&GAS: MIX


frac

  The fraction of the mixture taken up by the gas.

  The fractions do not necessarily have to add up to 1.

  [Each fraction is 0 by default.]

emin

  The lowest electron energy in the cross section, energy loss,
  mean free path and F0 plots. This parameter has no impact on
  the drift velocity and diffusion calculations.

  [By default 0.01 eV.]

emax

  The largest electron energy which is considered during the
  computations of F0, the drift velocity and the diffusion.
  This is also the largest electron energy shown in the
  cross section, energy loss, mean free path and F0 plots.

  This parameter should be chosen sufficiently large, otherwise
  the program might not be able to detect ionisation.
  The adverse effect of choosing this parameter too large
  is an increased CPU time consumption.

  [By default 25 eV.]

estep

  The largest step size allowed during integration.
  One should keep in mind that integration in each step is done
  using a 6-point Gauss technique and that the steps never
  bridge a change-over between two parametrisations.

  [By default 0.5 eV.]

frcrit

  Garfield warns if the fraction of F0 fraction above the first
  ionisation potential of any of the gas components exceeds
  the value of this parameter.

  [By default 0.01.]

RANGE

  The range of E/p. There is usually no problem with the
  computations for small E/p, but at high E/p one may hit
  the ionisation potential of one of the gas components.

  [By default 0.5 to 50.]

n

  Number of points in the drift velocity and diffusion tables.

  [By default 20.]

scale

  Selects whether the spacing of the E/p points should be linear
  or logarithmical.

  [Logarithmic by default.]

PLOT-F0

  Requests a plot of F0 for each E/p. This plot is useful when
  you wish to see which electron energies play a role.

  The curve is plotted using polyline representation FUNCTION-1
  if ionisation and excitation are not expected to be a problem,
  using representation FUNCTION-2 if a significant fraction of
  the energy distribution exceeds the first ionisation or
  excitation threshold.

  [This plot is made by default.]

PLOT-ENERGY-LOSS

  Requests a plot of the fraction of energy lost by an electron
  during collisions with the gas molecules / atoms.

  The curve is plotted using polyline representation FUNCTION-1.

  [This plot is by default not made.]

PLOT-CROSS-SECTION

  Requests a plot of the elastic electron scattering cross section.

  The curve is plotted using polyline representation FUNCTION-1.

  [This plot is made by default.]

PLOT-PATH

  Requests a plot of the mean free path of electrons in the gas.

  The curve is plotted using polyline representation FUNCTION-1.

  [This plot is by default not made.]

PRINT-TABLES

  Requests that the information contained in the 3 kinds of plots
  described before (energy loss, cross section, mean free path)
  be printed.

  [This table is by default not printed.]

MOBILITY

  MIX only computes the drift velocity and longitudinal diffusion
  for electrons, not for ions. This keyword enables adding an ion
  mobility to the tables.

  This format only allows for mobilities that are constant or depend
  in a simple way on E/p. In the latter case, the argument of MOBILITY
  should be a function with EP as variable.

  Since the ion mobility is usually constant or nearly so, this should
  be adequate, please contact the author if this proves a limitation.

  The Garfield unit for mobility is cm2/V.microsec.

  [By default: no mobility.]

TOWNSEND-COEFFICIENT

  MIX only computes only drift velocity and the longitudinal diffusion
  for electrons in the gas mixture. It does not compute the Townsend or
  attachment coefficient. This keyword enables adding the Townsend
  coefficient to the tables.

  This format only allows for Townsend coefficients that depend in a
  simple way on E/p. The argument of TOWNSEND-COEFFICIENT should be a
  function with EP as variable.

  Since the MIX instruction is only meant to provide an approximate
  table, the limitation to parametrisations should not be a severe
  limitation. MAGBOLTZ should be used if more accuracy is desired.

  The Townsend coefficient should be entered as alpha/pressure, with
  alpha in units 1/cm and the pressure in Torr.

  [By default: no Townsend coefficient.]

ATTACHMENT-COEFFICIENT

  MIX only computes only drift velocity and the longitudinal diffusion
  for electrons in the gas mixture. It does not compute the Townsend or
  attachment coefficient. This keyword enables adding the attachment
  coefficient to the tables.

  This format only allows for attachment coefficients that depend in
  a simple way on E/p. The argument of ATTACHMENT-COEFFICIENT should be
  a function with EP as variable.

  Since the MIX instruction is only meant to provide an approximate
  table, the limitation to parametrisations should not be a severe
  limitation. MAGBOLTZ should be used if more accuracy is desired.

  The attachment coefficient should be entered as beta/pressure, with
  beta in units 1/cm and the pressure in Torr.

  [By default: no attachment coefficient.]

Keyword index. Formatted on 10/11/98.