Effective Depth of X-Ray Production

By measuring x-ray emission profiles as a function of voltage, the depth of penetration of the cathode electrons involved may be calculated. Similarly, the effective depth of x-ray production may be obtained. Uncertainties exist because of conditions at the surface, so the rate of change of these depths with voltage may be established with greater confidence than the values themselves. For copper, the continuum yields values increasing from 300 A/kv to 480 A/kv over the 10-30 kv range. An average value of 450 A/kv is obtained from analysis of the less trustworthy line data. The effective depth obtained from the conventional calculation on the absorption edge is shown to have little physical meaning.