A 60 GHz electron cyclotron resonance ion source for pulsed radioactive ion beam production

Abstract

TUCO-A03International audienceElectron Cyclotron Resonance Ion Sources (ECRIS) are very efficient to produce continuous and pulsed ion beams. The ECRIS scaling laws show that the plasma density increases as the square of the microwave frequency. Consequently, the efficiency, the average charge of the ionic charge state distribution and the extracted currents increase as well. LPSC is developing a 60 GHz pulsed ion source prototype. In order to have efficient ionization, the ion source volume has to be small, and due to the frequency value, the magnetic field has to be high (6 T at the injection, 3 T at the extraction, a closed surface with |B| = 2.1 T and a magnetic mirror of 4 T). The generation of the high magnetic field requires the use of helix techniques developed at GHMFL. As a first approach, a cusp structure has been chosen. 2D and 3D simulations were used to define the geometry of the helixes. Calculus has shown that it is necessary to use 2 groups of 2 coaxial helixes. An aluminum helix prototype has been machined to test at low current density the accuracy of the calculations. The axial magnetic field of the prototype was measured and results are in very good agreement with the numerical values