Christian Roedel

Long-term operation of surface high-harmonic generation from relativistic oscillating mirrors using a spooling tape

Surface high-harmonic generation in the relativistic regime is demonstrated as a source of extreme ultra-violet (XUV) pulses with extended operation time. Relativistic high-harmonic generation is driven by a frequency-doubled high-power Ti:Sapphire laser focused to a peak intensity of 3·10(19) W/cm2 onto spooling tapes. We demonstrate continuous operation over up to one hour runtime at a repetition rate of 1 Hz. Harmonic spectra ranging from 20 eV to 70 eV (62 nm to 18 nm) were consecutively recorded by an XUV spectrometer. An average XUV pulse energy in the µJ range is measured. With the presented setup, relativistic surface high-harmonic generation becomes a powerful source of coherent XUV pulses that might enable applications in, e.g. attosecond laser physics and the seeding of free-electron lasers, when the laser issues causing 80-% pulse energy fluctuations are overcome.

Aberration Correction for Hard X-ray Focusing at the Nanoscale

We developed a corrective phase plate that enables the correction of residual aberration in reflective, diffractive, and refractive X-ray optics. The principle is demonstrated on a stack of beryllium compound refractive lenses with a numerical aperture of 0.49 10-3 at three synchrotron radiation and x-ray free-electron laser facilities, where we corrected spherical aberration of the optical system. The phase plate improved the Strehl ratio of the optics from 0.29(7) to 0.87(5), creating a diffraction-limited, large aperture, nanofocusing optics that is radiation resistant and very compact.

Deflection of laser accelerated protons from cryogenic hydrogen jets due to self-generated magnetic fields

Summary form only given. Laser-driven ion acceleration is of great interest across a range of disciplines with potential applications including the fast ignition approach to inertial confinement fusion and proton therapy. The most robust acceleration mechanisms studied to date however, based on target normal sheath acceleration (TNSA), do not satisfy the emittance, flux and ion energy requirements for direct applications. In this talk, we will first discuss alternative acceleration mechanisms utilizing cryogenic hydrogen jets to work towards a high-repetition rate proton source with suitable beam parameters for various applications. We will then show a study of the spatial distribution of the energetic protons produced from a high-intensity laser-plasma interaction in cylindrical geometry. In the laser forward direction, we will show that the proton beam is highly structured with a bubble-net pattern. In addition, we observe two well-defined bands, offset ±8-15° vertically from the laser plane and surrounding the target azimuthally. We will introduce the interpretation of these structures as caustics in linear proton radiography theory where the energetic protons are deflected due to self-generated magnetic fields. Finally, these results will be compared with 2D and 3D Particle-in-cell (PIC) simulations which confirm the role of the Weibel Instability in the formation of the bubble-net structure and qualitatively reproduce the observed bands due to Biermann Battery magnetic fields.

High-Power Laser Pump-Probe Experiments At The Linac Coherent Light Source

The Matter in Extreme Conditions end station at the Linac Coherent Light Source (LCLS) is a new tool enabling ultrafast pump-probe measurements of laser-matter interactions. This instrument combines the world’s brightest x-ray source, the LCLS x-ray beam, with high-power lasers consisting of two nanosecond Nd:glass laser beams and a 25 TW short-pulse Ti:sapphire laser. These lasers produce short-lived states of matter with high pressures, high temperatures or high densities whose properties are investigated with highly accurate x-ray measurements. Here, we report on new results using x-ray imaging, diffraction, and scattering that resolve the short-pulse laser beam propagation and heating of matter.