Progress in absorber R & D for muon cooling

≈ 10mm·rad and 200MeV/c muon momentum) and a 10–15% packingfractionofabsorberwithin thecoolingchannel, thecoolingrateofEq. 1impliestransverse emittance reduction by a factor 1/e in ≈ 50m, about 3% of themuon decay length. In practice, with β ≈ 20 − 50cm, one does a factor ≈ 2worse than this because of scattering and other effects [2].To minimize the effects of Coulomb scattering of the muons as they passthrough the absorber, it has been proposed to use liquid hydrogen (LH