Investigation of Ion Induced Secondary Ion Emissions of Plasma-Facing Materials

Secondary ion emission (SIE) is a crucial phenomenon to understand plasma material interactions, as it directly influences material erosion, plasma sheath characteristics, plasma chemistry, and plasma discharge efficiency. The sputtering yields and kinetic energies of sputtered positive and negative ions from tungsten, boronized tungsten, lithiated boron, and lithiated carbon were measured for H, D, and He projectile ions with an incident angle of 45°, and energies of 100-2000 eV. The experimental setup was utilized to perform ion exposures using an electron cyclotron resonance (ECR) plasma source in a high vacuum chamber known as the Sample Exposure Station (SES). The sputtered or ejected species resulting from the ion exposures were sampled and analyzed by a quadrupole mass spectrometer with an ion energy analyzer function. We prepared one-inch diameter tungsten foil discs (0.03”- thickness) as substrates by polishing the surface with a slurry of 1-micron alumina particles, ultrasonic cleaning with acetone and ethanol, and finally Ar plasma treatment in the SES. Boron deposition was performed by ion beam sputtering of a boron target, and lithium was deposited with a lithium evaporator. We measured sputtered H from the tungsten surface for all incident ion species, while H²⁺ or D²⁺ were detected due to reflection from the surface of H and D incident ions, respectively. We report calibrated yields and kinetic energies for the detected ions species.