4th Generation High-Brightness Electron Beam Shaping and Light Source Applications

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A novel plasma based concept for generation of electron beams of highest quality which has recently been conceived, patented and published by the applicant and his collaborators shall be experimentally demonstrated and optimized. At first, plasma sources based on lowest-ionization-threshold alkali metal vapors such as lithium, Rubidium and cesium shall be developed. Compact electron beams shall then self-ionize these vapors by virtue of their electric self-fields, and shall then drive an intense plasma wave. These plasma waves are excellently suited to accelerate electrons, since the collective electric fields of such plasma waves can be four orders of magnitude larger as compared to conventional accelerators. A synchronized, ultrashort laser pulse with a peak intensity about four orders of magnitude lower than in state-of-the-art laser-plasma-accelerators shall then ionize a second gaseous component in its focus, thus releasing electrons directly inside the plasma wave with minimal transversal momentum. This gas component shall have a higher ionization threshold than the medium constituting the plasma wave, for example helium. The laser-released helium electrons are now focused, trapped and rapidly accelerated in the plasma wave. Since the focus intensity of the release laser is minimized, the released electrons in this underdense photocathode plasma wakefield acceleration scheme are ultracold and form bunches of minimized emittance. The emittance, in turn, is crucial for electron beam based light sources based on free-electron-lasers, Compton backscattering or betatron oscillations in the plasma. Proof-of-concept experiments shall be developed at University of Hamburg and shall be carried through at laser-plasma-accelerator facilities in Germany, as well as at the Stanford Linear Accelerator (SLAC). Furthermore, preionization of the low-ionization-threshold component via laser pulses and discharges and translation of the release laser pulse in space and time with respect to the plasma wave shall be studied in order to optimize the acceleration distance and energy gain, as well as the stability and tunability of the scheme. Ultimately, the scheme shall pave the way to the controlled generation of electron beams of unprecedented quality, and the development of compact, cost-effective and superior light sources for medicine and fundamental research.