Resistance of Mirrors of a Nonresonant Photon Neutralizer of Powerful Beam Negative Ions to Bombardment by High-Energy Particles

Future fusion reactors will require highly efficient methods for maintaining and heating the plasma. One of the most promising methods for solving this problem is the use of atomic sources with an energy level of about 1 MeV. Currently, it is impossible to obtain a high neutral yield efficiency for negative ion sources using gas charge exchange targets. An alternative method for neutralization is to use the effect of photodetachment of an excess electron from the ion. The idea of this method is based on the accumulation of high-power laser radiation in a mirror trap. The effectiveness of this approach directly depends on the amount of accumulated energy in the system of dielectric mirrors with a high reflectivity of more than 0.9999. Owing to the location of the mirrors close to the flow of high-energy charged particles, it is necessary to study the dependence of the degradation of the reflectance on bombardment by these particles. This paper examines two models of mirrors coated with the most popular materials TiO2–SiO2 and ZrO2–SiO2. A mirror model with a protective finishing layer based on the above materials is also proposed. As estimates show, the most resistant is a mirror coated with zirconium oxide and silicon oxide. The expected damage level at a fluence of 1013 cm‒2 should not exceed the critical value of 6.1 × 1013 cm‒2, as for the modified mirror.