All-electrostatic split LEBT test results

An all-electrostatic LEBT for an RFQ has been assembled and tested with beam. The LEBT includes two quasi-einzel lenses, allowing a wider range of Twiss parameters to be accommodated, and the lenses are split into quadrants, allowing electrical steering of the beam. Moreover, mechanical steering by moving the entire LEBT with a special low-friction vacuum joint was also demonstrated. The LEBT was tested with unanalyzed protons from an RF-driven bucket source by measuring the beam directly and by measuring the transmission through a subsequent RFQ as a function of LEBT electrode parameters. Agreement between calculated LEBT beam characteristics and actual measured values is excellent. This LEBT offers fully unneutralized beam transport with steering and two-knob control of exit Twiss parameters, and can be applied to negative hydrogen as well as proton beams. (author)