Studies of magnetic shielding for phototubes

Abstract Phototubes associated with a Cherenkov counter, with a wall of scintillation counters for time-of-flight measurements and with a wall of lead glass blocks of an electro-magnetic calorimeter will operate in the fringe field of a superconducting solenoid in the GlueX experiment. The solenoid will be operated with a central magnetic field of ≈ 2.5 T . The maximum fringe field in the vicinity of the phototubes will be approximately 150 G . Various techniques for magnetic shielding of phototubes were studied using a 1-m diameter Helmholtz coil arrangement operated with a maximum central field of 200 G . Results are presented.