&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.]

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.

Also the energy distribution plot (see PLOT-F0) shows whether ionisation and excitation phenomena are likely to play a role.

[By default 0.01.]

E/P-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-E/P

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 logarithmic.

[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, and using representation FUNCTION-2 if a fraction frcrit or more 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.

ADD provides similar functionality, and caters in addition for mobilities that are available in tabular form.

The Garfield unit for mobility is cm\²/V.\μsec.

[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. ADD is more flexible in that it provides similar functionality, but it caters in addition for Townsend coefficients that are available in tabular form.

Note that MAGBOLTZ can be used to compute Townsend coefficients.

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

[By default: no Townsend coefficient.]

ATTACHMENT-COEFFICIENT

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. ADD is more flexible in that it provides similar functionality, but it caters in addition for attachment coefficients that are available in tabular form.

Note that MAGBOLTZ can be used to compute attachment coefficients.

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

[By default: no attachment coefficient.]

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Formatted on 21/01/18 at 16:55.