OXFORD, Miss. – Two University of Mississippi physicists
have been awarded a competitive grant to build equipment to
be used in the ongoing search for new subatomic particles.
The National Science Foundation major research
instrumentation award for $798,819 is for development of a
superconducting magnet coil and radio frequency cavity,
which researchers hope to use to accelerate tiny particles
called muons until they collide head-on, creating new kinds
of subatomic particles. Muons are similar to electrons, but
200 times more massive.
The project is part of a worldwide effort to study the mass
of neutrinos, tiny particles with no electrical charge, and
to detect the elusive Higgs boson, the particle thought to
hold the key to the relative masses of all other subatomic
particles.
Donald Summers and Lucien Cremaldi, UM professors of
physics and astronomy, are co-principal investigators for
the two-year project. Both are longtime members of the
university’s High Energy Physics Group, which is involved
in several international projects to understand the
fundamental forces of nature.
“The university, along with the Lawrence Berkley National
Laboratory in California and the Thomas Jefferson National
Accelerator Facility in Virginia, is making these cavities,
which resemble very large and powerful microwave ovens,”
Summers said. The radio frequency, or RF, cavities, made of
copper, are about 5 feet in diameter and look like giant
pill boxes. But instead of pills, these devices store
high-power radio waves.
Radio waves consist of oscillating electric and magnetic
fields, and the team plans to use the electric fields to
accelerate electrically charged particles, such as muons.
“The muons ride an electric wave just like a surfer rides
an ocean wave,” Summers explained. “Similarly, low-power
radio waves from cell phone towers accelerate electrons in
cell phone antennas to transmit phone calls.”
The muons, which are unstable and decay into other
particles in just a fraction of a second, are made by
colliding a beam of protons with a metal target, he said.
“This produces muons with a high temperature 50 million
degrees Fahrenheit. We plan to cool them to 5,000 degrees
Fahrenheit.”
The relatively cool muons are easier to handle, Cremaldi
said.
“As the muons are cooled, they form compact swarms such
that their collisions should generate the new matter,” he
said.
To focus the muons as they are accelerated, the team uses a
superconducting magnet coil. Each RF cavity is surrounded
by a 6-foot-diameter-by-1-foot long wire coil.
“Three million amps of electricity will run through each
coil, creating a magnetic field 100,000 times stronger than
the field of the Earth,” Cremaldi said.
Instead of copper, the wire coils are made of nobium and
titanium metals and cooled to minus 452 degrees Fahrenheit.
This reduces the electrical resistance of the coil to zero,
making it a “superconductor,” Summers said.
“If we used a copper coil to generate the magnetic field
rather than a superconducting coil, it would consume 26
megawatts,” he said. “The UM campus consumes 18 megawatts.”
The ultimate goal is to get the RF cavities to accelerate
muons until they can collide, Summers said. “That’s going
to take a little bit of practice,” he said.
The project promises to help physicists better understand
the fundamental principles of physics that hold the
universe together, Cremaldi said.
“If successful, this acceleration experiment could be the
next step toward the discovery of dark matter, the
subatomic particles some astronomers have said comprise 90
percent of the mass of our Milky Way galaxy,” he said.
“Dark matter holds the Milky Way galaxy together, but so
far only its gravitational influence has been observed.”
Along with its collaborators, the UM team is to operate the
RF cavities at the Fermi National Accelerator Laboratory
near Chicago. FermiLab has agreed to supply the radio
frequency power to the cavities and to supply beams of
subatomic particles for the RF cavities to accelerate,
Summers said.
Besides Cremaldi and Summers, the team includes several UM
undergraduate and graduate physics students who will help
gather data.
The team’s application for the grant was peer-reviewed and
was among only a few chosen for funding, Summers said. The
results of this project are eagerly awaited by researchers
worldwide.
“One of the most critical components of accelerator
research today is to investigate the performance
limitations of very high-gradient radio frequency cavities
operating in the presence of strong magnetic fields,” said
Harold Kirk of Brookhaven National Laboratory in New York.
“Mississippi’s work will be of great benefit to us at
Brookhaven, and we wish UM the best of success with this
project.”
For more information about the Department of Physics and
Astronomy, visit
http://www.olemiss.edu/depts/physics?and?astronomy