Theory ofKαgeneration by femtosecond laser-produced hot electrons in thin foils

Abstract

An analytical model of femtosecond K(alpha) x-ray generation from laser-irradiated foils is presented. Expressions are found for the photon emission yield in both forward and backward directions in integral form as a function of hot-electron temperature and target thickness. It is found that for any given target material, there is a foil thickness and a hot-electron temperature at which the K(alpha) emission is maximized. Conversion efficiencies are consistent with contemporary measurements of K(alpha) radiation produced with femtosecond lasers.

Scale-length optimizing of short pulse CuKα laser-plasma sources

“…The scaling of Reich et al 13 from particle-in-cell simulations of similar laser pulses gives T hot = 110͑I 17 ͒ 1/2 keV, where I 17 means the intensity in units of 10 17 W cm −2 . In that and similar works, 14,15 it has been shown that for a given energy into fast electrons the optimum K␣ production in a Cu slab rises swiftly as T hot approaches ϳ50 keV with a slow decay at higher temperature caused by fewer hot electrons and deeper penetration into the target where K␣ photons are reabsorbed. For our case, this optimum is reached at I ϳ 2 ϫ 10 16 W cm −2 and this is the average irradiance at an offset of ϳ420 m. For constant absorption, we would expect a broad peak in K␣ at this offset.…”

Efficient multi-keV X-ray generation from high-contrast laser plasma interaction

“…According to D. Salzmann's model [13], the absolutely K is given as a function of TE and the hot electron temperature T h :…”

Absolute Kα line spectroscopy for cone-guided fast-ignition targets

“…Assuming a single Maxwellian electron velocity distribution and one-way travel of hot electrons through the cone, energy transfer efficiency (TE) of incident LFEX laser to hot electrons was derived according to Salzmann's model [13]. Figure 3 shows the TE given as a function of hot electron temperatures.…”