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Key
Questions We Want to Answer:
The
Lambda Point Experiment (LPE) flew aboard the Space Shuttle
Columbia (STS-52) in 1992 with the U.S. Microgravity Payload
(USMP-1) mission. LPE was a vanguard experiment, taking
advantage of the Shuttle's microgravity environment to perform
ultra-precise measurements at the superfluid transition
of helium.
What We Already Know:
LPE
provided the strictest tests to date of theories that apply
to cooperative phase transitions. A cooperative phase transition
occurs in a material when it passes from a disordered state
to an ordered one. The lambda transition of liquid helium,
where supercooled helium transforms from a normal fluid
into a superfluid, is an example of a cooperative phase
transition. The lambda name came from the shape of helium's
specific heat curve near the transition point, which is
similar to the Greek letter lambda.
What We Hope to Find Out:
The
focus of the experiment was testing Kenneth G. Wilson's
Renormalization Group Theory, for which Wilson was awarded
the Nobel Prize. Renormalization Group Theory postulates
the nature of phase transitions, which are common occurrences
in nature. A phase transition is as familiar as ice melting,
as the water makes the change from a solid state into a
liquid state.
How We'll Conduct Our Experiment:
LPE
helped to build a wealth of data with wide-ranging implications
for the examination of theories of phase transition behaviors.
LPE pioneered technologies to make instruments and experiments
capable of delivering precise measurements at the low temperatures
of the lambda transition. Since this was the first major
experiment of this type, it has provided many kinds of information
that later experiments can utilize.
The
LPE instrument consisted of ultra-precise thermometers and
a test apparatus whose temperature could be held very stable.
The high-resolution thermometers functioned in conjunction
with a superconducting quantum interference device, nicknamed
SQUID. The experiment was performed by pulsing heat into
the well-isolated liquid helium sample and measuring the
change of temperature caused by the heat pulse. By operating
very close to the phase transition, the way that the helium's
specific heat changes as the transition is neared can be
deduced. Additional information:
Additional information:
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