First Operational Experience with the LHC Beam Dump Trigger Synchronisation Unit

Two LHC Beam Dumping Systems (LBDS) remove the counter-rotating beams safely from the collider during setting up of the accelerator, at the end of a physics run and in case of emergencies. Dump requests can come from 3 different sources: the machine protection system in emergency cases, the machine timing system for scheduled dumps or the LBDS itself in case of internal failures. These dump requests are synchronized with the 3 μs beam abort gap in a fail-safe redundant Trigger Synchronization Unit (TSU) based on a Digital Phase Locked Loop (DPLL), locked onto the LHC beam revolution frequency with a maximum phase error of 40 ns. The synchronized trigger pulses coming out of the TSU are then distributed to the high voltage generators of the beam dump kickers through a redundant fault-tolerant trigger distribution system. This paper describes the operational experience gained with the TSU since its commissioning with beam in 2009, and highlights the improvements, which have been implemented for a safer operation. This includes an increase of the diagnosis and monitoring functionalities and a more automated validation of the hardware and embedded firmware before deploying or executing a post-operational analysis of the TSU performance, after each dump action. In the light of this first experience the outcome of the external review performed in 2010 is presented. The lessons learnt on the project life cycle for the design of mission critical electronic modules are discussed.