A C. W. Duopigatron Multiply-Charged Ion Source

A systematic study of the duopigatron has shown that this type of source is very convenient for the production of intense D. C. ion beams (> 10𝔪A) of heavy elements with moderate charge states, if the operation and design parameters are properly matched. The charge state density distribution compares with the best results reported for d. c. duoplasmatrons, whereas the discharge power is less or equal. For Argon, with a 0.8 kW power the percentage of particles in the beam is : A+ = 38, A2+ = 50.4, A3+ = 11, A4+ = 0.5, A5+ ≃ 0.1; the overall gas utilization factor being 80 % if an insulating material (BN) is used for the anticathode and expansion cup construction. The total beam intensity is determined by the diameter of the hole bored on the axis of the anticathode electrode and the ion current density in this plane is comparable to that at the anode plane of a duoplasmatron (≃ 2 A/cm2). The normalized emittance of the beam is EN = 4 × 10-7 m × rd for a total beam intensity of 7.8 mA which corresponds to an emissive hole of 0.8 mm diameter and a brightness of BN ≃ 1010 Axm-2xrd-2. Therefore, one possible advantage of the duopigatron in the near future is that very intense ion beams of heavy elements can be emitted because the anticathode collects more than 1 A argon ions (≃ 10% of discharge current) over an area of 1 cm2.