Joy and toil as Fermilab sends first particles to SeaQuest

SeaQuest spokesperson Paul Reimer inspects part of the detector. Photo: Reidar Hahn

On the night of March 7, SeaQuest operators celebrated the detection of their first particles – a new milestone for the experiment.

For spokesperson Paul Reimer of Argonne National Laboratory, 13 years of planning, proposals, funding and construction have led to this moment, when SeaQuest switched from a long-sought goal to a current reality. Reimer hopes that data gained from this experiment will help scientists better understand the strong force, which is responsible for binding quarks together to form protons and neutrons and for binding protons and neutrons into atomic nuclei.

The day leading up to that moment began with Fermilab engineering physicist Mike Geelhoed and the Accelerator Division. They were tuning the beam to create a more stable stream of particles, having recently rejuvenated one of Fermilab’s old proton beamlines. The group was pushing to get protons to the experiment as soon as possible, but couldn’t guarantee an exact time. This is never a one-person job, Geelhoed stressed. Hundreds were involved in the process through several support groups from the AD, PPD and TD.

The SeaQuest team, while eager to see particles, expected a wait of several days for the beam to reach the hall.

“It is really lucky when it happens, but we don’t know when we’ll have beam until it happens,” said Markus Diefenthaler, a postdoctoral student at the University of Illinois at Urbana-Champaign and one of five people in the experiment control room that night.

At 9:30 p.m., the SeaQuest detectors suddenly jumped to life.

“It began with anomalous [irregular] signals,” Diefenthaler said. “And then we could verify that it was something coming into the detector.”

The rush of excitement and surprise in the room quickly turned to feverish studying, as the team scrambled to make sense of the data. The beamline, they discovered, was delivering small batches of protons that created about 10,000 muon particles per pulse to the SeaQuest hall, a sign that more adjustments were needed for a stable particle beam and for the experiment to begin taking data.

Then at 1 a.m., the test run finished, marking a much-needed break for the exhausted operators and scientists.

“After leaving, there were so many things running through my mind that I wanted to tune,” said Geelhoed. “But I had to get to bed.”

By 7 a.m. the next morning, the beam was back on and Geelhoed and the SeaQuest operators were ready to go full force with the experiment.

“Now we really are in a 24-hours-a-day, 7-days-a-week mode,” Diefenthaler said. “And it will get very exciting soon.”

—Brad Hooker