W. Kündig

An upper limit for the mass of upsi;e from tritium β-decay

Abstract The endpoint region of the tritium β -spectrum has been measured with 27 eV resolution, using a magnetic spectrometer. The tritium activity was implanted into a thin layer of carbon. The υ e mass determined is consistent with zero with an upper limit of 18 eV, which includes instrumental and statistical uncertainties due to the energy loss in the source and the final electronic states.

An Upper Limit for the Mass of anti-electron-neutrino from Tritium beta Decay

Abstract The endpoint region of the tritium β -spectrum has been measured with 27 eV resolution, using a magnetic spectrometer. The tritium activity was implanted into a thin layer of carbon. The υ e mass determined is consistent with zero with an upper limit of 18 eV, which includes instrumental and statistical uncertainties due to the energy loss in the source and the final electronic states.

Measurement of the electron neutrino mass from tritium β-decay

Measurements of the tritium s-spectrum are reported. Thin sources consisting of a monolayer of tritiated hydrocarbon molecules were used. No indication of a nonzero mass mν of the electron antineutrino was found. The result is m2ν=−24 ± 48 ± 61 eV2 (1σ). An upper limit mν < 11 eV (95% confidence level) is derived.

Local magnetic field at a positive muon in ferromagnetic gadolinium

Abstract The local magnetic field at a stopped positive muon has been measured in polycrystalline gadolinium as a function of temperature between 20 K and the Curie point. The measurements show that the muon occupies the octahedral interstitial site and demonstrate the sensitivity of the muon as a probe of the local magnetic structure.

Magnetic and electronic properties of YBa2Cu3Ox (6.5 < x < 7.0) studied by muon spin rotation

Abstract A systematic study of the local magnetic field distribution p(B) in the perovskite-type superconductor YBa2Cu3Ox is presented. Special attention is given to the second moment 〈 ΔB2 〉 of p(B) which is closely related to the superconducting carrier density ns and the effective mass m ∗ of the superconducting carriers. The influence of temperature, anisotropy and hole doping are investigated in detail. It is found that the temperature dependence of the magnetic penetration depth in YBa2Cu3Ox is in agreement with conventional s-wave pairing and suggests strong coupling. The anisotropic behavior of p(B) is well described by a theory for uniaxial type II superconductors, with an anisotropy ratio γ ∼- 5(1). Moreover, the zero-temperature values λab(0) = 130(10) nm and λc(0) ∼- 500–800 nm (penetration depth for screening currents flowing in the ab-planes and along the c-axis, respectively) were extracted from our data. μSR experiments performed on oxygen deficient samples indicate that the structural and electronic properties of YBa2Cu3Ox are strongly correlated via the oxygen content x.

Muonium centers in the alkali halides

Muonium centers (Mu) in single crystals and powdered alkali halides have been studied using the high-timing-resolution transverse field μSR technique. Mu has been observed and its hyperfine parameter (HF) determined inevery alkali halide. For the rocksalt alkali halides, the HF parameter Aμ shows a systematic dependence on the host lattice constant. A comparison of the Mu HF parameter with hydrogen ESR data suggests that the Mu center is the muonic analogue of the interstitial hydrogenHi0-center. The rate of Mu diffusion can be deduced from the motional narrowing of the nuclear hyperfine interaction. KBr shows two different Mu states, a low-temperatureMuI-state and a high-temperatureMuII-state.

μSR in oxygen deficient YBa2Cu3O x (6.5⩽x⩽7.0)

A systematic μSR study of the local magnetic field distribution in a series of oxygen deficient YBa2Cu3Ox samples with 6.5⩽x⩽7.0 is reported. Special attention was given to perform the experiments under the same conditions, so that the oxygen content of the measured samples was the only parameter varied. The behavior of the depolarization rate σ as a function of the oxygen contentx was found to have strong similarities with the behavior of the critical temperatureTc as a function ofx. In particular, two step-like increases of σ were observed abovex=6.7 and 6.9. The temperature dependence of the normalized depolarization rate σ(T)/σ(0) is well described by the two-fluid model forx⩾6.781(1) and clearly deviates from this behavior forx⩽6.704(1). Our results are compared to those obtained by other groups.

MEASUREMENT OF THE GRAVITATIONAL CONSTANT G BY MEANS OF A BEAM BALANCE

Abstract We present a new method to measure the gravitational constant G with high precision by means of a beam balance. The gravitational field is generated by two movable tanks. They were filled with water as a test and are presently filled with mercury. In this article we explain principle and weighing technique and present first results.

Muon spin rotation experiments in α-Fe2O3 and Cr2O3

Abstract The behaviour of the stopped muons in the isostructural antiferromagnetic insulators α-Fe 2 O 3 and Cr 2 O 3 indicate a localized state below 500 K. Local fields and relaxation rates are measured and interpreted.

Search for heavy neutrinos in the β-spectrum of 63Ni

Abstract The β -spectrum of 63 Ni has been measured with high precision in order to search for effects of heavy neutrinos. For assumed neutrino masses in the range 4 to 30 keV, upper limits of 10 −3 or less are reported for the mixing probability.