ABSTRACT
Ultra-intense lasers can nowadays routinely accelerate kiloampere ion beams. These unique sources of particle beams could impact many societal (e.g., proton-therapy or fuel recycling) and fundamental (e.g., neutron probing) domains. However, this requires overcoming the beam angular divergence at the source. This has been attempted, either with large-scale conventional setups or with compact plasma techniques that however have the restriction of short (<1 mm) focusing distances or a chromatic behavior. Here, we show that exploiting laser-triggered, long-lasting (>50 ps), thermoelectric multi-megagauss surface magnetic (B)-fields, compact capturing, and focusing of a diverging laser-driven multi-MeV ion beam can be achieved over a wide range of ion energies in the limit of a 5° acceptance angle.
ABSTRACT
Detailed angle and energy resolved measurements of positrons ejected from the back of a gold target that was irradiated with an intense picosecond duration laser pulse reveal that the positrons are ejected in a collimated relativistic jet. The laser-positron energy conversion efficiency is â¼2×10{-4}. The jets have â¼20 degree angular divergence and the energy distributions are quasimonoenergetic with energy of 4 to 20 MeV and a beam temperature of â¼1 MeV. The sheath electric field on the surface of the target is shown to determine the positron energy. The positron angular and energy distribution is controlled by varying the sheath field, through the laser conditions and target geometry.
ABSTRACT
Transverse, parasitic lasing has been observed in several large Ti:sapphire disk amplifiers. It severely limits the signal gain and the pulse energy that can be extracted from the amplifier. We have developed a technique for suppressing these parasitic lasing modes based on index matching the crystal edges with an absorbing doped polymer thermoplastic. The parasitics are completely suppressed for the range of aperture sizes and pump fluences studied here. A comparison of the amplifier performance before and after edge cladding is presented for several Ti:sapphire crystals.
ABSTRACT
We have developed an ultrashort-pulse laser system in which the final Ti:sapphire amplifier stage is pumped by the frequency-doubled output of a Nd:glass laser. The laser produces pulses with an energy in excess of 1 J on target and an estimated peak focused irradiance of 5 x 10(19) W/cm(2).
