xmpl3d73, 73rd'example' data file for CPO3D

Electron impact ion source.

This is a primitive ion source. No attempt has been made to optimise its properties.

The size of the ion source box is 20mm by 10mm by 10mm (x = -10 to 10, y and z = -5 to 5). There is a slot 10mm by 2mm in one face (at z = 5) and opposite the slot is a repeller plate 12mm by 4mm (at z = -4). Only a small number of segments has been used, for a quick simulation.

A cylindrical beam of electrons of diameter 6mm starts at one end of the box (at x = -10). There is a uniform magnetic field in the direction of the electron beam (the x direction).

After 3 iterations of the electron beam the electrons are replaced by positive ions. These are generated (using the 'rectangular beam' option in the databuilder) at points inside a volume inside the electron beam (from x = -4 to 4, y = -2 to 2, z = -2 to 2), between the repeller plate and the slot.

In this simulation the electron energy is 300eV, the current is 20mA, the magnetic field is 0.05T (500 gauss), the repeller is at 70V and the ions have mass 100 atomic units and charge +1 and an initial kinetic energy of 0.1eV. The electron and ion beams contain 36 and 54 rays respectively (but these numbers would obviously be increased for a more serious simulation).

Three iterations are used for the electron beam, all with the same current. In each iteration the electrons move in the space-charge created in the previous iteration. A reasonable convergence is achieved after 3 iterations (but more iterations might be required at higher currents). In the fourth and final iteration the electrons are replaced by the ions, which move in the space-charge created in the previous iteration, that is in the space-charge of the electron beam. The total time for this simulation is 48s.

It can be seen that most of the ions are trapped in the negative potential well created by the space-charge of the electron beam. These ions spiral backwards and forwards along the length of the electron beam (and in the present simulation they are stopped after 0.02ms). Only 7 of the 54 rays emerge through the slot. But remember that this is a primitive ion source and no attempt has been made to optimise its properties.

In Jan 2005 the CPO3DS program was extended to allow a cathode iteration to be followed a list of space-charge iterations.

Here is an example data file (which is for an arbitrary, non-practical system and is intended only for purposes of illustration). The geometry is based on the planar diode of xmpl3d10.dat, but is rotated through 90 degrees around the y axis, so that the main axis becomes the x axis (because the rectangular beam option produces a beam in the z direction).

CPO3D Second version of xmpl3d73.dat

temp73b.dat name of hidden output file, for processed data

temp73c.dat name of main output data file, for ray data

n n/p/m/a for segment printing level

0 1 0 0 voltage reflection symmetries in x,y,z,x=y planes

7 number of different voltages, time dependence

0.001 20 allowed consistency error, side/length ratio check

a apply inscribing correction (a/s/n=always/sometimes/never)

edi evenly-divided disc cathode

2.132 0 0 0 radius, centre of disc

10 0 0 any other point on axis

1 1 numbers of 2 applied voltages (can be same)

8 number of subdivisions

disc, even radial division cathode, outer part

2.132 0 0 0 1st radius, centre of disc

5 10 0 0 2nd radius, any other point on axis

1 1 numbers of 2 applied voltages (can be same)

36 0 total nr of subdivs and 0, or subdivs along radius and around axis

edi evenly-divided disc anode

5 10 0 0 radius, centre of disc

20 0 0 any other point on axis

2 2 numbers of 2 applied voltages (can be same)

40 number of subdivisions

cylindrical electrode

5 0 0 0 radius, centre of 1st end

2 0 0 centre of 2nd end

3 3 numbers of 2 applied voltages (can be same)

4 6 total nr of subdivs and 0, or subdivs along and around axis

cylindrical electrode

5 2 0 0 radius, centre of 1st end

4 0 0 centre of 2nd end

4 4 numbers of 2 applied voltages (can be same)

4 6 total nr of subdivs and 0, or subdivs along and around axis

cylindrical electrode

5 4 0 0 radius, centre of 1st end

6 0 0 centre of 2nd end

5 5 numbers of 2 applied voltages (can be same)

4 6 total nr of subdivs and 0, or subdivs along and around axis

cylindrical electrode

5 6 0 0 radius, centre of 1st end

8 0 0 centre of 2nd end

6 6 numbers of 2 applied voltages (can be same)

4 6 total nr of subdivs and 0, or subdivs along and around axis

cylindrical electrode

5 8 0 0 radius, centre of 1st end

10 0 0 centre of 2nd end

7 7 numbers of 2 applied voltages (can be same)

4 6 total nr of subdivs and 0, or subdivs along and around axis

end of electrode information

0 1 0.5 final number of segments, number of steps, weight

1e-07 charge inaccuracy, zero total charge

end of segment information

0.0000000E+00 cathode applied voltages

1.0000000E+02 anode, z=10

1.0000000E+01 V3, potential at z=1, proportional to z

3.0000000E+01 V4, potential at z=3

5.0000000E+01 V5, potential at z=5

7.0000000E+01 V6, potential at z=7

9.0000000E+01 0.85 0.85 V7, potential at z=9

n no more magnetic fields from menu

n n n no more potentials and fields along a line

start of ray information

d direct (d), or mesh (m) method and mesh spacing

p 'n/p/m/a' for 'nearlyzero/partial/most/all' printing level, rho/radius

-1 11 minimum and maximum x(mm) of screen 2D fields of view

-6 6 minimum and maximum y

-6 6 minimum and maximum z

-1 11 minimum and maximum x(mm) of rays

-6 6 minimum and maximum y

-6 6 minimum and maximum z

-1e+10 1e+10 minimum and maximum vx(m/s) of rays

-1e+10 1e+10 minimum and maximum vy

-1e+10 1e+10 minimum and maximum vz

-10 10 minimum and maximum rho (=sqrt(x**2+y**2))

+ y direction of time, stop when ray first hits an electrode

1e+10 final time (ms)

0.5 1 2 initial and max step length, interpolation points

0.0001 1e-05 fractional inaccuracies for (1) ray tracing and (2) potentials and fields

2 nr test planes,mult cross,iter foc,phase spc,scatt,quant

1 0 0 1 a,b,c,d of test plane defined by a*x+b*y+c*z=d

0 0 1 5 a,b,c,d of test plane defined by a*x+b*y+c*z=d

va 'el' for electron; or 'co' or 'va' for other particles

k kinetic energy (k); or total energy (t) and potential

thermionic cathode

-1 0.0005486 particle charge and atomic mass

-1 0.01 -(number of electrodes), initial current density (mA/sq-mm)

o 1 0 0 o for outside, and xyz of reference point

0 T, or kT in eV; arbitrary random start

0.6 6 distance for cathode region, number of interpolation points

Y calculate space-charges

0.25 radius of space-charge tubes

iterate previous cathode rays

0.1 0.5 2 final max current density (see Help), damping factor, nmbr of iterations

rectangular beam

non-random distribution

-1 2 4 z of window, thickness, number

4 6 4 min and max x, number of points in x dir, for window

-1 1 2 min and max y, number of points in y dir, for window

1e+10 z of pupil

0 0 1 min and max x, number of points in x dir, for pupil

0 0 1 min and max y, number of points in y dir, for pupil

100. 0 energy (eV), current (mA)

16. 1. particle atomic mass and charge number

finish of space-charge iterations