A new formula for secondary emission yield
Abstract
Mathematical expressions for the secondary emission yield as a function of impact voltage and direction are required by computer programs for ray tracing, which are also intended to follow secondary trajectories. It is shown that the accuracy requirements are quite severe for lower voltage impacts, up to about three times V(max), where V(max) is the voltage at which the normal secondary emission ratio reaches its maximum value, delta(max), but are less stringent above this range. A new formula for the lowvoltage region, which agrees with experimental data better than the formula of Lye and Dekker (1957), is proposed. For the voltage region above 4 V(max), the Lye and Dekker formula is retained, with a smooth transition centered between 3 and 4 V(max). The directional effect is modeled by adjusting the values of delta(max) and V(max) before applying either formula, rather than applying either Bruining's or Muller's correction factor afterward. This results in an automatic modeling of the known absence of any appreciable directional effect below about half V(max). Some experimental verification of the formula used to modify delta(max) is presented.
 Publication:

IEEE Transactions on Electron Devices
 Pub Date:
 September 1989
 DOI:
 10.1109/16.34278
 Bibcode:
 1989ITED...36.1963V
 Keywords:

 Electron Trajectories;
 Electron Tubes;
 Ray Tracing;
 Secondary Emission;
 Brillouin Effect;
 Computer Programs;
 Electron Impact;
 Microwave Tubes;
 Traveling Wave Tubes;
 Electronics and Electrical Engineering