  We report supercontinuum generation and pulse compression in two stacked
multipass cells based on dielectric mirrors. The 230 fs pulses at 1 MHz
containing 12 $\mu$J were compressed by factor 33 down to 7 fs, corresponding
to 1.0 GW peak power and overall transmission of 84 %. The source is
particularly interesting for such applications as time-resolved ARPES,
photoemission electron microscopy, and nonlinear spectroscopy.
