Excitation of X rays by electrons accelerated in air in the wake wave of a laser pulse

Prediction of the irradiation doses from ultrashort laser-solid interactions using different temperature scalings at moderate laser intensities

“…ten times higher than from K α line only at this intensity. Bremsstrahlung and K α efficiency ratio in copper was investigated by other authors [36] and they found threshold value, when K α efficiency starts to increase significantly. The bremstrahlung efficiency found at the investigated intensity was approximately one order of magnitude larger than K α efficiency (See figure 3 in publication [36]).…”

“…Bremsstrahlung and K α efficiency ratio in copper was investigated by other authors [36] and they found threshold value, when K α efficiency starts to increase significantly. The bremstrahlung efficiency found at the investigated intensity was approximately one order of magnitude larger than K α efficiency (See figure 3 in publication [36]). Bremsstrahlung and K α efficiency ratio in the materials depends on the laser intensity used, however for the sake of clarity for our further calculations we shall assume that bremsstrahlung and K α efficiency ratio is 10.…”

Characterization of X-ray radiation from solid Sn target irradiated by femtosecond laser pulses in the presence of air plasma sparks

“…The L α radiation production is very low for energies approximating to some hundreds of μJ probably because of the 10 2 contrast, which makes the prepulse to be not efficient in modifying the air index refraction. It is worth noting that in previous works K α radiation was found even for laser energy around some tens of μJ, working with a kHz high repetition laser (Faenov et al, 2010;Pikuz et al, 2010;Zhidkov et al, 2012). Even if in these works no punctual mention is given about the laser contrast, the K α production in the same configuration seems to be more efficient.…”

“…In the present work, the generation of L α line from air plasma sparks in front of a metal target is studied, following (Pikuz et al, 2010) where K α emission was used to perform micro-radiographies. Based on (Nagao et al, 2004;Faenov et al, 2010;Ledingham et al, 2011;Zhidkov et al, 2012), we optimized the X-ray radiation from a thick (2 mm) tin (Sn) target, by moving the target relative to the laser focus in the presence of the air plasma spark. In addition, at each point we conducted a scan by varying the energy ratio between the main pulse and a controlled prepulse.…”

“…The expected laser intensity in vacuum is such that X-rays in the keV region could be observed from the interaction with the solid target, nevertheless keV photons are unexpected when the interaction occurs in air. In previous works (Faenov et al, 2010;Ledingham et al, 2011;Zhidkov et al, 2012), kHz repetition laser were used showing a higher efficiency in the number of yield K α X-ray photons. This could be due at least to two reasons: the first is the higher efficiency of K α line production with respect to L α line through electron inelastic scattering inside metals; the second is related to the air refraction index properties, which on the millisecond scale can bring memory from the previous pulse to the next giving birth to focusing effects in some cases, increasing and maintaining the laser intensity over many Rayleigh lengths (Jhajj et al, 2014).…”