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The post‐acceleration of laser‐generated protons through conventional drift tube linear accelerators has been simulated with the particle code Parmela. The proton source is generated on the rear surface of a target irradiated by an high‐intensity (1019 W⋅cm−2) short‐pulse (350 fs) laser and focused by a microlens that allows selecting collimated protons at 7±0.1 MeV with rms unnormalized emittance of 0.180 mm.mrad. The simulations show that protons can be accelerated by one drift tube linac tank to more than 14 MeV with unnormalized emittance growth of 8 in x and 22.6 in y directions when considering a total proton charge of 0.112 mA. This result shows for the first time that coupling between laser‐plasma accelerators with traditional accelerators is possible, allowing a luminosity gain for the final beam.

Point‐projection K‐shell absorption spectroscopy has been used to measure absorption spectra of transient plasma created by an ultra‐short laser pulse. The 1s‐2p and 1s‐3p absorption lines of weakly ionized aluminum and the 2p‐3d absorption lines of bromine were measured over an extended range of densities in a low‐temperature regime. Independent plasma characterization was obtained using frequency domain interferometry diagnostic (FDI) that allows the interpretation of the absorption spectra in terms of spectral opacities. Assuming local thermodynamic equilibrium, spectral opacity calculations have been performed using the density and temperature inferred from the FDI diagnostic to compare to the measured absorption spectra. A good agreement is obtained when non‐equilibrium effects due to non‐stationary atomic physics are negligible at the x‐ray probe time.

In the last few years, intense research has been conducted on laser‐accelerated ion sources and their applications. These sources have exceptional properties, i.e. high brightness and high spectral cut‐oft high directionality and laminarity, short burst duration. These proton sources open new opportunities for ion beam generation and control, and could stimulate development of compact ion accelerators for many applications. We have studied the variations of the proton acceleration characteristic time with target and laser parameters. We used these variations to correct one of the model recently developed to predict maximum energies of laser‐accelerated protons for low energy, short duration laser pulses. We have also developed an ultra‐fast laser‐triggered micro‐lens that allows tunable control of the beam divergence as well as energy selection, therefore solving two of the major problems that these proton beams were facing. We used PIC simulations to explain the focusing and energy selection mechanisms, ...

Laser‐accelerated ion sources open new opportunities for ion beam generation and control, and could stimulate development of compact ion accelerators for many applications. The mechanisms of proton acceleration with solid targets have been intensively studied over the past years, and new target or laser setups are now needed to obtain even higher maximum proton energies. PIC simulations have shown that using ultra thin targets, the maximum proton energy can be greatly increased. The laser can pass through the target and heat target electrons more efficiently. Experiments were conducted to test the feasibility of ultra thin targets laser interaction. PIC simulations were performed and successfully compared to the experimental results. Recently, experiments have shown that a gaseous target can produce proton beams with characteristics comparable to those obtained with solid targets. PIC simulations were also used to study proton acceleration with an underdense target. The optimum thickness obtained corresponds to the thickness where the laser absorption and transmission are equal, and depends greatly on laser and target parameters. The plasma hot electron temperature has also been found to depend on both laser and target parameters. We developed a simple model for the scaling of the optimum thickness for proton acceleration on target and laser parameters.