Maximum Current Ramp Rates, Required Accuracies and Protection for the Corrector Circuits

Although single corrector magnets are designed to be self-protected in case of a quench, the protection of some arc corrector magnets connected in series requires the installation of resistors parallel to the magnet to avoid overheating of the super-conducting wire or an unacceptable voltage level. The installation of a parallel resistor has an impact during the current ramp as a leakage current flows via the resistor due to the inductive voltage over the magnet. The required ramp rates and accuracy of the corrector excitations have been evaluated to check whether the leakage current is acceptable. If the leakage current is too high the power converter control might have to compensate for this effect. The additional heat load that appears due to the leakage current must be considered and stay within the allowed cryogenic-power budget. This note summarises the maximum current ramp rate and accuracies as well as the required value of parallel protection resistors for the LHC corrector circuits (MCS, MS, MQT, MQTL). The individually powered closed-orbit correctors and inner triplet corrector magnets are not mentioned in this note, as these magnets do not require parallel resistors for the protection.