Prospects for particle beam pumped short wavelength lasers

This paper reports on heavy ion beam pumping which provides a laser excitation technique which is potentially significant for producing short wavelength high power lasers. Heavy ion accelerators providing ions from several MeV to several GeV have primarily been used for single collision nuclear and atomic physics experiments. Much of our data base on few electron ion transitions, transition rates and inner shell excitation have come from heavy ion beam experiments. Recent accelerator advances now allow the production of very intense, well-focused beams and have stimulated research in the field of heavy ion inertial confinement fusion. Beams developed for these programs may also be used for x-ray laser physics studies. The energy of a heavy ion beam is directly transferred to efficient ionization of atoms and ions; the specific energy loss is high in a cylindrical volume around the particle beam axis with the energy implying higher energy densities with the highest Z beams. High power is achieved with pulsed bunched beams from present accelerators, typical pulse widths being around 1 ns, and most accelerators have very attractive duty cycles compared to pulsed lasers. Instantaneous electric fields in ion-atom collisions can be several hundred e/a02 with correspondingly high time derivatives. This leads to large multiple ionization cross sections with relatively cool recoil ions moving transverse to the beam. Specific levels may be preferentially populated in fast recombination. The study of the physics of excited state formation and decay is the most important area of current research