Dynamag Ion Source with Open Cylindrical Extractor

A description is given of a duoplasmatron type ion source which features a novel, open cylindrical extractor electrode, a visible arc chamber and a short-path magnetic circuit. The glass spacer in the arc chamber permits observation of the plasma and filaments. The short magnetic circuit gives high plasma density at low magnet and arc currents. The open extraction geometry provides high pumping speed to the source and reasonable tolerances for anode alignment. Above a critical value of extraction voltage the ion emission is independent of voltage. At 16 kV, a 5 mA beam of mixed hydrogen ions can be obtained through an 0.008 in. anode aperture. Gas consumption is about 5 atm.-cc/ hr. with a conversion efficiency of about 70%. Proton yield is usually better than 50% of the total beam current under these conditions. The emittance (phase space area) is about 3 mrad.-cm. MeV¿ at 1.0 mA.