The compensating magnet for the Zeus detector

A bath-cooled superconducting solenoid with a 280-nm-diameter warm bore, a coil length of 1200 mm, and a central field of 5 T at the rated current of 950 A has been built. It will operate as the compensating coil inside the Zeus detector at HERA (the Hadron Electron Ring Accelerator) at Desy. The coil is shielded by a 3.5-ton low carbon steel cold yoke, and the cold helium chamber was designed to withstand a maximum pressure of 20 bar. The main results obtained during the cool down and energization are reported.