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Title: Helicon antenna radiation patterns in a high-density hydrogen linear plasma device

ORCiD logo [1];  [2];  [3]
  1. Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA, PRL, Research School of Physics and Engineering ANU, Canberra 0200, Australia
  2. PRL, Research School of Physics and Engineering ANU, Canberra 0200, Australia
  3. Center for Plasma-Material Interactions, Department of Nuclear, Plasma and Radiological Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
Publication Date:
Sponsoring Org.:
OSTI Identifier:
Grant/Contract Number:
Resource Type:
Journal Article: Publisher's Accepted Manuscript
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 24; Journal Issue: 11; Related Information: CHORUS Timestamp: 2018-02-14 16:19:42; Journal ID: ISSN 1070-664X
American Institute of Physics
Country of Publication:
United States

Citation Formats

Caneses, J. F., Blackwell, B. D., and Piotrowicz, P. Helicon antenna radiation patterns in a high-density hydrogen linear plasma device. United States: N. p., 2017. Web. doi:10.1063/1.5000848.
Caneses, J. F., Blackwell, B. D., & Piotrowicz, P. Helicon antenna radiation patterns in a high-density hydrogen linear plasma device. United States. doi:10.1063/1.5000848.
Caneses, J. F., Blackwell, B. D., and Piotrowicz, P. 2017. "Helicon antenna radiation patterns in a high-density hydrogen linear plasma device". United States. doi:10.1063/1.5000848.
title = {Helicon antenna radiation patterns in a high-density hydrogen linear plasma device},
author = {Caneses, J. F. and Blackwell, B. D. and Piotrowicz, P.},
abstractNote = {},
doi = {10.1063/1.5000848},
journal = {Physics of Plasmas},
number = 11,
volume = 24,
place = {United States},
year = 2017,
month =

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.1063/1.5000848

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  • In this paper, we investigate the propagation and damping of helicon waves along the length (~50 cm) of a helicon-produced 20 kW hydrogen plasma ( ~1-2 1019 m-3, ~1-6 eV, H2 8 mTorr) operated in a magnetic mirror configuration (antenna region: 50-200 G and mirror region: 800 G). Experimental results show the presence of traveling helicon waves (~10 G and ~ 10-15 cm) propagating away from the antenna region which become collisionally absorbed within 40 to 50 cm. We describe the use of the WKB method to calculate wave damping and provide an expression to assess its validity based onmore » experimental measurements. By comparing theory and experiment, we show that for the conditions associated with this paper classical collisions are sufficient to explain the observed wave damping along the length of the plasma column. Based on these results, we provide an expression for the scaling of helicon wave damping relevant to high density discharges and discuss the location of surfaces for plasma-material interaction studies in our device (MAGPIE).« less
  • Using laser induced fluorescence (LIF), radial profiles of azimuthal ion fluid velocity and ion temperature are measured in the controlled shear de-correlation experiment (CSDX) linear helicon plasma device. Ion velocities and temperatures are derived from the measured Doppler broadened velocity distribution functions of argon ions. The LIF system employs a portable, high power (>300 mW), narrowband ({approx}1 MHz) tunable diode laser-based system operating at 668.614 nm. Previous studies in CSDX have shown the existence of a radially sheared azimuthal flow as measured with time delay estimation methods and Mach probes. Here, we report the first LIF measurements of sheared plasmamore » fluid flow in CSDX. Above a critical magnetic field, the ion fluid flow profile evolves from radially uniform to peaked on axis with a distinct reversed flow region at the boundary, indicating the development of a sheared azimuthal flow. Simultaneously, the ion temperature also evolves from a radially uniform profile to a profile with a gradient. Measurements in turbulent and coherent drift wave mode dominated plasmas are compared.« less
  • Current free double layers (CFDLs) are localized potential structures having spatial dimensions - Debye lengths and potential drops of more than local electron temperature across them. CFDLs do not need a current for them to be sustained and hence they differ from the current driven double layers. Helicon antenna produced plasmas in an expanded chamber along with an expanding magnetic field have shown the existence of CFDL near the expansion region. A helicon plasma device has been designed, fabricated, and installed in the Institute for Plasma Research, India to study the role of maximum magnetic field gradient as well asmore » its location with respect to the geometrical expansion region of the chamber in CFDL formation. The special feature of this machine consisting of two chambers of different radii is its capability of producing different magnetic field gradients near the physical boundary between the two chambers either by changing current in one particular coil in the direction opposite to that in other coils and/or by varying the position of this particular coil. Although, the machine is primarily designed for CFDL experiments, it is also capable of carrying out many basic plasma physics experiments such as wave propagation, wave coupling, and plasma instabilities in a varying magnetic field topology. In this paper, we will present the details of the machine construction, its specialties, and some preliminary results about the production and characterization of helicon plasma in this machine.« less
  • Existing linear plasma materials interaction (PMI) facilities all use plasma sources with internal electrodes. An rf-based helicon source is of interest because high plasma densities can be generated with no internal electrodes, allowing true steady state operation with minimal impurity generation. Work has begun at Oak Ridge National Laboratory (ORNL) to develop a large (15 cm) diameter helicon source producing hydrogen plasmas with parameters suitable for use in a linear PMI device: n{sub e}{>=}10{sup 19} m{sup -3}, T{sub e} = 4-10 eV, particle flux {gamma}{sub p}>10{sup 23}m{sup -3} s{sup -1}, and magnetic field strength |B| up to 1 T inmore » the source region. The device, whose design is based on a previous hydrogen helicon source operated at ORNL[1], will operate at rf frequencies in the range 10-26 MHz, and power levels up to {approx}100 kW. Limitations in cooling will prevent operation for pulses longer than several seconds, but a major goal will be the measurement of power deposition on device structures so that a later steady state version can be designed. The device design, the diagnostics to be used, and results of rf modeling of the device will be discussed. These include calculations of plasma loading, resulting currents and voltages in antenna structures and the matching network, power deposition profiles, and the effect of high |B| operation on power absorption.« less
  • Tests of a high plasma density high-brightness helicon ion source for nuclear microscopy applications are underway. Experiments were performed with hydrogen, helium, and argon. Different extraction structures of the helicon rf ion source were investigated with an imposed external magnetic field. We present measurements of the extracted current as a function of the extraction voltage and rf power. The source has been diagnosed by a microwave interferometer. Plasma densities in the vicinity of the emission hole of up to 7.2x10{sup 12} cm{sup -3} (for argon), 1.6x10{sup 12} cm{sup -3} (for helium), and 6.0x10{sup 11} cm{sup -3} (for hydrogen) were obtainedmore » for working gas pressure of <5 mTorr and rf power <350 W (f{sub rf}=27.12 MHz). The ion current density was 80 mA/cm{sup 2} with high percentage of protons in the beam ({approx}80%). In the extraction structure, the cathode channel has a 3 mm length and a 0.6 mm diameter. The phase set degradation due to aberrations in the extraction structure of the helicon rf ion source was simulated for a fourth-order approximation in series expansion of the electrostatic potential and third-order approximation in series of the magnetic fields, by the matrizant method. The calculations were performed involving experimental data on ion energy spread, average ion energy, and plasma density of the helicon rf ion source with permanent magnets.« less