Junior Laura Salo spent the summer working with the Cornell Electron Storage Ring, running sim­u­la­tions to determine how dif­ferent mod­i­fi­ca­tions would affect the machine. Laura Salo | Courtesy

Only 40 feet under­neath Cornell University’s football field, electron and positron beams race around a half-mile loop of narrow piping nearly as fast as the speed of light in a machine known as the Cornell Electron Storage Ring, or CESR.

Junior Laura Salo’s research involving CESR at Cornell this past summer helped move the team one step closer to achieving the goals of the Cornell Lab­o­ratory for Accel­erator-Based Sci­ences and Edu­cation, CLASSE, to produce the brightest source of X-ray beams in the United States.

“As the par­ticles pass through deflecting mag­netic fields, X-rays are emitted and these are used for X-ray research at Cornell,” said Michael Billing, an accel­erator physicist at Cornell and Salo’s research super­visor.

Salo worked in the Wilson Lab­o­ratory at Cornell where she used a com­puter program to determine how some pro­posed mod­i­fi­ca­tions, called the CHESS-U upgrade, would affect the sta­bility of the par­ticle beam in the machine. After elec­trons and positrons have been accel­erated in a dif­ferent ring, they are moved into CESR, where these beams are main­tained near the speed of light, Salo said.

“When the beams get up to speed, they’ll exit the ring and go into the Cornell Electron Storage Ring, or CESR, and it’s in that storage ring that they are main­tained at this speed,” Salo said. “That’s also where they oscillate the beam to produce X-rays.”

The X-rays can then be used in other research projects to study the char­ac­ter­istics of dif­ferent samples as they interact with the destructive X-ray beams.

To improve the brightness of the X-ray beams pro­duced using CESR, researchers at the lab­o­ratory pro­posed adding new com­po­nents along the ring and replacing parts of the ring with narrow pipes that would require a more focused beam, Salo said.

Before they could make these mod­i­fi­ca­tions, however, the research team needed to know pre­cisely how the upgrade would affect the sta­bility of the par­ticle beam..

“You’ve got to have a pretty focused beam to get par­ticles moving near the speed of light to con­sis­tently shoot through a narrow pipe,” Salo said. “That’s what my project was doing. I was basi­cally cal­cu­lating how stable the beam was based on the impact from dif­ferent factors in the ring, like undu­lators, wig­glers, and col­li­mators — just dif­ferent things that they need to make the ring function or to gen­erate X-rays.”

Salo’s work cal­cu­lated how dif­ferent com­po­nents of the ring affected the oscil­lation of the beam as it travels around the ring. She focused on a par­ticular char­ac­ter­istic of the beam’s motion: the tune shift, and what limits that char­ac­ter­istics places on the beam’s overall sta­bility.

“They wanted to know how many elec­trons can be in the beam at one time, or basi­cally how bright they can make the beams,” Salo said. “Tune shift is going to limit that.”

To cal­culate the impact of each indi­vidual com­ponent and the overall tune shift, Salo wrote a com­puter program that esti­mated their effect on the beam’s sta­bility. She used undu­lators, a com­ponent of the ring where the beam pipe becomes much nar­rower, as a test case to make sure her program worked cor­rectly.

“Undu­lators cause huge tune shifts, and they want to put about five more undu­lators in the ring,” Salo said. “They don’t quite know what the effect will be from them. That’s why I wrote a com­puter program to predict what the tune shift will be after the upgrade.”

Once she obtained esti­mates from the program, Salo com­pared the numbers to her mentor’s the­o­retical cal­cu­la­tions and data from exper­i­mental runs done with the machine, and found them to be in good agreement, Salo said. After running another test with the col­li­mators, she ran the program to predict results for the upgrade.

Then, she pre­sented her findings to other researchers at Cornell who needed her results for their cal­cu­la­tions. The other researchers incor­po­rated her pre­dic­tions into their own parts of the project, Salo said.

“My results made them reex­amine some cal­cu­la­tions based on my numbers, but it was cool to be able to influence what they were doing,” Salo said.

She said she also enjoyed working in an office in the CESR control room, where she was able to meet some of the oper­ators and learn a lot about how the ring worked.

“It was really neat because I got firsthand knowledge of what was hap­pening with the machine the entire summer,” Salo said. “First thing I did when I walked in in the morning was to check the status of the machine: whether it was on or down and how long the beam had been running. Of course, when some­thing hap­pened, you heard the alarms go off, so I got used to what all the dif­ferent alarms meant. You’d hear one go off, and then a split second later you’d hear one of the oper­ators running across the floor to go do some­thing. It was fun to be right there in the control room.”

Physics department chair Ken Hayes said Salo was one of two Hillsdale stu­dents to conduct research at other col­leges over the summer through a national program that pro­vides under­graduate stu­dents with an oppor­tunity to conduct research.

“We encourage all of our physics majors to apply for summer REU posi­tions,” Hayes said in an email. “REU’s are very helpful for the stu­dents as they get to expe­rience what graduate-level research is like at a research uni­versity. Also, having done an REU greatly strengthens a student’s appli­cation to graduate school…Hillsdale College physics majors have been quite suc­cessful in obtaining REU posi­tions.”

Billing said future research will also use the same software Salo used over the summer.

“Laura’s results pre­dicted a rea­sonable oper­ating charge… and we will con­tinue to utilize this software to optimize the maximum charge [for dif­ferent parts of the beam],” Billing said in an email. “The higher charge per [section of the beam] allows enough decay time for the physi­cists to study the dynamics of mol­e­cules after being excited by X-rays before the X-rays from the suc­ceeding [beam section] arrive on the sample.”

Billing said Salo was diligent and focused on the project, and some­times worked long hours to achieve her research goals.

“Laura’s work during the summer was very suc­cessful, and my col­leagues and I enjoyed working with her,” Billing said in an email.