Experimental characterization of hot electron production under femtosecond laser plasma interaction at moderate intensities

Abstract

We discuss methods and algorithms of high-temperature laser plasma electron diagnostics based on hard x-ray yield and ionic time-of-flight (TOF) spectra measurements in comparison with the results of direct electronic spectrum recording, with the help of the electrostatic spectrometer. The latter shows clearly the two-component nature of the electron population, arising at femtosecond laser plasma interaction. 'Temperatures' of 200 eV and 6 keV for thermal and hot electronic components, correspondingly, were estimated from this measurement. We show that both ionic TOF measurements and doublechannel hard x-ray detection allows the assessment of mean hot electron energy in a single laser shot. The former also provides for estimation of the thermal electron temperature and plasma charge state. Good coincidence between the data obtained from the three methods employed is demonstrated. We also describe how to apply our hard x-ray detection method to the case of relativistic laser plasma interaction, where single shot assessment may become even more essential.

Femtosecond laser-plasma interaction with prepulse-generated liquid metal microjets

“…Combinations of different filters allowed assessing the mean hot-electron energy E hot in each laser shot. 33 All the detectors were calibrated absolutely.…”

“…33. The special filter sets (Be(0.2 mm)/ Al(0.5 mm) and Be(0.2 mm)/Al(0.5 mm)/Ta(26 lm) for the respective first and second detection channels) were used in this study to avoid contribution of the Ga line emission to the steep slope of the hard x-ray spectrum above 11 keV.…”

Si-Kαradiation generated by the interaction of femtosecond laser radiation with silicon

“…where E is the photon energy, α is a generalized plasma parameter, and T h is the temperature of hotelectrons [6]. When X-ray radiation is generated only by Bremsstrahlung, the measured energy of the X-rays with the photo-diodes w PD is proportional to …”

Registration of 14.4 keV [sup 57]Fe conversional decay after nuclei excitation induced with the help of plasma created by the powerful femtosecond laser pulse

“…The mean energy of hot electrons in the generated plasma was measured in each pulse by the two-detector filter method [6,7] from its X-radiation by means of two photoelectric multipliers with 5-mm-thick NaI scintillators and was found to be 13±2 keV on average. After each laser pulse, the target was shifted so that the radiation interacted with a smooth surface rather than with the crater remaining after the previous shot.…”

“…The angle of incidence of ions onto the second target was about 45°. Electrons knocked out from this target passed through deflecting plates of an electrostatic semi cylindrical spectrometer [7], whose entrance window (2 × 0.5 cm) was situated at a distance of 4 cm from the second target, approximately along the perpendicular to its surface. These electrons were detected by a chevron microchannel plate.…”