[en] Ba⁺ ions, confined in a r.f. quadrupole trap, were laser excited into the 6P₃sub(/)₂ state. Observation of the decay into the metastable 5D₃sub(/)₂ and 5D₅sub(/)₂ states yields the branching ratio R = [I(6P₃sub(/)₂ - 5D₅sub(/)₂)]/[I(6P₃sub(/)₂ - 5D₃sub(/)₂)] = 7.58 +-0.57. (orig.)

[en] The authors are designing a solenoid retardation spectrometer for the determination of the electron anti-neutrino rest mass from /sup 3/H β-decay similar to the proposal of Lobashev. The authors plan to use a tritium source in a high magnetic field (H/sub o/ ≅ 9 T) and an adiabatic transition into the low magnetic field of an electrostatic retardation spectrometer. The main advantages of the spectrometer proposed are: a large solid angle, high resolution, the use of atomic tritium as a source with well-defined final states, determination of spectral shape and endpoint energy of the spectrum. The latter will be very helpful in the future as there are experiments in progress with the aim to determine the /sup 3/H-/sup 3/He mass difference of about 1 eV. The problems associated with the proposal are: the magnetic confinement of tritium, background from tritium in the large volume of the detector, ionization of residual gas by trapped electrons. The status of the design and possible solutions to the problems mentioned are discussed

[en] At Mainz University a solenoid-retarding-spectrometer (SRS) for the investigation of the tritium β-spectrum close to the endpoint has been constructed. The performance of the apparatus has been tested with conversion electrons of ^83mKr. The measurements show that it reaches its design parameters of a resolution of E/E₀ = 5000 at an accepted solid angle of 40% of a 4π. First tests with a tritium source showed an excellent signal to background ratio. The improvement of the present m_ν limit should be possible in near future. (author) 6 refs., 4 figs

[en] This paper reports on precision measurements of conversion lines in the decay of ^83mKr with nuclear transition energies of 32.1 keV and 9.4 keV, respectively. The spectra were taken from a submonolayer surface of ^83mKr frozen onto a cold backing, using the new Mainz solenoid retarding spectrometer. The high luminosity and resolution of this instrument enables the observation of all allowed conversion lines up to the N-shell and to fully separate the elastic component from inelastic satellites. The combined analysis of the data yields the transition energies E_γ=32151.5±1.1 eV and 9405.9±0.8 eV, respectively. The experiment served also to pilote the application of this spectrometer to the question of a finite neutrino rest mass, searched for in the β-decay spectrum of tritium and to problems in precision electron spectroscopy in general. (orig.)

[en] With the compelling evidence for massive neutrinos from recent ν-oscillation experiments, one of the most fundamental tasks of particle physics over the next years will be the determination of the absolute mass scale of neutrinos. The absolute value of ν-masses will have crucial implications for cosmology, astrophysics and particle physics. We present the case for a next generation tritium β decay experiment to perform a high precision direct measurement of the absolute mass of the electron neutrino with sub-eV sensitivity. We discuss the experimental requirements and technical challenges of the proposed Karlsruhe tritium neutrino experiment (KATRIN) and outline its physics potential. (orig.)

[en] The KArlsruhe TRItium Neutrino experiment (KATRIN) aims to measure the electron neutrino mass with an unprecedented sensitivity of 0.2 eV/c², using β decay electrons from tritium decay. For the control of magnetic field in the main spectrometer area of the KATRIN experiment a mobile magnetic sensor unit is constructed and tested at the KATRIN main spectrometer site. The unit moves on inner rails of the support structures of the low field shaping coils which are arranged along the the main spectrometer. The unit propagates on a caterpillar drive and contains an electro motor, battery pack, board electronics, 2 triaxial flux gate sensors and 2 inclination senors. During operation all relevant data are stored on board and transmitted to the master station after the docking station is reached.

[en] Published in summary form only

[en] A new type of electron spectrometer is under construction at Mainz University that allows a measurement of the β-spectrum of tritium with high resolution and transmission in order to determine the neutrino rest mass. It consists of a source that contains atomic tritium, trapped in a high magnetic field, and a solenoid retarding spectrometer. (orig.)

[en] We have built an electrostatic electron spectrometer combining both high resolution and large luminosity. The instrument consists essentially of two superconducting solenoids separated by a system of ring electrodes of 4 m in length. Source and detector are placed in the high-field regions of the superconducting solenoids, whereas the repellent analyzing electrostatic potential of the ring electrodes peaks at the minimum of the magnetic field in between these solenoids. The magnetic guiding field provides (i) the acceptance of the full foreward solid angle of 2π, (ii) the transformation of the transverse cyclotron motion into longitudinal motion parallel to the magnetic field. The energy resolution of the electrostatic filter is determined by the ratio of the magnetic fields at the source and the analyzing plane. It is typically 5x10³ in our case. The spectrometer will serve first of all to investigate the limits of the rest mass of the electron antineutrino from ³H₂-β-decay. It has been tested by measuring conversion lines from a ^83mKr source which yielded an energy of E_γ=32151.5(11) eV for the corresponding nuclear transition. (orig.)

[en] Published in summary form only