Profiles

Chris Beltran

For graduate student Chris Beltran, the Los Alamos Neutron Science Center (LANSCE) at Los Alamos National Laboratory (the Laboratory) is the perfect assignment.

In a recent interview, he commented, "There are a lot of people around here who have been very helpful." He mentioned Robert Macek, Andrew Browman, and Tai-Sen Wang, all scientists at LANSCE. "We have meetings all the time," he said, and, "in general, the people around here have been very helpful if I have questions."

Graduate student Chris Beltran holds up a ferrite inductive insert as he discusses his research involving the Proton Storage Ring at the Los Alamos Neutron Science CenterHe's starting to write his thesis, and he hopes he can have his Ph.D. by the end of the year.

In the meantime, he is the lead author (with Browman and Macek) on an article entitled "Calculations and Observations of the Longitudinal Instability Caused by the Ferrite Inductors at the Los Alamos Proton Storage Ring (PSR)." And in May 2003, he presented this paper and described his work at the Particle Accelerator Conference in Portland, Oregon.

Beltran, originally from Las Vegas, New Mexico, has a fellowship through the National Physical Science Consortium—a fellowship that is sponsored by the Laboratory.

He earned his first degree, a bachelor of science in physics and mathematics, from New Mexico State University, and it was at NMSU that he first heard in detail about the work of the Laboratory. (A number of NMSU professors have collaborations at the Laboratory.)

Beltran went on to Indiana University, seeking a Ph.D. in physics, and found that his thesis advisor there, S.Y. Lee, was intrigued by the Proton Storage Ring (PSR) at LANSCE and its "interesting properties."

Lee spoke with Macek, and Macek felt that Beltran could do a good project at PSR—a project that would have value for the Laboratory while furthering Beltran's thesis.

PSR converts long macropulses of H- ions (hydrogen ions with two electrons) from the LANSCE linear accelerator into short, intense proton bursts that provide the capability for a variety of experimental programs. PSR "stores" the protons in its ring, holding them at different intensities—whatever the users need.

However, Beltran explained, "The Proton Storage Ring, at high intensities, has a large space-charge effect" that limits the intensity of the beam. In other words, the protons—all of which have a positive charge—repel each other, causing the beam to spread out instead of staying focused. For that reason, it is necessary to run the radiofrequency (RF) buncher at a higher intensity (energy) to keep the ball of protons bunched in the size desired.

Beltran is studying two things. The first is the process of PSR itself. The second is "inductive inserts."

These inserts—ferrite cores in annular shapes—have the ability to "counteract the space-charge effect and, therefore, eliminate the need to run the RF buncher at higher intensity," Beltran said. The result is a saving in electricity, which produces a saving in money. At present, there are two inserts (of 30 annular cores each) through which the beam is directed. Beltran is doing studies on the effectiveness of the process.

The inserts cure the space-charge effect, but there's a catch. Their presence produces another instability, a microwave instability at about 70 megahertz. So far, the only way to get rid of this second instability is to heat the cores up to about 350 degrees Fahrenheit—and this too takes power.

Beltran is working "to understand these ferrites and how they affect the beam and its properties"—why the new instability develops, for example. He is also seeking "a cure for this instability that does not require heating."

Is he enjoying his work and study? "Yes," he said. "I like the fact that my work has both experimental and modeling aspects. I also do a little bit of theory work." In addition, he said, "Any future high-intensity proton storage rings are going to have to deal with space-charge, so there is some future value in this work."

The next step in his career will be doing postdoctoral work, and, he said, "There's a good chance that I'll be doing it here." There is "much to be studied," he said, and the work seems worthwhile.

Photo: Graduate student Chris Beltran holds up a ferrite inductive insert as he discusses his research involving the Proton Storage Ring at the Los Alamos Neutron Science Center