We measured the neutron decay lifetime by counting in-beam neutron decay recoil protons trapped in a quasi-Penning trap. The absolute neutron beam fluence was measured by capture in a thin (6)LiF foil detector with known efficiency. The combination of these measurements gives the neutron lifetime: τ n = (886.8 ± 1.2 ± 3.2) s, where the first (second) uncertainty is statistical (systematic) in nature. This is the most precise neutron lifetime determination to date using an in-beam method.

The muon g-2 experiment at Brookhaven National Laboratory has the goal of determining the muon anomalous g-value aμ(=(g−2)/2) to the very high precision of 0.35 parts per million and thus requires a storage ring magnet with great stability and homogeniety. A superferric storage ring with a radius of 7.11 m and a magnetic field of 1.45 T has been constructed in which the field quality is largely determined by the iron, and the excitation is provided by superconducting coils operating at a current of 5200 A. The storage ring has been constructed with maximum attention to azimuthal symmetry and to tight mechanical tolerances and with many features to allow obtaining a homogenous magnetic field. The fabrication of the storage ring, its cryogenics and quench protection systems, and its initial testing and operation are described.

Harmonic potentials can be produced in cylindrical ion traps by means of dynamic orthogonalized anharmonicity compensation with use of two (or multiple) sets of compensation electrodes. One special example is for traps with multiple identical electrodes which are not only easy to construct and allow access to the center region of the trap for particle loading and releasing, laser beams, and microwaves, but also flexible in forming harmonic potential wells in many locations. The nested trap configuration and the side-by-side trap configuration are readily available in this special scheme. Analytical solutions for cylindrical traps with multiple sets of compensation potentials are presented. This work will be useful for studies involving Penning trap diagnostics, atomic and molecular interactions (including the production of antihydrogen atoms), accurate mass measurements of exotic particles, and precision measurements of the spin precession frequencies of trapped particles.

We have developed a NMR standard probe using a spherical pure water sample of 1 cm diameter to determine the absolute magnetic field B in terms of the free-proton NMR frequency fp with an accuracy of 3.4 × 10−8. Our standard probe can be used conveniently to calibrate other probes in the field range from 1.45 to 1.7 T and can readily be employed over a much wider field range. The probe design and the tests carried out to verify its precision and accuracy are presented.

Resonance line narrowing up to 1/2 of the natural linewidth has been observed for microwave magnetic-resonance transitions between Zeeman levels of ground-state muonium at a strong magnetic field of 1.7 T. The observed lines are in good agreement with predicted line shapes and are useful for a precision determination of Delta nu and mu(mu)/mu(p).

The authors have designed and constructed a special NMR standard probe using a spehrical pure water sample to determine the free proton NMR frequency f{sub p} at high field and an accuracy of 0.04 ppm has been achieved. Since the proton gyromagnetic ratio {gamma}{sub p} is less well known ({approx}0.1 ppm), the free proton NMR frequency measured by the probe may serve as a calibration standard for the magnetic field B. The standard probe can be used at various magnetic field values without introducing any additional magnetic perturbations. The probe is designed in such a way that a cylindrical sample or a small NMR probe can be inserted to replace the 1 cm diameter spherical water sample for systematic studies. Other NMR probes can be calibrated easily against the standard probe using a calibration form. Results will be presented and discussed.

Electric charges carried by positive and negative muons in units of an electric charge, e(mu+)/e = 1+/-1X10(-7) and e(mu-)/e = -1+/-2X10(-5), are derived from the theoretical and experimental values of the ground-state hyperfine-structure intervals Delta nu in muonium and muonic helium atoms as tests of electric-chage quantization for muons. These results also provide a test of CPT symmetry for positive and negative muon charges, with an accuracy of 2 parts in 10(5). Further improvements can be made from more precise theoretical and experimental values for Delta nu in muonium and muonic helium atoms with the approach described in this paper.

A chopped positive muon beam with high intensity, low momentum, and high purity has been developed at LAMPF using a high voltage chopper system. The rise and fall times of the chopped muon beam are approximately 100 ns, the repetition rate extends up to 100 kHz and the extinction ratio for muons is 0.3%. The beam chopper system is described and the test results are presented. This chopped high intensity μ+ beam is to be used to achieve resonance line-narrowing in a precision microwave spectroscopy experiment on muonium.