Investigation of GeV-scale electron acceleration in a gas-filled capillary discharge waveguide

Abstract

The generation of GeV-scale electron beams in a gas-filled capillary discharge waveguide with good reproducibility is discussed. Beams of electrons with energies above 900 MeV, and with root-mean-square divergences of 3.5 mrad, are observed for a plasma density of 2.2 × 10 18 cm −3 and a peak input laser power of 55 TW. The variation of the maximum electron energy with the plasma density is measured and found to agree well with simple models. Injection and acceleration of electrons at the to date lowest plasma density of 3.2 × 10 17 cm −3 are reported. The energy spectra of the generated electron beams exhibit good shot-to-shot reproducibility, with the observed variations attributable to the measured shot-to-shot jitter of the laser parameters. Two methods for correcting the effect of beam pointing variations on the measured energy spectrum are described.

Interaction of relativistically intense laser pulses with long-scale near critical plasmas for optimization of laser based sources of MeV electrons and gamma-rays

“…Interaction of the relativistic laser pulse with large-scale NCD-plasmas ensures a long acceleration path and results into effective coupling of the laser energy into energetic electrons. Experiments on the electron heating by a 80-100 J, 750 fs short laser pulse of 2-5×10 19 W cm −2 intensity demonstrated that the effective temperature of supra-thermal electrons increased from 1.5-2 MeV, in the case of the relativistic laser interaction with a metallic foil at high laser contrast, up to 13 MeV for the laser shots onto the pre-ionized 300-500 μm long foam layer with a NCD. The measurements showed high directionality of the acceleration process.…”

“…In this way, up to 60% of the laser energy was concentrated in the focal spot with a FWHM-size of 14±1×19±1 μm 2 . Shot-to-shot deviations of the laser energy and 30% uncertainties in the laser pulse duration resulted in the rather large confidential interval of the laser intensities ranging from 2.1 up to 5.1×10 19 W cm −2 . The corresponding normalized vector potentials are a L =3.9-6.0.…”

“…Great results have been achieved in the generation of monoenergetic electron beams. For instance, in experiments on the interaction of relativistic laser pulses with low density gas jets and capillary plasmas, the obtained energies range from hundreds of MeV up to several GeV [17][18][19][20]. Nevertheless, the charge carried by these electron beams does not exceed tens of pC, which is not sufficient to radiograph HED-samples in experiments with a high level of background radiation.…”

Optically controlled laser–plasma electron accelerator for compact gamma-ray sources

“…femtosecond) e-beams [25]. Besides, polychromatic (or 'comb-like') beams from an LPA, with the current modulated on a femtosecond scale, have been observed in experiments [26][27][28][29]. Simulations indicate that such beams readily lend themselves to all-optical manipulation, promising generation of spectrally controlled quasi-monochromatic, femtosecond γ-ray pulses, or trains of pulses with a femtosecond synchronization [9][10][11].LPAs, however, face a number of challenges, one of which is preservation of beam quality, that is, elimination of a high-charge, low-energy tail, which develops when acceleration is continued through electron dephasing [30][31][32][33][34].…”

“…femtosecond) e-beams [25]. Besides, polychromatic (or 'comb-like') beams from an LPA, with the current modulated on a femtosecond scale, have been observed in experiments [26][27][28][29]. Simulations indicate that such beams readily lend themselves to all-optical manipulation, promising generation of spectrally controlled quasi-monochromatic, femtosecond γ-ray pulses, or trains of pulses with a femtosecond synchronization [9][10][11].…”