We present results from a unique burst-mode femtosecond non-collinear optical parametric amplifier (NOPA) under development for the optical - x-ray pump-probe experiments at the European X-Ray Free-Electron Laser Facility. The NOPA operates at a burst rate of 10Hz, a duty cycle of 2.5% and an intra-burst repetition rate of up to 4.5MHz, producing high fidelity 15fs pulses at a center wavelength of 810nm. Using dispersive amplification filtering of the super-continuum seed pulses allows for selectable pulse duration up to 75fs, combined with a tuning range in excess of 100nm whilst remaining nearly transform limited. At an intra-burst rate of 188kHz the single pulse energy from two sequential NOPA stages reached 180µJ, corresponding to an average power of 34W during the burst. Acousto- and electro-optic switching techniques enable the generation of transient free bursts of required length and the selection of arbitrary pulse sequences inside the burst.
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