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Applied physics / B 127(4), 55 (2021). doi:10.1007/s00340-021-07586-w, Published by Springer, Berlin

The development of novel target concepts is crucial to make laser-driven acceleration of ion beams suitable for applications. We tested double-layer targets formed of an ultralow density nanostructured carbon layer (∼7 mg/cm3, 8–12 μm–thick) deposited on a μm–thick solid Al foil. A systematic increase in the total number of the accelerated ions (protons and C6+) as well as enhancement of both their maximum and average energies was observed with respect to bare solid foil targets. Maximum proton energies up to 30 MeV were recorded. Dedicated three-dimensional particle-in-cell simulations were in remarkable agreement with the experimental results, giving clear indication of the role played by the target nanostructures in the interaction process.

We report on the development of foam-based double-layer targets (DLTs) for laser-driven ion acceleration. Foam layers with a density of a few mg cm−3 and controlled thickness in the 8–36 μm range were grown on μm-thick Al foils by pulsed laser deposition (PLD). The DLTs were experimentally investigated by varying the pulse intensity, laser polarisation and target properties. Comparing DLTs with simple Al foils, we observed a systematic enhancement of the maximum and average energies and number of accelerated ions. Maximum energies up to 30 MeV for protons and 130 MeV for C6+ ions were detected. Dedicated three-dimensional particle-in-cell (3D-PIC) simulations were performed considering both uniform and cluster-assembled foams to interpret the effect of the foam nanostructure on the acceleration process.

We present polarization measurement of a Ni-like Ag X-ray laser working in the transient collisional excitation scheme. A calibrated membrane multilayer beam splitter was used to determine the energies of two mutually perpendicular polarization components (s and p components). As a result, we observed a high degree of polarization that fluctuated from shot to shot. The dominant polarization component switched from s to p when pumping was made stronger. The measurement results are discussed from the point of view of the general polarization theory and supported by a numerical simulation based on Maxwell-Bloch equations., 過渡利得方式のニッケル様銀レーザーの偏光を測定した。偏光選択性を予め校正した多層膜ビームスプリッターを用いて、二つの偏光成分(sおよびp偏光)のエネルギーを決定し、その結果、ショットごとにふらつきはあるものの、明確に偏光していることを見出した。強い偏光成分は、励起レーザー光を強くすることでs偏光からp偏光に代わることも見出した。実験結果をマクスウェル=ブロッホ方程式を用いた数値計算との比較により議論された。