G. H. Eaton

Measurement of the 1s-2s energy interval in muonium

The 1s-2s interval has been measured in the muonium (&mgr;(+)e(-)) atom by Doppler-free two-photon pulsed laser spectroscopy. The frequency separation of the states was determined to be 2 455 528 941.0(9.8) MHz, in good agreement with quantum electrodynamics. The result may be interpreted as a measurement of the muon-electron charge ratio as -1-1.1(2.1)x10(-9). We expect significantly higher accuracy at future high flux muon sources and from cw laser technology.

The RIKEN-RAL pulsed Muon Facility

Abstract RIKEN has constructed a pulsed muon facility at Rutherford Appleton Laboratory (RAL) in the UK under an international collaboration between RIKEN and RAL to promote muon science. We have confirmed that the facility produces a pulsed decay muon beam as well as a pulsed surface positive muon beam with the highest instantaneous intensity in the world and initiated the muon science research program, which includes muon catalyzed fusion, since June 1995.

Commissioning of the Rutherford Appleton Laboratory pulsed muon facility

Abstract The pulsed muon channel of the ISIS facility at the Rutherford Appleton Laboratory has been successfully commissioned as a tool for μSR research using polarised surface muons and for experiments requiring negative cloud muons. The beam line is described and the present performance given. At the present time, the pulsed muon beam gives 105 μ+/s (2000 μ+/pulse) with very thin production targets (2.5 mm thick carbon) and 30% of the ISIS design proton current. μSR test spectra demonstrate the capability of the source and instrumentation, the performance relative to the continuous sources at the meson factories, and the potential for new science.

New RIKEN-RAL pulsed µCF facility and X-ray studies on DT-µCF

In November 1994, the construction of a new superconducting muon channel of the RIKEN-RAL muon facility at ISIS of Rutherford Appleton Laboratory was completed. Subsequently, important features, such as the highest instantaneous intensity with a single-pulse structure and a high purity have been confirmed. Along with the installation of advanced µCF experimental equipment, including a high-purity D-T mixture target system with an in situ3He removal capability and a 4 T confinement magnet, an advanced µCF experiment, e.g. a precise X-ray measurement on µ-α sticking in dtµ-µCF will be realized. An account of the commissioning experiments, a plan for the earliest phase of the µCF experiment and possible future directions are reported.

A MEASUREMENT OF THE 1S-2S TRANSITION FREQUENCY IN MUONIUM

Doppler-free two-photon laser spectroscopy has been employed to measure the 12S12−22S12 transition in the muonium atom (μ+e−). A value of 2 455 529 002(33) (46) MHz has been obtained, which agrees with QED calculations within two standard deviations. The Lamb shift contributions are tested to the level 8×10−3. The corresponding measurements in hydrogen and deuterium using the same apparatus and laser system provide a test of the applied systematic corrections and have verified the systematic error of 46 MHz quoted. The mass of the positive muon has been derived from the isotope shift in this transition and yields a value of 105.65880(29)(43) MeVc2.

Construction of Riken-ral muon facility at ISIS and advanced μSR

By utilizing the intense pulsed proton beam available at the ISIS facility of RAL, the new muon facility project of an advanced superconducting muon channel funded by the RIKEN is now under construction. The new facility, by adopting the superconducting solenoid system, will produce the strongest backward decay pulsedμ+ orμ−in the momentum range from 20 MeV/c to 120 MeV/c. Also, by adopting the pulsed magnetic kicker, each one of two muon pulses will be supplied to two extraction channels simultaneously. Various important muon science experiments including advanced pulsedμ−SR andmu+SR experiments will be realized.

Positive muon data analysis at ISIS

The pulsed surface muon beam of the Rutherford Appleton Laboratory is well suited to performing μSR measurements in zero and low magnetic fields with the longitudinal set-up. In this paper we describe our data analysis procedure and the effect of the collimation on the spectra. The determination of the efficiency ratio of the telescopes is discussed. We point out that for some measurements it is important to take into account the muon beam structure properly.

Fast E-field switching of a pulsed surface muon beam: The commissioning of the European muon facility at ISIS

Abstract The ISIS pulsed muon facility at RAL has been upgraded by the inclusion of a fast E -field kicker which simultaneously divides and distributes the muon pulses at surface momentum to the three experimental areas at a repetition rate of 50 Hz. This upgraded facility has been successfully commissioned in conjunction with a new μSR spectrometer. It has been shown that this new spectrometer can operate as expected with a figure of merit for μSR experiments similar to that of the original spectrometer, in spite of receiving only half of the relative muon intensity. This twofold increase in experimental capability will be further increased in the near future by the incorporation of experimental equipment in the third beamline. Such a facility will be capable of satisfying a European wide demand for μSR research with pulsed surface muons.

Muon catalyzed fusion and muon to 3He transfer in solid T2 studied by X-ray and neutron detection

X-ray and neutron measurements were carried out for muon catalyzed fusion and related phenomena in solid T2. The X-ray originated from the μ- to α sticking in muon catalyzed fusion; t + t + μ-→ (μ-α) + 2n was measured for the first time, yielding Kα X-ray intensity of (μα) atom and the intensity ratio of Kβ to Kα. Utilizing the phenomena of 3He accumulation in solid T2, the X-ray in the μ- transfer process from (tμ) to 3He was detected, providing a formation rate and radiative decay branching-ratio of (t3Heμ) molecule. From fusion neutron measurements, estimated values were obtained for (ttμ) molecular formation rate as well as sticking probability ωt in ttμ fusion. A possible new insight in t + t fusion reaction process at a low energy limit is also obtained.

MEASUREMENTS OF 3HE ACCUMULATION EFFECT ON MUON CATALYZED FUSION IN THE SOLID/LIQUID DT MIXTURES

Abstract An effect on the muon catalyzed fusion (μCF) of the 3He originating from the tritium decay was studied by measuring the time-dependent change of the fusion-neutron disappearance rate (λn) in the deuterium and tritium (DT) mixtures with various tritium concentrations, C t =0.1, 0.2, …, 0.7 . A clear difference between the solid and the liquid DT mixtures due to the 3He accumulation effect was observed: in solid λn increased with the time after solidification, whereas in liquid λn did not change. This indicates that 3He produced in the solid DT mixtures is trapped. Admitting that all the 3He remain in solid, the muon transfer rate from tμ to 3He is determined to be about 4×109 s−1, consistent with the theoretical prediction.