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World-Class Work Coming from ODU Physics Lab

A series of physics experiments at the Super Proton Synchrotron (SPS) particle accelerator in Geneva, Switzerland, goes by the name COMPASS (for Common Muon and Proton Apparatus for Structure and Spectroscopy) and involves 240 of the smartest nuclear physics researchers on the planet. But the next phase of the project can't begin until some tedious work is done this summer on the campus of Old Dominion University.

ODU faculty and students are lending their expertise to the project together with counterparts from the University of Illinois at Urbana-Champaign and Abilene Christian University in Texas.

To understand the complexity of the task, one needs to start with basics. When physicists try to learn more about the fundamental makeup of matter, they smash particles at accelerator facilities such as SPS to try to identify how the particles are put together. But to do that, they have to be able to detect the sub-atomic particles that scatter from a collision, and that means collision sites have controlled environments called drift chambers into which the sub-particles fly.

ODU nuclear physicists over the years - largely as the result of their work with the Thomas Jefferson National Accelerator Facility in Newport News - have become very adept at building drift chamber/detectors. Now ODU has been enlisted to build components that will be airlifted to Europe as soon as they are finished in August to meet an early-autumn date for the beginning of a COMPASS experiment.

In the modern Physical Sciences Building on the ODU campus, the physicists have a High Bay Laboratory, and in it is a clean room with clear plastic walls and roof. Workers inside this dust-free womb dress much like doctors and nurses in a surgical suite. The drift chambers being built in the room are so sensitive that even a speck of dust could compromise their performance.

Each COMPASS component - eight must be built this summer - has a thin fiberglass frame about 9-feet-square. Across the expanse inside each square, workers stretch about 500 threads of 20 micrometers-thick gold-plated tungsten wire and 100 micrometers-thick gold-plated beryllium-copper wire. (The average width of a human hair is about 80 micrometers.)

"This is difficult work," said Stephen Bueltmann, ODU associate professor of physics and a project leader, as he watched two ODU students and three from Abilene Christian solder connection after connection while installing the wires. The "learning curve is steep," he added. "They are better at it than I am."

Bueltmann said the work is progressing well, but that he expects when the due date looms in August that the faculty members and students working on the project will have to "bear down," and work some overtime to get it done.

The high-tech, hot-air soldering tools - they don't need to actually touch the connections - must be handled very carefully, said Tom Hartlove, the senior laboratory specialist who presides over the High Bay. "That's really hot air."

At the SPS facility in Geneva, which is operated by the European Organization for Nuclear Research (CERN) and sits nearby the huge CERN Large Hadron Collider, the drift chamber components will be installed in such a way as to detect characteristics of particles scattering from collisions of an accelerated pion beam and a proton target. In other words, those hair-like, gold-plated threads, which will have an electrical current running through them, will be struck by the scattering sub-atomic particles, and characteristics such as the mass and spin of the particles can be gleaned from the strikes.

In Bueltmann's words, the research amounts to "a fundamental measurement comparing deep-inelastic scattering with the Drell-Yan process in pion production."

Precise installation of the threads, including exacting tension requirements for each one, require steady hands and watchful eyes - with some examinations requiring a microscope and computerized testing instruments.

ODU physics undergraduates Mathieu Ehrhart and Joshua Monroe are working on the project together with the Abilene Christian undergraduates Vicente Rojas Aguirre, Megan Cromis, James Mallon and Lacey Medlock.

Faculty leaders of the project include Bueltmann, IhnJean Choi and Caroline Riedl of the University of Illinois and Michael Daugherity of Abilene Christian. The University of Illinois is the lead institution in the international collaboration that is preparing for the next COMPASS experiment.

Two students from Ocean Lakes High School in Virginia Beach, where ODU assists with the Math and Sciences Academy, will be invited to join the project team later in the summer.

Even before the ODU nuclear physicists had their state-of-the-art High Bay they built drift chambers/detectors in an old warehouse on the east side of Hampton Boulevard, just off the main campus. That early work included construction completed in 1995 of the CLAS6 drift chambers for Jefferson Lab, a much lauded project led by Lawrence Weinstein, ODU Eminent Scholar and University Professor of Physics.

Since the High Bay became available almost six years ago, the physicists have completed work on the CLAS12, Region 2 drift chambers for Jefferson Lab. Beyond that, the members of the ODU nuclear physics group have designed, prototyped, constructed and maintained a recoil detector for an experiment in Jefferson Lab Hall A; silicon microstrip detectors for the STAR collaboration at Brookhaven National Laboratory, Long Island, N.Y.; and a novel radial time projection chamber for the BONuS experiment at Jefferson Lab.