Specifying rays in an iterative space-charge calculation.


You can either

(1) enter another ‘set’ of rays, or

(2) specify a beam of rays, with a uniform distribution, or

(3) use the previous rays with the currents multiplied by a factor, or

(4) iterate a cathode space-charge calculation, or

(5) terminate the space-charge iteration.


Further information on the second option is given in the note on volume-distributed sources.


For a non-space-charge calculation further such entries are not possible.


You can make any number of further entries of types 1 and 3, in any order, terminated with an entry of type 5. Also one entry of type 2 can be used.

For example in xmpl3d73.dat, which concerns a simulation of an electron beam ion source, there are 3 iterations of an electron beam, followed by an iteration in which an ion beam is generated using the ‘rectangular beam’ option. These ions move in the space-charge field of the last electron beam.


For a space-charge calculation that involves a cathode you can make further entries of type 1 and 3 followed a single entry of type 5. An example data file is given at the end of xmpl3d73.dat.

If you are a more expert user and you want to introduce a new set of individual rays then the following procedure should be followed:

(1) Choose the option ‘single ray’ from the list of repeat space charge options.

(2) Specify an arbitrary single ray.

(3) Exit databuilder, saving the primary data file.

(4) Prepare the required set of single rays in an external file, either by manual entries or by running a separate data file with the requires type of beam and using the trajectory information in the relevant output file (but note that the ‘polar’ option for velocity components is not allowed).

(5) Manually edit the primary data file to replace the single ray with the required set of rays.

(6) Do not use the databuilder again -that is, use ‘Open for running only’, because at present databuilder does not recognise a new set of individual rays.


This procedure allows the use of many different types of beam (too many for the databuilder to be able to handle).


See also notes on space-charge iterations.



Colours of the rays:

During an iterative calculation the previous rays are redrawn (for comparison) in green (colour number 2), so this colour should be avoided for the new rays.

(The green rays are redrawn without using the interpolation points.)


For users who are editing or constructing an 'input data file' without the use of the data-builder -that is, pre-processor:

But Manual editing is certainly not recommended -it is a relic from the time when the databuilder was not available All users are strongly encouraged to use the databuilder, which always gives the correct formats and which has many options for which the formats are not described or easily deduced.


You can either

(1) enter another set of rays (between a first line that starts with 'set' and a last line that starts with 'l', or

(2) specify a disc from which rays start, with a first line that starts with 'dis', and a second line that must start with 'u' (for 'uniform') when a space-charge simulation is being dealt with, or

(3) use the previous set of rays with the currents multiplied by a factor, by entering a line that starts with 'rep' followed by a line that contains the multiplying factor, or

(4) iterate a cathode space-charge calculation by entering a line that starts with 'ite' followed by 1 other line, or

(5) terminate the space-charge iteration by entering a line that starts with 'f', for 'finish'.