Laser transmission in the relativistically-induced transparency regime for high performance proton acceleration at PW laser systems (Conference Presentation)

Ion acceleration by compact laser-plasma sources promises a variety of applications, but reaching the required beam quality parameters demands a high level of understanding and control over the laser-plasma interaction process. Several advanced acceleration schemes, including the Relativistically Induced Transparency (RIT) regime, have been proposed and investigated in search of a stable acceleration regime for proton energies beyond 100 MeV. Central component in the RIT scheme is the absorption of the electromagnetic laser field by the target and the generated plasma respectively. In joint studies, we experimentally explore these interactions at the onset of transparency at the two laser systems DRACO PW (HZDR) and J-KAREN (KPSI). With our transmission diagnostics, we characterize this onset with respect to the laser temporal profile in order to learn about the sensitivity of laser input parameters to increase the process’s robustness. Using ultra-short, high and low-contrast laser pulses on thin solid density foil targets, we observe high performance proton beams in an expanded foil case. The results of spectral, spatial, and energy analysis of the effects on the transmission and its correlation with the acceleration performance indicate changes in the plasma interaction itself.