MERLIN for High Luminosity Large Hadron Collider Collimation

The large hadron collider (LHC) uses the most energetic and highest luminosity
man made proton beams on Earth. The high luminosity (HL-LHC)
[1] upgrade aims to increase the levelled luminosity of the LHC by a factor
of five, to 5 · 1034cm−2
s
−1
, by increasing the bunch population from 1 to
2.22·1011 protons, and decreasing emittance, and β
∗
. Thus the stored beam
energy increases from ≈ 362 MJ to ≈ 675 MJ per beam.
All synchrotrons encounter unavoidable proton losses. Protons that populate
the beam halo pose a threat to the performance and lifetime of certain
hardware, such as superconducting magnets, which in the LHC may be
quenched by an impact of ≈ 1 · 106 protons [2]. A multi stage collimation
system must operate at an efficiency such that no more than 2 · 10−5% of
protons incident on collimators may escape and impact upon these magnets
[3].
To predict and protect against proton losses in the HL-LHC, collimation
simulations must be performed. MERLIN, a C++ accelerator physics library,
has been updated to carry out such simulations for the HL-LHC.
Novel materials such as molybdenum graphite have been investigated as
collimator materials, and a novel technique - collimation enhancement via
a hollow electron lens (HEL) - has been studied. Using detailed simulations
the performance and operation of possible collimation upgrades are
explored.