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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 microsec
LENGTH Length of the drift line cm
DIFFUSION Integrated diffusion coefficient microsec
AVALANCHE exp(integral Townsend dz) probability
LOSS exp(-integral 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 microsec
LENGTH Length of the drift line cm
DIFFUSION Integrated diffusion coefficient microsec
AVALANCHE exp(integral Townsend dz) probability
LOSS exp(-integral 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` and `Hit_X_Replica`. `X` is the label that you have assigned to the wire.

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 eps_f.

[The default value is 10E-4, which is also the smallest reasonable value on computers like Vax and IBM. On Cray and other computers with 64 bit precision, eps_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 eps_pos.

[The default value is 10E-4, which is also the smallest reasonable value on computers like Vax and IBM. On Cray and other computers with 64 bit precision, eps_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 0108-03- at 19:47.