A concept for emittance reduction of DC radioactive heavy-ion beams

Numerical simulations indicate that it should be possible to use an electron beam to strip 1⁺ DC radioactive ion beams to 2 ⁺ or higher charge states with on the order of 40-80% efficiency. The device, which we call an electron-beam charge-state amplifier, is similar to an electron beam ion source, except that it is not pulsed, the beams are continuous. The 2⁺ beams are obtained in a single pass through a magnetic solenoid while higher charge states may be reached via multiple passes. An unexpected result of the ion optics simulations is that the normalized transverse emittance of the ion beam is reduced in proportion to the charge-state gain. Ion beams with realistic emittances and zero angular momentum relative to the optic axis before entering the solenoid will travel though the solenoid on helical orbits which intercept the axis once per cycle. With an ion beam about 2 mm in diameter and an electron beam about 0.2 mm in diameter, the ion stripping only occurs very near the optic axis, resulting in the emittance reduction