Manuel Hegelich

Proton spectra from ultraintense laser-plasma interaction with thin foils: Experiments, theory, and simulation

A beam of high energy ions and protons is observed from targets irradiated with intensities up to 5×1019 W/cm2. Maximum proton energy is shown to strongly correlate with laser-irradiance on target. Energy spectra from a magnetic spectrometer show a plateau region near the maximum energy cutoff and modulations in the spectrum at approximately 65% of the cutoff energy. Presented two-dimensional particle-in-cell simulations suggest that modulations in the proton spectrum are caused by the presence of multiple heavy-ion species in the expanding plasma.

Comparative spectra and efficiencies of ions laser-accelerated forward from the front and rear surfaces of thin solid foils

The maximum energy of protons that are accelerated forward by high-intensity, short-pulse lasers from either the front or rear surfaces of thin metal foils is compared for a large range of laser intensities and pulse durations. In the regime of moderately long laser pulse durations (300–850fs), and for high laser intensities [(1−6)×1019W∕cm2], rear-surface acceleration is shown experimentally to produce higher energy particles with smaller divergence and a higher efficiency than front-surface acceleration. For similar laser pulse durations but for lower laser intensities (2×1018Wcm−2), the same conclusion is reached from direct proton radiography of the electric fields associated with proton acceleration from the rear surface. For shorter (30–100fs) or longer (1–10ps) laser pulses, the same predominance of rear-surface acceleration in producing the highest energy protons is suggested by simulations and by comparison of analytical models with measured values. For this purpose, we have revised our previous ...

Correction of strong phase and amplitude modulations by two deformable mirrors in a multistaged Ti:sapphire laser

We describe a novel scheme consisting of two deformable bimorph mirrors that can free ultrashort laser pulses from simultaneously present strong wave-front distortions and intensity-profile modulations. This scheme is applied to the Max-Planck-Institut für Quantenoptik 10-TW Advanced Titanium-Sapphire Laser (ATLAS) facility. We demonstrate that with this scheme the focusability of the ATLAS pulses can be improved from 10(18) to 2x10(19) W/cm(2) without any penalty in recompression fidelity.

Theory of laser ion acceleration from a foil target of nanometer thickness

A theory for ion acceleration by ultrashort laser pulses is presented to evaluate the maximum ion energy in the interaction of ultrahigh contrast (UHC) intense laser pulses with a nanometer-scale foil. In this regime, the ion energy may be directly related to the laser intensity and subsequent electron dynamics. This leads to a simple analytical expression for the ion energy gain under the laser irradiation of thin targets. Significantly higher energies for thin targets than for thicker targets are predicted. The theory is concretized with a view to compare with the results and their details of recent experiments.

Dynamics of Nanometer-Scale Foil Targets Irradiated with Relativistically Intense Laser Pulses

In this letter we report on an experimental study of high harmonic radiation generated in nanometer-scale foil targets irradiated under normal incidence. The experiments constitute the rst unambiguous observation of odd-numbered relativistic harmonics generated by the ~ ~ B component of the Lorentz force verifying a long predicted property of solid target harmonics. Simultaneously the observed harmonic spectra allow in-situ extraction of the target density in an experimental scenario which is of utmost interest for applications such as ion acceleration by the radiation pressure of an ultraintense laser.

Intense ion beams accelerated by relativistic laser plasmas

We have studied the influence of the target properties on laser-accelerated proton and ion beams generated by the LULI multi-terawatt laser. A strong dependence of the ion emission on the surface conditions, conductivity, shape and material of the thin foil targets were observed. We have performed a full characterization of the ion beam using magnetic spectrometers, Thompson parabolas, radiochromic film and nuclear activation techniques. The strong dependence of the ion beam acceleration on the conditions on the target back surface was found in agreement with theoretical predictions based on the target normal sheath acceleration (TNSA) mechanism. Proton kinetic energies up to 25 MeV have been observed.

Intense ion beams accelerated by ultra-intense laser pulses

The discovery of intense ion beams off solid targets irradiated by ultra-intense laser pulses has become the subject of extensive international interest. These highly collimated, energetic beams of protons and heavy ions are strongly depending on the laser parameters as well as on the properties of the irradiated targets. Therefore we have studied the influence of the target conditions on laser-accelerated ion beams generated by multi-terawatt lasers. The experiments were performed using the 100 TW laser facility at Laboratoire pour l’Utilisation des Laser Intense (LULI). The targets were irradiated by pulses up to 5×1019 W/cm2 (∼300 fs,λ=1.05 μm) at normal incidence. A strong dependence on the surface conditions, conductivity, shape and purity was observed. The plasma density on the front and rear surface was determined by laser interferometry. We characterized the ion beam by means of magnetic spectrometers, radiochromic film, nuclear activation and Thompson parabolas. The strong dependence of the ion b...

Intense, high-quality ion beams generated by ultra-intense lasers

The advent of ultra-intense short-pulse laser systems has opened the field of relativistic laser-generated plasmas in which the electron temperature exceeds several MeV. One particularly exciting topic of recent interest has been the discovery of intense, collimated, energetic beams of ions off the back surface of solid targets. The beam currents exceed several hundreds of kiloamperes at a pulse duration of only a few picoseconds.

Short Pulse Laser Driven Ion Beams — Experiments and Applications

We present the results of a study on the acceleration of intense ion beams from solid targets irradiated with laser intensities up to 5×1019W/cm2. A strong dependence of the ion beam parameters on the conditions on the target conditions and laser parameter was found. The ion beam characteristic revealed a highly laminar acceleration and an excellent beam quality superior to that from conventional accelerators. We succeeded in shaping the ion beam by the appropriate tailoring of the target geometry and we performed a characterization of the ion beam quality. The production of a heavy ion beam could be achieved by suppressing the amount of protons at the target surfaces. Finally, we demonstrated the use of short pulse laser driven ion beams for radiography of thick samples with high resolution.

Adaptive optics in a multistage TiS laser

We describe a novel scheme consisting of two deformable mirrors that can free ultrashort laser pulses from simultaneously present severe wavefront distortions and strong intensity-profile modulations. This scheme is applied to the MPQ 10-TW TiS laser facility ATLAS. We demonstrate that thereby the focusability of the ATLAS pulses can be improved from 1018 to 2x1019 W/cm2 without any penalty in recompression fidelity by using adaptive optical system.