D. Haberberger

Fifteen terawatt picosecond CO 2 laser system

The generation of a record peak-power of 15 TW (45 J, 3 ps) in a single CO(2) laser beam is reported. Using a master oscillator-power amplifier laser system, it is shown that up to 100 J of energy can be extracted in a train of 3 ps laser pulses separated by 18 ps, a characteristic time of the CO(2) molecule. The bandwidth required for amplifying the short injected laser pulse train in a 2.5 atm final CO(2) amplifier is provided by field broadening of the medium at intensities of up to 140 GW/cm(2). The measured saturation energy for 3 ps pulses is 120 mJ/cm(2) which confirms that energy is simultaneously extracted from six rovibrational lines.

Amplification of multi-gigawatt 3 ps pulses in an atmospheric CO2 laser using ac Stark effect.

The 3 ps pulses are amplified to ~20 GW peak power in a TEA CO(2) laser using ac Stark broadening. Demonstration of such broadband coherent amplification of 10 μm pulses opens opportunities for a powerful mid-IR source at a high-repetition rate.

CO 2 Laser acceleration of forward directed MeV proton beams in a gas target at critical plasma density

The generation of 1–5 MeV protons from the interaction of a 3 ps TW CO 2 laser pulse with a gas target with a peak density around the critical plasma density has been studied by 2D particle-in-cell simulations. The proton acceleration in the preformed plasma with a symmetric, linearly ramped density distribution occurs via formation of sheath of the hot electrons on the back surface of the target. The maximum energy of the hot electrons and, hence, net acceleration of protons is mainly defined by Forward Raman scattering instability in the underdense part of the plasma. Forward directed ion beams from a debris free gaseous target can find an application as a high-brightness ion source-injector to a conventional accelerator operating up to kHz pulse repetition frequency.

Femtosecond Microbunching of Electron Beam in a 7th Harmonic Coupled IFEL

We report the results of studying electron beam microbunching in a 7th order IFEL interaction using coherent transition radiation emitted by the bunched beam as a diagnostic. The resonant wavelength for the undulator with a period of 3.3 cm and Ku2009=u20091.8 is 74.2u2009μm, but it was seeded by a CO2 laser with a seven times shorter wavelength of 10.6u2009μm. The ∼12.3u2009MeV electrons were efficiently bunched longitudinally inside a ten period long undulator producing the first, second, and third harmonics in a CTR spectrum. It is shown that in the case of approximately equal sizes of the electron and the seed radiation beams, the IFEL interaction results in transverse variation of bunching which significantly affects the CTR harmonic content. The measurements were compared to the predictions of IFEL simulations. These experimental results demonstrate for the first time feasibility of using very high order harmonic coupling for efficient IFEL/FEL interactions.