P. O. Egan

Development of a low-momentum “surface” muon beam for LAMPF☆

Abstract A low momentum positive muon beam has been developed at LAMPF, utilizing muons which originate from pion decays at rest near the surface of the pion production target and are transported by the LAMPF stopped muon channel. The muon beam has a total flux of 2.5 × 104μ+ per s per μA of a proton beam (8 × 106μ+ s−1 for the present operating current at LAMPF of 300 μA), an extremely narrow range spread of 50 mg/cm2 in CH2, and a positron contamination (e+/gm+) of 60%.

Low Energy Positron Production at the Livermore Linac

Beams of monoenergetic positrons with energies of a few eV to many keV have been used in experiments in atomic physics, solid state physics and materials science. The results of some of these experiments are given and the production of positron beams from a new source, an electron linac, is described. Intense, pulsed beams of low-energy positrons have been produced by a high-energy beam from an electron linac. The production efficiency for low-energy positrons has been determined for electrons with energies from 60 to 120 MeV. Low-energy positron beams produced with a high energy electron a linac can be of much higher intensity than those beams currently derived from radioactive sources. These higher intensity beams will make possible positron experiments previously infeasable.

Development of "subsurface" positive muon beam at LAMPF

A very low momentum, high purity positive muon beam has been developed at LAMPF, utilizing muons which originate from pion decays at rest in the target for the primary proton beam and are transported by the LAMPF stopped muon channel. The channel is tuned to transport muons with momenta as low as 3 MeV/c and hence selects muons originating some distance below the target surface (subsurface muons). A static E × B separator largely eliminates the e+ component in the beam.

Intense Positron Beams: Linacs

Beams of monoenergetic positrons with energies of a few eV to many keV have been used in experiments in atomic physics, solid state physics and materials science. The production of positron beams from a new source, an electron linac, is described.

Flash ADC time‐of‐flight spectrometer

We describe a time‐of‐flight spectrometer based on the direct readout of a 7‐bit, 15‐MHz flash ADC. The wide dynamic range of this device leads to several advantages over conventional time‐of‐flight methods, particularly with regard to noise reduction. The performance of a CAMAC‐based flash ADC/RAM unit for low‐energy electron time‐of‐flight measurements is described.

A precise microwave spectroscopy measurement of the muonium ground state: hyperfine structure interval and muon magnetic moment

An experiment is in progress at the Los Alamos Meson Physics Facility (LAMPF) to determine with high precision the hyperfine structure interval /spl Delta/v (to /spl sim/10 ppb) and the muon to proton magnetic moment ratio /spl mu//sub /spl mu////spl mu//sub p/(to /spl sim/60 ppb) in the ground state of muonium (/spl mu//sup +/e/sup -/). These precision goals correspond to increases in precision of /spl Delta/v and of /spl mu//sub /spl mu////spl mu//sub p/ by about a factor of 5 compared to present knowledge.