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&DRIFT: XT-PLOT


DATASET

Requests output of the x(t) relation to a dataset [no dataset is written by default].

dsname

The dataset name. The name should be enclosed in single quotes if it contains any of the following: blank, comma, colon, double quote, equal sign. This means in practice that the quotes are required on a Vax for all dataset access outside the home disk. On VM/CMS, the blanks between file-name and file-type (and perhaps file-mode) may be replaced by dots, thus avoiding the need to add the quotes. On Unix systems, the name should be surrounded by double quotes so as to avoid case conversion of the file name.

member

An identification string of at most 8 characters. This string is used by the various dataset commands and it is also needed if you keep more than one object (member) of the same type (cell, gas, track etc) in the same dataset.

remark

A string of at most 29 characters that serves as a comment helping you to recognise a member in a dataset. The default remark for x(t) relations states the wire number and the angle.

angle

The angle of the lines over which the drift time is minimised, measured with respect to the y-axis. The accuracy of the calculations becomes less when this angle becomes large.

[Default: 0 degrees.]


xmin-xmax

The range in x to be covered by the x(t) relation.

[By default the whole x-range of the drift area is taken.]


xstep

The distance between successive x points for which a corresponding minimal drift time is computed.

[By default chosen such that the step size is a reasonable number for about 20 data points.]


jump

The number of points between two accurately calculated points. The drift times for the intermediate points are obtained by interpolating the minimising drift line from the adjacent points, a procedure that is slightly less accurate than full drift line calculation.

[By default, no point is interpolated.]


itermax

The maximum number of iterations allowed.

[Default: 5.]


eps

An accuracy parameter, to be adjusted with great care.

[Default: 1E-4.]


angle_range

To save CPU time whilst gaining precision, it sometimes makes sense to explore only a limited angular range as seen from the target sense wire.

This option should be used with great caution if a magnetic field is present since the drift lines in this case normally approach the wire at a (substantial) angle.

[The default range is +90 to -90 degrees both left and right.]


PRINT-XT-RELATION

Requests a printout of the x(t) relation.

[On by default.]


PLOT-XT-RELATION

Requests a graph of the x(t) relation.

The graph usually shows 2 curves:

Both curves are interrupted if the procedure has doubts about the accuracy of a neighbouring point - markers are used if both neighbours of a reliable point are considered unreliable.

[On by default.]


SCALE

Can be used to force a vertical scale in the x(t) relation plot, e.g. when you wish to overlay several of them.
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Formatted on 0103-05-16 at 14:05.