Synchrotron Radiation Turns The Big Five-O
In May 1947, Elder, Gurewitsch, Langmuir, and Pollock published a letter entitled "Radiation from Electrons in a Synchrotron," in which they reported their visual observation of synchrotron radiation from the 70-MeV electron synchrotron (shown above) at General Electric Research Laboratory, Schenectady, NY. We quote Pollock's account of the history of the discovery from his letter to Ivanenko dated September 25, 1970.
"If the accelerator tube of the 100-MeV betatron at Schenectady had not been opaque, the visual observation would probably have been made three years earlier by Westendorp or Blewett soon after the publication of your letter to the Physical Review (Phys. Rev. 65:343, 1944). Unfortunately they were not able to see through the silvered wall of the betatron donut.
In 1946 at Schenectady we began the construction of a synchrotron, both to test the synchrotron principle which McMillan had recently proposed and to see if electron injection by the betatron principle could lead to additional reduction in accelerator size. On October 24, 1946, my associate Langmuir wrote to McMillan that we had a synchrotron beam. But we did not "see" the beam until April 24, 1947 as I shall explain.
On April 24, Langmuir and I were running the machine and as usual were trying to push the electron gun and its associated pulse transformer to the limit. Some intermittent sparking had occurred and we asked the technician to observe with a mirror around the protective concrete wall. He immediately signaled to turn off the synchrotron as "he saw an arc in the tube." The vacuum was still excellent, so Langmuir and I came to the end of the wall and observed. At first we thought it might be due to Cerenkov radiation, but it soon became clearer that we were seeing Ivanenko and Pomeranchuk radiation."
Excerpted from the Handbook on Synchrotron Radiation, Volume 1a, Ernst-Eckhard Koch, Ed., North Holland, 1983.
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