Time-of-flight methodologies with large-area diamond detectors for ion characterization in laser-driven experiments

The time-of-flight technique coupled with semiconductor detectors is a powerful instrument to provide real-time characterization of ions accelerated because of laser-matter interactions. Nevertheless, the presence of strong electromagnetic pulses (EMPs) generated during the interactions can severely hinder its employment. For this reason, the diagnostic system must be designed to have high EMP shielding. Here we present a new advanced prototype of detector, developed at ENEA-Centro Ricerche Frascati (Italy), with a large-area (15 mm × 15 mm) polycrystalline diamond sensor having 150 μm thickness. The tailored detector design and testing ensure high sensitivity and, thanks to the fast temporal response, high-energy resolution of the reconstructed ion spectrum. The detector was offline calibrated and then successfully tested during an experimental campaign carried out at the PHELIX laser facility (100 J, fs, W/cm2) at GSI (Germany). The high rejection to EMP fields was demonstrated and suitable calibrated spectra of the accelerated protons were obtained

Bright betatron radiation from direct-laser-accelerated electrons at moderate relativistic laser intensity

Direct laser acceleration (DLA) of electrons in a plasma of near-critical electron density (NCD) and the associated synchrotron-like radiation are discussed for moderate relativistic laser intensity (normalized laser amplitude a0 ≤ 4.3) and ps length pulse. This regime is typical of kJ PW-class laser facilities designed for high-energy-density (HED) research. In experiments at the PHELIX facility, it has been demonstrated that interaction of a 1019 W/cm2 sub-ps laser pulse with a sub-mm length NCD plasma results in the generation of high-current well-directed super-ponderomotive electrons with an effective temperature ten times higher than the ponderomotive potential [Rosmej et al., Plasma Phys. Controlled Fusion 62, 115024 (2020)]. Three-dimensional particle-in-cell simulations provide good agreement with the measured electron energy distribution and are used in the current work to study synchrotron radiation from the DLA-accelerated electrons. The resulting x-ray spectrum with a critical energy of 5 keV reveals an ultrahigh photon number of 7 × 1011 in the 1–30 keV photon energy range at the focused laser energy of 20 J. Numerical simulations of betatron x-ray phase contrast imaging based on the DLA process for the parameters of a PHELIX laser are presented. The results are of interest for applications in HED experiments, which require a ps x-ray pulse and a high photon flux

Shock Hugoniot data for water up to 5 Mbar obtained with quartz standard at high-energy laser facilities

In this work, we present experimental results on the behavior of liquid water at megabar pressure. The experiment was performed using the HIPER (High-Intensity Plasma Experimental Research) laser facility, a uniaxial irradiation chamber of GEKKO XII (GXII) at the Institute of Laser Engineering (ILE), and the PHELIX at GSI (GSI Helmholtz Centre for Heavy Ion Research), a single-beam high-power laser facility, to launch a planar shock into solid multilayered water samples. Equation-of-state data of water (H2O) are obtained in the pressure range 0.50–4.6 Mbar by tuning the laser-drive parameters. The Hugoniot parameters (pressure, density, etc.) and the shock temperature were simultaneously determined by using VISAR and SOP as diagnostic tools and quartz as the standard material for impedance mismatch experiments. Finally, our experimental results are compared with hydrodynamic simulations tested with different equations of state, showing good compatibility with tabulated SESAME tables for water.The authors would like to acknowledge the support of the laser technical team at GEKKO XII (ILE) and PHELIX (GSI). This work received funding from the Euratom Research and Training Program 2014–2018 and 2019-2020 (Grant agreement no. 633053). The involved teams were operated within the framework of the Enabling Research Project ENR-IFE19.CEA-01, Study of Direct Drive and Shock Ignition for IFE: Theory, Simulations, Experiments, Diagnostics Development. JIHT RAS team members were supported by the Ministry of Science and Higher Education of the Russian Federation (State Assignment no. 075-00460-21-00).Peer reviewe