The science
Accelerators generate beams of subatomic particles for cutting-edge science. The greater a beam’s intensity, the more opportunities there are to study particle interactions. One way to increase the intensity is to merge two beams with a technique called slip-stacking. However, when combining them, the beams’ interaction may cause instability.
Here, I summarize the results of a study in which I modeled these effects and concluded that a special feedback would make the beams much more stable. The required feedback was then designed and implemented by Nathan Eddy and his Fermilab team. The result was a 20% increase in proton beam intensity and a reduction in beam loss by a factor of 2.
A new method improves the circulating beams in the Recycler Ring (located beneath the ponds shown here), a major component of Fermilab’s accelerator chain. Photo: Reidar Hahn
The impact
Slip-stacking doubles the intensity of particle beams. However, it makes them more prone to instabilities and particle losses. To suppress these undesirable effects, an analysis and resulting feedback helped pave the way for future particle accelerators that rely on slip-stacking to achieve high intensities.
Summary
By stacking two separate, full-to-the-brim beams, researchers maximize the number of particles circulating through the ring. That’s good for creating high-intensity beams, but there’s a trade-off.
Accelerator-generated beams are made of bundles of particles called bunches. Accelerating two separate beams that are not only in close proximity but whose constituent bunches are in a constant dance with each other is a highly charged situation. In Fermilab’s Recycler Ring — a major component of the lab’s accelerator chain — each beam comprises about 500 bunches. Such a high number made coupled-bunch interaction a powerful source of collective instabilities. Partly because the distances between the two slip-stacking beams’ bunches are always changing, the beam dynamics is complicated to model.
One major effect is that the interacting bunches bump each other off their orbits. A mathematical model of the two-beam system was suggested and analyzed, followed by a proposal for a feedback suppressing these undesirable departures from the path. In the feedback system, pickup sensors placed inside the circular accelerator measure the offsets of the bunches from their intended orbits. An amplifier receives this information and then sends it to a kicker that gives the straying bunches a kick that sends them on the right path.
Soon after the idea of the special feedback was proposed, an accelerator team led by Eddy designed and installed the device into the Recycler Ring. As a result, the Recycler beam losses were nearly halved, and the beam intensity increased by 20%; the proton beam power achieved 700 kilowatts, one of the goals of Fermilab’s accelerator program.
Alexey Burov is a Fermilab scientist.
Editor’s note: This article was originally issued by the Department of Energy.
WASHINGTON, D.C. – On June 4, the U.S. Department of Energy (DOE) announced $75 million in funding for 66 university research awards on a range of topics in high energy physics to advance knowledge of how the universe works at its most fundamental level.
The projects involve scientists at 51 U.S. institutions of higher learning across the nation, and include both experimental and theoretical research into such topics as the Higgs boson, neutrinos, dark matter, dark energy and the search for new physics.
“Research in high-energy physics not only advances our understanding of the universe, but is also critical to maintaining American leadership in science,” said Under Secretary for Science Paul Dabbar. “These research efforts, at dozens of universities across the nation, will not only yield fresh insights into such problems as dark matter and dark energy, but also help build and sustain the nation’s science and technology workforce.”
Projects include experimental work on neutrinos at DOE’s Fermi National Accelerator Laboratory; the search for dark matter with the LZ (LUX-ZEPLIN) experiment one mile below the Black Hills of South Dakota; the analysis of observatory data relating to dark energy and the expansion of the universe; and investigation of the Higgs boson from data collected at the Large Hadron Collider at CERN.
Other projects are aimed at further developments in particle physics theory, in advanced particle accelerators, and in new detector technologies, which scientists will use in continued explorations of the subatomic world.
High energy physics serves as a cornerstone of America’s science efforts. It plays a major role in nurturing top scientific talent and building and sustaining the nation’s scientific workforce. It also provides a deeper understanding of how our universe works at its most fundamental level.
This year’s projects were selected by competitive peer review under the DOE Funding Opportunity Announcement for Research Opportunities in High Energy Physics, sponsored by the Office of High Energy Physics within the DOE Office of Science.
Total funding is $75 million for projects lasting up to four years in duration. The list of projects and more information can be found here.