Change of Optical Properties of Beryllium Mirrors Under Deuterium Ion Bombardment

Modification of optical properties of Be mirrors under bombardment by deuterium ions

“…1 and 2 as well as those published earlier [2,3] agreed with the concept that the drop of Be mirror reflectance under short exposure times to high energy deuterium ions is a result of partial chemical transformation occurring inside the BeO film. The results supporting this concept are:…”

“…Some results of experiments on Be mirrors with ECH discharge plasmas were discussed in papers [2,3] for one kind of beryllium. In contrast, the results of experiments in a reflex discharge were not analyzed yet.…”

“…Modelling experiments were begun in Kharkov three years ago and some results were previously presented [2,3]. The most important result was observation of the sharp drop of reflectance in the wavelength 220-650 nm after beryllium mirrors were subjected to bombardment by keV ions of deuterium plasma.…”

Changes to the reflectance of Be mirrors due to deuterium plasmas contaminated with oxygen

“…Since a Be film as thin as 20 nm would convert the reflectance of a mirror of any other material to a reflectance close to that of beryllium, it may make more sense to begin operation in ITER with solid Be mirrors. This reasoning has led to the investigation of the behavior of Be mirrors exposed to deuterium plasmas, with some results published in previous papers [1][2][3].…”

“…In this paper, we review the latest results on experiments with Be mirrors with the following intentions: (i) the properties of deposited films strongly depend on the deposition conditions, and it is possible that the reflectance of the Be film deposited on some in-vessel mirrors would be similar to the reflectance of a bulk Be mirror; (ii) new results are available which help to explain the changes to the optical properties of Be mirrors observed in [1][2][3] as being the result of surface chemistry involving oxygen impurities in the deuterium plasma; (iii) since beryllium is being used, or is planned for mirrors on space-based telescopes (e.g. [5,6]), the chemical processes on the surface of Be mirrors subjected to mixtures of hydrogen and oxygen ions may also simulate the experience of Be mirrors on such satellites.…”