X-ray And EUV Spectroscopy Of Highly Charged Tungsten Ions

摘要

The Berlin EBIT has been established by the Max-Planck-Institut fur Plasmaphysik to generate atomic physics data in support of research in the field of controlled nuclear fusion, by measuring the radiation from highly charged ions in the x-ray, extreme ultraviolet and visible spectral ranges and providing valuable diagnostics for high temperature plasmas [I]. In future fusion devices, for example ITER, currently being constructed at Cadarache, France, the plasma facing components will be armored with high-Z materials, most likely tungsten, due to the favorable properties of this element [2]. At the same time the tremendous radiation cooling of these high-Z materials represents a threat to fusion and obliges one to monitor carefully the radiation. With EBIT a selected ensemble of ions in specific charge states can be produced, stored and excited for spectroscopic investigations. Employing this technique, we have for example resolved the wide structure observed around 5 nm at the ASDEX Upgrade tokamak as originating from El -transitions into the open 4d shell of tungsten ions in charge states 25+ to 37+ producing a band-like emission pattern [3]. Further, these ions emit well-separated MI lines in the EUV range around 65 nm suitable for plasma diagnostics [4]. Kr-like to Cr-like tungsten ions (38+ to 50+) show strong soft-x-ray lines in the range 0.5 to 2 and 5 to 15 nm. Lines of even higher charged tungsten ions, up to Ne-like W~(64+) , abundant in the core plasma of present and future fusion test devices, have been investigated with high resolution Bragg-crystal spectroscopy at 0.13 nrn [5]. Recently, x-ray spectroscopic measurements of the dielectronic recombination LMn resonances of W~(60+) to W~(67+) ions have been preformed and compare well with atomic structure calculations.