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&DRIFT: MINIMISE

f_min

The function to be minimised has to depend on at least one of the following variables:

Symbol Meaning Unit
TIME Total drift time \μsec
LENGTH Length of the drift-line cm
DIFFUSION Integrated diffusion coefficient \μsec
AVALANCHE exp(\∫ Townsend dz) probability
LOSS exp(-\∫ attachment dz) probability
All variables are of type Number.

Further details can be found under the methods used to integrate the diffusion, the multiplication and the attachment.

[The default function to be minimised is TIME.]

f_select

This function should return a Logical, i.e. either the value True or the value False. If False is returned, then the point will not be considered anymore during the minimisation process.

The following variables can be used:

Symbol Meaning Unit
TIME Total drift time \μsec
LENGTH Length of the drift-line cm
DIFFUSION Integrated diffusion coefficient \μsec
AVALANCHE exp(\∫ Townsend dz) probability
LOSS exp(-\∫ attachment dz) probability
STATUS What happened to the particle see below

All variables are of type Number except for STATUS which is a String and which can have one of the following values: `Left_Area`, `Too_Many_Steps`, `Abandoned`, `Hit_Plane`, `Left_Drift_Medium`, `Left_Mesh`, `Hit_X_Wire`, `Hit_X_Replica` and `Hit_X_Solid`. `X` is the label that you have assigned to the wire or solid.

Further details can be found under the methods used to integrate the diffusion, the multiplication and the attachment.

[The default selection curve returns always True.]

ON

ON should be followed be a parametrisation in terms of the variable T of the curve over which the minimisation should take place.

The range of T can be specified via RANGE.

[No default curve is provided.]

RANGE

RANGE should be followed by the minimum and the maximum value the variable T is allowed to take during minimisation, see ON for further information on T.

[No default RANGE is provided.]

N

The number of points on the curve for the initial scan of the curve.

[The default value for N is 20.]

ELECTRON

Requests that the minimisation be carried out for electrons.

[This is the default.]

ION

Requests that the minimisation be carried out for ions.

[By default, minimisation is done for electrons.]

POSITIVE

Requests that the minimisation be carried out for positively charged electrons or ions.

[The default is NEGATIVE.]

NEGATIVE

Requests that the minimisation be carried out for negatively charged electrons or ions.

[This is the default.]

FUNCTION-PRECISION

The procedure assumes it has converged if the relative change in function value has dropped below \ε_f.

[The default value is 10\<SUP\>-4\</SUP\>, which is also the smallest reasonable value on computers like Vax and IBM. On Cray and other computers with 64-bit precision, \&epsilon;_f can be made smaller.]

POSITIONAL-RESOLUTION

The procedure assumes it has converged if the relative change in position of the minimum has dropped below \&epsilon;_pos.

[The default value is 10\<SUP\>-4\</SUP\>, which is also the smallest reasonable value on computers like Vax and IBM. On Cray and other computers with 64-bit precision, \&epsilon;_pos can be made smaller.]

ITERATE-LIMIT

The maximum number of iteration steps during the minimisation process.

[By default 20.]

PRINT

Requests some printout during the minimisation procedure.

[This is default.]

DATASET

Requests dataset output of the minimisation results.

[No such output is produced by default.]

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

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