  The Einstein Telescope (ET) is a third generation gravitational wave detector
that includes a room-temperature high-frequency (ET-HF) and a cryogenic
low-frequency laser interferometer (ET-LF). The cryogenic ET-LF is crucial for
exploiting the full scientific potential of ET. We present a new baseline
design for the cryogenic payload that is thermally and mechanically consistent
and compatible with the design sensitivity curve of ET. The design includes two
options for the heat extraction from the marionette, based on a monocrystalline
high-conductivity marionette suspension fiber and a thin-wall titanium tube
filled with static He-II, respectively. Following a detailed description of the
design options and the suspension thermal noise (STN) modelling, we present the
sensitivity curves of the two baseline designs, discuss the influence of
various design parameters on the sensitivity of ET-LF and conclude with an
outlook to future R&D activities.
