A superconducting iron-dominated quadrupole for CEBAF

The current design for the high-resolution spectrometers at CEBAF (Continuous Electron Beam Accelerator Facility) requires a front quadrupole that has a gradient * length of 6.8 T with a 'good field' aperture (1*10/sup -3/ uniformity in gradient) of 16 cm radius. A room-temperature design was found too power hungry and interferred with the beam. Engineering and construction of a small cos 2 theta magnet was considered to be quite expensive. A Panofsky design was not considered due to the extreme sensitivity of the field quality to errors in conductor placement. A conformal mapping of a window-frame dipole into quadrupole geometry worked well. A conceptual design has been developed with the following characteristics: physical length (total)=1.2 ; iron length=1.1 m; iron outer dimensions=54 cm*80 cm; peak gradient=6.2 T/m; pole radius=20 cm; 'good field' radius=16 cm; coil peak field=1.5 T; conductors=1 mm diameter; Cu/NbTi=7:1; current=400 A; turns=250/quadrant; and stored energy=50 kJ.<>