MUCOOL MINUTES Friday 4/30/99 (Please report any errors to kaplan@fnal.gov.) I. Muon Capture ------------ Valery presented his proposal for a bunched muon beam using quadrupoles. The goal is several million muons/bunch. He starts with an 8-GeV proton beam incident on a current-carrying tungsten target followed by a lithium lens, then a FODO channel with interspersed RF modules at 805 MHz. He considered two options for the channel, one with a 60-degree phase advance per cell and the other with 90 degrees. The 90-degree cell has the advantage that two adjacent short quads essentially cancel each other so can be omitted, leaving more room for the RF modules. It accepts 3.4 times as many muons as the 60-degree option, over an emittance of 5 x 10^-3 pi m.rad. Since the muons are lower-momentum than the pions, the fields need to be scaled down to keep the muons channeled - he used a scaling factor of 0.866 relative to the nominal pion momentum. A 32m channel can be built using quads from the Brookhaven D2 beamline. About 70% of the pions decay within the channel at p_pi = 400 MeV. Steve asked about adding a bend to eliminate the pions and sign-select the muons. Valery said this would be bad because of the large dispersion it would introduce. II. More on Muon Capture -------------------- Nikolai presented his MARS simulation results based on Valery's "option 2." The target is 15 cm long and 1 cm in radius with a 5.88 T/cm field gradient, and the lens is 20.5 cm long with 8-cm radius and 0.1534 T/cm gradient. He considered pion momenta of 400 and 500 MeV. The 500-MeV tune gives more muons, about (1 - 3) x 10^-4 per proton on target, depending on the time structure of the booster beam. This meets the design goal given that the booster can provide 2e10 protons/bunch. Two booster bunch lengths were considered: 0 (which of course cannot be achieved in practice) and 30 cm, which we believe to be an overestimate since attempts to measure the length of a bunch gave < 1/4 ns (i.e. too small to be measured with the technique that was being used). Within the in-time bucket, the channeled beam is mostly mu- in the 500-MeV simulation, with 19% pi-, 8% mu+ and 4% pi+. The mean kinetic energies in MeV are 406 (mu-), 455 (mu+), 555 (pi-), and 483 (pi+). Steve asked how this could be cleaned up. Presumably in addition to the particles just mentioned there will also be lots of uninteracted full-energy protons. Ideas suggested: tilt the target by perhaps 20 - 30 mr, maybe with no current, absorb the hadrons in material. III. Summary of Optics Meeting ------------------------- At the Optics meeting on 4/26 Weishi Wan presented his COSY results on a toy emittance-exchange section consisting of 2 solenoids, a dipole, 2 more solenoids, and a wedge. Readers are directed to Paul's minutes for the details. Weishi will try to put in a bent solenoid next.