Coil failure effect in geomagnetic field compensation for particle detectors

Photomultiplier tubes (PMTs) in large Cherenkov detectors suffer from efficiency loss due to the Earth’s geomagnetic field, which alters electron trajectories. Active compensation using current-carrying coils is an effective solution but is susceptible to failures that can compromise the homogeneity of the compensated field and degrade detector performance. This study systematically analyzes the impact of individual coil failures on geomagnetic compensation, focusing on key evaluation parameters: the proportion of PMTs exposed to residual perpendicular magnetic field exceeding acceptable limits ( P₁₀₀ P 100 ) and the average residual perpendicular field ( < Bₚₑᵣₚ> < B perp > ). Furthermore, a fail-safe connection system utilizing multi-core cables and external reconnection points is introduced, mitigating the effects of coil malfunctions and ensuring more stable long-term performance of large-scale detectors.