CLIQ Protection Design for the Graded Nb₃Sn Research Racetrack Dipole Demonstrator (R2D2)

The Research Racetrack Dipole Demonstrator (R2D2) is being studied as a demonstrating magnet for future FCC magnets. The R2D2 is meant to prove the feasibility of grading in block-coil Nb3Sn dipoles and explore quench behaviors at a very high current. This short model provides an opportunity to study quench protection concepts which will be needed for the full-scale FCC magnets. Both quench heaters and CLIQ (coupling loss induced quench) are under study. This paper presents the research work on the CLIQ protection. The work includes CLIQ design methods and configurations, and comparative studies of various CLIQ configurations for maximizing the CLIQ effectiveness. The results show that the most effective CLIQ configuration is able to quench 80% of the coil turns at the nominal current within 3 ms, leaving 20 ms for detection and validation time while keeping the maximum hotspot temperature within 350 K. The study shows that protection of R2D2 using only CLIQ may be feasible under certain assumptions.