Realization of the conceptual ideal for x-ray amplification

Abstract

The Xe(L) system is an amplifier with fundamentally different dynamic characteristics from all previously developed laser amplifiers; it represents the conceptual ideal through full utilization of the Kramers–Kronig relations that fundamentally couple the dispersive and absorptive components. The dispersive response of the system, through optimal governance of the power compression, rules the amplification and establishes a minimum gain for the amplifier. Accordingly, the amplification requires a minimum value of the dispersion to be surpassed; the corresponding gain follows automatically. As a leading consequence, since this minimum gain is sufficiently high, the key experimental observation is the uniform presence of saturated amplification signaled by strong spectral hole burning on all transitions exhibiting amplification, including double-vacancy lines. This cardinal signature demonstrates that the amplification is legislated by the saturated gain gs, not the corresponding small signal value g0. The chief outcome is that explosive dispersion yields perforce explosive amplification and the efficient generation of maximally bright coherent power.

Laser-intensity requirements for generating enhanced kilovolt bremsstrahlung emission in intense laser-cluster interactions

“…[7] xenon cluster experiments, the laser pulsewidth was τ ∼ 2.5 × 10 −13 s while the bremstrahlung emissions of interest lie above 5.6 keV. In this case, ω ′ ≥ 8.5×10 18 s −1 and…”

“…The experiments that were modeled are described in Ref. [7] and in the references cited therein. In these experiments, KrF laser radiation was focused to intensities greater than 10 19 W/cm 2 in a gas of xenon clusters.…”

“…The development of ultra-high intensity KrF lasers, which have photon energies of 5 eV and intensities ≥ 10 19 W/cm 2 , has allowed experiments to be conducted in which xray amplification at 2.8Å was observed [7] when a gas of xenon clusters was irradiated with intensities ≥ 10 19 W/cm 2 . Recently, in an attempt to determine whether the gain coefficient data that was inferred from these experiments could be modeled and thereby replicated theoretically, a time dependent molecular-plus-ionization dynamic xenon model was constructed [8,10].…”

“…[9,10] is used in this section to compute the dynamical response of a xenon cluster of 200 atoms to an intense pulse of KrF laser radiation that is taken to peak at an intensity of 2 × 10 19 W/cm 2 , which is comparable to the intensities achieved in the experiments of Ref. [7]. In a molecular dynamics calculation, average electron and ion densities and effective electron and ion temperatures are first calculated in response to this KrF pulse.…”

“…In a molecular dynamics calculation, average electron and ion densities and effective electron and ion temperatures are first calculated in response to this KrF pulse. These quantities are then used as input to an ionization dynamics calculation in which photoionization rates were chosen to correlate with the field-free bremsstrahlung emission rate and that were taken to have a peak value that produces the population inversions and the x-ray amplifications at 2.8Å that were measured in the experiments [7]. Using these rates, one computes a photoionization power input to the cluster.…”