For the development of new techniques to control particle beams, Dmitry Teytelman (ARDA) will receive the 2004 APS Outstanding Doctoral Thesis Research in Beam Physics Award. Teytelman did his research at SLAC while a graduate student in Stanford’s Electrical Engineering Department and is now an engineer in ARDA.

Dmitry Teytelman is the sixth SLAC graduate student to win the APS’s award since it was first bestowed in 1991. (Photo by Diana Rogers)

Scientists who use electron storage rings have insatiable appetites for higher beam current, which translates into more data and brighter synchrotron light sources.

But you can’t just keep packing more particles into a ring. Put bunches of particles close enough, and they become electromagnetically coupled. Think of the bunches as rubber balls connected by springs—if one rubber ball hits a bump, the springs transmit the shock to all the other balls. In a high-current ring, the moving particles excite electromagnetic fields, which in turn bump the beam and make it so unstable that it is almost instantaneously lost.

Teytelman worked out new techniques that sample the motion of bunches in the ring, compute the best way to damp the beam’s longitudinal deviation from the desired path and generate signals to correct the beam. The task requires parallel processing of billions of operations per second.

"These particles can be moving at very nearly the speed of light, in bunches just nanoseconds apart," says John Fox, Teytelman’s advisor. "Dmitry found some very, very clever ways to understand what beams are doing and respond."

An International Solution

Because many labs would be facing the same challenge, Fox helped form a collaboration to address it among SLAC, LBL, and LNF, the Italian lab that is home to DAFNE. "Labs usually do very one-of-a-kind custom things," Fox said. "We did a very general solution and all the labs can directly share the operating experience. It’s been a great thing to do."

Teytelman first worked on these longitudinal multibunch feedback systems in the Advanced Light Source (ALS) at LBL. From this initial testbed, the SLAC/LBL/LNF group went on to construct instability control systems for the PEP-II B factory at SLAC; DAFNE, the phi-meson factory in Italy; the Pohang Light Source in Korea; and the BESSY II light source in Germany. Teytelman commissioned all of these systems, each of which uses his control techniques and software.

"Twelve or thirteen years ago, people recognized that beam instability in a high-current ring would be a serious problem," said John Byrd, leader of the Beam Electrodynamics Group at LBL. "Now, it’s a solved problem, thanks to the approach championed by John Fox and in large part designed and implemented by Dmitry when he was a graduate student."

"Solving the instability problem is critical for this kind of machine," said Greg Stover, ALS project electronics engineer. "Dmitry’s undaunted efforts and creative intelligence were the sine qua non of the commissioning process; it just wouldn’t have happened without him."

"Dmitry Teytelman is internationally recognized as one of the top experts in the field," said Mario Serio, leader of DAFNE’s beam diagnostics and controls group. "I consider his work a major step toward the comprehension and control of high-current multibunch dynamics in storage rings present and future. The whole accelerator community has gained from his activities."

Teytelman’s career path had a few perturbations of its own. The son of two mathematicians, he received an electronics kit for his tenth birthday with which he constructed such devices as a radio signal generator and a moisture detector. "I’d always been interested in math and physics; that got me interested in electronics," he said.

After completing high school in his home town of Minsk, Teytelman entered the prestigious Moscow Institute of Physics and Technology. A year later, in 1990, he experienced a major longitudinal shift: he immigrated with his family to Brooklyn.

Teytelman presented himself at the admissions office of Columbia University, where he was informed that March was too late to apply for admission the next fall, and that his transcript from Moscow did not carry the same weight here as in the former Soviet Union. Demoralized, he went to work as a technician in a TV/VCR repair shop.

Through his younger brother, Teytelman met a professor from the City University of New York, Staten Island, who generated a well-calculated correction signal: "Come down tomorrow to register. These are the courses you’ll take your first semester." Three years later, Teytelman had completed two B.S. degrees, in electrical engineering and in physics.

When Teytelman began graduate studies at Stanford, he was interested in "the pure electronics" of very fast systems. But, as the path of an electron in a particle beam is influenced by the electrons ahead of it, his interest began to shi. as he worked at SLAC with accelerator physicists.

"At SLAC, I came into contact with top-notch people in accelerator physics. Working alongside them was a great learning experience," Teytelman said.

"His thesis wasn’t pure theory, and it wasn’t pure technology," said Fox. "It was a beautiful combination that required deep mastery of both the beam dynamics and the technology of digital signal processing."

The annual award includes an honorarium of $2,500, a certificate and an invitation to present the work at the Division of Physics of Beams annual meeting.

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