Berlin 2001 – wissenschaftliches Programm

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AMPD: EPS AMPD

AMPD 9: Sitzung 9

AMPD 9.3: Vortrag

Freitag, 6. April 2001, 11:20–11:45, H105

Highly Charged Ions in an Electron–Beam–Ion Trap (EBIT) — •Gerd Fussmann — Max–Planck–Institut für Plasmaphysik, Bereich Plasmadiagnostik, Berlin, Germany

Whereas in the past highly ionized atoms with charge states Z > 30 could only be produced in large accelerator facilities, the newly developed EBIT device allows the creation of all kind of ions (up to fully ionized uranium) under common laboratory conditions. Worldwide there are momentary about ten such sources in operation. In the Berlin EBIT we have so far focussed our research activities on Ar–, Kr–, and W–ions which are of particular importance in the context of hot fusion plasmas. Ar–ions are used mainly for diagnostic purposes (ion and electron temperature measurements); Kr is proposed to be injected deliberately into a fusion reactor in order to cool the boundary region, while highly ionized W–ions, penetrating into such plasmas as a result of wall material erosion, may lead to critical radiation losses in the core region. Investigations at EBIT enabled us in particular to analyze the complex spectra of the W²⁰⁺ − W⁵⁰⁺ ions in the soft x–ray and EUV range, including a number of magnetic dipole transitions probably useful for plasma diagnostic purposes. In addition the elements Fe, Au and U are of interest for other reasons: iron because of its relatively large abundance in cosmic plasmas; H–like gold and uranium ions show large Lamb shifts, thus allowing to measure QED–effects with high precision. By rapid modulation of the electron beam energy in EBIT it is also possible to determine cross–sections for a number of processes such as collisional excitation and dielectronic recombination, being of relevance in many astro– and plasmaphysical aspects. The talk will also address some crucial questions concerning the confinement properties in the combined E– and B–fields of EBIT, the heating of the ions, and the methods applied to cool them. Important properties are the maximum filling capacity of the trap and the possibility to extract the ions for external interaction studies.