Vol. 31 - Crystal Collimation for LHC

Future upgrades of the CERN Large Hadron Collider (LHC) may demand improved cleaning performance of its collimation system. Very efficient collimation is required during regular operations at high intensities, because even a small amount of energy deposited on superconducting magnets can cause an abrupt loss of superconducting conditions (quench). The present collimation system has accomplished its tasks during the LHC Run I very well, where no quench with circulating beam took place with up to 150 MJ of stored energy at 4 TeV. On the other hand, uncertainty remains on the performance at the design energy of 7 TeV and with 360 MJ of stored energy. In particular, a further increase up to about 700 MJ is expected for the high luminosity upgrade (HL-LHC), where improved cleaning performance may be needed together with a reduction of collimator impedance. The possibility to use a crystal-based collimation system represents an option for improving both cleaning performance and impedance compared to the present system. A bent crystal can in theory replace primary collimators and steer all halo particles onto one single absorber, providing better cleaning with reduced impedance than the present multi-stage collimation system, which is based on massive amorphous blocks of material that surround the beam. Although promising results on the principle of crystal collimation were obtained during experimental tests at the CERN Super Proton Synchrotron (SPS), feasibility studies at the LHC are mandatory before relying on this approach for future upgrades. The main goal of this Ph.D. thesis is the design of an optimised prototype crystal collimation system for these tests in the LHC, which has been installed during April 2014.