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International audience; The advent of multi-PW laser facilities world-wide opens new opportunities for nuclear physics. With this perspective, we developed a neutron counter taking into account the specifics of a high-intensity laser environment. Using GEANT4 simulations and prototype testings, we report on the design of a modular neutron counter based on boron-10 enriched scintillators and a high-density polyethylene moderator. This detector has been calibrated using a plutonium-beryllium neutron source and commissioned during an actual neutron-producing laser experiment at the LULI2000 facility (France). An overall efficiency of 4.37(59)% has been demonstrated during calibration with a recovery time of a few hundred microseconds after laser-plasma interaction.

The DIRAC spectrometer installed at CERN PS was upgraded in order to study simultaneously A2π and AπK atoms, namely the bound states of two π mesons, and of π and K mesons, respectively. The detector system can now accept a high intensity beam of 2–6×1011 primary protons per second. The electronics and the data-acquisition system can handle a very large amount of data to identify π, K, p, e and µ, allowing the selection of ππ and πK pairs in the offline analysis. The resolution of the longitudinal and transverse components of the relative momentum Q of each meson pair in their center-of-mass system with respect to the direction of the pair was substantially improved. The analysis of their distributions allowed an reliable separation between the meson pairs originating from hadronic atoms and the backgrounds permitting the measurement of the lifetimes of hadronic atoms in the ground state and π–π, π–K s-wave scattering lengths. The upgraded setup also allowed the study of the long-lived excited states of ππ atoms.

The adapted DIRAC experiment at the CERN PS accelerator observed for the first time long-lived hydrogenlike π+π- atoms, produced by protons hitting a beryllium target. A part of these atoms crossed the gap of 96 mm between the target and a 2.1 μm thick platinum foil, in which most of them dissociated. Analyzing the observed number of atomic pairs, nAL=436-61+157|tot, the lifetime of the 2p state is found to be τ2p=(0.45-0.30+1.08|tot)×10-11 s, not contradicting the corresponding QED 2p state lifetime τ2pQED=1.17×10-11 s. This lifetime value is three orders of magnitude larger than our previously measured value of the π+π- atom ground state lifetime τ=(3.15-0.26+0.28|tot)×10-15 s. Further studies of long-lived π+π- atoms will allow us to measure energy differences between p and s atomic states and so to discriminate between the isoscalar and isotensor ππ scattering lengths with the aim to check QCD predictions.

Nowadays, it is possible to accelerate bunches of particles in the interaction of ultrahigh intensity (UHI) laser pulses with matter. Electrons, protons, ions, and high-energy photon beams can be produced in experiments and reach kinetic energies close to hundreds of megaelectronvolts for protons and gigaelectronvolts for electrons and for the associated Bremsstrahlung photons. At these energies, these beams can induce a large variety of nuclear reactions, which can be detected and studied using $\gamma $ -ray spectroscopy techniques. At standard accelerator facilities, scintillator detectors are commonly used to perform prompt $\gamma $ -ray spectrometry studies. However, during laser–matter interactions, high fluxes of X-rays (mostly soft) are generated, which lead to instantaneous huge energy deposits (~1 $\mu \text{J}$ ) in these scintillators. Depending on the laser characteristics (energy and pulse duration), the detector recovery time after these X-ray flashes can reach several milliseconds, which makes any prompt or “in beam” measurement impossible. The origin of this long-duration signal is investigated in the case of a LaBr3 crystal coupled to different photodetectors. While it was impossible using standard photomultiplier tubes to detect $\gamma $ -ray emissions before a few milliseconds after a laser shot, we could, using a hybrid photodiode, resolve single $\gamma $ -ray emission a few tens of microseconds after the laser shot. Furthermore, we have also shown that the LaBr3 scintillator presents an unexpected long-lived light emission (afterglow). Directions are suggested for future studies in order to minimize the effects of this afterglow emission.

The Preshower (PSh) detector is a component of the DIRAC setup. It is designed to improve rejection efficiency of e-e+ pairs background in the {\pi}{\pi} and K{\pi} pair measurement. To increase the overall efficiency, a new two-layer structure scintillator Preshower detector has been realized in the region where the Nitrogen Cherenkov detector has been shortened to introduce new detectors. The new Preshower-Cherenkov combination ensures the electron rejection efficiency better than 99.9% in momentum region 1-7 GeV/c., Comment: to be published in NIMA

International audience; Short intense pulses of fast neutrons were produced in a two stage laser-driven experiment. Protons were accelerated by means of the Target Normal Sheath Acceleration (TNSA) method using the TITAN facility at the Lawrence Livermore National Laboratory. Neutrons were obtained following interactions of the protons with a secondary lithium fluoride (LiF) target. The properties of the neutron flux were studied using BC-400 plastic scintillation detectors and the neutron time of flight (nTOF) technique. The detector setup and the experimental conditions were simulated with the Geant4 toolkit. The effects of different components of the experimental setup on the nTOF were studied. Preliminary results from a comparison between experimental and simulated nTOF distributions are presented.

After having announced the statistically significant observation ($5.6\ensuremath{\sigma}$) of the new exotic $\ensuremath{\pi}K$ atom, the DIRAC experiment at the CERN proton synchrotron presents the measurement of the corresponding atom lifetime, based on the full $\ensuremath{\pi}K$ data sample: $\ensuremath{\tau}=(5.{5}_{\ensuremath{-}2.8}^{+5.0})\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}15}\text{ }\text{ }\mathrm{s}$. By means of a precise relation ($\ensuremath{\approx}1%$) between atom lifetime and scattering length, the following value for the $S$-wave isospin-odd $\ensuremath{\pi}K$ scattering length ${a}_{0}^{\ensuremath{-}}=\frac{1}{3}({a}_{1/2}\ensuremath{-}{a}_{3/2})$ has been derived: $|{a}_{0}^{\ensuremath{-}}|=(0.07{2}_{\ensuremath{-}0.020}^{+0.031}){M}_{\ensuremath{\pi}}^{\ensuremath{-}1}$.

The results of a search for hydrogen-like atoms consisting of $\pi^{\mp}K^{\pm}$ mesons are presented. Evidence for $\pi K$ atom production by 24 GeV/c protons from CERN PS interacting with a nickel target has been seen in terms of characteristic $\pi K$ pairs from their breakup in the same target ($178 \pm 49$) and from Coulomb final state interaction ($653 \pm 42$). Using these results the analysis yields a first value for the $\pi K$ atom lifetime of $\tau=(2.5_{-1.8}^{+3.0})$ fs and a first model-independent measurement of the S-wave isospin-odd $\pi K$ scattering length $\left|a_0^-\right|=\frac{1}{3}\left|a_{1/2}-a_{3/2}\right|= \left(0.11_{-0.04}^{+0.09} \right)M_{\pi}^{-1}$ ($a_I$ for isospin $I$)., Comment: 14 pages, 8 figures

The observation of hydrogenlike πK atoms, consisting of π^{-}K^{+} or π^{+}K^{-} mesons, is presented. The atoms are produced by 24 GeV/c protons from the CERN PS accelerator, interacting with platinum or nickel foil targets. The breakup (ionization) of πK atoms in the same targets yields characteristic πK pairs, called "atomic pairs," with small relative momenta Q in the pair center-of-mass system. The upgraded DIRAC experiment observed 349±62 such atomic πK pairs, corresponding to a signal of 5.6 standard deviations. This is the first statistically significant observation of the strange dimesonic πK atom.

The observation of hydrogenlike πK atoms, consisting of π^{-}K^{+} or π^{+}K^{-} mesons, is presented. The atoms are produced by 24 GeV/c protons from the CERN PS accelerator, interacting with platinum or nickel foil targets. The breakup (ionization) of πK atoms in the same targets yields characteristic πK pairs, called "atomic pairs," with small relative momenta Q in the pair center-of-mass system. The upgraded DIRAC experiment observed 349±62 such atomic πK pairs, corresponding to a signal of 5.6 standard deviations. This is the first statistically significant observation of the strange dimesonic πK atom.

The DIRAC experiment at CERN has achieved a sizeable production of + atoms and has significantly improved the precision on its lifetime determination. From a sample of 21227 atomic pairs, a 4% measurement of the S-wave scattering length di erence ja0 a2j = 0:2533 +0:0080 0:0078 stat

A preshower (PSh) detector has been prepared, tested and used at the CERN-DIRAC experiment [B. Adeva, et al., DIRAC proposal, CERN/SPSLC 95-1, SPSLC/P 284, 1995]. The aim of this experiment was to test some nonperturbative QCD predictions [J. Gasser, H. Leutwyler, Phys. Lett. B 125 (1983) 325; J. Gasser, H. Leutwyler, Ann. Phys. 158 (1984) 142; J. Gasser, H. Leutwyler, Nucl. Phys. B 250 (1985) 465; J. Bijnens, G. Colangelo, G. Ecker, J. Gasser, M.E. Sainio, Phys. Lett. B 374 (1996) 210] by measuring pionium (π+π− hadronic atom) lifetime. In this context the PSh detector, together with the Cherenkov detector, pursued to reject the background electron pairs in the region 1–4 GeV where the pion pairs from atom breakup were present. The technique used for pion/electron separation was to probe the electron shower development in the early formation stage in Pb converter. We have studied the dependence of the amplitude spectra on particle momentum and converter and scintillator thickness. The estimated electron rejection efficiency was better than 85% with a pion loss less than 5% for a preshower detector with Pb converter thickness wPb=2.5 cm and scintillator slab wSc=1 cm. The PSh track efficiency within the DIRAC setup has been measured with a global efficiency per arm better than 99%, slab efficiency per arm better than 96% and corresponding pair events efficiency per arm ∼99% and per slab ∼93%.

We present evidence for the first observation of electromagnetically bound $\pi^\pm K^\mp$-pairs ($\pi K$-atoms) with the DIRAC experiment at the CERN-PS. The $\pi K$-atoms are produced by the 24 GeV/c proton beam in a thin Pt-target and the $\pi^\pm$ and $K^\mp$-mesons from the atom dissociation are analyzed in a two-arm magnetic spectrometer. The observed enhancement at low relative momentum corresponds to the production of 173 $\pm$ 54 $\pi K$-atoms. The mean life of $\pi K$-atoms is related to the s-wave $\pi K$-scattering lengths, the measurement of which is the goal of the experiment. From these first data we derive a lower limit for the mean life of 0.8 fs at 90% confidence level., Comment: 15 pages, 9 figures

Molecular dynamics of the ammonium dihydrogen phosphate, ADP, was studied by neutron scattering spectroscopy using an energy window of 100 μeV. This compound exhibits an order–disorder phase transition at T c = 148 K from antiferroelectic phase to paraelectric phase. The entire ADP lattice dynamics is dominated by a network of different N–H⋯O and O–H⋯O hydrogen bonds that are broken above critical temperature T c . In the ordered phase the molecular electric dipoles appear as a result of hydrogen ordering lateral configuration around PO 4 groups. The dynamics of ammonium group NH 4 plays also an important role in the phase transition. The quasielastic lines give information about ammonium reorientational diffusion above T c while the inelastic part of the spectrum provides useful information about ordered proton modes coupled with acoustic ADP lattice modes. At the same time the low energy transfer domain between 2 meV and 8 meV is very sensitive to phase transition. In the disordered phase the number of states increases compared with ordered phase, in a way similar with the solid–glass phase transition.

The production of neutron beams having short temporal duration is studied using ultraintense laser pulses. Laser-accelerated protons are spectrally filtered using a laser-triggered microlens to produce a short duration neutron pulse via nuclear reactions induced in a converter material (LiF). This produces a similar to 3 ns duration neutron pulse with 10(4) n/MeV/sr/shot at 0.56 m from the laser-irradiated proton source. The large spatial separation between the neutron production and the proton source allows for shielding from the copious and undesirable radiation resulting from the laser-plasma interaction. This neutron pulse compares favorably to the duration of conventional accelerator sources and should scale up with, present and future, higher energy laser facilities to produce brighter and shorter neutron beams for ultrafast probing of dense materials.

In the present work the moss biomonitoring technique and the combination of two analytical techniques - Particle Induced X-ray Emission (PIXE) [3] and Inductively Coupled Plasma (ICP) [4] - were applied for assessing environmental situation from the point of view of air polluting along the transect from north to south of the Dambovita County. PIXE analysis at the Tandem Accelerator FN-8 of the National Institute of Nuclear Physics - Horia Hulubei of Magurele, Bucharest, allowed determination of P, S, Cl, K, Ca, Mn, Fe, Ni, Cu, Zn, As, Sr, Cd and Pb in samples. ICP analyses were made using a Baird ICP2070 - Sequential Plasma Spectrometer in Targoviste and we determined in samples the concentration of Li, B, Na, and Mg together with Cd and Pb. The obtained results will permit to determine the regional extent of heavy metals and toxic elements atmospheric pollution and to identify specially affected areas and local sources of

International audience; The neutralization of noble gas singly charged ions on large band gap ionic insulators may take place through two distinct mechanisms involving two valence band electrons. One is a kinetically assisted Auger neutralization, and the other a simultaneous double electron capture. Both lead to the same final states, that is at grazing incidence angles a scattered neutral projectile connected to a surface excited state (trion) or an ejected electron. So it is virtually impossible to experimentally identify the neutralization process. From comparison to systems whose neutralization mechanism is clearly identified, the incidence angle dependence of the trion population relative to the total neutral fraction appears as a robust parameter for distinguishing the primary capture process.

Sediment cores collected from lakes Mesteru and Furtuna (eastern part), Sontea channel and soil samples collected from Caraorman bar, all located in the Danube Delta, were analyzed for 42 elements (Ag, Al, As, Be, Na, Mg, P, S, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, As, Se, Br, Rb, Sr, Y, Mo, Ag, Cd, In, Sn, Sb, Cs, Ce, Hf, Hg, Tl. Pb, Bi, Th. U) by instrumental neutron activation analysis (INAA), thick target proton induced X-ray emission (TT-PIXE) and inductively coupled plasma-mass spectrometry (ICP-MS). The INAA and TTPIXE yielded total concentrations whereas the ICP-MS data reflected the fractions soluble in 14M HNO3. The ICP-MS data exhibited surface enrichment relative to the lower part of the sediment core of Cu, Zn, As, Ag, Cd, In, Sn, Sb, Hg, Tl, Pb, and Bi, most prominently by Cd and Hg. Their vertical distribution in the investigated cores generally reflected the pollution history of recent sediments in Danube delta, showing a steady increase until the end of the 1980s followed by a slow decrease after 1990. The vertical profiles of most remaining elements were characterized by a relatively uniform distribution along the cores. In some cases, the concentrations of As, Cd, Cu, Cr, Mn, Ni and Pb exceeded minimum thresholds of safety, as defined by the Romanian regulations. The elemental composition of the sediment below 20 cm depth (total concentrations) was similar to that of the upper continental crust (UCC) for most elements. Values distinctly higher than UCC were observed for As, Sb (factor ~5) and Cr, Ni, Cu (factor 2 to 3). The nitric acid soluble element concentrations in the soil samples in some cases showed increased values at the surface as compared to 30 cm depth, either due to air pollution or to the action of plants. In no case a large contribution to the topsoil from atmospheric deposition was evident, indicating that the surface contamination of the sediments was mainly by riverine transport.

International audience; The measurement of energy spectra of neutrons and gamma rays emitted by nuclei, together with charge particles spectroscopy, are the main tools for understanding nuclear phenomena occurring also in high power laser driven experiments. However, the large number of particles emitted in a very short time, in particular the strong X-rays flash produced in laser-target interaction, impose adaptation of technique currently used in nuclear physics experiment at accelerator based facilities. These aspects are discussed (Section 1) in the context of proposed studies at high power laser system of ELI-NP. Preliminary results from two experiments performed at Titan (LLNL) and ELFIE (LULI) facilities using plastic scintillators for neutron detection (Section 2) and LaBr3 (Ce) scintillators for gamma detection (Section 3) are presented demonstrating the capabilities and the limitations of the employed methods. Possible improvements of these spectroscopic methods and their proposed implementation at ELI-NP will be discussed as well in the last section.

An extensive process of modernizing the research infrastructure started 6 years ago at the tandem accelerator in IFIN-HH. Major improvements of the 9 MV FN tandem accelerator installed in IFIN-HH in ′73 were done in the late years, making it a very reliable machine, suited for basic and applied research experiments. The developments opened the way for new experiments made for the first time in our laboratory. Two new Cockroft-Walton tandem accelerators were also installed in 2012. The 1 MV HVE Tandetron accelerator is dedicated to AMS measurements, especially for 14C dating, while the 3 MV HVE Tandetron accelerator has the reaction chambers and detection system prepared for ion beam analysis measurements, microprobe experiments and ion implantation.

QENS experiments are very suitable for the study of water‐polysaccharides systems both for slow polymer chains dynamics as well as for faster solvent molecules dynamics. By a suitable choice of experimental conditions as well as a properly data processing we can get information about the motion modes of various molecular groups of polymer chains in aqueous solutions presumes. Virtually we can distinguish the polymer protons motions at nanosecond time scale by choosing a narrow energy resolution window. The present work presents the QENS measurements performed at LLB, MIBEMOL neutron spectrometer on sodium alginate hydrated samples. The experimental spectra were fitted using one lorentzian fit. At high polymer concentration the quasielastic part of the line is given by the translational‐rotational diffusion performed by heavy water molecules in confined spaces created by the polymer coils. The experimental data are well described by Chudley Elliot and Hall‐Ross models.

The paper presents the quasielastic neutron scattering results on ADP at different temperatures below and under critical temperature — where the molecular crystal undergoes the antiferroelectric‐paraelectric phase transition. The reorentational diffusion motion of ammonium group is discussed.

After observing and investigating the double-exotic $\pi^+\pi^-$ atom with the ground state lifetime $\tau$ of about $3 \times 10^{-15}$~s, the upgraded DIRAC experiment at the CERN PS accelerator observes for the first time long-lived states of the same atom with lifetimes of about $10^{-11}$~s and more. The number of characteristic pion pairs resulting from the breakup (ionisation) of long-lived $\pi^+\pi^-$ atoms amounts to $436\pm61$, corresponding to a signal-to-error ratio of better than 7 standard deviations. This observation opens a new possibility to measure energy differences between $p$ and $s$ atomic states and so to determine $\pi \pi$ scattering lengths., Comment: 13 pages, 7 figures

Accepted for publication in Physical Review Letters; An atomic clock based on X-ray fluorescence yields has been used to estimate the mean characteristic time for fusion followed by fission in reactions 238U + 64Ni at 6.6 MeV/A. Inner shell vacancies are created during the collisions in the electronic structure of the possibly formed Z=120 compound nuclei. The filling of these vacancies accompanied by X-ray emission with energies characteristic of Z=120 can take place only if the atomic transitions occur before nuclear fission. Therefore, the X-ray yield characteristic of the united atom with 120 protons is strongly related to the fission time and to the vacancy lifetimes. K X-rays from the element with Z = 120 have been unambiguously identified from a coupled analysis of the involved nuclear reaction mechanisms and of the measured photon spectra. A minimum mean fission time $\tau$_f$ = 2.5×10−18s has been deduced for Z=120 from the measured X-ray multiplicity.