Speaker
Description
Relativistic fast electrons are generated in the interaction of ultrashort (tens of fs) ultrahigh intensity laser (>1018W/cm2) pulses with solid target.Investigation of thegeneration and transport of fast electrons in solid material is a subject of intense research investigation not only for fundamental understanding of laser matter interaction in extreme condition but also for various potential applications including laser driven fast ignition approach of laser fusion, MeV proton and ion acceleration, creation of ultrashort x-ray sources and warm dense matter.
At Laser Plasma Division, RRCAT, Indore, India, we have carried out the experimental studies on the generation and transport of fast electrons in intense ultra-short laser foil interaction using high-power (150 TW, 25 fs) Ti:sapphire laser in the intensity regime of ~1018 - 7x1019W/cm2. Investigations involved both direct measurement of fast electrons as well as indirect measurement using K x-rays and hard x-rays emitted during interaction.A clear signature of JB acceleration in oblique incidence laser interaction with foil target was demonstrated through the observation of fast electron beam along laser direction.We also observedstrong polarization dependence of JB acceleration on fast electron flux. The possible mechanism was studied by varying the preformed plasma scale length in front of the solid target. We demonstrated super ponderomotive acceleration at longer scalelength whereas the fast electron temperature was much lower than the ponderomotive scaling. Next, we studied the transport of fast electrons through dense solid through K x-ray line radiation measurement using indigenously developed HAPG crystal spectrograph and2D high resolution monochromatic imaging usingspherically bent quartz crystal spectrograph. In particular, refluxing of fast electrons due to excitation of electrostatic sheath field and fast electron divergence angle inside solid to infer therole of self-generated magnetic fields on collimating fast electrons at such high laser intensity was investigated. In this talk details of the investigations performedand physical understanding of the processes involved will be presented.
