Laser driven ion source from ultrathin foils and its biomedical application

Laser driven ion acceleration has attracted considerable attention due to its potential practical applications, such as in ion cancer therapy, proton imaging and fast ignition. Utilization of nanometer thin targets and ultrahigh contrast laser pulses has enabled a quantum leap in laser particle acceleration, offering much improved ion pulses as compared to plasma expansion schemes such as target normal sheath acceleration. Moreover, such nano-targets offer the possibility to control the ion beam by the laser parameters. We present the observation of well-collimated proton beams with a divergence as low as 1-2 degree and energies up to 8 MeV with a laser pulse of 0.4 J and 30 fs duration irradiating ultrathin DLC foils. The divergence strongly depends on the focal size of the laser and the highest energetic protons are generated even with moderate laser intensity as low as 3×1018 W/cm2. These remarkable features enabled us to irradiate living cells with a single shot dose of up to 7 Gray in one nanosecond for the first time, utilizing MPQ's table top ATLAS laser system. Although many issues still remain to solve, our demonstration of the feasibility of a very compact laser-driven beam line for proton acceleration, transport and delivery bolsters future applications such as laser driven hadron therapy.