Articles you may be interested in Improved spectral data unfolding for radiochromic film imaging spectroscopy of laser-accelerated proton beams Rev. Sci. Instrum. 85, 043305 (2014); 10.1063/1.4870895 Direct high-resolution ion beam-profile imaging using a position-sensitive Faraday cup array Rev. Sci. Instrum. In recent years, the development of high power laser systems led to focussed intensities of more than 10 22 W/cm 2 at high pulse energies. Furthermore, both, the advanced high power lasers and the development of sophisticated laser particle acceleration mechanisms facilitate the generation of high energetic particle beams at high fluxes. The challenge of imaging detector systems is to acquire the properties of the high flux beam spatially and spectrally resolved. The limitations of most detector systems are saturation effects. These conventional detectors are based on scintillators, semiconductors , or radiation sensitive films. We present a nuclear activation-based imaging spectroscopy method, which is called NAIS, for the characterization of laser accelerated proton beams. The offline detector system is a combination of stacked metal foils and imaging plates (IP). After the irradiation of the stacked foils they become activated by nuclear reactions, emitting gamma decay radiation. In the next step, an autoradiography of the activated foils using IPs and an analysis routine lead to a spectrally and spatially resolved beam profile. In addition, we present an absolute calibration method for IPs.

This Letter demonstrates the transporting and focusing of laser-accelerated 14 MeV protons by permanent magnet miniature quadrupole lenses providing field gradients of up to 500 T/m. The approach is highly reproducible and predictable, leading to a focal spot of (286 x 173) microm full width at half maximum 50 cm behind the source. It decouples the relativistic laser-proton acceleration from the beam transport, paving the way to optimize both separately. The collimation and the subsequent energy selection obtained are perfectly applicable for upcoming high-energy, high-repetition rate laser systems.

The properties of beams of high energy protons accelerated during ultraintense, picosecond laser-irradiation of thin foil targets are investigated as a function of preplasma expansion at the target front surface. Significant enhancement in the maximum proton energy and laser-to-proton energy conversion efficiency is observed at optimum preplasma density gradients, due to self-focusing of the incident laser pulse. For very long preplasma expansion, the propagating laser pulse is observed to filament, resulting in highly uniform proton beams, but with reduced flux and maximum energy

This article reports on the development and application of a Thomson parabola (TP) equipped with a (90x70) mm(2) microchannel-plate (MCP) for the analysis of laser-accelerated ions, produced by a high-energy, high-intensity laser system. The MCP allows an online measurement of the produced ions in every single laser shot. An electromagnet instead of permanent magnets is used that allows the tuning of the magnetic field to adapt the field strength to the analyzed ion species and energy. We describe recent experiments at the 100 TW laser facility at the Laboratoire d'Utilization des Lasers Intenses (LULI) in Palaiseau, France, where we have observed multiple ion species and charge states with ions accelerated up to 5 MeV/u (O(+6)), emitted from the rear surface of a laser-irradiated 50 microm Au foil. Within the experiment the TP was calibrated for protons and for the first time conversion efficiencies of MeV protons (2-13 MeV) to primary electrons (electrons immediately generated by an ion impact onto a surface) in the MCP are presented.

Ion-driven fast ignition (IFI) may have significant advantages over electron-driven FI due to the potentially large reduction in the amount of energy required for the ignition beam and the laser driver. Recent experiments at the Los Alamos National Laboratory’s Trident facility employing novel Au flat-top cone targets have produced a fourfold increase in laser-energy to ion-energy efficiency, a 13-fold increase in the number of ions above 10MeV, and a few times increase in the maximum ion energy compared to Au flat-foil targets. Compared to recently published scaling laws, these gains are even greater. If the efficiency scales with intensity in accordance to flat-foil scaling, then, with little modification, these targets can be used to generate the pulse of ions needed to ignite thermonuclear fusion in the fast ignitor scheme. A proton energy of at least 30MeV was measured from the flat-top cone targets, and particle-in-cell (PIC) simulations show that the maximum cutoff energy may be as high as 40–45MeV at modest intensity of 1×1019W∕cm2 with 20J in 600fs. Simulations indicate that the observed energy and efficiency increase can be attributed to the cone target’s ability to guide laser light into the neck to produce hot electrons and transport these electrons to the flat-top of the cone where they can be heated to much higher temperatures, creating a hotter, denser sheath. The PIC simulations also elucidate the critical parameters for obtaining superior proton acceleration such as the dependence on laser contrast/plasma prefill, as well as longitudinal and transverse laser pointing, and cone geometry. These novel cones have the potential to revolutionize inertial confinement fusion target design and fabrication via their ability to be mass produced. In addition, they could have an impact on the general physics community studying basic electron and radiation transport phenomena or as better sources of particle beams to study equations of state and warm dense matter, or for hadron therapy, as new radioisotope generators, or for compact proton radiography sources.