  The High Luminosity Large Hadron Collider (HL-LHC) at CERN is expected to
collide protons at a center-of-mass energy of 14 TeV and to reach the
unprecedented peak instantaneous luminosity of $7.5 \times 10^{34}
\text{cm}^{-2} \text{s}^{-1}$ with an average number of pileup vertices of 200.
This will allow the ATLAS and CMS experiments to collect a data sample with an
integrated luminosity up to $4000\,\mathrm{fb}^{-1}$ during the project's
lifetime. To adapt to these harsh conditions, the CMS detector will be
substantially upgraded before starting the HL-LHC, a plan known as CMS Phase-2
upgrade. The entire CMS silicon pixel detector (IT) will be replaced and the
new detector will feature increased radiation hardness, higher granularity and
capability to handle higher data rate and longer trigger latency. The upgraded
IT will be composed of a barrel part, TBPX, as well as small and large forward
disks, TFPX and TEPX. The TEPX detector has four large disks on each end,
extending the coverage up to $\lvert \eta \rvert \approx 4.0$. In TEPX, the
modules are arranged in five concentric rings. In this contribution the new
TEPX detector will be presented, with particular focus on the mechanics design
and thermal performance, using finite element methods. Effects of the material
choice for the cooling pipes and disk support structures connecting the modules
with the CO$_2$ coolant are presented as well.
