Optimization of space-charge dominated injection beam line of high current proton RFQ

Abstract

Design of a space charge dominated proton beam-line from an ECR ion source to a high current RFQ has been carried out using analytical formulation. The parameters of the beam-line consisting of two solenoids, a slit for selecting H+ and rejecting H2+, and buncher are optimized to match the proton beam with the acceptance of RFQ . Analytical formulation for multispecies beam instead of conventional optical code has helped in simultaneously achieving different objectives within a compact but optimum length. Disc model having finite input energy width for longitudinal calculations and K-V transverse envelope equations for individual macro-discs including the bunching effect has been used. Selected parameters have been further corroborated by particle tracking using the 3D field of buncher and RFQ . Efficient selection/rejection of species has been verified with different type of input particle distributions in particle tracking. Finally the transmitted H+ and remaining H2+ has been tracked through the RFQ . The ratio of H+ to H2+, which is roughly 7:3 at exit of ECRIS could be reduced to 32:1 after the slit, while through RFQ remaining H2+ gets only transmitted but without any acceleration.

Proton beam intensity and proton fraction measurement of the 2.45 GHz ECR ion source

“…The hydrogen ion beam extracted from the ECR ion source mainly comprises H + 1 , H + 2 and H + 3 . Proton fraction is one of the key parameters to hydrogen beam quality, and for the most applications it needs to be maximized [3,4]. Waldmann et al measured the dependence of the proton fraction on wall materials and found a substantial increase in proton fraction when boron nitride (BN) replaced steel [5].…”