Foxhole for Neutrinos

One of the Tanganyikan delegates to the U.N. was duly exercised. The U.S., he said, was plotting with South Africa to test atom bombs. He had read all about it in the newspapers.

Whatever he had read, Khari R. Baghdelleh had obviously not understood it. And no reasonable man would suspect the U.S. of joining South Africa in any international hanky-panky. Still, rumors about atomic weaponry have a habit of swelling rapidly into dangerous controversies. U.S. Representative to the U.N. Adlai Stevenson wasted no time in pointing out that the only scientific experiment now scheduled to involve both the U.S. and South Africa has nothing to do with bombs: it will be a delicate and determined effort to detect some elusive particles of matter.

Rare Events. The experiment will generate no atomic blast, but if it pays off it may have an explosive impact on the new and booming subscience of neutrino physics. Neutrinos are littleknown particles that have no mass of their own and no electric charge. They have nothing much except energy; they interact hardly at all with known kinds of matter. They are generated copiously in the centers of stars, and they move with the speed of light as they slip out into space and pass right through any stars they happen to hit. It has been calculated that a stream of neutrinos could pass through 10 billion earths without being absorbed.

This elusiveness makes neutrinos hard to deal with. Though scientists have been convinced that the particles exist, they were not directly detected until 1956 when Physicists Frederick Reines and Clyde Cowan Jr., of the Los Alamos Scientific Laboratory, set up a monstrous apparatus near the Atomic Energy Commission's Savannah River reactor, which looses vast floods of neutrinos. A few times each hour while the reactor was working, the detector registered an "event." This meant that a single neutrino, out of many billions of billions per second, had actually hit something.

Now there are newer and better detection systems, but neutrinos are still fantastically hard to catch. Dr. Reines, who landed the first ones, is in charge of the South African work. The site was chosen because a deep mine was needed to screen out cosmic rays, which would interfere with the experiment. India has such a mine, but the Indians wanted to boss the experiment themselves. Reines turned to South Africa where the University of the Witwatersrand offered him an unusual laboratory: a gold mine near Johannesburg shielded by 10,492 ft. of solid rock.

In this snug foxhole, Reines will assemble a vast neutrino trap, designed at Cleveland's Case Institute. Even the most powerful cosmic rays do not penetrate to the depth of the gold mine, but the entire universe is believed to be swarming with neutrinos that will be deterred not at all by two miles of rock. Some of them are believed to carry unusual amounts of energy, and these fat neutrinos should be easier to detect than leaner ones.

Ashes of Creation. Part of the Reines apparatus will lie in wait for fat neutrinos. Another part will have several hundred square yards of scintillation counters to watch for mu-mesons generated by neutrinos that hit particles in the rock surrounding the mine. On the earth's surface these neutrino-induced mu-mesons are almost impossible to identify because of confusion caused by cosmic rays.

Physicists believe that neutrinos are extremely important in the affairs of the universe. There are four kinds al ready known, and there may be more. They may be the "ashes" of ordinary matter, or they may have something to do with the creation of matter. The deep-down experiment in South Africa may place them at the very center of man's understanding of physics.

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