The feasibility of the generation of bright ultrashort gamma-ray pulses is demonstrated in the interaction of a relativistic electron bunch with a counterpropagating tightly focused superstrong laser beam in the radiation-dominated regime. The Compton scattering spectra of gamma radiation are investigated using a semiclassical description for the electron dynamics in the laser field and a quantum electrodynamical description for the photon emission. We demonstrate the feasibility of ultrashort gamma-ray bursts of hundreds of attoseconds and of dozens of megaelectronvolt photon energies in the near-backwards direction of the initial electron motion. The tightly focused laser field structure and the radiation reaction are shown to be responsible for such short gamma-ray bursts, which are independent of the durations of the electron bunch and of the laser pulse. The results are measurable with the laser technology available in the near future.

Interaction of a frequency-chirped laser pulse with single protons and a hydrogen gas target is studied analytically and by means of particle-in-cell simulations, respectively. Feasibility of generating ultra-intense (10 7 particles per bunch) and phase-space collimated beams of protons (energy spread of about 1%) is demonstrated. Phase synchronization of the protons and the laser field, guaranteed by the appropriate chirping of the laser pulse, allows the particles to gain sufficient kinetic energy (around 250 MeV) required for such applications as hadron cancer therapy, from state-of-the-art laser systems of intensities of the order of 10 21 W/cm 2 .PACS numbers: 52.38. Kd, 37.10.Vz, 52.75.Di, 52.59.Bi, 52.59.Fn, 41.75.Jv, 87.56.bd Interaction of high-intensity lasers with solid targets has attracted much interest over the past decade, due to its potential utilization in laser acceleration of particles [1][2][3][4][5][6][7][8][9][10][11][12][13]. This has given much needed impetus to efforts directed at replacing conventional accelerators in the near future by compact and relatively low-cost devices based on an all-optical acceleration mechanism [14]. In particular, hadron cancer therapy [15,16] may benefit from this trend.Several regimes are now in existence for laser-plasma acceleration [17]. For laser intensities of 10 18 − 10 21 W/cm 2 and solid targets with a thickness ranging from a few to tens of micrometers, target normal sheath acceleration (TNSA) is the prevailing mechanism. In TNSA, a strong quasi-static electric field is induced at the rear surface of a thin foil, as a result of emission and acceleration of the electrons caused by an intense linearly polarized laser field. Ion acceleration, by the sheath electric field, has been extensively studied [1][2][3][4][5][6][7][8][9][10]. The regime of radiation-pressure-dominant acceleration (RPA), has become recently accessible by decreasing the target thickness. Circularly polarized lasers at normal incidence have been employed, which suppress electron heating and let all particle species co-propagate as a quasi-neutral plasma bunch in front of the light wave ("light sail"-mechanism) [18]. Despite recent experimental [19] and theoretical [20] progress, clinically useful ion beams [21] have not yet been produced within a scheme which operates at currently available laser parameters.In this Letter, we demonstrate the theoretical feasibility of creating proton beams, of unprecedented energy and quality, from illuminating a hydrogen gas target with an appropriately chirped laser pulse of intensity accessible by state-of-the-art laser systems [22]. The basic idea of our model stems from the realization that an incoming highly relativistic laser pulse quickly ionizes hydrogen in the cell and accelerates the electrons away from the much heavier protons, as the pulse intensity rises. At high enough laser intensities the protons get accelerated directly by the laser field. Chirping of the laser pulse ensures optimal phase synchronization among the protons and...

Autoresonance laser acceleration of electrons is theoretically investigated using circularly polarized focused Gaussian pulses. Many-particle simulations demonstrate feasibility of creating over 10-GeV electron bunches of ultra-high quality (relative energy spread of order 10^-4), suitable for fundamental high-energy particle physics research. The laser peak intensities and axial magnetic field strengths required are up to about 10^18 W/cm^2 (peak power ~10 PW) and 60 T, respectively. Gains exceeding 100 GeV are shown to be possible when weakly focused pulses from a 200-PW laser facility are used

Results from theoretical investigations are presented which show that protons can be accelerated from rest to a few hundred MeV by a 1-PW chirped radially polarized laser pulse of several hundred femtosecond duration and focused to a waist radius comparable to the radiation wavelength. Single-particle calculations are supported by many-particle and particle-in-cell simulations. Compared with laser acceleration by a similar linearly polarized pulse, the gained energies are less, but have better beam quality. For a suitable initial phase, a particle bunch gets accelerated by the axial component Ez of the laser pulse and, initially focused by the transverse electric field component Er. Beam diffraction finally sets in due to the particle-particle Coulomb repulsion, after interaction with the pulse ceases to exist

Detailed single- and many-particle calculations are carried out for the acceleration of protons employing linearly polarized plane-wave and tightly focused chirped laser pulses of several ten to several hundred femtosecond durations, petawatt peak powers, and relativistic peak intensities. Analytic and numerical methods of calculation are used in the single-particle cases (in vacuum), and particle-in-cell (PIC) simulations (underdense plasma) are employed in the many-particle investigations, without and with electromagnetic particle-particle interactions, respectively. The investigations cover a wide range of cases corresponding to upchirped as well as downchirped pulses