A Machine Called Indomitable by Kleinfield Sonny;

Author:Kleinfield, Sonny;
Language: eng
Format: epub
Publisher: Open Road Integrated Media, Inc.

TEN

It was the hardest work either of them had ever known. Onerous as Goldsmith’s job might be, the assignment to build the dewars that Damadian and Minkoff were tackling was far worse. When they took breaks and sat, staring at the disassembled pieces of metal, both men found themselves formidably short-tempered, and they sometimes drifted into a loser’s mind-set and wondered if they were up to the task. Each doughnut-shaped dewar was to be ten feet tall, six feet wide, and eighteen inches deep. Each one would weigh one and a half tons. Damadian would later say that had he known how arduous an undertaking it was to build the dewars, he never would have attempted it.

A dewar is a highly sophisticated thermos bottle. It has to keep heat outside, because helium is liquid only at a temperature of at least minus 269 degrees centigrade (absolute zero is minus 273.15 degrees). Were the thermos to warm up to, say, a mere minus 250 degrees, the helium would turn into a gas and, for the purpose of a superconducting magnet, be utterly useless.

A dewar acts to interrupt the three main modes of heat transfer—conduction (heat moving through a solid), convection (heat moving through a gas), and radiation. The dewar design that Damadian followed consisted of a nest of three huge silver doughnuts. The doughnuts were to fit one inside the other. The smallest doughnut, made of stainless steel and polished to a high sheen to act as a shield against radiation, was to contain the magnet and be filled with liquid helium. To take care of conduction, the magnet was designed so that it wouldn’t touch any other containers but would be mounted on special supports made out of a material that is a poor heat conductor. The second doughnut was to be filled with liquid nitrogen, which would cool the helium. It was to be made out of aluminum and had to be wrapped with eighty-five layers of super-insulation, thin sheets of aluminized Mylar, that would serve to bounce radiation off it. The last and biggest doughnut was to be a half-inch-thick aluminum vacuum can. When it was assembled, all the air would have to be pumped out of the interior, using a special vacuum working at ten to the minus ninth atmosphere.

The large parts for the dewar were constructed in outside shops. To create the myriad smaller parts, Damadian relied on his Chinese machinist, Nean Hu. His interest in NMR and the possible applications of the technology was negligible. But he proved to be an absolute whiz at machining.

As the dewar pieces came off Hu’s workbench, Damadian and Minkoff wrestled with them, trying to get them to fit together. Sometimes they would slip together just right. Often they wouldn’t. The rate of work was running at about half what Damadian had originally predicted, and there seemed little likelihood that it would pick up. As one colleague of Damadian’s was to say of the effort, “It was sort of like the Egyptians building the pyramids.

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