  We have used an unbiased, spectral line-survey that covers the frequency
range from 211 to 275 GHz and was obtained with ALMA (angular resolution of 0.4
arcsec) to study the small-scale structure of the dense gas in Sagittarius B2
(north). Eight filaments are found converging to the central hub and extending
for about 0.1 pc. The spatial structure, together with the presence of the
massive central region, suggest that these filaments may be associated with
accretion processes. In order to derive the kinematic properties of the gas in
a chemically line-rich source like Sgr B2(N), we have developed a new tool that
stacks all the detected transition lines of any molecular species. This permits
to increase the signal-to-noise ratio of our observations and average out line
blending effects, which are a common problem in line-rich regions. We derive
velocity gradients along the filaments of about 20-100 km s$^{-1}$ pc$^{-1}$,
which are 10-100 times larger than those typically found on larger scales (1
pc) in other star-forming regions. The mass accretion rates of individual
filaments are about 0.05 M$_\odot$ yr$^{-1}$, which result in a total accretion
rate of 0.16 M$_\odot$ yr$^{-1}$. Some filaments harbor dense cores that are
likely forming stars and stellar clusters. The stellar content of these dense
cores is on the order of 50% of the total mass. We conclude that the cores may
merge in the center when already forming stellar clusters but still containing
a significant amount of gas, resulting in a "damp" merger. The high density and
mass of the central region, combined with the presence of converging filaments
with high mass, high accretion rates and embedded dense cores already forming
stars, suggest that Sgr B2(N) may have the potential to evolve into a super
stellar cluster.
