MONOBOB: A radiation-hard and efficient 2.45-GHz ECRIS dedicated to radioactive ion production
Résumé
MONOBOB, a new electron cyclotron resonance ion source (ECRIS) has been designed to ionise the radioactive elements coming from the production target of the SPIRAL II project. The goal was to build a long-lived ECRIS to work in the hostile environment of the target while presenting good ionisation efficiencies for gases. The numerous constraints related to the operation in a facility classed as ‘nuclear' have been taken into account during the design of the source. In this paper, however, we have concentrated in particular on (i) the radiation hardness of the magnetic structure, (ii) the injection of the RF power, (iii) the ionisation efficiency for noble gases, (iv) the ability of the source to work despite major outgassing and (v) the beam emittance. The first version of this source was tested to validate its principle by measurements of its performance. The results obtained with He, Ne and Ar permit us to predict ionisation efficiencies for Kr and Xe of the order of 80%, even with outgassing flows of the order of 1.2 × $10^16$ particle $s_1$. Under the same working conditions, between 60% and 80% of the beam current is included within an emittance of 30$\pi$ mm mrad at 20 kV, which could still be improved. Using the results obtained with the first version of the source, a second version respecting all the SPIRAL II constraints has now been designed and is under construction.