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Hove, Arthur (ed.) / Wisconsin alumnus
Volume 62, Number 14 (June 1961)

Smashing the atom,   p. 15


Page 15


This model atom smasher is the first machine to test the colliding beam principle
experimentally. Two beams of electrons will be
accelerated in opposite directions around the orbit described by the ring
of magnets shown above.
Smashing the Atom
p HYSICISTS at the Midwestern Uni-
   versities Research Association on the
University of Wisconsin campus are
modifying the 38-million volt atom
smasher of new design for tests this
spring and summer. The machine, first
operated last year, is the first particle
accelerator to collide two beams of
oppositely directed electrons. MURA
scientists designed and constructed this
atom smasher to test the principle of the
fixed-field, alternating-gradient acceler-
ator which, it is hoped, MURA will in-
corporate eventually into a huge multi-
billion volt machine.
  Keith Symon, a Wisconsin physicist,
is technical director of the MURA
group which has been working out the
new design.
  Basically, atom smashers have two
tasks-to give nuclear particles high
energy by accelerating them to high
Wisconsin Alumnus,.June, 1961
speeds, and to aim the particles at tar-
gets of atoms or other nuclear particles.
Physicists study the resulting collisions
to learn more about the structure of
matter. New accelerators such as the
proposed MURA multi-billion volt ma-
chine represent attempts to bring more
and more particles to higher and higher
energies prior to collision.
  Prof. Francis Cole, a visiting MURA
scientist from the State University of
Iowa, said modifications now under way
on the 38-million volt machine include
the addition of coils to correct the
shape of the magnetic field. This field
guides electrons   along  a  prescribed
path within the atom smasher. The
present magnetic field differs by a few
per cent from that desired theoretically.
  MURA scientists also are construct-
ing a device to measure the electron
beam intensity. Such a device is unusual
-most atom smashers have mechanisms
to detect the position, but not the in-
tensity, of the electron beam.
   Measurement of the beam's intensity
is useful with the MURA machine be-
cause new focusing methods enable it
to accelerate a thousand times as many
particles as was possible with previous
atom smashers.
   This is accomplished by circulating
batches of particles at different energy
levels. The batches can be accelerated
in steps, then left to coast while other
batches are raised to the same energy.
   The large quantity of highly-ener-
gized particles produced in FFAG ma-
chines will be useful for studies of
extremely rare collisions. To be conclu-
sive, such studies often demand a great
number of observations, making them
impractical now but possible with the
proposed multi-billion volt accelerator.
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