F. Hannachi

Response functions of Fuji imaging plates to monoenergetic protons in the energy range 0.6-3.2 MeV.

We have measured the responses of Fuji MS, SR, and TR imaging plates (IPs) to protons with energies ranging from 0.6 to 3.2 MeV. Monoenergetic protons were produced with the 3.5 MV AIFIRA (Applications Interdisciplinaires de Faisceaux dIons en Région Aquitaine) accelerator at the Centre dEtudes Nucléaires de Bordeaux Gradignan (CENBG). The IPs were irradiated with protons backscattered off a tantalum target. We present the photo-stimulated luminescence response of the IPs together with the fading measurements for these IPs. A method is applied to allow correction of fading effects for variable proton irradiation duration. Using the IP fading corrections, a model of the IP response function to protons was developed. The model enables extrapolation of the IP response to protons up to proton energies of 10 MeV. Our work is finally compared to previous works conducted on Fuji TR IP response to protons.

Response functions of imaging plates to photons, electrons and 4He particles.

Imaging plates from Fuji (BAS-SR, MS, and TR types) are phosphor films routinely used in ultra high intensity laser experiments. However, few data are available on the absolute IP response functions to ionizing particles. We have previously measured and modeled the IP response functions to protons. We focus here on the determination of the responses to photons, electrons, and (4)He particles. The response functions are obtained on an energy range going from a few tens of keV to a few tens of MeV and are compared to available data. The IP sensitivities to the different ionizing particles demonstrate a quenching effect depending on the particle stopping power.

NATALIE: A 32 detector integrated acquisition system to characterize laser produced energetic particles with nuclear techniques

We present a stand-alone system to characterize the high-energy particles emitted in the interaction of ultrahigh intensity laser pulses with matter. According to the laser and target characteristics, electrons or protons are produced with energies higher than a few mega electron volts. Selected material samples can, therefore, be activated via nuclear reactions. A multidetector, named NATALIE, has been developed to count the β(+) activity of these irradiated samples. The coincidence technique used, designed in an integrated system, results in very low background in the data, which is required for low activity measurements. It, therefore, allows a good precision on the nuclear activation yields of the produced radionuclides. The system allows high counting rates and online correction of the dead time. It also provides, online, a quick control of the experiment. Geant4 simulations are used at different steps of the data analysis to deduce, from the measured activities, the energy and angular distributions of the laser-induced particle beams. Two applications are presented to illustrate the characterization of electrons and protons.

Absolute energy distributions of Al, Cu, and Ta ions produced by nanosecond laser-generated plasmas at 1013 W cm−2

The charge state and energy distributions of ions produced by a pulsed 1u2009J, 9u2009ns Nd:YAG laser focused onto solid aluminum,copper, and tantalum targets were measured with an electrostatic analyzer coupled with a windowless electron multiplier detector. Special attention was paid to the detector response function measurements and to the determination of the analyzer transmission. Space charge effects are shown to strongly affect this transmission. Measured absolute energy distributions are presented for several charge states. They follow Boltzmann-like functions characterized by an effective ion temperature and an equivalent accelerating voltage. These parameters exhibit power laws as a function of I λ2 which open the possibility to predict the expected shape of the relative energy distributions of ions on a large range of laser intensities (106–1016u2009Wu2009cm−2u2009μm2).

Charged particle feeding of hyperdeformed nuclei in the A=118?126 region

A breakthrough was recently obtained in the analysis of the so-called Hyper-Long-HyperDeformed (HLHD) experiment made at the EUROBALL-IV γ-detector array (EB). The 64Ni + 64Ni ⇒ 128Ba* fusion reaction was studied at Ebeam = 255 and 261 MeV, reaching the highest angular momentum that the compound nuclei can accommodate. To date no discrete HD rotational bands have been identified. However, rotational patterns in the form of ridge-structures in three-dimensional (3D) rotational mapped spectra are identified with dynamic moments of inertia J(2) ranging from 71 to 1112 MeV-1 in 12 different nuclei selected by charged particle- and/or γ-gating. The four nuclei, 118Te, 124Cs, 125Cs and 124Xe found with moment of inertia J(2)≥100 2 MeV-1, are most likely hyperdeformed, the remaining nuclei with smaller values of J(2), are considered to be superdeformed, in qualitative agreement with recent theoretical calculations.

Hyperdeformed Shapes and Jacobi Transitions in 126Ba

Systematic searches for exotic shapes, hyperdeformation (HD) and Jacobi transitions, have been made in Hf, Nd, Ba, Xe, Sn and Cd nuclei during the last 4 years, guided by theoretical predictions. The most promising results showing patterns of rotational correlations (e.g. 2. order ridges of multiple rotational bands) are found for 126Xe and 126Ba when the very highest multiplicity cascades are selected by various techniques. In particular, the results on 126Ba obtained in 3 different experiments, using both Gammasphere in Berkeley and Euroball IV in Strasbourg are discussed and compared to theoretical predictions and to simulations by a double‐potential statistical model for population and γ‐decay. A very surprising result was obtained in the last experiment at Euroball, in a full month running time, namely that the observed ridge structure depends very sensitively on the bombarding energy, which points to entrance channel effects. The analysis shows that a discrete HD yrast band intensity will be signifi...

Calculation of the rate of nuclear excitation by electron transition in an

One promising candidate for the first detection of nuclear excitation in plasma is the 463-keV, 20.26-min-lifetime isomeric state in Rb84, which can be excited via a 3.5-keV transition to a higher lying state. According to our preliminary calculations, under specific plasma conditions, nuclear excitation by electron transition (NEET) may be its strongest excitation process. Evaluating a reliable NEET rate requires, in particular, a thorough examination of all atomic transitions contributing to the rate under plasma conditions. We report the results of a detailed evaluation of the NEET rate based on multiconfiguration Dirac Fock (MCDF) atomic calculations, in a rubidium plasma at local thermodynamic equilibrium with a temperature of 400xa0eV and a density of 10−2g/cm3 and based on a more precise energy measurement of the nuclear transition involved in the excitation.

^{84m}\mathbf{Rb}

In this paper, we present the electron bunches extracted from a dense plasma produced by the interaction of a ns laser at an intensity of 1013u2009W cm−2 with a solid target, when this plasma expands in an electric field. The plasma expansion dynamics measured in the previous works [M. Comet et al., J. Appl. Phys. 119, 013301 (2016)] is used to determine the electron charge density profile at different instants after the laser shot. When applying the electric field, a few 1013 electrons are extracted with continuous energy distributions. Particle-In-Cell simulations are run to understand the extraction process and reproduce the measured energy distributions, with the electron charge density profiles used as inputs. These simulations show that the electron extraction proceeds from the plasma front edge throughout the plasma expansion.

plasma under the hypothesis of local thermodynamic equilibrium using a multiconfiguration Dirac-Fock approach

Summary form only given. The development of a bright and pulsed source of low energy (multi-keV) electrons is essential to measure cross sections of nuclear excitation by inelastic electron scattering which are expected to occur in hot and dense plasmas1-4. Due to the small values of the calculated cross sections of this excitation process (10-33/10-30 cm2), bunches of electrons with up to 1013-1014 particles in a few tens of ns are necessary with energies ranging from 10 keV to 100 keV. We are developing an original electron source based on the capacity of laser heated plasmas to produce large numbers of free electrons at low energies (a few eVs). These electrons could be extracted and post-accelerated by traditional electrostatic optics. First studies have been performed to characterize the dynamics of the expanding plasma produced with a ns laser pulse at 1013 W.cm-2 in which 1015 free electrons are produced5. Using electrostatic devices, electron bunches have been extracted from the expanding plasma in an energy range of a few keV. Several characteristics of these electrons have been measured and confronted with PIC simulations in order to better understand the dynamics of the extraction, and to identify key parameters to optimize the number of extracted electrons.

Energy distributions of electrons emitted by a biased laser-produced plasma at 1013 W cm−2

The γ decay of the nuclei 124,125 Ba has been investigated with the EUROBALL array, using the reaction 64 Ni+ 64 Ni at Ebeam = 255 and 261 MeV. Six new E1 transitions have been found in the nucleus 125 Ba, suggesting a significant role of octupole correlations in the origin of its parity doublets. The J π = 3 − level