Broad ion energy distributions in helicon wave-coupled helium plasma

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 ...

[1]  B. Blackwell,et al.  Collisional damping of helicon waves in a high density hydrogen linear plasma device , 2016 .

[2]  J. Knaster,et al.  Materials research for fusion , 2016, Nature Physics.

[3]  Shuichi Takamura,et al.  Experimental identification for physical mechanism of fiber-form nanostructure growth on metal surfaces with helium plasma irradiation , 2015 .

[4]  Boyd Blackwell,et al.  RF compensation of double Langmuir probes: modelling and experiment , 2015 .

[5]  L. Velásquez-García,et al.  Microfabricated Retarding Potential Analyzers With Enforced Aperture Alignment for Improved Ion Energy Measurements in Plasmas , 2015, Journal of Microelectromechanical Systems.

[6]  Francis F. Chen,et al.  Helicon discharges and sources: a review , 2015 .

[7]  G. Wright,et al.  An experiment on the dynamics of ion implantation and sputtering of surfaces. , 2014, The Review of scientific instruments.

[8]  M. Balden,et al.  Nanostructuring of molybdenum and tungsten surfaces by low-energy helium ions , 2012 .

[9]  John E. Scharer,et al.  Ion acceleration in a helicon source due to the self-bias effect , 2012 .

[10]  John R. Terry,et al.  Tungsten nano-tendril growth in the Alcator C-Mod divertor , 2012 .

[11]  A. Arefiev,et al.  Measurements and modeling of radio frequency field structures in a helicon plasma , 2011 .

[12]  Wataru Sakaguchi,et al.  Formation process of tungsten nanostructure by the exposure to helium plasma under fusion relevant plasma conditions , 2009 .

[13]  L. Raja,et al.  Resonant power absorption in helicon plasma sources , 2006 .

[14]  S. Takamura,et al.  Formation of Nanostructured Tungsten with Arborescent Shape due to Helium Plasma Irradiation , 2006 .

[15]  C. Franck,et al.  Measurements of spatial structures of different discharge modes in a helicon source , 2005 .

[16]  A. Lichtenberg,et al.  Principles of Plasma Discharges and Materials Processing: Lieberman/Plasma 2e , 2005 .

[17]  Boris N. Breizman,et al.  Theoretical components of the VASIMR plasma propulsion concept , 2004 .

[18]  R. Boswell,et al.  Modulated plasma potentials and cross field diffusion in a Helicon plasma , 2002 .

[19]  J. Faure,et al.  Different operational regimes in a helicon plasma source , 2001 .

[20]  M. Lieberman,et al.  Absolute measurements and modeling of radio frequency electric fields using a retarding field energy analyzer , 2000 .

[21]  Breizman,et al.  Radially localized helicon modes in nonuniform plasma , 1999, Physical review letters.

[22]  M. Light,et al.  Downstream physics of the helicon discharge , 1996 .

[23]  Hong-young Chang,et al.  A study on ion energy distribution functions and plasma potentials in helicon wave plasmas , 1996 .

[24]  J. Perrin,et al.  Retarding‐field analyzer for measurements of ion energy distributions and secondary electron emission coefficients in low‐pressure radio frequency discharges , 1993 .

[25]  Noah Hershkowitz,et al.  Techniques for using emitting probes for potential measurement in rf plasmas , 1986 .

[26]  Jen-Shih Chang,et al.  Double-probe theory for a continuum low-density plasma , 1976 .

[27]  L. Malter,et al.  A Floating Double Probe Method for Measurements in Gas Discharges , 1950 .