16mm Camera for Recording Movement of Electroscope Fibers (1930s)

These unusual looking devices are 16mm movie cameras designed and built by Hugh Carmichael at the Cavendish Laboratory, ca. 1934.

Carmichael electroscope

The box (ca. 9" x 9" x 2.5") is possibly made of birch while the metal components are brass and steel.

Carmichael electroscope

This photograph shows a camera that has been opened up so as to permit a view of the film transport mechanism. 

The lens of the camera was focused on the fiber of an electroscope connected to a large ionization chamber. Cosmic ray interactions in the chamber would cause a sudden deflection of the fiber and this deflection was recorded on the slowly advancing (0.1 mm/sec) film. The filming not only facilitated investigation of these relatively infrequent events, it also permitted a mathematical analysis that would give the size of an off-scale deflection.

Donated by Hugh Carmichael.

Carmichael electroscope

This figure shows two sections of 16mm film indicating the normal fluctuations of cosmic rays and two ionization bursts.