A four-meter long superconducting magnetic flux exclusion tube for particle physics experiments

The design and construction of a field-free channel through the transverse central magnetic field of a 54 inch aperture magnet is described. This flux-free path is an essential part of an experiment at the Stanford Linear Accelerator Center to measure the electron production of neutral rho mesons. The flux exclusion tube itself is made of Nb3Sn tape bonded with lead-tin solder to form a rigid tube of laminated superconducting material, approximately four meters long and from 6 to 25 mm in diameter. The transverse magnetic field shielded exceeds 1.5 T. The performance of the tube and its associated cryostat is discussed.