Modelling and Analysis of the Electrical and Thermal Transients following the Quench of a Superconducting Electromagnetic Coil within the Large Hadron Collider’s Inner Triplet System

Operators of complex machinery must always think ahead to consider possible future operational threats to, or limitations of, the system. With this in mind, the ability to simulate and analyse the system in operation under potentially dangerous scenarios can be very useful, as it can make important predictions regarding its stability and safety. The following report details the work completed, by the author, while working with the Performance Evaluation Section of the Machine Protection and Electrical Integrity Group of the Technology Department (TE-MPE-PE) at the European Organization for Nuclear Research (CERN), from June 2011 to December 2011. The main aim of the project was to design and construct a circuit model of a magnet powering system, specifically the Inner Triplet System (ITS) currently in use within the Large Hadron Collider (LHC), which had to be capable of accurately simulating the electrical and thermal transients following a quench within one of the system’s superconducting magnet coils. The model was then to be used for the simulation and analysis of future, potentially dangerous, scenarios. After the initial research and acquisition of relevant information, the design methods used involved: the modelling of the electrical circuit using Cadence® Allegro® Design Entry HDL (DEHDL) circuit design and modelling software; the simulation of the ITS system in operation using Cadence® Allegro® AMS simulator; the comparative analyses of simulated data with that of measured data using MathsWorks® MATLAB®; and the subsequent refining of the circuit model and the repetition of comparative analyses until accurate to within a specified accuracy tolerance. The resultant comparative analyses of simulation data with recorded data proved that the constructed model could simulate the desired system scenarios to well within the required levels of accuracy. Subsequent analyses of a quench in the system, running at close to maximum allowable currents, predict that the system’s magnet would ‘self-protect’ and the system would remain stable under these circumstances. However, in analysing scenarios in which a vital aspect of the system were to fail, catastrophic misdirection of current occurs and further analysis of these plausible events is called for. With the successful completion of the specified aims, it can be concluded that DEHDL software can be used to adequately model the electrical and thermal transients following a quench in a high energy, complex powering system, containing superconducting magnets. It also follows that the circuit model is now available for future use when attempting to understand unexplained events occurring within the system or for the prediction of the system’s stability and safety under particular scenarios.