High Power Laser Laboratory at the Institute of Plasma Physics and Laser Microfusion: equipment and preliminary research

Phys. Rev. Accel. Beams

Costa

2020

The ions acceleration through an fs laser irradiating a reduced graphene oxide foil in a target-normalsheath-acceleration regime is investigated using a SiC detector connected in time-of-flight configuration. The experimental data indicated maximum proton energy of 1.8 MeV and a large number of carbon ions accelerated at different energies depending on their charge state. Particle-in-cell (PIC) simulations were applied to the studied target given the electron density as a function of the space and time and permitted one to evaluate the electrical field developed in the rear side of the foil driving the forward ion acceleration. The simulation indicates that the carbon ions are subjected to a lower acceleration with respect to protons, due to their slow velocity, depending on the charge-to-mass ratio. The latter does not permit carbon ions to be affected by the maximum electric field but a lower intensity due to the fast time decay of the electric field. Considering the angular emission of protons and the six carbon ions, the charge particles assume a Boltzmann energy distribution with a fixed cutoff at high energy, in agreement with the experimental measurements of ion energy.

Section: Methodsmentioning

confidence: 98%

Ion acceleration by fs laser in target-normal-sheath-acceleration regime and comparison of time-of-flight spectra with particle-in-cell simulations

Phys. Rev. Accel. Beams

Costa

2020

“…The used fs laser is a TeraWatt (TW) titanium sapphire operating at 810 nm wavelength, with a maximum pulse energy of 700 mJ, the main pulse duration of 40 fs, and a high amplified spontaneous emission contrast of about 10 9 , with p‐polarized radiation. The laser beam can be focused on the target surface at 10 microns spot diameter reaching an intensity of about 2 × 10 19 W/cm 2 …”

Section: Methodsmentioning

confidence: 99%

“…The laser beam can be focused on the target surface at 10 microns spot diameter reaching an intensity of about 2 × 10 19 W/cm 2 . [9] The irradiated foils consist of pure polymethylmethacrylate (PMMA) with four microns in thickness and in PMMA films covered by a physical vapour deposition thin film of Cu with a thickness of 50, 100, and 200 nm. The PMMA is a transparent hydrogenated acrylic glass with the stoichiometry (C 5 O 2 H 8 ) n , with a density of 1.18 g/cm 3 and a refractive index of 1.49 at 589 nm.…”

Section: Methodsmentioning

confidence: 99%

Investigation of the effect of plasma waves excitation on target normal sheath ion acceleration using fs laser‐irradiating hydrogenated structures

Cutroneo

Contributions to Plasma Physics

et al. 2019

Measurements of ion acceleration in polymethylmethacrylate foils covered by a thin copper film irradiated by fs laser in target normal sheath acceleration regime are presented. The ion acceleration depends on the laser parameters, such as the pulse energy; depends on the irradiation conditions, such as the focal point position of the laser with respect to the target surface; and depends on the target properties, such as the metallic film thickness. The proton acceleration increases in the presence of the metallic film enhancing the plasma electron density, reaching about 1.6 MeV energy for a focal position on the target surface. The plasma diagnostics uses SiC detectors, absorber foils, Faraday cups, and gafchromic films. Employing p‐polarized laser light and a suitable oblique incidence, it is possible to increase the proton acceleration up to about 2.0 MeV thanks to the effects of laser absorption resonance due to plasma waves excitation.

“…The laser focal spot was circular with 10 µm diameter; the focal position could be moved from −500 µm (in front of the target surface) to 0 µm (at the target surface), and to +500 µm (inside the target surface) using a micrometric step motor controllable in high vacuum (10 −6 mbar). With a pulse contrast (pre‐pulses and amplified spontaneous emission [ASE]) of 10 8 , the laser was employed to study the TNSA forward ion acceleration at high intensity when thin foils are irradiated at normal incidence …”

Section: Experimental Set‐upmentioning

confidence: 99%

Near‐3‐MeV protons from target‐normal‐sheath‐acceleration femtosecond laser irradiating advanced targets

Contributions to Plasma Physics

Cutroneo

Rosiński

et al. 2019

Advanced targets based on graphene oxide and gold thin film were irradiated at high laser intensity (10 18 -10 19 W/cm 2 ) with 50-fs laser pulses and high contrast (10 8 ) to investigate ion acceleration in the target-normal-sheath-acceleration regime. Time-of-flight technique was employed with SiC semiconductor detectors and ion collectors in order to measure the ion kinetic energy and to control the properties of the generated plasma. It was found that, at the optimized laser focus position with respect to the target, maximum proton acceleration up to about 3 MeV energy and low angular divergence could be generated. The high proton energy is explained as due to the high electrical and thermal conductivity of the reduced graphene oxide structure. Dependence of the maximum proton energy on the target focal position and thickness is presented and discussed.