This paper deals with the contribution of secondary electron emission, produced during the slowing down of fast electrons, on the intensity and temporal shape of the generated Kα pulse. The problem is treated in a general manner emphasizing laser–plasma interactions, where it was suggested in the literature that these electrons could play an important role on the temporal duration. Here, we make use of a hybrid model which includes secondary emission in conjunction with the continuous slowing down approximation (CSDA). The results are compared with those obtained from a simple CSDA calculation, with no detailed accounting of secondary emission and without straggling. Secondary electrons were calculated to contribute up to an additional 20% to the total Kα yield and in the case of monoenergetic electron beams in thick targets also to influence the temporal shape. The pulse duration is not affected in a significant manner by the secondary electrons.

Lead cut-outs used to shape fields in kilovoltage radiotherapy can increase the surface dose on the patient. The physical processes leading to increased surface doses are summarised, and an empirical investigation of the efficacy of various coatings in reducing the skin dose generated by secondary electrons released in the lead during irradiation is presented, based on measurements using a thin window parallel plate ionisation chamber in 135 kVp and 225 kVp beams from a Pantak DXT-300 kilovoltage therapy unit. A new flexible coating for lead cut-outs has been formulated and tested. This coating, which is a combination of Copydex and emulsion paint, has been shown to be effective in reducing the skin dose generated by secondary electrons released in the lead during irradiation. The coating is easy to clean, and its inherent elasticity prevents cracking of the coating in clinical use. Its only disadvantage is that rough handling, or contact with sharp objects, can peel the coating at the point of contact.