This work presents the production and extraction of the short-lived radionuclide 6 He in yet unmatched yields from the ISOLDE facility at CERN. It is the first report of 6 He production using spallation neutrons via the 9 Be(n, α) 6 He reaction. These neutrons are produced from the 1.4 GeV proton beam of the Proton Synchrotron Booster (PSB) striking a tungsten converter, and are impinging on a porous BeO material. The central position of 6 He in future experiments is due to its role as a necessary radioactive nucleus to realize the β-beam at CERN, a next-generation facility to study neutrino oscillation parameters, and hence neutrino masses. In the β-beam scenario, an intense beam of radioactive 6 He nuclei will be produced, accelerated to multi-GeV energies and stored in a dedicated storage ring. The resulting virtually mono-directional anti-neutrino beam from the decay of the stored 6 He nuclei will be directed towards a remote underground neutrino detector. A similar beam of, e.g., 18 Ne will provide neutrinos, an ideal concept to test CP violation in the neutrino sector. The results of the present experiment demonstrate for the first time that the necessary conditions for the realization of the proposed β-beam scheme with anti-neutrinos can be fulfilled.

Abstract. In 1964 Penzias and Wilson detected the Cosmic Microwave Background (CMB). Its spectrum follows Planck's black body radiation formula and shows a remarkable constant temperature of T 0γ ≈ 2.7 K independent of the direction. The present photon density is about 370 photons per cm 3 . The size of the hot spots, which deviates only in the fifth decimal of the temperature from the average value, tells us, that the universe is flat. About 380 000 years after the Big Bang at a temperature of T 0γ = 3000 K already in the matter dominated era the electrons combine with the protons and the 4 He and the photons move freely in the neutral universe. So the temperature and distribution of the photons give us information of the universe 380 000 years after the Big Bang. Information about earlier times can, in principle, be derived from the Cosmic Neutrino Background (CνB). The neutrinos decouple already 1 second after the Big Bang at a temperature of about 10 10 K. Today their temperature is ∼ 1.95 K and the average density is 56 electron-neutrinos per cm 3 . Registration of these neutrinos is an extremely challenging experimental problem which can hardly be solved with the present technologies. On the other hand it represents a tempting opportunity to check one of the key element of the Big Bang cosmology and to probe the early stages of the universe evolution. The search for the CνB with the induced beta decay ν e + 3 H → 3 He + e − is the topic of this contribution. The signal would show up by a peak in the electron spectrum with an energy of the neutrino mass above the Q value. We discuss the prospects of this approach and argue that it is able to set limits on the CνB density in our vicinity. We also discuss critically ways to increase with modifications of the present KATRIN spectrometer the source intensity by a factor 100, which would yield about 170 counts of relic neutrino captures per year. This would make the detection of the Cosmic Neutrino Background possible. Presently such an increase seems not to be possible. But one should be able to find an upper limit for the local density of the relic neutrinos (Cosmic Neutrino Background) in our galaxy. a

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The Cosmic Microwave Background (CMB) yields information about our Universe at around 380 000 years after the Big Bang (BB). Due to the weak interaction of the neutrinos with matter the Cosmic Neutrino Background (CNB) should give information about a much earlier time of our Universe, around one second after the Big Bang. Probably the most promising method to 'see' the Cosmic Neutrino Background is the capture of the electron neutrinos from the Background by Tritium, which then decays into 3 He and an electron with the energy of the the Q-value = 18.562 keV plus the electron neutrino rest mass. The 'KArlsruhe TRItium Neutrino' (KATRIN) experiment, which is in preparation, seems presently the most sensitive proposed method for measuring the electron antineutrino mass. At the same time KATRIN can also look by the re- * Author footnote. † Affiliation footnote.

A dedicated study of the quenching of the weak axial-vector coupling strength g A in nuclear processes has been performed by the COBRA collaboration. This investigation is driven by nuclear model calculations which show that the β-spectrum shape of the fourfold forbidden non-unique decay of 113 Cd strongly depends on the effective value of g A . Using an array of CdZnTe semiconductor detectors, 45 independent 113 Cd spectra were obtained and interpreted in the context of three nuclear models. The resulting effective mean values are g A (ISM) = 0.914 ± 0.008, g A (MQPM) = 0.910 ± 0.013 and g A (IBFM-2) = 0.955 ± 0.035. These values agree well within the determined uncertainties and deviate significantly from the free value of g A . This can be seen as a first step towards answering the long-standing question regarding quenching effects related to g A in low-energy nuclear processes.