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This paper reports on recent results of a series of experiments on laser-generated ion beams. The experiments were done at the 30 TW ‘Trident’ laser system at the Los Alamos National Laboratories in New Mexico, USA, and we demonstrated the first accelerated ions at the 10 TW beamline of the PHELIX laser system at Gesellschaft fur Schwerionenforschung, Darmstadt, Germany. The experiments show the dependence of the Target Normal Sheath Acceleration Process (TNSA) on laser imprint and target parameters. The results are compared to a simple model for the ion propagation. It shows that TNSA-driven protons form an ion beam with superior beam quality, following the versatile spatial beam-shaping approaches.

European activities on inertial fusion energy are coordinated by “keep in touch activities” of the European Fusion Programme coordinated by the European Commission. There is no general inertial fusion program in Europe. Instead, a number of activities relevant to inertial fusion are carried out by university groups and research centers. The Helmholtz-Research Center GSI-Darmstadt (Gesellschaft fur Schwerionenforschung) operates accelerator facilities which provide the highest intensity for heavy ion beams and therefore key issues of ion beam driven fusion can be addressed. In addition to the accelerator facilities, one high-energy laser system is available (nhelix: nanosecond high-energy laser for ion experiments) and another one is under construction (PHELIX: petawatt high-energy laser for ion experiments). The heavy ion synchrotron facility, SIS18 (Schwer-Ionen-Synchrotron 18) recently delivered an intense uranium beam that deposits about 1 kJ/g specific energy in solid matter. Using this beam, experiments have been performed where solid Pb- and Ta-targets have been heated to the level of 1 eV. Experiments to study interaction mechanism of heavy ion beams with matter have been continued and are reported here.

The Kα X-ray emission spectra of the low-density SiO2 aerogel target bombarded by 48Ca ions with initial energy of 11.4 MeV/u were measured with a high spectral and spatial resolution along 80% of the ion beam stopping path. The Si KαL0 diagram and KαLn (up to n = 5) X-ray satellite lines corresponding to the radiative decays of atomic states with one hole in the K-shell and n-holes in the L-shell were measured. Energy shifts of the KαLn satellites with respect to their diagram Kα lines were determined and compared with the results of multiconfiguration Dirac–Fock (MCDF) calculations. The experimental energy shifts are smaller than values obtained from free-ion MCDF theory assuming an empty M-shell. The influence of the valence M-shell configuration on the satellite X-ray spectra is discussed.

Intense beams of protons and heavy ions have been observed in ultra-intense laser-solid interaction experiments. Thereby, a considerable fraction of the laser energy is transferred to collimated beams of energetic ions (e.g. up to 50 MeV protons; 100 MeV fluorine), which makes these beams highly interesting for various applications. Experimental results indicate very short pulse duration and an excellent beam quality, leading to beam intensities in the TW range. To characterize the beam quality and its dependence on laser parameters and target conditions we performed experiments at several high-power laser systems. We found a strong dependence on the target rear surface conditions allowing to tailor the ion beam by an appropriate target design. We also succeeded in the generation of heavy ion beams by suppressing the proton amount at the target surface.

The acceleration of ions by ultra-intense lasers has attracted great attention due to the unique properties and the unmatched intensities of the ion beams. In the early days the prospects for applications were already studied, and first experiments have identified some of the areas where laser accelerated ions can contribute to the ongoing inertial confinement fusion (ICF) research. In addition to the idea of laser driven proton fast ignition (PFI) and its use as a novel diagnostic tool for radiography the strong dependence on the electron transport in the target was found to be helpful in investigating the energy transport by electrons in fast ignitor scenarios. More recently an additional idea has been presented to use laser accelerated ion beams as the next generation ion sources, and taking advantage of the luminosity of the beams, to develop a test bed for heavy ion beam driven inertial confinement fusion physics. We review our recent experiments and simulations relevant to ICF research presenting a possible scenario for PFI as well as the prospects for next generation ion sources.

The laminarity of high current multi-MeV proton beams produced by irradiating thin metallic foils with ultra-intense lasers has been measured. For proton energies >10 MeV, the transverse and longitudinal emittance are, respectively, −4 eV s, i.e. at least 100-fold and may be as much as 10 4 -fold better than conventional accelerators beams. The ion beam source size is measured to be 10 MeV. Magnetic stripping of the co-moving electrons out of the beam after a few cm of debunching is not observed to induce emittance growth.

A method for space resolved measurements of the fast heavy ion velocity during the interaction with matter are presented. The main idea is based upon the fact that the characteristic radiation from ions traveling in the stopping media undergoes the Doppler shift, which varies along the ion beam trajectory due to the ion deceleration. High spectrally (λ/Δλ=1000–3000) and spatially (up to 30–100 μm) resolved x-ray K-shell spectra of Ca projectile ions as well as of the ionized stopping media have been obtained using focusing spectrometers with spatial resolution (FSSR). Spherically bent crystals of quartz and mica with small curvature radii R=150 mm and large apertures (15×50 mm) have been used as dispersive elements. Fast Ca+6 ions with energies of 5.9 and 11.4 MeV/u were stopped in quartz, SiO2 aerogels and CaF2 targets. High spectral and spatial resolution of the spectra allowed measuring the velocity of heavy projectile ions at different points along the beam trajectory. A method based on the utilizatio...

Variation of the velocity of Ca6+ ions with initial energies of 5.9 and 11.4 MeV/nucleon has been experimentally studied in the course of ion stopping in a solid aerogel target. The method is based on measuring the Doppler shift in the K-shell spectrum of decelerated Ca19+ and Ca18+ ions. High spatial resolution (30–50 mm) in the direction of the ion beam propagation achieved simultaneously with high spectral resolution (λ/Δλ=1000–3000) in the X-ray wavelength interval of 2–4 A allowed the ion beam dynamics in the solid target to be directly measured. By measuring variations in the relative intensity of spectral lines, it is possible to monitor the redistribution of the ions over charged states during their motion in the target.

We report on a new experimental setup for ion energy loss measurements in dense moderately coupled plasma which has recently been developed and tested at GSI Darmstadt. A partially ionized, moderately coupled carbon plasma (ne ≤ 0.8• 1022 cm-3, Te = 15 eV, z = 2.5, Γ = 0.5) is generated by volumetrical heating of two thin carbon foils with soft X-rays. This plasma is then probed by a bunched heavy ion beam. For that purpose, a special double gold hohlraum target of sub-millimeter size has been developed which efficiently converts intense laser light into thermal radiation and guarantees a gold-free interaction path for the ion beam traversing the carbon plasma. This setup allows to do precise energy loss measurements in non-ideal plasma at the level of 10 percent solid-state density.

K-shell radiation of fast heavy ions penetrating solid matter was used to analyze the stopping dynamics of ions over more than 80% of the stopping path. The most important advantage of this method is that the data is obtained with a high spatial resolution directly from the interaction volume. In experiments 11.4 MeV/ u Ca projectile were slowed down in solid quartz and low-density SiO2 aerogel targets. Characteristic projectile and target spectra in the photon energy range of 1.5–4 keV were registered by means of spherically bent crystal spectrometers with high spectral and spatial resolution in the direction of the ion beam propagation. K-shell spectra of heavy ions induced by close collisions with target atoms provided information about the projectile charge state and velocity dynamics. The line intensity distribution of the K-shell transitions arising from ions with different ion charges represents the charge state distribution along the ion beam track. The variation of the line Doppler shift due to the ion deceleration in the target material was used to determine the ion velocity dynamics. The spectroscopic analysis of the stopping process was complemented by measurements of the energy loss and ion charge state distribution after the ion beam emerged from the target using a standard time-of-flight method and magnet spectrometer.

The study of heavy ion stopping dynamics using associated K-shell projectile and target radiation was the focus of the reported experiments. Ar, Ca, Ti, and Ni projectile ions with the initial energies of 5.9 and 11.4 MeV/u were slowed down in quartz and arogels. Characteristic radiation of projectiles and target atoms induced in close collisions was registered. The variation of the projectile ion line Doppler shift due to the ion deceleration measured along the ion beam trajectory was used to determine the ion velocity dynamics. The dependence of the ion velocity on the trajectory coordinate was measured over 70–90% of the ion beam path with a spatial resolution of 50–70 μm. The choice of SiO 2 aerogel with low mean densities of 0.04–0.15 g/cm 3 as a target material, made it possible to stretch the ion stopping range by more than 20–50 times in comparison with solid quartz. It allowed for resolving the dynamics of the ion stopping process. Experimentally, it has been proven that the fine porous nano-structure of aerogels does not affect the ion energy loss and charge state distribution. The strong increase of the ion stopping range in aerogels made it possible to resolve fast ion radiation dynamics. The analysis of the projectile Kα-satellites structure allows supposing that ions propagate in solid in highly exicted states. This can provide an experimental explanation for so called gas-solid effect.

Intense heavy ion beams from the Gesellschaft fur Schwerionenforschung ~GSI, Darmstadt, Germany! accelerator facilities, together with two high energy laser systems: petawatt high energy laser for ion experiments ~PHELIX! and nanosecond high energy laser for ion experiments ~NHELIX! are a unique combination to facilitate pioneering beam-plasma interaction experiments, to generate and probe high-energy-density ~HED! matter and to address basic physics issues associated with heavy ion driven inertial confinement fusion. In one class of experiments, the laser will be used to generate plasma and the ion beam will be used to study the energy loss of energetic ions in ionized matter, and to probe the physical state of the laser-generated plasma. In another class of experiments, the intense heavy ion beam will be employed to create a sample of HED matter and the laser beam, together with other diagnostic tools, will be used to explore the properties of these exotic states of matter. The existing heavy ion synchrotron facility, SIS18, deliver an intense uranium beam that deposit about 1 kJ0g specific energy in solid matter. Using this beam, experiments have recently been performed where solid lead foils had been heated and a brightness temperature on the order of 5000 K was measured, using a fast multi-channel pyrometer that has been developed jointly by GSI and IPCP Chernogolovka. It is expected that the future heavy ion facility, facility for antiprotons and ion research ~FAIR! will provide compressed beam pulses with an intensity that exceeds the current beam intensities by three orders of magnitude. This will open up the possibility to explore the thermophysical and transport properties of HED matter in a regime that is very difficult to access using the traditional methods of shock compression. Beam plasma interaction experiments using dense plasmas with a G-parameter between 0.5 and 1.5 have also been carried out. This dense Ar-plasma was generated by explosively driven shockwaves and showed enhanced energy loss for Xe and Ar ions in the energy range between 5.9 to 11.4 MeV.

Since their discovery, laser accelerated ion beams have been the subject of great interest. The ion beam peak power and beam emittance is unmatched by any conventionally accelerated ion beam. Due to the unique quality, a wealth of applications has been proposed, and the first experiments confirmed their prospects. Laser ion acceleration is strongly linked to the generation and transport of hot electrons by the interaction of ultra-intense laser light with matter. Comparing ion acceleration experiments at laser systems with different beam parameters and using targets of varying thickness, material and temperature, some insight on the underlying physics can be obtained. The paper will present experimental results obtained at different laser systems, first beam quality measurement on laser accelerated heavy ions, and ion beam source size measurements at different laser parameters. Using structured targets, we compare information obtained from micro patterned ion beams about the accelerating electron sheath, and the influence of magnetic fields on the electron transport inside conducting targets.

We present the results of a detailed study on the acceleration of intense ion beams by relativistic laser plasmas. The experiments were performed at the 100 TW laser at the Laboratoire pour L'Utilisation des Lasers Intenses. We investigated the dependence of the ion beams on the target conditions based on theoretical predictions by the target normal sheath acceleration mechanism. A strong dependence of the ion beam parameters on the conditions on the target rear surface was found. 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.

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...

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.

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.