xmpl3d89, 89th 'example' data file for CPO3D

Pulsed photocathode.


The geometry is the same as xmpl3d48, photocathode, but now the source is pulsed.

As before, no attempt has been made in this simulation to optimise the performance.


Here the photoelectrons are produced in the time interval 0 to 50fs (which is entered as 5.E-11ms in the data file).


Unfortunately the pulse mode cannot be used with a cathode source, so the following procedure has been used:

(1) Copy this file under another name.

(2) Remove the pulse mode and use the cathode as a thermionic cathode, with kT = 0.1eV, current density = 10mA/sq-mm (these values are arbitrary in the present simulation), cathode depth = 0.02mm, second test plane added, printing level for rays = 'most'.

(3) Take the ray information from the ray output file and manually put this information back into the present data file (any redundant information at the ends of the ray data is removed by the program -this is explained in the online Help).

Then there are 48 individual rays that start with the correct energies and with the required initial energy and angular distributions. It is also important that each of these rays starts at the centre of a segment, where the potential is most accurate.


The advanced option to change the radius of the space-charge tubes has been used to create narrower tubes in the region of the waist. This option requires the use of the advance option to change the step lengths (although in fact these have been kept constant).


After running the present file, zoom in at the waist, then use the space-charge contour option, colour, time = 8.5e-8 (which is the approximate time at the waist), averaging radius = 0.02, then the maximum charge density can be seen to be at the waist.