Inefficient Magnetic-Field Amplification in Supersonic Laser-Plasma Turbulence.

We report a laser-plasma experiment that was carried out at the LMJ-PETAL facility and realized the first magnetized, turbulent, supersonic (Ma_{turb}≈2.5) plasma with a large magnetic Reynolds number (Rm≈45) in the laboratory. Initial seed magnetic fields were amplified, but only moderately so, and did not become dynamically significant. A notable absence of magnetic energy at scales smaller than the outer scale of the turbulent cascade was also observed. Our results support the notion that moderately supersonic, low-magnetic-Prandtl-number plasma turbulence is inefficient at amplifying magnetic fields compared to its subsonic, incompressible counterpart.

The Neutrons for Science Facility at SPIRAL-2.

The neutrons for science (NFS) facility is a component of SPIRAL-2, the new superconducting linear accelerator built at GANIL in Caen (France). The proton and deuteron beams delivered by the accelerator will allow producing intense neutron fields in the 100 keV-40 MeV energy range. Continuous and quasi-mono-kinetic energy spectra, respectively, will be available at NFS, produced by the interaction of a deuteron beam on a thick Be converter and by the 7Li(p,n) reaction on thin converter. The pulsed neutron beam, with a flux up to two orders of magnitude higher than those of other existing time-of-flight facilities, will open new opportunities of experiments in fundamental research as well as in nuclear data measurements. In addition to the neutron beam, irradiation stations for neutron-, proton- and deuteron-induced reactions will be available for cross-sections measurements and for the irradiation of electronic devices or biological cells. NFS, whose first experiment is foreseen in 2018, will be a very powerful tool for physics, fundamental research as well as applications like the transmutation of nuclear waste, design of future fission and fusion reactors, nuclear medicine or test and development of new detectors.

First set of gated x-ray imaging diagnostics for the Laser Megajoule facility.

The Laser Megajoule (LMJ) facility located at CEA/CESTA started to operate in the early 2014 with two quadruplets (20 kJ at 351 nm) focused on target for the first experimental campaign. We present here the first set of gated x-ray imaging (GXI) diagnostics implemented on LMJ since mid-2014. This set consists of two imaging diagnostics with spatial, temporal, and broadband spectral resolution. These diagnostics will give basic measurements, during the entire life of the facility, such as position, structure, and balance of beams, but they will also be used to characterize gas filled target implosion symmetry and timing, to study x-ray radiography and hydrodynamic instabilities. The design requires a vulnerability approach, because components will operate in a harsh environment induced by neutron fluxes, gamma rays, debris, and shrapnel. Grazing incidence x-ray microscopes are fielded as far as possible away from the target to minimize potential damage and signal noise due to these sources. These imaging diagnostics incorporate microscopes with large source-to-optic distance and large size gated microchannel plate detectors. Microscopes include optics with grazing incidence mirrors, pinholes, and refractive lenses. Spatial, temporal, and spectral performances have been measured on x-ray tubes and UV lasers at CEA-DIF and at Physikalisch-Technische Bundesanstalt BESSY II synchrotron prior to be set on LMJ. GXI-1 and GXI-2 designs, metrology, and first experiments on LMJ are presented here.

A new compact, high sensitivity neutron imaging system.

We have developed a new small neutron imaging system (SNIS) diagnostic for the OMEGA laser facility. The SNIS uses a penumbral coded aperture and has been designed to record images from low yield (10(9)-10(10) neutrons) implosions such as those using deuterium as the fuel. This camera was tested at OMEGA in 2009 on a rugby hohlraum energetics experiment where it recorded an image at a yield of 1.4 × 10(10). The resolution of this image was 54 µm and the camera was located only 4 meters from target chamber centre. We recently improved the instrument by adding a cooled CCD camera. The sensitivity of the new camera has been fully characterized using a linear accelerator and a (60)Co γ-ray source. The calibration showed that the signal-to-noise ratio could be improved by using raw binning detection.

X-ray grating spectrometer for opacity measurements in the 50 eV to 250 eV spectral range at the LULI 2000 laser facility.

An x-ray grating spectrometer was built in order to measure opacities in the 50 eV to 250 eV spectral range with an average spectral resolution ∼ 50. It has been used at the LULI-2000 laser facility at École Polytechnique (France) to measure the Δn = 0, n = 3 transitions of several elements with neighboring atomic number: Cr, Fe, Ni, and Cu in the same experimental conditions. Hence a spectrometer with a wide spectral range is required. This spectrometer features one line of sight looking through a heated sample at backlighter emission. It is outfitted with one toroidal condensing mirror and several flat mirrors cutting off higher energy photons. The spectral dispersion is obtained with a flatfield grating. Detection consists of a streak camera sensitive to soft x-ray radiation. Some experimental results showing the performance of this spectrometer are presented.

Development of the large neutron imaging system for inertial confinement fusion experiments.

Inertial confinement fusion (ICF) requires a high resolution (~10 µm) neutron imaging system to observe deuterium and tritium (DT) core implosion asymmetries. A new large (150 mm entrance diameter: scaled for Laser MégaJoule [P. A. Holstein, F. Chaland, C. Charpin, J. M. Dufour, H. Dumont, J. Giorla, L. Hallo, S. Laffite, G. Malinie, Y. Saillard, G. Schurtz, M. Vandenboomgaerde, and F. Wagon, Laser and Particle Beams 17, 403 (1999)]) neutron imaging detector has been developed for such ICF experiments. The detector has been fully characterized using a linear accelerator and a (60)Co γ-ray source. A penumbral aperture was used to observe DT-gas-filled target implosions performed on the OMEGA laser facility. [T. R. Boehly, D. L. Brown, R. S. Craxton, R. L. Keck, J. P. Knauer, J. H. Kelly, T. J. Kessler, S. A. Kumpan, S. J. Loucks, S. A. Letzring, F. J. Marshall, R. L. McCrory, S. F. B. Morse, W. Seka, J. M. Soures, and C. P. Verdon, Opt. Commun. 133, 495 (1997)] Neutron core images of 14 MeV with a resolution of 15 µm were obtained and are compared to x-ray images of comparable resolution.

Opacity of iron, nickel, and copper plasmas in the x-ray wavelength range: theoretical interpretation of 2p-3d absorption spectra.

This paper deals with theoretical studies on the 2p-3d absorption in iron, nickel, and copper plasmas related to LULI2000 (Laboratoire pour l'Utilisation des Lasers Intenses, 2000J facility) measurements in which target temperatures were of the order of 20 eV and plasma densities were in the range 0.004-0.01 g/cm(3). The radiatively heated targets were close to local thermodynamic equilibrium (LTE). The structure of 2p-3d transitions has been studied with the help of the statistical superconfiguration opacity code SCO and with the fine-structure atomic physics codes HULLAC and FAC. A new mixed version of the sco code allowing one to treat part of the configurations by detailed calculation based on the Cowan's code RCG has been also used in these comparisons. Special attention was paid to comparisons between theory and experiment concerning the term features which cannot be reproduced by SCO. The differences in the spin-orbit splitting and the statistical (thermal) broadening of the 2p-3d transitions have been investigated as a function of the atomic number Z. It appears that at the conditions of the experiment the role of the term and configuration broadening was different in the three analyzed elements, this broadening being sensitive to the atomic number. Some effects of the temperature gradients and possible non-LTE effects have been studied with the help of the radiative-collisional code SCRIC. The sensitivity of the 2p-3d structures with respect to temperature and density in medium-Z plasmas may be helpful for diagnostics of LTE plasmas especially in future experiments on the Δn=0 absorption in medium-Z plasmas for astrophysical applications.

Experimental demonstration of X-ray drive enhancement with rugby-shaped hohlraums.

Rugby-shaped hohlraums have been suggested as a way to enhance x-ray drive in the indirect drive approach to inertial confinement fusion. This Letter presents an experimental comparison of rugby-shaped and cylinder hohlraums used for D2 and D3He-filled capsules implosions on the Omega laser facility, demonstrating an increase of x-ray flux by 18% in rugby-shaped hohlraums. The highest yields to date for deuterium gas implosions in indirect drive on Omega (1.5x10{10} neutrons) were obtained, allowing for the first time the measurement of a DD burn history. Proton spectra measurements provide additional validation of the higher drive in rugby-shaped hohlraums.

Broadband, high dynamics and high resolution charge coupled device-based spectrometer in dynamic mode for multi-keV repetitive x-ray sources.

We present a new operating mode, using a charged coupled device as dispersionless spectrometer dedicated to repetitive x-ray sources in the multi-keV domain. This enables to get spectra with high statistics in a short acquisition time and a way compatible with the operation of other diagnostics requiring accumulation. Several reconstruction algorithms for the spreading events are discussed, and a near Fano-limited resolution is demonstrated by using single pixel events. In this case, a method to take into account partial canceling of the events is presented. Experimental characterization and detailed modeling of the detector are performed, which allow to determine absolute number of photon with +/-35% accuracy. Characterization of the 5-25 keV x rays emitted by a short pulse laser-produced plasma is reported, as well as their dependency with the atomic number, the laser duration, and energy.

X-ray diagnostic calibration with the tabletop laser facility EQUINOX.

The broadband x-ray emission of a target irradiated by a laser can be used to check the calibration of detectors. At CEA-DIF we have a tabletop picosecond laser facility called EQUINOX with 0.3 J at 800 nm. The laser is focused inside a target chamber onto a solid target and produces bright radiation in the 100-2000 eV spectral range. The x-ray source is routinely monitored with a pinhole camera for source dimension measurement and with x-ray diodes for flux measurement. In addition an x-ray transmission grating spectrometer, a crystal spectrometer, and a single count charge coupled device camera measure the x-ray spectrum between 100 eV and 15 keV. The absolute calibration of those sets of spectrometers allows us to fully characterize x-ray emission spectra. Typical duration is less than 100 ps. The spectrum can be tuned by changing target material, pulse length, and x-ray filters. An application to checking the calibration of x-ray diodes used in the broad band spectrometer DMX with single shots will be presented.

Diagnostics hardening for harsh environment in Laser Megajoule (invited).

The diagnostic designs for the Laser Megajoule (LMJ) will require components to operate in environments far more severe than those encountered in present facilities. This harsh environment will be induced by fluxes of neutrons, gamma rays, energetic ions, electromagnetic radiations, and, in some cases, debris and shrapnel, at levels several orders of magnitude higher than those experienced today on existing facilities. The lessons learned about the vulnerabilities of present diagnostic parts fielded mainly on OMEGA for many years, have been very useful guide for the design of future LMJ diagnostics. The present and future LMJ diagnostic designs including this vulnerability approach and their main mitigation techniques will be presented together with the main characteristics of the LMJ facility that provide for diagnostic protection.

Observation of subpicosecond x-ray emission from laser-cluster interaction.

We present the first experimental evidence of the subpicosecond duration of x-ray pulses emitted from laser-irradiated clusters, demonstrating the suitability of such a debris free target for ultrafast x-ray science applications. The K-shell emission (approximately 3 keV) from large Ar clusters (6 x 10(5) to 4 x 10(6) atoms) is time resolved, when irradiated by ultrashort (40 fs to 5 ps) and intense laser pulses (10(15-17) W/cm2). The observations are supported by hydrodynamical and collisional-radiative calculations, that reproduce the extremely short x-ray pulse duration.

[Biomedical research in France: what has changed since 2004]. / La recherche biomédicale en France: ce qui a changé depuis 2004.

The public health law passed in 2004 is the implementation into French law of the European Clinical Trial directive 2001/20/EC on the implementation of good clinical practice in conducting clinical trials on medicinal products for human use. This law goes further than the European directive since it reconsiders all the components related to all fields of biomedical research. It has (i) standardized communication with the authorities (French Drug Agency/French Health Authority and the Ethics Committee); (ii) reinforced protection to participants in clinical trials and modified the information delivered to participants and how their informed consent is obtained; (iii) added risk-benefit assessment; and (iv) increased transparency for the public.

Investigation of laser-irradiated Ar cluster dynamics from K-shell x-ray emission measurements.

Intense (up to a few 10(17) W/ cm2) femtosecond (down to 40 fs) laser pulses are focused onto a partially clusterized argon gas jet. The target was previously characterized and optimized in order to get a homogeneous and dense jet of clusters with a well controlled size. The interaction leads to x-ray emission that is absolutely calibrated and spectrally resolved using a high resolution time-integrated spectrometer in the K-shell range (from 2.9 to 4.3 keV). X-ray spectra are investigated as a function of different laser temporal parameters such as the nanosecond prepulse contrast, the laser pulse duration, and the femtosecond delay between two different laser pulses. The cluster size ranges from 180 to 350 angstroms and irradiation by laser pulses with both linear and circular polarization is investigated. The experimental results are discussed in terms of the laser-cluster interaction dynamics. They are compared with the predictions of collision-dominated nanoplasma models. However, further interaction processes are required in order to explain the observed characteristic lines demonstrating highly charged ions up to Ar16+.

Treatment of PC12 cells by nerve growth factor, dexamethasone, and forskolin. Effects on cell morphology and expression of neurotensin and tyrosine hydroxylase.

Several lines of anatomical, neurochemical, electrophysiological, and behavioral evidence suggest the existence of physiological interactions between neurotensin (NT) and the brain dopaminergic systems. Thus, NT has been shown to exert a neuroleptic-like action and could be implicated in the pathogenesis and treatment of schizophrenia. It is thus of particular importance to develop in vitro cell culture systems as models to study such interactions. Rat adrenal pheochromocytoma PC12 cells, which expressed high levels of tyrosine hydroxylase, were used in the present study. In contrast to rat brain cells in primary cultures, PC12 cells did not express functional NT receptors. However, they were able to express both NTmRNA and NT in response to NGF, forskolin, and dexamethasone. Those neurochemical modifications furthermore may be related to changes in the morphology of the PC12 cells in response to NGF, forskolin, and dexamethasone alone or in combination. These data suggest that PC12 cells may provide a useful model to study in vitro the regulation of both catecholamine and neurotensin phenotypes.

Automatic cell culture quantitation with TRAKCELL: application to cell toxicology and differentiation.

An automated system, TRAKCELL, was developed for the quantitation of cells in culture. It enabled cell counting, classification according to morphological cell characteristics and measurement of cell proliferation and differentiation. The system was tested on the toxic effect of ascorbic acid on rat brain catecholaminergic neurons in primary culture. In parallel, the effects of nerve growth factor, dexamethasone and forskolin on cell differentiation were studied using rat pheochromocytoma PC12 cells. The results show that the system permits rapid and reproducible measurements of cell density and of the morphological changes observed following various drug treatments.