Quench Detection Method for the Inductively Coupled Superconducting Magnets of KATRIN

The next-generation neutrino mass experiment KATRIN uses series of superconducting magnet systems. For the protection of the inductively coupled magnets of KATRIN, a distinct quench detection is essential. For example, the Cryogenic Pumping Section (CPS) of KATRIN has seven superconducting solenoids that are electrically connected in series. The quench detection for the magnet system is not trivial, because the inductive coupling effect between neighboring solenoids is not negligible, although the coupling coefficients are small and below 0.04. The electrical simulations show that a quench in the neighboring magnets can cause a high unbalancing signal in the quench detection system of the CPS, without inducing a quench in the CPS magnets. Therefore, a concept for the identification of a quench in one of the CPS magnets has been developed, using a combination of a global detector and two or more detectors based on the conventional bridge method and a programmable logic controller. This distinct quench detection helps activating quench heater effectively and minimizing unnecessary loss of liquid helium and operation time. This paper describes the concept of the quench detection method for the inductively coupled superconducting magnets of the CPS.