Synchrocyclotron for 450-Mev Protons

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Abstract
A 170‐inch synchrocyclotron recently completed at the Institute for Nuclear Studies, The University of Chicago, is described. It is capable of accelerating protons to an energy of 450 Mev, deuterons to an energy of 256 Mev, and alpha‐particles to an energy of 512 Mev. The magnet poles are especially contoured to give a field of 18,600 gauss in the center decreasing to 17,600 gauss at radius 76 inches. The radiofrequency is modulated by means of a rotating condenser in a three‐quarter wave resonant line oscillator. A circulating beam of about one microampere of 450‐Mev protons is normally obtained. This beam falling on an internal beryllium target produces about 4×1010 π‐mesons per second. Some of these π‐mesons emerge from the cyclotron, pass through channels in a heavy shield and are available in well‐collimated beams, well‐defined in energy. The present beams range in energy from 66 Mev to 230 Mev for π− mesons and from 66 to 145 Mev for π+ mesons. In the external 122‐Mev π− beam there are 1000π− mesons per square centimeter per second available over an area of about 50 square centimeters at 20 feet from the target. The energy spread is about ±4 Mev.