In the darkroom, a photographic film is exposed to alpha rays.
After developing this film, one sees the spot created by the impact of alpha particles.
This is a glass container with a thick wall.
We insert a source of alpha rays.
A very thin gold leaflet is positioned before the source .
In the darkroom we line the container with a photographic film.
The container is closed.
The closure is air-tight.
Air is evacuated and the container is abandoned like that for a long time.
This is the film after developing.
On the central spot, there are many impact points of alpha particles.
Around that, impact points are quite scarce.
