xmpl3d15, 15th 'example' data file for CPO3D

Hairpin cathode with potential drop and current.


The set-up is as in xmpl3d12, except that a voltage difference of 2 V is applied across the hairpin, and a current of 2 A through the hairpin is simulated to provide a local magnetic field. The voltage difference causes a shift in the position of the beam at the anode.


Only a small number of segments is used to give a quick demonstration.


The set-up is as in xmpl3d12, but with the following main changes:

(1) the x and z coordinates are exchanged, to allow a potential difference to be applied across the hairpin cathode,

(2) there are no plane of symmetry, and so some subdivision numbers are increased,

(3) a voltage difference of 0.2 V is applied across the hairpin,

(4) 2 lengths of current, both 2A, are added along the axes of the straight parts of the hairpin,

The results show that the centre of the beam section at the anode has been shifted 0.009 mm in the plane of the hairpin, mostly due to the presence of the magnetic field.

The beam section at the anode has approximately the same size as that found in xmpl3d12.dat.

The planar lens mentioned in the notes to xmpl3d12.dat could be used also as a weak deflector, to correct the shift.

For a comprehensive study of hairpin cathodes see L Boesten and K Okada, Meas. Sci. Technol. 11 (2000) 576-583.

Improved and used new option, May 2013.