The Consequences of Abnormal Beam Dump Actions on the LHC

The consequences of abnormal LHC beam dump actions on the collimation system are evaluated. We consider both an asynchronous beam dump, where all 15 kicker modules fire together, and the pre-firing of one kicker module, followed by the firing of the remainder. The frequency of such failures is difficult to predict. It is assumed that they will happen at least once per year. Using the measured kicker field waveform, the expected beam impact on the collimators is calculated. It is shown that a total of 20 nominal LHC bunches can impact on a single collimator jaw, within a transverse area of about 1 mm (full width) 200 m (rms). Due to the uneven horizontal distribution a peak impact of about 6 nominal bunches can occur in the first 200 m from the edge of the collimator jaw. The design of a collimation system able to withstand such an impact appears difficult.1