Solar neutrinos are detected from the world-renown Sudbury Neutrino Lab. This lab is located two kilometers underground. The engineers, lab technicians, doctoral students, and physicists take a 30 minute walk underground to the observatory. During this half-hour journey, the group walks through 1.5 kilometers of dusty, towering tunnels and alongside a narrow gauge rail track. The destination is an extraordinary 10-story laboratory entrenched in the hard rock of the 100 year-old nickel mine, the Canadian Shield. The natural temperature of the rock is 42 C because of the heat generated year-round by the earth’s core. However, Inco’s impressive air-cooling system which creates a wind tunnel reduces the temperature to a pleasant 20 C. However, it also increases the amount of airborne particles.
One of the keys to SNO’s success is the ultra-clean environment of its lab even though mining activity is a sheer 200 meters away. When the group reaches the outer chambers of the laboratory, they shower, shampoo, and change into clothes that are laundered on the premises. They are also dusted off in an “air shower” and the soles of their shoes are squeaked clean by a series of mats covered with a flypaper-like adhesive. 
To seal out the rock and its bad influences (dust and radon gas, mainly) the builders put nine coats of spray-on concrete on the walls of their cavern, each a different color to make definite that the previous layer was completely covered. The SNO’s lab equipment is kept as immaculate as possible. It is transported in airtight containers; each part is pressure-washed with super-pure water. Dust levels are constantly monitored to maintain air purity that is 10,000 times cleaner than the mine.
Once in the spotless lab, the group is still required to wear helmets. Everyone has to examine the same safety practices as the miners. SNO’s neutrino detector is an acrylic sphere 12 meters in diameter and filled with 1,000 tons of heavy water. Heavy water is made with a deuterium atom in place of one of the hydrogen elements in its H2O. Deuterium is “heavy” hydrogen; it has an extra particle in its nucleus. The sphere is composed of 125 curved panels assembled underground. Naturally, the panels and other equipment used in the construction were restricted by the size of the Creighton mine-shaft. The dark sphere is suspended in a cavity filled with 7,000 tons of normal water which absorbs gamma rays and neutrons from radioactivity in the surrounding rock.
This system works because thousands of photo sensors register neutrino interactions with heavy-water molecules and generate tiny flashes of light.
The cavity carved out of the host non-ore bearing rock is the largest at its depth in the world. The detector is built this far underground to avoid intervention from cosmic rays which would also interact with heavy water. The walls of the cavity are lined with urylon, a thick plastic coating that prevents water seepage and reduces potential contamination from radiation of the host rock.
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