Experimental Investigation Of Laser Driven Ion Acceleration Using High Repetition Rate Targets

Ultra-intense laser driven ion acceleration has received much interest in the last few decades because of its potential applications such as advanced imaging source,fast-ignition fusion scheme,warm dense matter production,cancer therapy and injector to conventional accelerators.In order to be promising for the practical applications,advanced intense laser facilities with high repetition rate are required,which are under development or will be in operation in next few years.Besides,development of compatible target systems at high repetition rate has become an equally important field among laser-driven ion acceleration community.In this context,study of laser driven ions at high repetition rate would allow statistical correlations among the parameters of incident laser pulses and the accelerated ion beams which would be prerequisite for their control and enhancement in all-optical ion accelerators.This thesis reports on the experimental investigation of laser driven ions at high repetition rate using a recently built tape drive target system.Ultra-intense laser pulses at a rate of one shot per 5 second(0.2 Hz)are made possible to irradiate a commercially available video home system(VHS)tape target in the experimental campaigns.Stability of the proton beam is shown for 50consecutive shots.Protons with maximum energies of?6±0.3 MeV are measured with a stability of less than 5%in their cut-off energy.Results from the investigation of parametric scaling of the proton beam with laser parameters are presented.Different scalings of proton maximum energy with laser intensity were observed for laser energy and focal spot variations,which are I?^0.6 and I?^0.3 respectively.In contrast,the maximum energy of proton beam is weakly dependent on laser pulse duration.Experimental results of Carbon ion acceleration are also presented as a function of laser intensity.Moreover,low-charge-state carbon ions were found to have regular modulations on their energy spectrum.Particle-in-cell simulations reveal that the modulations are attributed to fast electron recirculation dynamics.The high repetition rate system was employed to optimize laser driven proton acceleration using a deformable mirror with an active feedback loop having information from proton energy spectrum.The results show improvement in the maximum energy of the protons and control over spectral shape of the proton beam.These results will be helpful in the development of automated and operator independent optimization schemes for all-optical ion accelerators.Finally,results from an experimental assessment of laser driven ion acceleration from a near critical density gas jet target system with Helium atomic density of the order of 10²⁰ cm^-3 are presented.Preliminary results show that the ions may be emitted along a direction 30 degree off from the laser axis.To further explorer the ion acceleration,the proton beam from tape-drive target could be utilized to uncover the plasma evolution dynamics,which are opaque to optical probe.