Combined electron cyclotron resonance and radio frequency discharges in the TOMAS facility

The experiments carried out in hydrogen at the TOMAS facility show the possibility of controlling plasma parameters such as temperature and electron density in a combined electron cyclotron resonance and radio frequency (ECR+RF) discharge. A maximum plasma density of up to ≈6 × 10¹⁶ m⁻³ and electron temperature of up to 35 eV are observed in the combined ECR+RF discharge. The propagation of RF waves in hydrogen plasma under a weak magnetic field is analyzed. Depending on RF frequency and experimental conditions, such as radial distribution of plasma density and magnetic field, there can be several cases: only the slow wave can propagate, simultaneously slow and fast waves can propagate, or only the fast wave can propagate. The injection of additional RF power into the ECR discharge allows us to change the flux of neutral particles and their distribution function. Even the injection of small RF power of ≈ 0.26 kW relative to microwave power of ≈ 1.7 kW leads to an increase in the hydrogen flux by a factor of ∼2.5. At RF power P_RF ≈ 1.57 kW, the H⁰ flux increases by a factor of ∼9.3. The ability to control the fluxes and energies of particles leaving the plasma volume is important to approach the conditions necessary to study plasma-surface interactions in wall conditioning and fusion edge plasmas.