Marvelous engineering
The article on Fermi’s magnet (symmetry, Dec 2006) included the quote, “When it became superconducting, it was ugly and took weeks and weeks to come online.” This quote is not accurate and takes away from the marvelous achievement of converting the Chicago Cyclotron Magnet (CCM) from normal conducting to superconducting. The work done by Eddie Leung, Howard Hart, Gene Smith, and the whole Lab 3 team in Research Services deserves proper recognition.
Although it is correct that it took a week or so to cool such a large magnet down, powering it took less than one hour. The conversion saved an order of magnitude in the 2 MW electrical power consumption of the magnet (taking into account the power needed for helium refrigeration and buss work). Despite its huge size, the CCM in operation had a smaller heat leak than a single superconducting dipole magnet in the Tevatron collider. This was true despite the 1.2 million pounds of force attracting each coil to the iron yoke when excited. There was some excellent Fermilab engineering in that magnet!
Bob Kephart, Fermilab
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