&GAS: MAGBOLTZ: ANALYTIC-INTEGRATION

ORDERS

Can be used to set the number of terms to be included in energy distribution function, to ensure higher accuracy for the transport properties.

Values larger than 1 are not compatible with ITERATE-ALPHA, this setting is overruled by the SWITCH option.

This option can only be used with ANALYTIC-INTEGRATION integration.

[Default: n=2, equivalent to SECOND-ORDER-TERMS.]

Requests inclusion of zeroth, first and second order terms in the calculation of the energy distribution function. Selecting this option ensures a higher accuracy for the transport properties, but is not compatible with the ITERATE-ALPHA option which improves the accuracy of the Townsend coefficients.

SWITCH overrules this selection.

HIGH-PRECISION is synonymous to SECOND-ORDER-TERMS.

This option can only be used with ANALYTIC-INTEGRATION integration, available only in Garfield version \  and earlier.

[This is the default order, but is overruled by SWITCH.]

FIRST-ORDER-TERMS

Only the zeroth and first order terms will be included in the energy distribution function. This setting guarantees a reasonable accuracy and is compatible with the ITERATE-ALPHA option which improves the accuracy of the Townsend coefficients.

LOW-PRECISION is synonymous to FIRST-ORDER-TERMS.

This option can only be used with ANALYTIC-INTEGRATION integration, available only in Garfield version\ 7 and earlier.

[The default is SECOND-ORDER-TERMS.]

ITERATE-ALPHA

This option enables a refinement of the calculation of the Townsend coefficient. This is particularly useful if the Townsend coefficients are large (larger than say 50). But the option is not compatible with inclusion of higher order terms.

This option can only be used with ANALYTIC-INTEGRATION integration, available only in Garfield version\ 7 and earlier.

[This is not default.]

SWITCH

The SWITCH option combines ITERATE-ALPHA and SECOND-ORDER-TERMS in the following way:

If \α/pressure is smaller than the threshold, the quantities are computed with SECOND-ORDER-TERMS, NOITERATE-ALPHA

Otherwise, they are computed with FIRST-ORDER-TERMS, ITERATE-ALPHA.

This guarantees that the drift velocity, diffusion and Lorentz angle are accurate at low field values, which is where they matter most, whereas the Townsend coefficient is accurate at higher field values, at the price of a somewhat reduced accuracy for the other quantities.

This option can only be used with ANALYTIC-INTEGRATION integration, available only in Garfield version\ 7 and earlier.

[This option is default, \α/pressure is set to 50/pressure.]

diffusion

Magboltz offers several ways of computing the diffusion:

The method from the textbook of Huxley and Crompton, for both the transverse and the longitudinal diffusion, either with the F0 or the H1 distribution functions.
These formulae are only valid when the approximation that the longitudinal and transverse diffusion are equal is true. This is of course never true, but one can get a correction to the longitudinal diffusion from the ratio of the longitudinal to transverse diffusion without the magnetic field in the given gas at the E-field of interest. [from Steve Biagi]
These diffusion coefficients are obtained when you specify F0-TRANSVERSE-DIFFUSION, H1-TRANSVERSE-DIFFUSION, F0-LONGITUDINAL-DIFFUSION and H1-LONGITUDINAL-DIFFUSION. The correction to the longitudinal diffusion is applied, using the G0 estimate of the longitudinal diffusion.
F0-TRANSVERSE-DIFFUSION is default.
For the transverse diffusion, an alternative estimate based on the mean energy, computed with F0, is offered.
For the longitudinal diffusion, Magboltz computes on request a more accurate value using the so-called G0 functions. This is the default.

These options can only be used with ANALYTIC-INTEGRATION integration, available only in Garfield version\ 7 and earlier.

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