LHC Beam Dump System: Analysis of beam commissioning, performance and the consequences of abnormal operation

The LHC accelerates proton beams to a momentum of up to 7 TeV/c. At this energy level and with nominal beam intensity the stored energy of 360 MJ per beam is sufficient to melt 500 kg of copper. In addition up to 10 GJ are stored within the LHC magnet system at top energy. It is obvious that such a machine needs well designed safety and protection systems. The LHC Beam Dump System (LBDS) is such a system and one of the most critical once concerning machine protection and safe operation. It is used to dispose of high intensity beams between 450 GeV and 7 TeV and is thus designed to fast extract beam in a loss free way and to transfer it to an external absorber. For each ring systems of 15 horizontal fast kicker magnets (MKD), 15 vertically deflecting magnetic septa (MSD) and 10 diluter kicker magnets (MKB) are installed. This thesis is concerned with the analysis of the LBDS performance under normal operating parameters as well as under abnormal conditions like in the event of asynchronous beam abort or missing MKD elements. Therefore a sophisticated simulation environment was developed based on the use of the MAD-X tracking code. A system of tracking jobs was set up to study failure cases and losses for various dump events. Those jobs can be distributed to available CPU power and be calculated in parallel. Studies into the consequences of abnormal beam dump actions have been performed. Different error scenarios have been evaluated including an asynchronous dump action, prefire cases, and the impact of different orbit and collimator settings. Losses at locations in the ring and the beam dump transfer lines have been quantified as a function of different settings of the dump system protection elements. The implications for the setup and operation of these protection elements are discussed. Particle distributions can be created according to the used orbit. Simulations with different orbit parameters (including magnet field errors, beam position read out errors, misalignments, mechanical apertures and tolerances) as well as different collimator settings for the TCDQ protection system in IR6 can be done in parallel, considering time dependent kicks as applied for the fast MKD and MKB magnets with a 5ns resolution. The developed architecture allows simulating on the basis of realistic machine settings and allowed to verify in a first step some safety relevant LBDS design parameters already before the actual beam commissioning started. The results obtained show that the LBDS is very well designed, with sufficient margin to accept the failure cases which are expected to happen during its operation. Eventual partial beam losses during abnormal operation parameters are discussed. The future precise validation of simulation results will allow to use such techniques to evaluate safety and operation parameter settings for higher energy levels. This is particularly interesting as machine development and measurement at top energy is time consuming due to long beam generation cycles as well as it is a concern of machine safety. Hence simulations can give useful starting points to minimize the measurement effort.