@InProceedings{vongoeler83,
  author =       {Schweickhard E. von Goeler and James E. Stevens and
                  Charles F. F. Karney and Stefano Bernabei and
                  Manfred L. Bitter and Tsu-Kai Chu and
                  Phillip C. Efthimion and Kenneth W. Hill and
                  William M. Hooke and Forrest C. Jobes and
                  Ernesto Mazzucato and E. B. Meservey and
                  Robert W. Motley and Phyllis G. Roney and
                  Ned R. Sauthoff and Steven S. Sesnic and Gary Taylor
                  and Fred H. Tenney and Ernest J. Valeo},
  title =        {Determination of the Electron Velocity Distribution
                  from the Soft and Hard {X}-Ray Emission during Lower
                  Hybrid Current Drive on {PLT}},
  preprint =     {Princeton Univ. Rept. \eref{PPPL-2012}{PPPL--2012}
                  (June 1983) 21 pp.},
  booktitle =    {Proc. Fifth Topical Conf. on Radio Frequency Plasma
                  Heating},
  pages =        {96-103},
  year =         1983,
  volume =       2,
  note =         {Meeting held at University of Wisconsin, Madison, WI,
                  Feb. 22--24, 1983},
  abstract =     {During lower hybrid heating in low-density-tokamak
                  discharges, a non-Maxwellian tail of high energy
                  electrons is formed.  This tail carries the plasma
                  current.  Utilizing the fact that relativistic
                  electrons emit bremsstrahlung predominantly in the
                  forward direction, we investigate the shape of the
                  electron distribution by measuring the dependence of
                  the X-ray emission on the angle between the magnetic
                  field and the line of sight.  The experimental data
                  indicate that the distribution function is
                  predominantly peaked in the forward direction,
                  although a small fraction of the electrons is in the
                  backward cone.  The energy dependence of the X-ray
                  spectra is consistent with that of a velocity
                  distribution which has a plateau extending out to
                  several hundred kilo-electron volts.  Radial profiles
                  show that the hot electrons are located in the central
                  plasma region and form a high conductivity plasma with
                  the current profile frozen in.  The slope of the
                  spectrum depends on the rf power and on the phasing of
                  the waveguide grill, but not on the externally applied
                  plasma voltage.  Relaxation oscillations occur shortly
                  after switching the rf off.  They also appear during
                  the rf for low rf power and at the high density limit
                  of the lower hybrid current drive.  The X-ray spectra
                  confirm that parallel energy is transferred to
                  perpendicular energy during the instability,
                  suggesting an instability due to the anomalous Doppler
                  effect.}
}