Detection of alpha particles from 7Li(p,α)4He and 19F(p,α)16O reactions induced by laser-accelerated protons using CR-39 with potassium hydroxide-ethanol-water etching solution.

Alpha particles generated by 7Li(p,α)4He and 19F(p,α)16O reactions are selectively detected in the presence of abundant primary protons by reducing the proton sensitivity of CR-39 using a potassium hydroxide-ethanol-water (PEW) etching solution. These nuclear reactions are induced in a LiF crystal using the laser-accelerated protons (4 × 1011 protons/pulse with a maximum energy of 3.3 MeV) generated and accelerated by the interaction of a 40-fs laser pulse with a polyethylene thin film target at a peak intensity of 5 × 1019 W/cm2. Subsequent etching of the CR-39 in the PEW solution (KOH: 17 wt. %; C2H5OH: 25 wt. %; H2O: 58 wt. %) permits the selective detection of 4.0 MeV alpha particles, which is independently confirmed by an experiment using alpha particles from an 241Am source. The described method is expected to be useful for research into nuclear reactions in laser plasma.

Induction of subterahertz surface waves on a metal wire by intense laser interaction with a foil.

We have demonstrated that a pulsed electromagnetic wave (Sommerfeld wave) of subterahertz frequency and 11-MV/m field strength can be induced on a metal wire by the interaction of an intense femtosecond laser pule with an adjacent metal foil at a laser intensity of 8.5×10^{18}W/cm^{2}. The polarity of the electric field of this surface wave is opposite to that obtained by the direct interaction of the laser with the wire. Numerical simulations suggest that an electromagnetic wave associated with electron emission from the foil induces the surface wave. A tungsten wire is placed normal to an aluminum foil with a gap so that the wire is not irradiated and damaged by the laser pulse, thus making it possible to generate surface waves on the wire repeatedly.

Single plasma mirror providing 104 contrast enhancement and 70% reflectivity for intense femtosecond lasers: publisher's note.

This note points out a missed correction to the math on p. 5648 of [Appl. Opt.5, 5647 (2016)APOPAI0003-693510.1364/AO.55.005647].

Single plasma mirror providing 104 contrast enhancement and 70% reflectivity for intense femtosecond lasers.

To efficiently eliminate picosecond pre-pulses that accompany ultrashort pulses emitted from high-power chirped-pulse-amplification laser systems, we have developed a high-performance plasma mirror system. By reducing the reflectivity of the antireflection coating on the substrate for the plasma mirror to the limit of current technology (∼0.006%), we achieved the highest pre-pulse contrast enhancement reported to date for a single plasma mirror of 104 at 1 ps before the pulse peak. By optimizing the laser incidence to the plasma mirror and the laser fluence, the reflectivity of the plasma mirror has been improved to 70%. The contrast improvement indicates extensibility to 100 PW class lasers by doubling this plasma mirror system. Contrast enhancement of 108 should be possible without a serious reduction in energy (no more than 50%).