Development Of Electron Magnetic Spectrometer And Measurement Of Hot Electrons Temperature

Development of electron magnetic spectrometer was first introduced in this paper. Electron moves as a circle due to Lorenz force action in uniformity magnetic field. Actually , In plasma physics ,other forces should be considered , such as gravity excursion, magnetic grads excursion and curvature excursion . Therefore , B was selected at upright direction . Thus , gxB=0 , and gravity excursion was eliminated . Magnetic grads excursion and curvature excursion were dispelled by increasing magnetic field height and landscape orientation scale as well as using magnetic uniformity technology .In order to have electrons move in a plane, we have electrons vertically enter magnetic field , so as to electrons are easily detected . In principle, small magnetic field intensity can enhance spectrometer resolving power . considering the factor of vacuum chamber , we select the magnetic field 0.037T .Since the number of hot electron produced during ultrashort laser pulse irradiated solid target is not very large and the number of hot electron entering spectrometer is much more smaller , so LiF TLD was selected as detector because it can accumulate hot electron radiation . The sensitivity, linear absorption coefficient ( =1.31mm-1) and derivation, repeatability for LiF thermoluminescence dosemeter(TLD) are measured by using a standard source-137Cs- . And we have calibrated the spectrometer by using a standard source -90Sr- .The spectrum of hot electrons was measured at the normal of target by utilizing the magnetic spectrometer from the interaction of high intensity (1017W/cm2), pre-pulse free , P-polarized, UV(248nm) ,ultrashort pulse (440fs) laser with solid (Cu ) plasmas with 45 . The spectrum presents double-temperature Mexwellian feature and the temperature of hot electron is 81KeV . According to the scaling law of generating hot electron, the dominant absorption mechanism of laser is VH( Vacuum heating ). In order to validate the exist of ponderomotive force , we have measured the Dopplerfrequency shift of UV laser and found there was no obvious frequency shift , but there should have been of 0. 407nm frequency shift according to-experimental formula .So it is possible for L/A <0. 1 and VH( Vacuum heating ) is the dominant mechanism of generating hot electron . RA (resonance absorption) probably works too since the compress of ponderomotive force is asymmetrical . Result of the experiment can offer some data for researching UV laser pulse fast ignition (ICF).