Two alternate high gradient quadrupoles; an upgraded Tevatron IR and a "pipe" design

The present Fermilab IR quadrupole lenses achieve a 50% increase in gradient over their predecessors. This was accomplished by the following developments: (a) a more dense winding (Kapton insulation only, eliminating the fiberglass-epoxy), (b) an improvement in critical current density to J/sub c/(5T, 4.2K)=3 kA/mm/sup 2/ and (c) a higher aspect ratio cable >11/1 and (d) finer strand (0.53 mm diameter). The natural evolution of this design to the CERN 70 mm aperture quadrupole results in the following: (a) a reduction in operational temperature (4.8K-1.9K), (b) improvement of J/sub c/(10 T, 2.0 K)>2 kA/mm/sup 2/ and (c) a higher aspect ratio cable >13/1 and (d) finer strand (0.48 mm diameter). These two-layer designs should achieve the required operational gradient of 250 T/m with at least a 5% margin on the short-sample load-line intersection. These high current densities also require turn-off times <0.2 s after transition to the normal state. Such a short time requires an advanced protection heater design. The status of the design and the experimental development will be reported. New design concept quadrupole calculations are presented as well. This concept, using an active flux return is being proposed as a possible candidate design for a future higher gradient requirement.