SPACESHIP EARTH: BUILDING NAIN NEUTRON MONITOR

Nain site
The Nain neutron monitor shares a site owned by the Canadian Broadcasting Corporation (CBC). Here, the three vans that house the monitor can be seen left of the CBC building. They were loaded with lead and other components of the monitor and then shipped to Nain by barge. In front of the vans are unloaded pallets of lead rings to be used in monitor construction.

PROLOGUE. The idea of a cosmic ray monitoring station in Nain was hatched by University of Delaware scientists in 1994, when computer simulations showed that a station in northern Labrador would fill a major gap in the existing network of neutron monitors. Nain, the northernmost Town in Labrador, is near the optimal location. After obtaining research funds from the US National Science Foundation, a team from the University of Delaware visited Nain in May 1998 and confirmed that the Town has the technical resources and infrastructure needed to support a modern cosmic ray monitoring station.


Blast rock fill
The monitor vans with contents weigh more than 12 tons each, so frost heave and settling in the soft Nain soil was a concern. Our contractor excavated a 10 foot deep trench and filled it with 30 truckloads of blast rock --- a sound foundation for the project.

PHASE 1 CONSTRUCTION. The heavy lifting was done in Phase 1. Materials required for the station were shipped to Nain via barge during the Summer of 1999. In September 1999 rock fill and footings were installed, and the monitor vans were placed on site. The lead and polyethylene enclosure for the detector tubes (6 in each van) were assembled on platforms in each van. The vans were then shut to await Phase 2 Construction.

Van at site Van put in place
Timber footings 12 feet long and 4 feet wide were placed on the rock fill to support the ends of each van. A backhoe was used to lift the vans into place.
Platform Platform with plywood
A neutron monitor is very sensitive to its surroundings. In Nain, we were concerned about drifting snow outside the van. To mitigate this sensitivity, we built a steel platform to hold the monitor a few feet above ground level.
Poly container Lifting the lead
The outer shell of the monitor consists of white polyethylene sheets. This shell was partially constructed, and then the lead rings --- or "rings with wings" as they are poetically called --- were lifted in place with the help of a motorized hoist.
Lead rings in place Ready for the detectors
A column of 18 lead rings, each weighing 200 pounds, was assembled for each detector tube. The outer polyethylene shell was then finished, and an inner circular sleeve of polythethylene was slid into each column of lead. The monitor assembly is now ready to receive the detector tubes.
Site view from front
The completed assemblies in each van are ready to receive the detector tubes and data collection units. This view is from the North, as seen from a nearby road.
View from SE View from NE
Two views from the rear of the site: (Left) From the southwest. (Right) From the southeast.

Electronics Rack 1
The main data collection hardware was installed in the center van.
Electronics Rack 2
Neutron monitor computer and electronics rack.

PHASE 2 CONSTRUCTION. At the heart of a neutron monitor are particle detectors called "proportional counters." The proportional counters used in Nain are aluminum tubes filled with the helium isotope 3He. When the 3He atom absorbs a neutron, there is a nuclear interaction that releases energy into the proportional counter. This energy is detected by the detector electronics system and recorded on a computer for analysis by scientists at the University of Delaware and other research institutions around the world.

The 18 proportional counters were installed by a University of Delaware team in November 2000. The data collection computer and main electronics rack were installed in the central van, together with a phone connection which permits remote downloading of recorded data. First cosmic ray counts of the Nain neutron monitor were recorded on November 10, 2000 at 19:21:40 Universal Time.

A research team from Boston University requested permission to use our facility in Nain as a site for their magnetometer experiment. The magnetometer was installed near our vans at the same time as our Phase 2 construction, and the associated data collection system was placed inside one of our vans.

Although the neutron monitor was now operating, something important was still missing. This was remedied in Phase 3 Construction

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Magnetometer Enclosure
The Boston University magnetometer is in a small enclosure near the neutron monitor vans.

PHASE 3 CONSTRUCTION. Neutron monitors are very sensitive to surrounding material, especially material overhead. A changing level of snow and ice on the roof causes variations in the neutron monitor count rate that can mask the true cosmic ray variations we want to study. This was a problem during the first winter that Nain neutron monitor collected data, because snow and ice did indeed collect and then melt on the flat roofs of the shipping vans.

To solve this problem, steep roofs were installed on the monitor vans during a third and final phase of construction in November 21-24, 2001. You can see the roofs in the photos below. Don't they look cool!

Roof 1 Roof 2
The monitor vans have steep roofs to shed snow.

For more information about neutron monitors and the uses of cosmic ray data, please visit our Neutron Monitor Home Page.


CREDITS

  • Spaceship Earth Concept: John W Bieber and Paul Evenson
  • Funding: US National Science Foundation
  • Engineering, Photography: Leonard Shulman and James Roth
  • Contractors: D & J Construction Ltd, Bonnie Bay Contractors Ltd, Sea Box Inc, Commercial Transport International, All-Fab Building Components Inc, and Southern-B Construction
  • Assistance and Advice: Nain Town Council, Nain Town Manager, CBC St Johns

THANKS TO ALL !

Send feedback to john@bartol.udel.edu
Last modified: 2002 January 11