E. W. Otten

Final results from phase II of the Mainz neutrino mass searchin tritium \({\beta}\) decay

Abstract.This paper reports on the improved Mainz experiment on tritium

Nuclear magnetic resonance imaging with hyperpolarised helium-3

\beta

A solenoid retarding spectrometer with high resolution and transmission for keV electrons

spectroscopy which yields a 10 times higher signal to background ratio than before. The main experimental effects and systematic uncertainties have been investigated in side experiments, and possible error sources have been eliminated. Extensive data taking took place in the years 1997 to 2001. A residual analysis of the data sets yields for the square of the electron antineutrino mass the final result of

High precision measurement of the tritium β spectrum near its endpoint and upper limit on the neutrino mass

m^2(\nu_e) = (-0.6 \pm 2.2_{\mathrm{{stat}}} \pm 2.1_{\mathrm{{syst}}})

Nuclear radii and moments of unstable isotopes

eV2/c4. We derive an upper limit of

Spins, moments and charge radii of barium isotopes in the range 122–146Ba determined by collinear fast-beam laser spectroscopy☆

m(\nu_e)\leq 2.3

Realization of a broad band neutron spin filter with compressed, polarized 3He gas☆

eV/c2 at 95% confidence level for the mass itself.

Assessment of a single-acquisition imaging sequence for oxygen-sensitive 3He-MRI

BACKGROUND Magnetic resonance imaging (MRI) relies on magnetisation of hydrogen nuclei (protons) of water molecules in tissue as source of the signal. This technique has been valuable for studying tissues that contain significant amounts of water, but biological settings with low proton content, notably the lungs, are difficult to image. We report use of spin-polarised helium-3 for lung MRI. METHODS A volunteer inhaled hyperpolarised 3He to fill the lungs, which were imaged with a conventional MRI detector assembly. The nuclear spin polarisation of helium, and other noble gases, can be greatly enhanced by laser optical pumping and is about 10(5) times larger than the polarisation of water protons. This enormous gain in polarisation easily overcomes the loss in signal due to the lower density of the gas. FINDINGS The in-vivo experiment was done in a whole-body MRI scanner. The 3He image showed clear demarcation of the lung against diaphragm, heart, chest wall, and blood vessels (which gave no signal). The signal intensity within the air spaces was greatest in lung regions that are preferentially ventilated in the supine position; less well ventilated areas, such as the apices, showed a weaker signal. INTERPRETATION MRI with hyperpolarised 3He gas could be an alternative to established nuclear medicine methods. The ability to image air spaces offers the possibility of investigating physiological and pathophysiological processes in pulmonary ventilation and differences in its regional distribution.

VERY LONG NUCLEAR RELAXATION TIMES OF SPIN POLARIZED HELIUM 3 IN METAL COATED CELLS

Abstract 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 in the analyzing plane. It is typically 5 × 10 3 in our case. The spectrometer will serve first of all to investigate the limits of the rest mass of the electron antineutrino from 3 H 2 s-decay. It has been tested by measuring conversion lines from a 83m Kr source which yielded an energy of Eγ = 32151.5(11) eV for the corresponding nuclear transition.

Study of mechanical compression of spin-polarized 3He gas

Abstract The Mainz neutrino mass experiment investigates the endpoint region of the tritium β decay spectrum to determine the mass of the electron antineutrino. By the recent upgrade the former problem of dewetting T2 films has been solved and the signal-to-background-ratio was improved by a factor of 10. The latest measurement leads to m ν 2 =−3.7±5.3 stat ±2.1 sys eV 2 /c 4 , from which an upper limit of m ν eV/c 2 (95% C.L.) is derived. Some indication for the anomaly, reported by the Troitsk group, was found, but its postulated half year period is contradicted by our data.