title: Generation of hard x rays by femtosecond laser pulse interaction with solid targets in atmosphere.
abstract: X ray radiation as high as 50 keV, including K(α) of Ba and Mo, have been observed from a solid target during the interaction of low energy ~0.65 mJ, 1 kHz 40 femtosecond laser pulses focused in air at atmospheric pressure. Energetic electrons generating such x rays are possibly produced when the field strength in laser pulse wake exceeds the runaway threshold in air. Two dimensional particle-in-cell simulations that include optical field ionization of air and elastic collisions support this mechanism.
authors.affiliation: PPC, Osaka University and JST, CREST, 2-1, Yamadaoka, Suita, Osaka 565-0871, Japan.
authors.forename: Alexey G
authors.initials: AG
authors.lastname: Zhidkov
authors.forename: Sergey A
authors.initials: SA
authors.lastname: Pikuz
authors.forename: Anatoly Ya
authors.initials: AY
authors.lastname: Faenov
authors.forename: Oleg V
authors.initials: OV
authors.lastname: Chefonov
authors.forename: Andrey V
authors.initials: AV
authors.lastname: Ovchinnikov
authors.forename: Mikhail B
authors.initials: MB
authors.lastname: Agranat
authors.forename: Arie
authors.initials: A
authors.lastname: Zigler