Broad ion energy distributions in helicon wave-coupled helium plasma

• Main Authors: Woller, Kevin Benjamin (Contributor), Whyte, Dennis G (Contributor), Wright, Graham (Contributor)
• Other Authors: Massachusetts Institute of Technology. Department of Nuclear Science and Engineering (Contributor), Massachusetts Institute of Technology. Plasma Science and Fusion Center (Contributor)
• Format: Article
• Language: English
• Published: American Institute of Physics (AIP), 2018-07-25T18:47:58Z.
• Subjects: Article
• Online Access: Get fulltext

 Helium ion energy distributions were measured in helicon wave-coupled plasmas of the dynamics of ion implantation and sputtering of surface experiment using a retarding field energy analyzer. The shape of the energy distribution is a double-peak, characteristic of radiofrequency plasma potential modulation. The broad distribution is located within a radius of 0.8 cm, while the quartz tube of the plasma source has an inner radius of 2.2 cm. The ion energy distribution rapidly changes from a double-peak to a single peak in the radius range of 0.7-0.9 cm. The average ion energy is approximately uniform across the plasma column including the double-peak and single peak regions. The widths of the broad distribution, ΔE, in the wave-coupled mode are large compared to the time-averaged ion energy, 〈E〉. On the axis (r = 0), ΔE/ 〈E〉 ≲ 3.4, and at a radius near the edge of the plasma column (r = 2.2 cm), ΔE/ 〈E〉 ∼ 1.2. The discharge parameter space is scanned to investigate the effects of the magnetic field, input power, and chamber fill pressure on the wave-coupled mode that exhibits the sharp radial variation in the ion energy distribution.