Electron cyclotron resonance charge breeder plasma parameters from the modeling of 1+ beam stopping

Abstract

As a part of SPIRAL1 upgrade, several experiments were carried out to understand the transport of $1+$ (monocharged) ion beam through the SP1 ECR charge breeder ion source and to investigate the physical processes involved in charge breeding. Ion beam transport simulations were performed to reproduce the trends of the experimental results (charge breeding efficiency versus $1+$ beam injection energy $\mathrm{\ensuremath{\Delta}}\mathrm{V}$) by transporting the $1+$ beam through a potential map that reflects the presence of the ECR (electron cyclotron resonance) plasma. The role of Coulomb collisions in the capture of $1+$ beam leads to a necessary detailed analysis for an accurate description of the charge breeding process. This was done by using a full six-dimensional (6D) phase space Monte Carlo charge breeding (MCBC) code. MCBC models Coulomb collisions of the injected $1+$ beam in an ECR plasma and atomic processes (ionization and charge exchange). A simplified background ECR plasma model is implemented in the code to reproduce the trends of three different experiments (interaction of ${\mathrm{Na}}^{1+}$ with He plasma, ${\mathrm{K}}^{1+}$ with He plasma and ${\mathrm{K}}^{1+}$ with ${\mathrm{O}}_{2}$ plasma). The model is able to reproduce the low charge state ($1+$ and $2+$) experimental trends by tuning each plasma parameter (plasma density, plasma ion temperature and electron temperature) independently. The estimated plasma parameters obtained from each case are presented and their contribution in charge breeding process are discussed.