in $1928$.
Davisson and Thomson shared the Nobel Prize in $1937$ for their experimental discovery of the diffraction of electrons by crystals.
Experimental arrangement: The figure shows the schematic arrangement of the Davisson and Germer experiment.
It consists of an electron gun which comprises a tungsten filament $F$,coated with barium oxide and heated by a low voltage power supply ($L.T.$ battery). The filament is heated by passing a current through the $L.T.$ battery.
When the filament is heated,electrons are emitted due to thermionic emission,which are then accelerated by an $H.T.$ battery to a desired velocity.
These electrons are made to pass through a cylinder with fine holes along its axis,producing a fine collimated beam. The beam is made to fall on the surface of the nickel crystal.
Electrons are scattered in all directions by the atoms of the crystal.
The intensity of the electron beam scattered in a given direction is measured by an electron detector (collector).
The detector can be moved on a circular scale and is connected to a sensitive galvanometer which records the current.
The deflection of the galvanometer is proportional to the intensity of the electron beam entering the collector.
The entire apparatus is enclosed in an evacuated chamber.