Observation of Monoenergetic Electrons from Two-Pulse Ionization Injection in Quasilinear Laser Wakefields.

The generation of low emittance electron beams from laser-driven wakefields is crucial for the development of compact x-ray sources. Here, we show new results for the injection and acceleration of quasimonoenergetic electron beams in low amplitude wakefields experimentally and using simulations. This is achieved by using two laser pulses decoupling the wakefield generation from the electron trapping via ionization injection.

Optimization of the electron beam dump for a GeV-class laser electron accelerator.

The advances of laser-driven electron acceleration offer the promise of great reductions in the size of high-energy electron accelerator facilities. Accordingly, it is desirable to design compact radiation shielding for such facilities. A key component of radiation shielding is the high-energy electron beam dump.

Seidel aberrations in grating pulse stretchers.

We derived a formula for calculation of the spectral phase of ultrashort pulses propagating through aberrated stretchers. Our approach is based on Seidel aberration theory. The dependence of spectral phase dispersion terms and residual angular dispersion on the individual Seidel aberration coefficients is found.

Field trial of active remote sensing using a high-power short-wave infrared supercontinuum laser.

Field trial results of a 5 W all-fiber broadband supercontinuum (SC) laser covering the short-wave infrared (SWIR) wavelength bands from ~1.55 to 2.35 μm are presented.

Finite spot effects on radiation pressure acceleration from intense high-contrast laser interactions with thin targets.

Short pulse laser interactions at intensities of 2×10(21) W cm(-2) with ultrahigh contrast (10(-15)) on submicrometer silicon nitride foils were studied experimentally by using linear and circular polarizations at normal incidence. It was observed that, as the target decreases in thickness, electron heating by the laser begins to occur for circular polarization leading to target normal sheath acceleration of contaminant ions, while at thicker targets no acceleration or electron heating is observed. For linear polarization, all targets showed exponential energy spreads with similar electron temperatures.

Control of energy spread and dark current in proton and ion beams generated in high-contrast laser solid interactions.

By using temporal pulse shaping of high-contrast, short pulse laser interactions with solid density targets at intensities of 2 × 10(21) W cm(-2) at a 45° incident angle, we show that it is possible to reproducibly generate quasimonoenergetic proton and ion energy spectra. The presence of a short pulse prepulse 33 ps prior to the main pulse produced proton spectra with an energy spread between 25% and 60% (ΔE/E) with energy of several MeV, with light ions becoming quasimonoenergetic for 50 nm targets. When the prepulse was removed, the energy spectra was broad.

Generation of GeV protons from 1 PW laser interaction with near critical density targets.

The propagation of ultraintense laser pulses through matter is connected with the generation of strong moving magnetic fields in the propagation channel as well as the formation of a thin ion filament along the axis of the channel. Upon exiting the plasma the magnetic field displaces the electrons at the back of the target, generating a quasistatic electric field that accelerates and collimates ions from the filament. Two dimensional particle-in-cell simulations show that a 1 PW laser pulse tightly focused on a near-critical density target is able to accelerate protons up to an energy of 1.

Accelerating monoenergetic protons from ultrathin foils by flat-top laser pulses in the directed-Coulomb-explosion regime.

We consider the effect of laser beam shaping on proton acceleration in the interaction of a tightly focused pulse with ultrathin double-layer solid targets in the regime of directed Coulomb explosion. In this regime, the heavy ions of the front layer are forced by the laser to expand predominantly in the direction of the pulse propagation, forming a moving longitudinal charge separation electric field, thus increasing the effectiveness of acceleration of second-layer protons. The utilization of beam shaping, namely, the use of flat-top beams, leads to more efficient proton acceleration due to the increase of the longitudinal field.

Accelerating protons to therapeutic energies with ultraintense, ultraclean, and ultrashort laser pulses.

Proton acceleration by high-intensity laser pulses from ultrathin foils for hadron therapy is discussed. With the improvement of the laser intensity contrast ratio to 10(-1) achieved on the Hercules laser at the University of Michigan, it became possible to attain laser-solid interactions at intensities up to 10(22) W/cm2 that allows an efficient regime of laser-driven ion acceleration from submicron foils. Particle-in-cell (PIC) computer simulations of proton acceleration in the directed Coulomb explosion regime from ultrathin double-layer (heavy ions/light ions) foils of different thicknesses were performed under the anticipated experimental conditions for the Hercules laser with pulse energies from 3 to 15 J, pulse duration of 30 fs at full width half maximum (FWHM), focused to a spot size of 0.

Ultra-high intensity- 300-TW laser at 0.1 Hz repetition rate.

We demonstrate the highest intensity - 300 TW laser by developing booster amplifying stage to the 50-TW-Ti:sapphire laser (HERCULES). To our knowledge this is the first multi-100TW-scale laser at 0.1 Hz repetition rate.

Quasi-flat-top frequency-doubled Nd:glass laser for pumping of high-power Ti:sapphire amplifiers at a 0.1 Hz repetition rate.

A Nd:glass laser based on a novel design delivers up to 120 J energy pulses with a quasi-flat-top spatial profile at a 0.1 Hz repetition rate. The laser output is frequency-doubled with 50% efficiency and used to pump Ti:sapphire amplifiers.

Generation of 10(11) contrast 50 TW laser pulses.

We demonstrate what we believe to be the highest-contrast (10(11)), multiterawatt, chirped-pulse amplification (CPA) Ti:sapphire laser by applying the modified cross-polarized-wave (XPW) generation method. This method produces a contrast improvement of 3 orders of magnitude using microjoule input energy. Microjoule energy can be achieved by direct amplification without the complications of a double CPA system.