High frequency RFQ design and LEBT matching for the CERN TwinEBIS ion source

An Electron Beam Ion Source (EBIS) is being developed at CERN [1] for production of highly charged ions, for instance fully stripped 12C. The focus has so far been on the electron gun design, aiming for a high current compression, which results in a rapid ionisation process and thereby high repetition rate. Initial commissioning tests of such an electron gun, the so-called MEDeGUN [2], have already been performed and we are now in the process of designing a multi-purpose ion extraction and diagnostics line. The Low Energy Beam Transport (LEBT) line will transport the ions into the downstream Radio Frequency Quadrupole (RFQ) with a nominal energy of 15 keV/u. The 750 MHz RFQ is designed to accelerate ions from 15 keV/u up to the final energy of 2.5 MeV/u. After the RFQ design was finalized and its acceptance calculated, the beam matching to the RFQ was studied, finding a set of parameters for the LEBT that maximize the transmission through the RFQ. Details of the RFQ design, of the LEBT matching procedure and its final results are illustrated in this paper.