Neutrino beams using the main injector

TM-1946 summarizes the status of the NuMI project. This note presents more details on the technical design of the various NUMI beams. Several beam]Line options are investigated for producing neutrinos--(l) a wide-band beam(WBB) using horns, (2) a beam using a single lithium Lens, and (3) a two stage narrow-band beam(NBB) using a Lithium Lens, quadrupoles and dipoles. The first two are designed to maximize the muon neutrino event rate; the third is designed to have a tunable range of parent momenta from 5-60 GeV/c. In the context of NuMI, the Double Horns-and its target were concepts first described in 1991. The lithium Lens has been used at Fermilab for pbar production for several years. With recent upgrades, it forms the basis of what will be used by NuMI. Narrow band beams using conventional dipoles and quadrupoles have been studied, but have less acceptance than one using a lithium lens. The following practical limits are imposed on each of the systems: (1) Horns: The necks will not have a smaller radius than 1 cm; the maximum current will not exceed 170 kAmp. Keeping the inside diameter large allows the primary proton beam to vary in position, yet not strike the fragile neck. In addition, there is a trade-off between decreasing the radius and increasing the wall thickness to maintain the required strength in the conductor material. (2) Magnets: Reasonable conventional designs are used. The maximum gradient for quadrupoles is 12 kG/half-aperture; the maximum field for dipoles is about 16 kG; larger apertures scale the gradients and fields downward. Although not a primary consideration, optically it is desirable for the magnification in each plane to be comparable (within a factor of 2 or 3 is OK). (3) Lithium Lens: The maximum radius is 1.0 cm with a maximum gradient of 100 kG/cm. (4) Dumps: At the place where the primary protons are absorbed, the transverse beam center is ∼ 1 inch off the edge of the acceptance