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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
TIME total drift time [micro seconds]
LENGTH length of the drift line [cm]
DIFFUSION integrated diffusion coefficient [cm]
AVALANCHE integrated and exponentiated Townsend coefficient
LOSS integrated and exponentiated attachment coefficient

[The default function to be minimised is TIME.]


f_select

This function should return either True or 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
TIME total drift time [micro seconds]
LENGTH length of the drift line [cm]
DIFFUSION integrated diffusion coefficient [cm]
AVALANCHE integrated and exponentiated Townsend coefficient
LOSS integrated and exponentiated attachment coefficient
STATUS information on what happens to the particle

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.

[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 teh 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.]


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Formatted on 0100-08-24 at 22:37.