The LBNF Excavations and Structures

Science experiments typically require customized buildings, structures or spaces to house them and their ancillary equipment, and infrastructure and utilities to support construction, installation and operational activities. These types of facilities are known as Conventional Facilities. Since DUNE’s science program requires a source of neutrinos (a neutrino beam) and a near detector at Fermilab and a far detector at SURF, LBNF will build conventional facilities at both sites.

Facilities at Fermilab, the Near Site

The LBNF Near Site Conventional Facilities (NSCF) effort is preparing facilities at Fermilab for the LBNF beamline and for the DUNE near detector, a moderately-sized neutrino detector that will sit near the western border of the lab in the path of the neutrino beam.

CAD rendering of the embankment, buildings and spaces to be constructed around the beamline and near detector. Image credit LBNF.

LBNF will construct a series of underground enclosures and surface buildings for the beamline technical systems, and an embankment (small hill), about 60 feet (18 meters) high at its peak, to contain the primary beam — the beam made up of protons before they collide with the target. This series of structures starts from the point where the primary beam is extracted from the Main Injector, and extends through the target and absorber to the far end of the decay pipe. 

CAD rendering of the spaces to be constructed around the beamline. The beam travels at a slight downward angle from left to right in the image. The target is the slender grey bar at left in the green area, the target chase is shown in blue, and the decay pipe in brown, at right. Image credit LBNF.

CAD rendering of the underground Near Detector Hall (at bottom) the above-ground service building, and the shafts connecting them. Image credit LBNF.

The DUNE near detector and its ancillary equipment will be located about 1,800 ft (574 m) downstream of the beamline target. To house this detector LBNF will excavate and outfit a detector hall and support rooms about 200 ft (60 m) below grade, as well as provide the necessary infrastructure to operate it once the installation is complete.  Two shafts will connect these underground spaces to the surface, where a service building will provide an area for the receipt, partial assembly and operation of the equipment and technical components for the detector before they are transported underground to complete the installation.

The Far Site: Large Excavations a Mile Underground

The Sanford Underground Research Facility (SURF) is located at the site of the former Homestake Gold Mine in Lead, SD. This facility, with underground spaces as far below ground as 8,000 ft (2,440 m), has since been repurposed and extensively modified in order to accommodate underground science experiments.

The LBNF Far Site Conventional Facilities (FSCF) effort is preparing facilities both at the surface and at 4,850 ft (1,480 m) underground — called 4850L — for the DUNE experiment’s liquid argon far detector.

Configuration of the chambers for the four six-story-high cryostats proposed to house the DUNE detector modules at 4,850 ft (1,480 m) underground. A central utility cavern houses cryogenics and other equipment. Passageways (drifts) are also shown. Credit: FNAL

The FSCF activities are phased to support the sequential construction and installation of the cryostats and the DUNE far detector modules.

Some excavated spaces already exist at 4850L, but the combined space is not nearly enough for DUNE’s four far detector modules. LBNF is preparing to excavate four enormous chambers to house the detector modules, a central cavern to house the utilities needed to support the detector modules, installation areas, and passageways to access all these spaces. LBNF will also outfit these underground spaces with power, ventilation and cooling systems for the liquid cryogens, cyberinfrastructure, water, and other systems to ensure the safety of personnel and experimental equipment.

Over the course of about three years, approximately 350,000 cubic yards (267,000 cubic meters) of rock — equivalent to the mass of eight Nimitz class aircraft carriers, according to LBNF Project Director and retired admiral Chris Mossey — will be lifted to the surface where a conveyor will transport it to a roughly mile-long quarry that was dug while searching for gold in the 1980's.

On the surface at the Far Site, LBNF will upgrade electrical substations and distribution to increase power. A new building to support liquid cryogen transfer from the surface to the underground will be added as well as a small control room in an existing building for DUNE scientists to use during operations.