5.
A Semi-Automatic Analyser
Frisch
began to concentrate on developing devices to measure
the tracks in bubble chamber photographs. The first
machine, TARA, was built with the help of Alan Oxley.
TARA stands for 'Track Analysing and Recording Apparatus'.
It was slow, manually operated and similar to machines
built in the USA, but was enough to make Frisch and
the Cavendish group useful to other bubble chamber physicists.
The Cavendish group were given film from CERN, and in
return showed teams abroad how to use the measuring
devices.
In
1960 Frisch published a paper that described TARA. The
machine was not fully automatic. Two photographic films
from bubble chamber cameras were projected from below
to form a sterescopic image on a screen. A cross-hair
was fixed on the screen, and the film could be moved
to align points of interest under the cross-hair. The
operator then pressed a button to record the co-ordinates
of the point on a punch-tape which could be read by
EDSAC, the early electronic computer at Cambridge.
The
user could view the film in detail at thirteen times
magnification, and move it easily by hand using a 'pantograph',
a device which reduced the motion by a factor of eight.
But images could strain the eyes of the operator, and
the speed of operation was limited by the time taken
to align the films under the cross-hair. Frisch worked
on improving this first device.
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