Fermilab Today Tuesday, Nov. 15, 2011

LBNE coming into focus

The selected beamline design details a proton beam, above ground level, running through a hill and to a ground-level target.

As the Long-Baseline Neutrino Experiment (LBNE) moves closer to its CD-1 review this coming spring, the project team has steadily honed its conceptual design to reduce cost while maintaining necessary functionality and safety features. The LBNE team plans to construct a beamline and near detector at Fermilab and a neutrino detector 1,300 km away in a former gold mine in Lead, South Dakota.

On Nov. 10, the project team chose its final beamline design for CD-1. Scientists will extract a proton beam from a new point on the Main Injector, MI-10, and send it through a beamline, above ground level, covered by a hill half the height of Wilson Hall. Inside this hill magnets will bend the beam downward toward a ground-level target, and the resulting secondary beam will continue to a shallow decay pipe and absorber. The final neutrino beam will continue through the Earth's mantle, aimed at the far detector. This shallow beamline design allows for standard facilities construction practices, as opposed to more complicated methods, making it less costly, according to Project Engineer Elaine McCluskey.

The LBNE team has been developing two far-detector conceptual designs, a liquid argon time projection chamber and a water Cherenkov detector, and initially planned to implement both. However, in this era of tight budgets, the project team will need to choose between the two technologies before the end of the year.

"The selection of a far detector preferred technology will focus us on what needs to be done to move beyond the pre-conceptual design stage for both the near and far detectors," said Bob Svoboda, LBNE co-spokesperson. "It also will help us to gel as a collaboration by showing we can make difficult recommendations and function as needed to design and build a new beam and detector complex."

The project team formulated a process for making this important decision. It involves the near-completion of the design and costing documentation for CD-1 and a series of reviews by independent, expert committees. After much discussion within the LBNE leadership, all of the considerations will culminate in a recommendation to the project manager, Jim Strait, who will make the formal decision. LBNE's plan ensures that all the relevant factors will be weighed carefully and fairly.

"The overriding goal is to do the best science for the dollar," Strait said.

In parallel with the far-detector decision process, LBNE is developing plans to provide a smooth transition to a single-technology experiment, as well as to address the continued development of the non-chosen technology. The liquid argon detector development takes place primarily at Fermilab, while Brookhaven is leading the water Cherenkov research effort.

"Fermilab and all the other participating national labs and universities have a big stake in seeing LBNE move forward successfully," Svoboda said. "This is more important, in the long run, than LBNE's adoption of any particular detector technology."

Anne Heavey, Computing Sector

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