The radial structure of a steady-state surface-wave-sustained cylindrical argon plasma submitted to a static, axial magnetic field is described in the context of a hydrodynamic model using three-moment equations for electrons and two-moment equations for ions. This plasma model is coupled self-consistently to Maxwell’s equations and yields the radial profile of the electron density and temperature, as well as the radial distribution of excited species, in the 3p56d orbital configuration of argon. In this paper, the discussion focuses on the radial structure of the plasma as a function of the operating conditions (magnetic field intensity, gas pressure, wave frequency, plasma tube radius). It is found that the electron density profile is, generally, weakly modified, as these parameters are changed. In contrast, the electron temperature profile and, consequently, the excited atom density distribution are very sensitive functions of the operating conditions.
Earlier works on discharges sustained by electromagnetic surface waves in absence of a magnetic field have revealed the central role played by the power balance per electron. This balance relation stated that, provided energy transport is negligible, the power θL lost by the electron on the average in collisions with heavy particles is exactly compensated under steady-state conditions by the power θA taken by the electron on the average from the high frequency (hf) field, their common value being the parameter θ. Then, because θL is to a first approximation the same in all hf discharges under given discharge conditions and power density, a simple discharge model valid for all hf plasmas was used. The present article is an extension of this approach to hf magnetized plasmas, using surface-wave plasma columns placed in an axially directed static magnetic field as a means of investigation. We observe that θ decreases monotonously when increasing the magnetic field intensity B0, showing no extremum at or close to the electron cyclotron resonance frequency match over the gas pressure range (5–100 mTorr) investigated. We show that θ is controlled either by classical ambipolar diffusion or anomalous diffusion, the actual diffusion regime depending on whether the novel parameter B0p (p is gas pressure) is small or large. Our measured θ values are further used to estimate the average electron density in helicon sources given the power density, showing fair agreement with the reported values.
A new kind of magnetic mass spectrometer is described. It consists of (n) magnetic prisms integrated into a single pole piece and (n-1) mirrors which return the beam from one prism to the other. It is shown that by an appropriate choice of the parameters of the apparatus the resolving power increases linearly with the number of passages in the prism. Experimental results verify the theory. Other properties of this system are also discussed.
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