Groundbreaking in Extreme Conditions

by Kurt Riesselmann

The title of the Wednesday afternoon colloquium on May 31 should have been a warning. Theorist Frank Wilczek from Princeton's Institute for Advanced Study came to Fermilab to talk about Quantum Chromodynamics in Extreme Conditions.

Indeed, it turned out to be an afternoon of extreme conditions.

About 70 guests and Fermilab employees had gathered to break ground for the Neutrinos at the Main Injector (NuMI) construction project when meteorological hell broke loose in the form of a howling Midwest thunderstorm.

"It was a classical case of horizontal rain," remembers Fred Ullrich of Fermilab's Visual Media Services.

The ceremony was supposed to be held in a tent set up at the site of the future access shaft to the detector hall. But the tent was no match for lightning, heavy rain and winds of more than 40 miles an hour. Organizers quickly moved the event to the more welcoming ñ and much drier ñ environment at Ramsey Auditorium.

Despite the last-minute changes, Fermilab's director Michael Witherell took the stage to make his opening remarks only a few minutes late.

"This is where civil construction meets the nature of the universe," Witherell said, referring to the physics goals of the neutrino experiments related to NuMI. The thunderclaps in the background gave his words a whole new meaning.

The rock at the end of the tunnel

The symbolic groundbreaking marked the start of construction for tunnels and access shafts that will house a new beamline for the NuMI project. To produce a beam of neutrinos, physicists will send a beam of 120 GeV protons from Fermilab's Main Injector through the new tunnel, smashing them into a graphite target and creating a secondary beam containing pions and kaons, which quickly decay into muons and muon neutrinos.

The muons are stopped using a 750-foot-thick absorber made of rock and steel. The muon neutrinos easily pass this barrier, continuing their flight to the two detectors of the Main Injector Neutrino Oscillation Search (MINOS) experiment. The near MINOS detector, located just beyond the absorber, will verify that the beam only consists of muon neutrinos. The far MINOS detector, located about 450 miles away in a former iron mine at Soudan, Minnesota, will again monitor the neutrino beam. Physicists expect to find that the muon neutrino beam has transformed ("oscillated") into a mixture of muon and tau neutrinos, possibly also containing some electron neutrinos, by the time it gets to the far detector.

Fortunately, no tunnel has to be constructed between Fermilab and Soudan, since neutrinos can easily traverse the earth. As a matter of fact, most of the neutrino beam will also traverse the two MINOS detectors without leaving a trace. Only one of a million million neutrinos will leave a signal in either one of the detectors.

Studying the exact content of the NuMI neutrino beam one millionth of a second (near detector) and 2.5 milliseconds (far detector) after its creation is essential to determining the difference in mass of the three kinds of neutrinos known to particle physicists. Since physicists think that the entire universe contains an enormous amount of ñ mostly undetectable ñ cosmic neutrinos, the knowledge of the combined amount of these particles' mass should have profound consequences for explaining how the universe evolved.

"In the case of telescopes, people are anxiously waiting to see the first light. Today we start waiting to see the first neutrino," Witherell told his audience at the groundbreaking ceremony. The MINOS collaboration will begin taking data in fall of 2003.

A special challenge

Robert San Martin, head of the Chicago office of the Department of Energy, pointed out the significance of the NuMI project beyond the physics point of view.

"This project again represents an opportunity to demonstrate that DOE, Fermilab, and all of our partners can do a good job at managing large complex projects, reminding everyone that we can jointly effectively manage and deliver top quality science facilities," he said.

Fermilab's Main Injector, dedicated just one year ago, is only the latest in the laboratory's tradition of building large projects on time and on budget. The NuMI project, however, presents a special challenge because the 30.5 million-dollar price tag for its tunnels and halls has all but eaten up the project's margin of "contingency" funding.

"At the present time all construction, including underground construction, is heavily committed," explained Dixon Bogert, NuMI project manager. "The labor market is tight. All bidders submitted offers that significantly exceeded the original estimate made during the development of the project engineering. Financial experts did not accurately predict the effect of a full-employment economy."

The MINOS collaborators, of course, hope that the NuMI project will deliver its neutrino beam on time.

"You may be able to start taking data if the detector is not quite complete, but you cannot do anything if you don't have a beam," said MINOS spokes-person Stan Wojcicki. "The NuMI construction clearly defines the critical path to finish the project on time."

Value engineering changes, which were made to reduce construction costs, delayed the award of the contract to excavate the NuMI tunnels and access shafts at Fermilab by six months. Bogert acknowledged that "DOE officials have been very helpful in finding a solution to the tight financial situation. They also helped us to draw up a project schedule which still should allow us to finish on time." Project time, though, has been reduced to a minimum.

Knowing that any underground construction is subject to surprises regarding the geological conditions found when excavation actually takes place, Bogert is aware that he and his co-workers still have a challenging time ahead.

First blasting at depth of 66 feet

So far the excavation for the NuMI project is on schedule. In March, DOE gave notice to proceed. Employees of the S.A. Healy Company, the subcontractor chosen to carry out the underground work, started working. The first step is to construct the access shaft of the NuMI target hall. Digging through the soil has been completed, and Healy has maintained their schedule to date.

The first blasting of rock at the target shaft at a depth of 66 feet was scheduled to take place at the same time as the groundbreaking ceremony at the detector shaft, with the two events a safe distance of about 3000 feet apart. The extreme weather forced a delay in blasting, and sent the groundbreakers to Wilson Hall where they used gold-toned shovels to turn over soil in a planter.

"Doing the NuMI groundbreaking in a flower box isn't so unusual," said Dave Ferguson, representing the S.A. Healy Company at the groundbreaking. "I have been at many ground-breaking ceremonies where they just put a sandbox someplace."

If this is the most extreme situation encountered during the NuMI construction, finishing on schedule should not be a problem.