  The Large Hadron Collider (LHC) at CERN is a 7 TeV proton synchrotron, with a
design stored energy of 362 MJ per beam. The high-luminosity (HL-LHC) upgrade
will increase this to 675 MJ per beam. In order to protect the superconducting
magnets and other sensitive equipment from quenches and damage due to beam
loss, a multi-level collimation system is needed. Detailed simulations are
required to understand where particles scattered by the collimators are lost
around the ring in a range of machine configurations. Merlin++ is a simulation
framework that has been extended to include detailed scattering physics, in
order to predict local particle loss rates around the LHC ring. We compare
Merlin++ simulations of losses during the squeeze (the dynamic reduction of the
\beta-function at the interaction points before the beams are put into
collision) with loss maps recorded during beam squeezes for Run 1 and 2
configurations. The squeeze is particularly important as both collimator
positions and quadrupole magnet currents are changed. We can then predict,
using Merlin++, the expected losses for the HL-LHC to ensure adequate
protection of the machine.
