The choice of materials for divertor targets

The trapping efficiency of divertor targets which react exothermically with hydrogen, such as V, Nb, Ta, Ti, Zr and Li, has been calculated using the theory of Hotston and McCracken. Of the above materials only Ti, Zr and Li are likely to be of use in experiments working at or near the conditions anticipated in a thermonuclear reactor. In order for the targets to trap efficiently for a time of 6000 s, the suggested burn time of a reactor design study, stringent control of the target temperature will be required (±25 K). It is shown that in most cases a simple theoretical model not requiring long numerical calculation is sufficient to predict the performance of the target.