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

MURA physicists are becoming bubble watchers,   p. 14


Page 14


MURA physicists are becoming
                                               Bubble Watchers
University scientists
     record the track
          of an atomic
particle to uncover
             new secrets
A $600,000 BUBBLE CHAMBER-
     one of the largest of such devices
in the world-is being designed and
built at Midwest Universities Research
Association (MURA) in Madison.
  A bubble chamber allows physicists
to see atomic particles and "watch"
their collisions. Invention of this device,
now used extensively by atomic physi-
cists, won the 1960 Nobel Prize for
University of California physicist Dr.
Donald A. Glaser.
  Bubble chambers are essentially large
metal cylinders filled with a superheated
liquid-one just on the verge of boil-
ing. A tiny charged atomic particle pass-
ing through the chamber is enough to
start the liquid boiling and leaves a line
of bubbles behind it.
  Physicists "watch" atomic particles in
a bubble chamber just as we "watch"
a high flying jet plane by following its
white track.
  The MURA bubble chamber is now
in the design stage under direction of
University of Wisconsin physicist Dr.
W. D. Walker. Working with Dr.
Walker are two physicists from Purdue
University, Dr. George Tautfest and
Dr. Harry Fechter, and another Wiscon-
sin physicist, Dr. Robert March.
  The chamber is a stainless steel cylin-
der 30 inches in diameter. It will be
filled with liquid hydrogen which boils
at about 400 degrees Fahrenheit below
zero.
  A 150-ton magnet surrounding the
chamber will bend the paths of the
charged particles moving through it,
helping each type of particle to leave
its own signature written in a line of
bubbles.
  The bubble chamber's cylinder is
fitted with a piston which puts pressure
on the liquid hydrogen. When the pis-
ton is released, lowering the pressure,
the liquid becomes superheated. For
about one hundredth of a second, the
liquid is sensitive to particles passing
through it, then it begins to boil, and
the piston is pushed down, stopping the
boiling.
  The cycle is repeated over and over
again, and photographs are made of the
paths left by the particles.
  High energy atomic particles are con-
tinually present in the earth's atmos-
phere as a result of cosmic rays bom-
barding the earth from space. But physi-
cists produce these particles in large
quantities and under controlled condi-
tions in particle accelerators, or atom
smashers.
  The MURA bubble chamber, after
completion, will be   moved   to  the
Argonne National Laboratory near Chi-
cago to be used with a particle acceler-
ator under construction there.
  Physicists now have discovered 30
atomic particles-relatives of electrons,
protons, and neutrons. They understand
"weak-interactions" of these particles to
a certain extent, but know little about
"strong interactions." The new bubble
chamber probably will be used in re-
search to learn more about the strong
interactions of the  30-odd  building
blocks of matter.
  The Atomic Energy Commission is
financing construction of the new cham-
ber for MURA.
  MURA is a non-profit corporation
organized to operate a research center
in the Midwest. It is composed of 15
educational institutions: University of
Chicago, University of Illinois, Indiana
University, State University of Iowa,
Iowa State University, University of
Kansas, University of Michigan, Michi-
gan State University, University of Min-
nesota, Northwestern University, Uni-
versity of Notre Dame, Ohio State Uni-
versity, Purdue University, Washington
University of St. Louis, and the Univer-
sity of Wisconsin.
     Wisconsin Alumnus, June, 1961
14


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