Hot electron and x-ray generation by sub-ns kJ-class laser-produced tantalum plasma

Abstract

This paper presents experimental investigation of temperature scaling and threshold of instability in hot electron and bremsstrahlung radiation from the interaction of sub-nanosecond and kilo-joule class laser pulse with tantalum foil target at Prague Asterix Laser System (PALS). The laser intensity was varied between 4×10^{15} and 3×10^{16} W . cm^{-2} at the target focus. The energy distribution functions of electrons were measured by an angular array of magnetic spectrometers indicating the electron temperature in the range between 30 keV and 70 keV. The bremsstrahlung spectrum was characterized using a scintillator based calorimeter. Specially, we show the laser-energy scaling of the total flux of hot electrons in forward and backward directions with respect to the laser vector, the conversion efficiency of the laser energy to the energy carried by hot electrons, and temperature of hot electrons as well as the unfolded bremsstrahlung temperature using Monte Carlo code consistent with signals of the scintillator detector. The scaling shows that the electron flux increases discontinuously with increasing laser intensity from ∼ 1−2×10^{16} W . cm^{-2} with consequent instability in the production of hot electrons and bremsstrahlung radiation.

Magnetic field generation using single-plate targets driven by kJ-ns class laser

“…The measured magnetic field in the TGG crystal was rescaled using the simulated field profile shown in figure 1(d) to calculate the magnetic field at the center of the coil and the current through the coil. The simulated profile shown in figure 1(d) was obtained by using RADIA [20] code, which provided a magnetostatic model for the fields [26].…”

Advanced Diagnostics of Electrons Escaping from Laser-Produced Plasma

“…It is the multi-channel electron spectrometer and the induction target probe that make it possible to reliably measure the number of electrons escaping from the plasma and the target, as well as to compare the results of both diagnostics. Experiments performed at the PALS facility make it possible to measure the total flux of hot electrons that have escaped from the plasma using the multi-channel magnetic electron spectrometer ranging from 50 keV to 1.5 MeV or from 250 keV to 5 MeV [53,71]. The spectrometers incorporate a plastic electron collimator designed to suppress the secondary radiation by absorbing the wide angle scattered electrons and photons inside the collimator.…”

“…Plasma 2024, 7, FOR PEER REVIEW 14 spectrometer ranging from 50 keV to 1.5 MeV or from 250 keV to 5 MeV [53,71]. The spectrometers incorporate a plastic electron collimator designed to suppress the secondary radiation by absorbing the wide angle scattered electrons and photons inside the collimator A total of 12 spectrometers can be placed inside the vacuum chamber around the target at about 30 cm from the target at angles of −39°, −27°, −17°, 0°, 17°, 27°, 39°, 153°, 163°, 180° 197°, and 207° from the laser axis, as Figure 8 shows.…”

Instruments for best target position determination in the high-intensity laser-solid interaction experiment

“…High-intensity laser-solid interaction 1 is an important way of generating high harmonics 2,3,4 in the extreme ultraviolet and soft X-ray spectral ranges, as well as to accelerate electrons 5 and ions 6,7,8 and produce gamma rays 9,10 . In experiments with tight focusing 11 of multi-joule femtosecond laser pulses into a ~1-µm focal spot with an ultrarelativistic intensity of ~10 22 W/cm 2 , one of the most critical issues is the precise positioning of the target within the super-short Rayleigh length which is of the order of ~10 µm.…”