Protection Strategy and Quench Study of MCBXF Magnets

Nested combined orbit correctors are needed for the upgrade of LHC. They are developed at CIEMAT, in collaboration with CERN in the framework of HL-LHC project. There are two types of magnets, so-called MCBXFA and MCBXFB, with different lengths (2.5 and 1.5 m, respectively), but sharing the same cross section. The coils of both magnets are wound with the same Rutherford-type NbTi cable, composed of 18 strands of 0.48 mm diameter, insulated with a braided glass fiber sleeve. Various magnet protection schemes were considered for MCBXF magnets. In this work, self-protection, energy extraction resistor and quench heaters are discussed emphasizing advantages and disadvantages of each strategy. This analysis is supported by quench calculations performed with Squid (CIEMAT in-house developed code) and Roxie. Selected quench simulation results are presented and compared with measurements done on magnet prototypes. Based on the presented study, a protection scheme with energy extraction resistor was selected for the series magnets. The value of the resistor was optimized and related quench calculations are also included.