M. Geissel

High energy heavy ion jets emerging from laser plasma generated by long pulse laser beams from the NHELIX laser system at GSI

High energy heavy ions were generated in laser produced plasma at moderate laser energy, with a large focal spot size of 0.5 mm diameter. The laser beam was provided by the 10 GW GSI-NHELIX laser systems, and the ions were observed spectroscopically in status nascendi with high spatial and spectral resolution. Due to the focal geometry, plasma jet was formed, containing high energy heavy ions. The velocity distribution was measured via an observation of Doppler shifted characteristic transition lines. The observed energy of up to 3 MeV of F-ions deviates by an order of magnitude from the well-known Gitomer ~Gitomer et al., 1986! scaling, and agrees with the higher energies of relativistic self focusing.

X-ray spectromicroscopy of fast heavy ions and target radiation

A new technique for X-ray spectromicroscopy of fast heavy ion radiation during the ion interaction with stopping media is presented using focusing spectrometers with spatial resolution. Spherically bent crystals of quartz and mica with small curvature radii, R ¼ 150 mm, and large apertures were used as dispersive elements in experiments on fast Ni ions with energies of 5.9 and 11.2 MeV/u which are being stopped in different media: Ar gas, SiO2-aerogels and solid quartz. Spectrally high (l=Dl ¼ 100023000) and spatially high (up to 10–100mm) resolved Ka-satellite spectra of Ni projectiles as well as of the ionized stopping media were observed. r 2002 Elsevier Science B.V. All rights reserved.

High-resolution x-ray imaging spectroscopy diagnostic of hollow ions in dense plasmas

Abstract The formation of hollow ions in dense Z-pinch and laser produced plasmas is investigated by means of high-resolution X-ray spectroscopy and atomic data calculations. Dense plasma effects are found to result in highly populated excited states which open up excitation channels not accessible in low-density plasma sources. This makes fs-laser radiation interacting with matter an important tool for modern atomic physics investigations.

Heavy-ion-induced hydrodynamic motion in lead targets

The hydrodynamic response of metal targets to volume heating by energy deposition of intense heavy-ion beams was investigated experimentally. Recent improvements in beam parameters led to a marked increase in specific deposition power: 2-10 10 40 Ar 18+ ions of 300 MeV/u focused to a spot size of 300 μm (σ) X 540 μm (σ) yield a specific deposition energy in solid lead of approximately 1 kJ/g in the Bragg peak, delivered within 250 ns [full width at half maximum (FWHM)]. This value allowed us for the first time to observe heavy-ion-beam-induced hydrodynamic expansion of metal volume targets. Measurements comprise expansion velocities of free surfaces of up to 290 ± 20 m/s, surface temperatures of ejected target matter of 1600-1750 K, and pressure waves in solid metal bulk targets of 0.16 GPa maximum absolute value and 0.8 μs FWHM. The experimental results agree well with the results of a 2D hydrodynamic code. Inside the interaction zone, which can only be accessed by simulation, maximum temperatures are 2800 K and maximum pressures are 3.8 GPa.

Observation of MeV ions in long-pulse, large-scale laser-produced plasmas

A new approach for investigation of the generation of fast ions and hot electrons inside the same plasma volume in laser-produced plasmas is proposed. It is based on the spectroscopic observation of line radiation from singly and doubly excited levels with simultaneous high spectral and spatial resolution. The experimental results demonstrate the observation of fast ions from highly charged target material inside the plasma volume and suggest that the generally accepted scaling relations are seriously invalid under certain conditions. Even at rather modest intensities ions with energies of several MeV are observed.

Energy deposition of heavy ions in matter

The energy loss of heavy ions in matter is completely different from the case of laser beams. Whereas laser radiation produces a plasma on the surface of the target and heats the volume mostly by shock waves, heavy ions penetrate deep into the target with an almost-constant energy loss in the beginning and a very high energy loss at the end of the range, the so called “Bragg peak.” This special behavior offers excellent possibilities for the examination of critical points of different materials, the measurement of benchmarks for equations of state, production and detection of X-rays and XUV radiation, investigations in physics of overdense plasma, and many more topics. In particular, heavy ion beams are considered to be a very efficient driver for an inertial confinement fusion power plant. Thus, research on the elementary processes of the energy deposition of heavy ions in matter with respect to inertial fusion energy is of primary interest.

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...

High Density Neon‐Plasma Created by Intense Gold Beams

The expansion of a heavy ion beam heated lead pusher has been utilized to compress solid cryogenic neon. Diagnostics have been developed to measure the equation of state parameters and transport coefficients. Advanced compression schemes for two-dimensional compression have been prepared.

Physics: A tabletop neutron source

The molecular clock not only controls the rhythmic expression of genes with physiological roles, but also regulates the creation of ribosomes — molecular machines that translate messenger RNA into protein. Frédéric Gachon at the University of Lausanne in Switzerland and his colleagues found that mRNAs that encode components of the translation machinery — including some involved in making ribosomes — are rhythmically expressed in the livers of mice. Production of these RNAs peaks in the nocturnal animals shortly before nightfall, when the energy needed for protein synthesis is most likely to be available.

Recent Advances in Proton Acceleration and Beam Shaping

A report on recent-developments will be given with focus on experiments to control and combine laser-accelerated ion-beams with beam-transport structures and new targets and results using geometries for ion-driven fast-ignition and the generation of warm-dense-matter.