Gamma rays and X-ray
also tried using radium bromide to produce gamma-radiation.
He saw the same cloud tracks as he had seen for beta-particles,
but the tracks were in all directions, rather than directed
from the source. The walls of the chamber were absorbing
the gamma-radiation and emitting beta-radiation from
Wilson tried using X-rays. He saw 'minute streaks and
patches of cloud' throughout the region in the path
of the beam. The clouds were mainly short thread-like
objects, few of them moving in straight lines and some
of them even looping round. Wilson saw this as 'a very
direct proof' that X-rays liberated energetic electrons
in the gas, and that these electrons caused ionisation along
the path of the X-rays.
perfected his cloud chamber by 1912, and used it to
produce many wonderful photographs of the alpha, beta
and X-ray tracks. With his cooperation cloud chambers
were manufactured commercially by the Cambridge Scientific
Instruments Company, and remained the principle detector
for studying particle tracks until the invention of
the bubble chamber in the 1950s.
original cloud chamber is on display in the museum at
the Cavendish Laboratory.
to Cambridge Physics index