A permanent-magnet microwave discharge ion source at KAHVELab

Abstract

A new Permanent Magnet Microwave Discharge Ion Source (PM-MDIS) has been designed and constructed at Boğaziçi University Kandilli Detector, Accelerator, and Instrumentation Laboratory (KAHVELab). The PM-MDIS design includes a plasma chamber surrounded by permanent magnets, a hydrogen gas supply to sustain the plasma, the waveguide system used to transfer power to the plasma chamber, a dualelectrode extraction system used to extract ions from the chamber, and a Faraday cup to measure the beam current. The aim is to extract ions from the thermal hydrogen plasma generated using a 2.45 GHz microwave source. In order to extract ions from the plasma medium, a magnetic field exceeding 875G has to be applied over the plasma chamber to ensure Electron Cyclotron Resonance (ECR) condition is satisfied. Since the plasma chamber is to be operated on the high voltage (HV) platform, higher system stability can be achieved by using the permanent magnet configuration shown in this work. Based on the designed magnetic field profile of the constructed system, the dual-electrode extraction system has also been designed using IBSIMU integrated DemirciPro software and produced to transmit proton beams from the plasma chamber to the beamline. The determination of the magnetic field profile, and the vacuum, HV, and beam tests are completed before integration with the rest of the beamline. Finally, how the transmitted proton beams behaved on the existing Low Energy Beam Transport (LEBT) line has been examined, and the LEBT line configuration has been optimized accordingly. In addition, besides the protons, the trajectories of H+ 2 and H+ 3 ions from the PM-MDIS have also been studied to optimize the LEBT beam optics. As a result of this study, the PM-MDIS has been integrated with the proton beamline, and 0.38mA mean beam current has been measured with the Faraday cup in the experiments performed at 20 kV and 0.01 sccm gas flow.