Hard x-ray generation by low energy, tightly focused laser pulses

The interaction of λ2 laser pulses with plasma is studied to scale the high-field physics from high power laser systems to low-energy, high-repetition-rate lasers. For this purpose, 20mJ, 40fs Ti:sapphire laser pulses were focused in a spot of 2.2×2.3μm2 with a maximum intensity of I∼1019W∕cm2. Efficient generations of energetic electrons (∼1MeV) and hard x-rays with energies of over 100keV were obtained by irradiating the low-energy, tightly focused laser pulses on a massive Cu target.