LAPTECH Highlights

The LAPTECH JRA is focussed on investigating and developing methods of accelerating electrons to high energies, using the electrostatic forces of laser-driven plasma waves and the ponderomotive force of intense short laser pulses.

To explore acceleration in the 100-500 TW regime, the Strathclyde team, in collaboration with teams from IST and Glasgow University, have undertaken experiments using preformed plasma waveguides on the ASTRA-Gemini laser. The 5 J, 55 fs duration laser pulse was focussed into a preformed plasma waveguide with a plasma density of 2×10^18 cm-3. The initial vector potential a0≈2 is enhanced as a result of relativistic self-focussing and longitudinal compression and easily reaches a value 3 times higher, which subsequently leads to self-injection and quasi-monoenergetic electron bunches with energies in the range of 300-850 MeV.

At LOA, with a 40 TW laser of "Salle Jaune", the electron injection location and the acceleration length in laser plasma accelerators, have been measured by imaging the betatron radiation at the capillary exit. Using the CTR (Coherent Transition Radiation), it has been shown that the duration of the electron bunch is extremely short with a duration of 1.5 fs RMS to which corresponds a peak current of 4 kA.

Measured CTR spectra. The continuous lines corresponds to theoretical spectra for the case of gaussien bunches for different duration (from O. Lundh et al., Nature Physics 7 (2011))