A chopped high intensity muon beam at the Stopped Muon Channel at LAMPF

High Precision Measurements of the Ground State Hyperfine Structure Interval of Muonium and of the Muon Magnetic Moment

“…Then using (4), (5), and measurements of the transition frequencies n 12 and n 34 , we extract Dn and m m ͞m p for positive muons [3].…”

“…These were transported to the experimental apparatus by the stopped muon channel (SMC) [4], which was tuned to accept m 1 of 28 MeV͞c which were nearly 100% polarized, had a FWHM Dp͞p of 10%, and yielded an average intensity of a few 310 7 m 1 ͞s. Impurities in the beam were reduced by gas barriers and an E 3 H separator which reduced the ratio e 1 ͞m 1 in the beam from about 10 to 0.03 [5].…”

“…Observing "old muonium" atoms which have lived several times longer than t m while interacting coherently with the microwave magnetic field results in narrower lines with larger signal amplitude. This was achieved through the use of an E field chopper [5] which modulated the m 1 beam with a 4 ms beamon period followed by a 10 ms beam-off period, during which the beam was nearly 99% extinguished. Decay positron counts were accumulated in eleven 0.95 ms wide windows, with each successive window observing increasingly old muonium atoms.…”