EBIT x-ray spectroscopy studies for applications to photo-pumped x-ray lasers
Several pumping mechanisms have been suggested for x-ray lasers including collisional excitation, recombination, photo-ionization and photo-pumping. The success of photo-pumping as an x-ray laser scheme hinges on sufficient overlap of the emission and adsorption lines. For such a scheme to exhibit gain, the difference of the energies of the two lines must be within the line widths determined by the plasma dynamics, such as Doppler and opacity broadening. Typically, an overlap of a few parts in 10{sup 4} is required. Due to correlation effects, high-n levels of multi-electron ions are difficult to calculate and are reliable to roughly a part in 10{sup 3}. These differences are large enough to preclude accurate predictions of successful overlaps. As a result, precise measurements of the overlaps are needed. The continued interest in photo-pumping schemes lies in its potential to improve the laser output. It also allows the excitation of lasing transitions not accessible to other mechanisms and thus to the test laser kinetics from a different perspective. We have studied several such photo-pumping schemes at the LLNL electron beam ion trap. The N-like isoelectronic sequence 3d-5f and 3d-6f transitions were studied for photo-pumping by He-like ions, the Ne-like 2p-4d transitions were studied for photo-pumping by N-like 3d-4f transitions, and Ni-like 3d{sub 5/2}-6f{sub 7/2} transitions were studied for photo-pumping by H-like Ly-{alpha} transitions. A number of other chance coincidence pairs which do not follow an isoelectronic sequence were also studied. The data were taken with a flat-crystal vacuum spectrometer, a flat-crystal helium atmosphere spectrometer, or a curved-crystal spectrometer in the von Hamos geometry. The advantage of EBIT over laser-produced or tokamak plasmas for such experiments is its ability to control the charge balance and the excitation process. By choosing the electron beam energy, we can select a dominant charge state.
- Research Organization:
- Lawrence Livermore National Lab., CA (United States)
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- W-7405-ENG-48
- OSTI ID:
- 10173834
- Report Number(s):
- UCRL-JC-116836; CONF-940592-5; ON: DE94016701
- Resource Relation:
- Conference: 4. international colloquium on X-ray lasers,Williamsburg, VA (United States),16-20 May 1994; Other Information: PBD: 10 May 1994
- Country of Publication:
- United States
- Language:
- English
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