Relativistic interaction of ultra-high contrast femtosecond laser pulses with core-shell nanostructures

Structuring the target surface at micro and nanoscale significantly improves the laser energy deposition into the target volume resulting in remarkable enhancement of the flux and energy of generated particles and also yield of X-rays. Here, we present experimental results on the relativistic interaction of intense ultra-short laser pulses with arrays of composite nanowires using complex diagnostics including X-ray and particle spectra. Arrays of nanowires consist of low-Z (Si) core nanowires, 100 nm diameter, coated by a 25 nm thick layer of TiO2 (high-Z cladding). The experiments were conducted at the Jena multi-terawatt Ti:Sapphire laser system JETI 40 delivering 0.7 J, 30 fs laser pulses at 0.8 mm wavelength and 10 Hz repetition rate. We used the second harmonic beam of JETI 40 laser to ensure high temporal contrast and the beam was also focused under 90º incidence angle on the target reaching intensities above 3×1019 W/cm2 (a0≈2). We observed strong enhancement in energy and flux of protons generated from nanowire array targets as compared with those from reference flat target. The spectral analysis of K-shell X-ray emission lines revealed stronger emission from Si12+ (He-like) and Si13+ (H-like) ionic states of Si and also more than an order of magnitude increase in the yield of emission lines from Ti He-like ionic state (Ti20+) from nanowire arrays compared to the reference flat target.  More strikingly, 1D imaging of the X-ray emission from the Ti plasma shows the existence of anomalously long living of kiloelectronvolt temperature, high-density plasma with nanosecond scale lifetime from composite nanowire arrays but not from the reference flat targets!

More details on the measurements will be presented at the seminar.

Zoom-Meeting
https://gsi-fair.zoom.us/j/96629963798

Meeting-ID: 966 2996 3798
Kenncode: 130302