In this contribution, we review the status and perspectives of direct neutrino mass experiments, which investigate the kinematics of β-decays of specific isotopes (3H, 187Re, 163Ho) to derive ...model-independent information on the averaged electron (anti)neutrino mass. After discussing the kinematics of β-decay and the determination of the neutrino mass, we give a brief overview of past neutrino mass measurements (SN1987a-ToF studies, Mainz and Troitsk experiments for 3H, cryobolometers for 187Re). We then describe the Karlsruhe Tritium Neutrino (KATRIN) experiment currently under construction at Karlsruhe Institute of Technology, which will use the MAC-E-Filter principle to push the sensitivity down to a value of 200 meV (90% C.L.). To do so, many technological challenges have to be solved related to source intensity and stability, as well as precision energy analysis and low background rate close to the kinematic endpoint of tritium β-decay at 18.6 keV. We then review new approaches such as the MARE, ECHO, and Project8 experiments, which offer the promise to perform an independent measurement of the neutrino mass in the sub-eV region. Altogether, the novel methods developed in direct neutrino mass experiments will provide vital information on the absolute mass scale of neutrinos.
We present the idea and proof of principle measurements for an angular-selective active filter for charged particles. The motivation for the setup arises from the need to distinguish background ...electrons from signal electrons in a spectrometer of MAC-E filter type. While a large fraction of the background electrons exhibit predominantly small angles relative to the magnetic guiding field (corresponding to a low amount of kinetic energy in the motion component transverse to the field lines, in the following referred to as transverse energy) and pass the filter mostly unhindered, signal electrons from an isotropically emitting source interact with the active filter and are detected. The concept is demonstrated using a microchannel plate (MCP) as an active filter element. When correctly aligned with the magnetic field, electrons with a small transverse energy pass the channels of the MCP without interaction while electrons with large transverse energies hit the channel walls and trigger an avalanche of secondary electrons that is subsequently detected. Due to several drawbacks of MCPs for an actual transverse energy filter, an alternative detection technique using microstructured Si-PIN diodes is proposed.
The KATRIN experiment aims to determine the neutrino mass scale with a sensitivity of 200
meV
/
c
2
(90% C. L.) by a precision measurement of the shape of the tritium
β
-spectrum in the endpoint ...region. The energy analysis of the decay electrons is achieved by a MAC-E filter spectrometer. To determine the transmission properties of the KATRIN main spectrometer, a mono-energetic and angular-selective electron source has been developed. In preparation for the second commissioning phase of the main spectrometer, a measurement phase was carried out at the KATRIN monitor spectrometer where the device was operated in a MAC-E filter setup for testing. The results of these measurements are compared with simulations using the particle-tracking software “Kassiopeia”, which was developed in the KATRIN collaboration over recent years.
More than 80 years after the prediction of their existence, there are still many open questions regarding the nature and properties of neutrinos. Among these questions is the issue of neutrino mass. ...While oscillation experiments have proven that neutrinos possess non-zero masses, these measurements cannot determine the absolute mass scale. Information on absolute neutrino masses can be deduced either from cosmological observations of large scale structure formation, from the search for neutrino-less double β-decay or from the study of the kinematics of weak decays. While the first two methods are subject to model dependencies or rather large systematical uncertainties, measurements based on the kinematics of nuclear β-decay or electron-capture reactions offer a model-independent way to determine the neutrino mass. This paper provides an overview of status and sensitivities of direct neutrino mass experiments currently under construction (KATRIN, MARE) or in development (Project 8, ECHO).
An optical technique to study the longitudinal distribution of ions in a bunched ion beam circulating in a storage ring is presented. It is based on the arrival-time analysis of photons emitted after ...collisional excitation of residual gas molecules. The beam-induced fluorescence was investigated in the ultraviolet regime with a channeltron and in the visible region using a photomultiplier tube. Both were applied to investigate the longitudinal shape of bunched and electron-cooled 209Bi80+ ion beams at about 400MeV/u in the experimental storage ring (ESR) at GSI Helmholtzzentrum für Schwerionenforschung in Darmstadt, Germany. Bunch lengths were determined with an uncertainty of about 0.5m using the UV-sensitive channeltron and with slightly lower accuracy from the photomultiplier data due to the slower transitions in the red region of the spectrum. The Gaussian shape of the longitudinal distribution of ions inside the bunch was confirmed. With the information of the transverse beam size that can be measured simultaneously by a newly installed ionization profile monitor (IPM) at the ESR, an accurate determination of the ion density in the bunched beam will be allowed.
► Optical methods to measure the bunch shape of ion beam at storage ring. ► High resolution of bunch length was obtained from the UV-sensitive channeltron. ► The Gaussian shape of longitudinal distribution of the ions in the bunch was confirmed.
The hyperfine splitting in heavy highly charged ions provide the means to test QED in extremely strong magnetic fields. In order to provide a meaningful test, the splitting has to be measured in ...H-like and Li-like ions to remove uncertainties from nuclear structure. This has been achieved at the experimental storage ring ESR but a discrepancy to the theoretical prediction of more than 7
σ
was observed. We report on these measurements as well as on NMR measurements that were performed to solve this issue.
Spin–isospin excitations of the medium-mass nucleus 58Co were studied using the (n,p)-type (d,2He) charge-exchange reaction at an incident energy Ed=170 MeV and small scattering angles. The achieved ...energy resolution of 130 keV, full width at half maximum, allowed the extraction of Gamow–Teller strength to 13 peaks at excitation energies lower than 4.1 MeV in the residual nucleus 58Co and is consistent with the results of a multipole-decomposition analysis. The identification of Gamow–Teller transitions is possible by comparison of the measured cross sections with DWBA calculations. The results are used to discuss the relevance of the Gamow–Teller strength distribution at low excitation energy with regard to electron-capture rates used in calculations for the final stage of a massive star.
The LIBELLE experiment performed at the experimental storage ring (ESR) at the GSI Helmholtz Center in Darmstadt aims for the determination of the ground state hyperfine (HFS) transitions and ...lifetimes in hydrogen-like (209Bi82+) and lithium-like (209Bi80+) bismuth. The study of HFS transitions in highly charged ions enables precision tests of QED in extreme electric and magnetic fields otherwise not attainable in laboratory experiments. While the HFS transition in H-like bismuth was already observed in earlier experiments at the ESR, the LIBELLE experiment succeeded for the first time to measure the HFS transition in Li-like bismuth in a laser spectroscopy experiment.
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