Stability of high field superconducting dipole magnets

Superconducting dipole magnets of the window-frame type were constructed and operated successfully at Brookhaven National Laboratory. Examples of this type of magnet are the 6 T ''Model T'' magnet, and the 4 T 8/sup 0/ superconducting bending magnet. The latter magnet operated reliably since October 1973 as part of the proton beam transport to the north experimental area at the BNL AGS with intensities of typically 8 x 10/sup 12/ protons at 28.5 GeV/c passing through the magnet in a curved trajectory with the proton beam center only 2.0 cm from the beam pipe at both ends and the middle of each of the two units comprising the magnet. The energy in the beam is approximately 40 kJ per 3 ..mu..sec pulse. Targets were inserted in the beam at locations 2 m and 5.6 m upstream of the first magnet unit to observe the effects of radiation heating. The 8/sup 0/ magnet demonstrated ultrastability, surviving 3 ..mu..sec thermal pulses delivering up to 1 kJ into the cold magnet at repetition periods as short as 1.3 sec.