Intense $\gamma$-Ray Source in the Giant-Dipole-Resonance Range Driven by 10-TW Laser Pulses

A $\gamma$-ray source with an intense component around the giant dipole resonance for photonuclear absorption has been obtained via bremsstrahlung of electron bunches driven by a 10-TW tabletop laser. 3D particle-in-cell simulation proves the achievement of a nonlinear regime leading to efficient acceleration of several sequential electron bunches per each laser pulse. The rate of the $\gamma$-ray yield in the giant dipole resonance region ($8<E_{\gamma }<17.5\mathrm{MeV}$) was measured, through the radio activation of a gold sample, to be $4\times {10}^8$ photons per joule of laser energy. This novel all-optical, compact, and efficient electron-$\gamma$ source is suitable for photonuclear studies and medical uses.

Figure 1

Spatially resolved spectral data of the accelerated electrons from the SHEEBA detector.

Figure 2

Typical electron spectrum obtained by the magnetic spectrometer.

Figure 3

Spectrum of the $\gamma$ radiation produced by the electron bunches crossing the 2 mm tantalum slab, as calculated from the postprocessing activity measurements.

Figure 4

Snapshots from the 3D simulation. (a) Electron density distribution when the laser pulse is at about 1.65 mm after the entrance in the gas jet. (b)–(d) Electron momentum distribution along the propagation axis when the laser pulse is at 1, 2, and 2.5 mm, respectively.