High-field superconducting window-frame beam-transport magnets

The window-frame design for high field superconducting beam transport magnets was first applied to two, 2 m long, 4 T modules of an 8° bending magnet which has operated for nine years in the primary proton beam line at the Brookhaven National Laboratory Alternating Gradient Synchrotron (AGS). The design of two 1.5 m long, 7.6 cm cold bore superconducting window-frame magnets, described in this paper, intended for the external proton beam transport system at the AGS incorporated evolutionary changes. These magnets generated a maximum aperture field of 6.8 T with a peak field in the dipole coil of 7.1 T. Measured fields are very accurate and are compared to values calculated using the computer programs LINDA and POISSON. Results of quench propagation studies demonstrate the excellent thermal stability of the magnets. The magnets quench safely without energy extraction at a maximum current density, J = 130 kA/cm2in the superconductor, correspoding to J = 57.6 kA/cm2overall in the conductor at B = 6.7 T.