Design and optimizations of electrostatic low energy intense beam transport for H^- ion source in LINAC4 at CERN

Abstract The electrostatic low energy beam transport (ELEBT) is used to handle low energy and intense beams from ion sources. It is preferred over magnetostatic low energy beam transport (MLEBT) for many reasons such as compactness, no space charge compensation and no transverse phase space coupling, more beam current handling capacity and less emittance growth as well as beam losses. The MLEBT has served in Linear accelerator 4 (LINAC4) at CERN and has been in operation at the test stand for about a decade but with demands of increasing luminosity and source upgradation to provide more beam current, there is a need of compact LEBT design which may overcome the limitations of MLEBT. The paper describes the novel design of an ELEBT by means of numerical simulation with many advantages over previous configurations and is designed to deliver the 70 mA H - beams at 45 keV energy within targeted rms normalized emittances of 0.5 π mm-mrad. We adopt the most reliable method for multiparticle beam dynamics simulation by first extracting 3D electric field data of optimized ELEBT generated by FEM computational tool and then running multiparticles with the appropriate grid. The numerical studies show the 100 % beam transmission in the proposed ELEBT. It has lower output beam emittances compared to measured beam emittances from existing MLEBT. With more numerical optimization, the energy spread and transverse twiss parameters at the end of the ELEBT are maintained within the existing RFQ acceptance. The beam optical, electrical and hardware specifications of the ELEBT section are presented in detail along with thermal analysis.