The Production and Acceleration of Metal Ions in the Harwell Variable Energy Cyclotron

Abstract
The range of ions accelerated by the V.E.C. has recently been extended to metal ions. For example, a 5 to 10 μA beam of 48 MeV 58Ni6+ is now available and has been used by a customer. This beam has become possible as a result of success in adapting the normal ion source for the production of metal ions. The problem was to add to the ion source a controlled source of metal vapour without increasing the size of the ion source or adding separate oven heaters and controls. This has been achieved by inserting a graphite liner into the existing ion source chimney, the metal being embedded in the liner and out of direct contact with the arc. Provided the arc power exceeds a few kilowatts, the metal becomes molten and the vapour diffuses through the graphite into the arc which then becomes self-sustaining. With nickel (the most widely tested so far), intensity at full radius of between 10 and 20 μA of 6+ ions and 1μA of 8+ ions is readily obtained and source life averages about 4 hours. Other metals such as cobalt, iron, chromium and copper give similar results.

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