He II Balmer series line shifts in a dense z-pinch plasma
J P Marangos; D D Burgess; K G H Baldwin; J P Marangos; Blackett Lab., Imperial Coll., London, UK; D D Burgess; Blackett Lab., Imperial Coll., London, UK; K G H Baldwin; Blackett Lab., Imperial Coll., London, UK
Журнал:
Journal of Physics B: Atomic, Molecular and Optical Physics
Дата:
1988-10-28
Аннотация:
Describes measurements of He II Balmer series line shapes and shifts, using both absorption and emission techniques, in a dense (N<sub>e</sub>=2+or-0.5*10<sup>18</sup> cm<sup>-3</sup>), cool (T<sub>e</sub>=3.4 eV) helium z-pinch plasma. Tunable coherent VUV radiation was generated around 1640 AA by Raman up-conversion in H<sub>2</sub> and around 1215 AA by frequency tripling in krypton. An absorption measurement was made on the near wing profile of the He II Balmer-alpha line (1640 AA) using the Raman up-converted light source. Emission measurements were made on the He II Balmer-beta (1215 AA) line profile; these were complemented by an accurate wavelength calibration using the tunable coherent VUV light from the frequency tripled light source. A shift in the wavelength of the Balmer-beta line centre of 0.7+or-0.2 AA to the red was observed. Discussion is given of this shift in relation to existing theories of the plasma polarisation shift.
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