28th example file, carbon nano-tube, for field emission source


The tube has inner and outer diameters of 6 and 10nm respectively, and has a  semi-circular end.  To create a field a plate is placed arbitrarily 100nm away, with a potential 

 of 20V.

 The semi-circular end is taken as the cathode.  It is subdivided into 10  segments, and the program starts a ray from the centre of each of these  segments.

 Including the line:

    'field emission cathode  xa 3.' 

 has the effect of adding 3eV to each initial kinetic energy.  See the comments  at the end of xmpl2d28.dat for an explanation.

 The 5 rays coming from the lower half of the semi-circle carry currents that  are much smaller than those carried by the rays in the top half.


 The maximum field at the surface of the nano-tube is approximately  2.8E6 V/mm.  Compared with the nominal field of 20V over 0.0001mm, this is  approximately 14 times larger, which is therefore the 'enhancement factor'.