Spring 1998

Small Universe

Throwing Subatomic Baseballs

by Margie Shetterly
photos by Doug Sesny

Through his work with the Thomas Jefferson National Accelerator Facility in Newport News, Va., JMU physics professor Kevin Giovanetti has given his students a chance to be in on the ground floor of a state-of-the-art national research facility. He also has provided students with hands-on experience in problem solving, working side by side with some of the top physicists in the world.

Dr. Kevin Giovanetti rides the lift above the detector.

"It's an opportunity senior Justin Voshell describes as an "immersion experience – much like going to a foreign country. Here's a place with 1,000 geniuses, and you get to ask questions for free.

"The best thing that comes out of it is seeing the level of work" being conducted at the Continuous Electron Beam Accelerator Facility at the Jefferson Lab, Voshell says. That, in turn, puts the textbook material he has learned in classes into context and gives it relevance. "A lab like this gives you a reason to learn the physics," he says.

For approximately 20 JMU undergraduates, CEBAF has been that off-campus lab – a state-of-the-art particle accelerator where students combine theory with practicality and learn that applied physics is really an interdisciplinary exercise.

Giovanetti's involvement in the $554 million project dates to the late 1980s, during the conceptual and design phase of CEBAF. Last summer, he and five JMU students helping with his project finished the construction and installation phase of their calibration system. Then in the fall, they started final testing and collecting data from experiments.

Giovanetti's work centers on the huge electromagnetic calorimeter in Experimental Hall B, a detector that records what happens when, for example, a speeding electron strikes it. "It's like a bullet fired into a block of wood," Giovanetti explains. "The energy from the bullet is transferred to the block of wood, and most of that energy shows up as heat energy." In the case of CEBAF experiments, the bullet is a scattered electron or another subatomic particle and the block of wood is the detectors.

Giovanetti's main responsibility at CEBAF has been to design and install the calibration system for the calorimeter so that it can accurately measure the energy given off when the particles collide and what changes happen to those particles. Included in that calibration is the design and installation of a laser with a fiber-optic distribution system and computer-controlled slit patterns. This system, which directs light to specific elements in the detector, monitors the response of critical components.

His secondary responsibilities have included testing the whole calorimeter, assisting in running experiments, helping with data analysis and planning experiments. Voshell, who is double majoring in physics and mathematics, has been focusing on the mechanical aspects of the calibration system. One particular concern was building in safeguards to prevent damage when remotely moving the slit patterns. He also wired the entire device, which includes hundreds of different wire connections. The work, both painstaking and crucial, mirrors the entire CEBAF operation. "Millions of things have to go right each time," Voshell says.

Voshell describes his work as "almost more of an engineering problem," – making mechanical parts work and interface with the computer at CEBAF. In that respect, CEBAF research reflects much that's typical in the field. "It's far more than physics," Voshell says. It also encompasses "all these things you have to learn to do well to be able to do the physics." Someone who excels in the field of physics "is not just this guy that knows Newton's laws," Voshell notes. Rather, training involves combining expertise in a number of disciplines. "Physics is simultaneously the most theoretical and most applied of the sciences."

Jefferson Lab Continuous Electron Beam Accelerator Facility

An electron "gun" (A) sends a continuous beam of electrons at near-light speed into an injector, which increases the beam's speed and directs it into a three-quarter-mile "track."

The beam makes laps around the track through two accelerators, which again increase the speed, until the beam reaches maximum energy (4 GeV). Then the beam and its electrons divert to three experimental halls. JMU activity occurs in Hall B.

Hall B's Detector and calorimeters

Inside Hall B, electrons from the accelerator strike a target at the center of the CLAS detector (A). The resulting interactions produce particles that are tracked and measured by components of the detector. Components include a superconducting magnet and thousands of wires in the detector's center (A), known as wire chambers, and Cherenkov and time-of-flight detectors (B and C).

Several calorimeters, which measure the energy of resulting particles, comprise the final layer of detectors. Kevin Giovanetti and his students have concentrated on the performance of the forward calorimeter (D) by developing and maintaining its calibration system.

Walter Opaska, a senior physics major, blended physics with an interest in computer programming to design the programs for the computer controls of the calibration system and to make sure those programs work with CEBAF's main computer network.

For Opaska, the CEBAF project has provided hands-on experience in problem solving. Giovanetti assigns his student researchers a specific task, gives them an overview of what needs to be done, and provides guidance and advice along the way. But basically, it's up to the students to figure out the best way to do it, Opaska says. "A lot of it was sink or swim."

"It says something for Dr. G that he can take a ragtag group of undergraduates and give them a chance and the trust and independence" to succeed, Voshell says.

Their work with CEBAF was the topic of papers that both students presented in 1997 at the National Conference of Undergraduate Research in Austin, Texas. Those presentations and the continued research at CEBAF will add up to big pluses for both when it comes to landing jobs or admission to graduate programs.

Last summer found Voshell working with Giovanetti on the CEBAF research as the facility entered a new phase in its short history – shifting from a huge construction project to an active, fully operational research facility. During the fall '97 semester, he was left in charge of the day-to-day responsibilities of the CEBAF project while Giovanetti spent a semester abroad teaching in Italy.

Opaska spent the early part of last summer at JMU working on the CEBAF project and then participated in a research program for undergraduate students in Atlanta. He spent the fall '97 semester at Los Alamos National Laboratory.

For these students and top physicists in the world alike, CEBAF has opened new opportunities for research and inquiry into the world of subatomic particle physics that previously were unavailable.

Unlike other existing particle accelerators that pulse the electron beam on and off, and in the process create thousands of nuclear collisions or interactions at once, CEBAF offers a continuous beam that can produce a steady flow of distinct nuclear collisions that can be recorded and analyzed.

"It's just like throwing baseballs," Giovanetti says. You can bombard the catcher with 200 baseballs all at once, but he probably won't catch many. But if you throw them one at a time, the results are far more successful. The same holds true with CEBAF, Giovanetti says. "There's just no other way to get those baseballs caught and put in the bucket."

Physicists are interested in measuring what happens during and after the collisions to find clues to the most fundamental of scientific questions – How are subatomic particles put together? How do they react under controlled collisions? How much energy is needed to create new particles? and What does this tell us about the quarks and gluons that comprise protons and nuclei?

Since the results of the collisions can't be detected by the eye, a series of sensitive detectors are positioned around the target to measure the properties – energy, charge, mass, speed and direction – of the scattered particles.

With the designing, installing and testing of the calibration system that makes it possible for the detectors to measure these properties now complete, Giovanetti, like CEBAF, is entering a new phase. "I'll look to getting my experiments done and defining a role for JMU at CEBAF." He is sure that role will continue to offer both him and his students hands-on experience at one of the country's premiere particle accelerator facilities.

CEBAF and the Jefferson Lab are funded by the U.S. Department of Energy and are managed by SURA, the Southeastern Universities Research Association, a consortium of 41 universities. More than 100 universities have been involved with the program, which also attracts physicists from around the world.

Giovanetti's research at CEBAF has been funded by $90,000 in construction grants from SURA/CEBAF and two three-year grants from the National Science Foundation for $120,000 and $90,000. Additionally, JMU has supported Giovanetti's work through the JMU Foundation's LaRose Faculty Fellowship.

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