RESUMO
We demonstrate coherent combination of two high-gain and high-power single-mode 1 µm fiber amplifiers via direct pump current modulation. Each all-fiber amplifier channel, which is built as a master oscillator-multiple amplifier architecture, can operate either continuous waves or 4 ns, 1 MHz pulses with average power of 50 W and more than 55 dB gain. These two amplifiers are coherently combined by modulating the pump currents of the preamplifiers in a multidither arrangement. The key feature of the scaling scheme is the insertion of a designated second stage preamplifier between the first stage preamplifier and the final power amplifier stage, so as to improve the coherency and to minimize the gain variation of the preamplifier to the power amplifier. Otherwise, overall phase control of the fiber amplifiers with this method is not possible at such a high power level.
RESUMO
The successful utilization of an ion channel in a plasma to wiggle a 28.5-GeV electron beam to obtain broadband x-ray radiation is reported. The ion channel is induced by the electron bunch as it propagates through an underdense 1.4-meter-long lithium plasma. The quadratic density dependence of the spontaneously emitted betatron x-ray radiation and the divergence angle of approximately (1-3)x10(-4) radian of the forward-emitted x-rays as a consequence of betatron motion in the ion channel are in good agreement with theory. The absolute photon yield and the peak spectral brightness at 14.2-keV photon energy are estimated.
