Chou, M.-C.M.-C.ChouLin, P.-H.P.-H.LinLin, C.-A.C.-A.LinLin, J.-Y.J.-Y.LinWang, J.J.WangChen, S.-Y.S.-Y.Chen2020-06-022020-06-02200700319007https://scholars.lib.ntu.edu.tw/handle/123456789/496481Dramatic enhancement of optical-field-ionization collisional-excitation x-ray lasing is achieved by using an optically preformed plasma waveguide. With a 9-mm-long pure krypton plasma waveguide prepared by using the axicon-ignitor-heater scheme, lasing at 32.8 nm is enhanced by 400 folds relative to the case without the plasma waveguide. An output level of 8×1010photon/shot is reached at an energy conversion efficiency of 2×10-6. The same method is used to achieve x-ray lasing in a gas jet for the high-threshold low-gain transition at 46.9 nm in neonlike argon. © 2007 The American Physical Society.[SDGs]SDG7Electric excitation; Energy conversion; Energy efficiency; Ionization; Plasma filled waveguides; Energy conversion efficiency; High threshold low gain transition; Optically preformed plasma waveguides; X ray lasing; X ray lasersjournal article10.1103/PhysRevLett.99.063904