&GAS: ADD

item

Can be any of the following:

Item	Explanation	Unit
`ATTACHMENT-COEFFICIENT`	Attachment coefficient/pressure	1/cm.Torr
`DRIFT-VELOCITY`	Drift velocity	cm/\μsec
`ION-DISSOCIATION`	Ion dissociation coefficient	1/cm.Torr
`ION-MOBILITY`	Ion mobility	cm\²/\μsec.V
`LONGITUDINAL-DIFFUSION`	Longitudinal diffusion \√p	cm.\√Torr for 1\ cm
`LORENTZ-ANGLE`	Lorentz angle	degrees
`TOWNSEND-COEFFICIENT`	Townsend coefficient/pressure	1/cm.Torr
`TRANSVERSE-DIFFUSION`	Transverse diffusion \√p	cm.\√Torr for 1\ cm

Note that the same scalings have to be applied as for the TABLE.

function

The function may depend on the following variables:

Variable	Meaning	Unit
`ANGLE_EB`	Angle between E and B	degrees
`ATTACHMENT`	Attachment coefficient / p	1/cm.Torr
`B`	Magnetic field strength	Tesla
`BOLTZMANN`	Boltzmann constant	1.380658 10\<SUP\>-23\</SUP\> J/K
`DISS`	Ion dissociation coefficient	1/cm.Torr
`ECHARGE`	Electron charge	1.60217733 10\<SUP\>-19\</SUP\> C
`EP`	Electric field / p	V/cm.Torr
`LORENTZ`	Lorentz angle	degrees
`MOBILITY`	Ion mobility	cm\²/\μsec.V
`P`	Pressure	Torr
`SIGMA_L`	Longitudinal diffusion \√ p	cm.\√Torr for 1\ cm
`SIGMA_T`	Transverse diffusion \√p	cm.\√Torr for 1\ cm
`T`	Temperature	K
`TOWNSEND`	Townsend coefficient / p	1/cm.Torr
`VELOCITY`	Electron drift velocity	cm/\μsec

The variable EP can always be used, ANGLE_EB and B can only be used in tables prepared for magnetic fields. The transport properties can be used only insofar as they have been entered already.

VS

If you wish to add experimental data to a table, you should prepare

a 1-dimensional Matrix that contains the E/p values at which the measurements were done;
a 1-dimensional Matrix that contains the corresponding measured values of the selected item.

The E/p vector should in principle cover the entire range of the table. Values outside the range of the E/p vector are left untouched - no attempt is made to extrapolate. Since most items are initialised to values outside their permissible range, an error will in general be reported from the checks that are carried out while leaving the gas section. To avoid this, one can first set the item with an approximate function and then override in part with more precise values. This is illustrated here for He\<SUP\>+\</SUP\> in He:

// Experimental data
Vector E_He_He K_He_He
   0  10.5
   6  10.3
   8  10.2
  10  10.2
  12  10.1
  15  10.0
  20   9.90
  25   9.74
  30   9.60
  40   9.28
  50   8.97
  60   8.67
  80   8.12
 100   7.67
 120   7.25
 150   6.78
 200   6.12
 250   5.60
 300   5.19
 400   4.58
 500   4.17
 600   3.81
 700   3.57

// Scaling from Td to V/cm.Torr and from V/cm\&sup2;.sec to V/cm\&sup2;.\&mu;sec
Global E_He_He = E_He_He/(0.010354*300)
Global K_He_He = K_He_He*1e-6
// Fit an exponential to the shape
Call fit_exponential(E_He_He,K_He_He,1e-8,p0,p1,p2,p3,ep0,ep1,ep2,ep3)
// Provisionally set the mobility to the exponential function
add ion-mobility exp({p0}+{p1}*ep+{p2}*ep^2+{p3}*ep^3)
// Override the values that are in the range
add ion-mobility K_He_He vs E_He_He

The E/p values in your vector do not have to coincide with the E/p values present in the table - your vectors will be interpolated at the values of the table and these interpolations are stored instead of the values from the vector.

order

Selects the degree of polynomial interpolation in the pair of vectors.

When the data is smooth, a value of 2 (quadratic interpolation) is a good choice. This may however lead to intermediate points with a negative value in for instance Townsend coefficient tables that usually start at 0. For such tables, linear interpolation is advised.

Instead of ORDER 1, you may also type LINEAR. QUADRATIC is a synonym for ORDER 2, CUBIC for ORDER 3.

Go to the top level, to &GAS, to ADD, to the topic index, to the table of contents, or to the full text.

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