| Symbol | Meaning | Note |
|---|---|---|
X, Y, Z |
Position | R, PHI for polar cells |
EX, EY, EZ, E |
E-field at (x,y,z) | ER, EPHI for polar cells |
BX, BY, BZ, B |
B-field at (x,y,z) | only if there is a B-field |
VDX, VDY, VDZ, VD |
Local drift velocity | VDR, VDPHI for polar cells |
LORENTZ |
Local Lorentz angle | - |
TIME |
Total drift time | - |
PATH |
Total drift path length | - |
DIFFUSION |
Integrated diffusion | only if data is available |
AVALANCHE |
Avalanche multiplication | only if data is available |
LOSS |
Survival probability | only if data is available |
STATUS |
Numeric status code | See below |
P |
Pressure of the gas | - |
Further details can be found under the methods used to integrate the diffusion, the multiplication and the attachment. The numeric status code is a Number, not a string.
Other variables can be added on request.
Contours are drawn in the part of the viewing plane that is located within the current AREA box.
The contours are labelled with the function value if the LABEL option is on (which is by default the case).
If you request AUTOMATIC scaling of the range, contours are drawn at decent function heights covering the range of the function on the AREA. The number of contours is used to compute a rough distance between two contours; the distance is rounded downwards. The number of contours actually drawn may therefore be larger than the number you request.
Note that much better equal time contours can be obtained with the DRIFT WIRES ISOCHRONS=delta NODRIFT-PLOT instruction which takes the end-point of the drift-lines into account when deciding which points of the contours are to be joined with a line.
Contours are plotted starting from their crossings with a regular GRID covering the AREA. Very small contours are not found if the grid is course. It is therefore usually preferable to use a fine grid for contours, even though plotting the contours takes more time.
You may also wish to optimise the CONTOUR-PARAMETERS, especially if your AREA is very small or highly non-isometric.
The contours are drawn with the representation CONTOUR-NORMAL and are labelled with CONTOUR-LABELS.
[The default function is VD, the drift velocity, and the contour range is by default adjusted automatically. By default, about 20 contours are plotted.]
The geometric aspects of the track, if used, should be set by means of the TRACK command before calling PLOT-FIELD. Other aspects of the track, such as the clustering model, are not used in the present context.
A curve should be parametrised in terms of T which will run from 0 to 1. All 3 coordinates of the curve should be specified. Note that ON expects only one argument, the parametrisation should therefore be enclosed in quotes, e.g.
'cos(pi*t),sin(pi*t),0'would be appropriate to describe a semi-circle in the z=0 plane.
The SCALE option can be used to force a vertical scale in the plot, this can for instance be useful if you intend to overlay various graphs.
If you select the PRINT option, then the values plotted in the graph will also be printed out. Re-routing of the output (> file) can be used to write the values to a file.
The number of sampling points can be set with N, default is 200.
[The default function is VD, the drift velocity.]
This kind of plot can be useful to estimate for instance the spread in drift time over a given region.
The automatic search for proper binning (AUTOMATIC) uses the first few entries to set the range. Since the grid is scanned in a regular sequence, these entries are not necessarily representative for the entire sample, in particular if the number of bins is small compared to the grid size. See AUTOSCALE for details on the automatic binning procedure.
[The default function is VD. The number of bins is preset to 100 and the range is by default chosen automatically.]
The plot is first rotated by \φ degrees around the z-axis and then tilted by \θ degrees from the z-axis.
This plot is decorative but it is generally agreed upon that it is hard to extract any meaningful information from it\ ...
[The default function is VD, i.e. the magnitude of the drift velocity. The default viewing angles are 30\° and 60\°. The viewing angles are remembered from one call to the next.]
The z-component is set to 0, if not explicitly specified. For other than (x,y) views, this may give incorrect impressions.
The vectors are normalised in 3 dimensions when they are plotted - the length of the vectors shown does not contain information on the magnitude of the quantity that is plotted. A vector that appears point like has no component in the viewing plane.
It is advisable to have roughly equal ranges in view of the scaling that is performed on the vectors.
The vectors are plotted using the FUNCTION-1 representation. The appearance of the arrow is influence by the ARROW-TIP-ANGLE and ARROW-TIP-LENGTH settings.
[The default functions are VDX, VDY, VDZ, i.e. the drift velocity.]
[This is default.]
[This is not default.]
The POSITIVE option forces the charge to be positive, no matter whether the particle is an electron or an ion.
The NEGATIVE option forces the charge to be negative, no matter whether the particle is an electron or an ion.
Runge Kutta integration is easier to use than Monte Carlo stepping in that the integration parameters are more tolerant.
The parameters controlling the accuracy are adjusted for chambers that are several centimetres large. When studying much smaller structures, at the \μm scale, one may wish to request more accuracy.
The Runge Kutta algorithm is well suited for smooth fields, such as those obtained with analytic potentials. The field computed from field maps is sometimes not even continuous, and one should in such cases prefer the Monte Carlo algorithm.
[The initial default is RUNGE-KUTTA-DRIFT.]
When using this option, care has to be taken that the step size has been set to a value appropriate to the chamber, see in particular the step_size as set with the INTEGRATION-PARAMETERS command.
[The initial default is RUNGE-KUTTA-DRIFT.]
Formatted on 21/01/18 at 16:55.