High current, high energy proton beams accelerated by a sub-nanosecond laser

The sub-nanosecondlasersystemavailableatPALSfacilityinPraguehasbeenusedinordertoproduce MeV protonbeamswithtypicalcurrentdensityapproaching1A/cm2 at fewtensofcentimetersfromthe target surface.Inspiteoftherelativelylongpulseduration(0.3ns)andlowintensity(1016 W/cm2), far away fromtheforefrontlaserfacilitiesusedforadvancedprotonbeamaccelerationintherecentyears (from tensoffemtosecondstofewpicoseconds),theobtainedresultsarepromisingbothintermsof maximumprotonenergyandfastprotoncurrent.Real-timediagnosticssystems,mainlyintime-of-flight (TOF)configuration,havebeenusedinordertoestimatemaximumandpeakenergyoftheplasmafast protoncomponent,peakcurrentdensity,totalnumberoffastprotonsandconversionefficiencyoflaser energy intoacceleratedfastprotontotalenergy.Optimizationofthemaximumattainableprotonenergy and currenthasbeencarriedoutbyirradiatingtargetsofdifferentcompositionaswellasvaryingthelaser energy andthefocalspotdiameter.Experimentalresults,aswellaspossibleapplicationsinmaterial scienceandnuclearphysics,arediscussedandcomparedwithliteraturedata.