No abstract available

No abstract available

[en] The solar neutrino problem is surveyed. The standard solar model predicts a given amount of solar neutrinos, based on the known solar energy flux, on the theory of thermonuclear processes going on in the core of the Sun, and on the particle physical theories describing neutrinos. The measured discrepancy, the 'loss' of solar neutrinos can be due to the failure of both the solar models and the neutrino-theories. The proposed solutions of the puzzle are summarized, including new solar models, neutrino decay and neutrino oscillation theories. The planned gallium experiment (GALLEX) which can decide in the favour of one or other theory is described in detail. Evaluation and calibration problems and the financial support of the experiment are discussed as well. (D.Gy.)

[en] The brief history of neutrinos is overviewed. The four experiments for solar neutrino research are outlined. (R.P.)

[en] The structure determination of biological macromolecules by single-crystal diffraction techniques requires an experimental solution of the phase problem inherent in the structure analysis. This chapter describes a method for the phase determination which uses the nuclear resonance scattering of an ⁵⁷Fe nucleus as reference. The basic features of the method are discussed and different techniques are compared. The pertinent amplitude for nuclear resonance scattering is derived. First test experiments on single crystals of myoglobin are described. Technical problems arise from the necessity of using gamma-ray sources with limited intensities. In particular, the optimization of ⁵⁷Co sources, the development of large-area position-sensitive proportional counters, and the necessary freezing of protein crystals are discussed. The measuring time required for a structure determination of bacterial catalyse is estimated. (orig.)

[en] The determination of the rest mass of the neutrinos remains one of the most important unsolved problems in physics. Neutrino oscillations provide information on weak interaction mixing and on neutrino masses. Many efforts have been made to search for such oscillations. The paper reviews the experimental situation and presents the limits obtained to date

[en] The high-flux reactor of the Institute Max von Laue--Paul Langevin at Grenoble, equipped with cold source, hot source, neutron guides and a large variety of neutron spectrometers, serves as a unique central facility for a large number of laboratories in many different areas of research. The paper describes the Institute, its Reactor and the associated neutron beam installations

[en] 67 years after neutrinos had been introduced into physics many of their properties remain unknown. An open question of whether neutrinos have masses is addressed in the present lecture. After reviewing briefly limits on neutrino masses obtained in direct experiments, indirect searches for neutrino masses are discussed. Particular attention is paid to the search for neutrino oscillations. The Sun is a particularly strong source of neutrinos and for this reason has been used for pertinent experiments. The different solar neutrino experiments are compared in the lecture. (author)

[en] New detectors operated at temperatures in the millidegree range offer the possibility for detecting radiation of nuclear origin with improved energy resolution and energy threshold. Basic features of two types of such detectors are described: (1) Calorimetric detectors, measuring phonons via transition edge thermometers. The resistance matching problems of such thermometers can be solved with SQUID readout techniques. (2) Detectors based on superconducting tunnel diodes, measuring excitations of quasielectrons. Diffusion loss and ambiguity in signal response occurring with such diodes can be coped with by employing proper geometries and quasielectron trapping techniques. (author)

[en] The light-optical resonance fluorescence has been known since the beginning of this century. The phenomenon is induced by electrons of the outer shell of an atom which, through emission of a photon, are transferred from an excited state to the normal energy level. Absorption of a photon of the same energy on the other hand transfers those electrons from the ground state to the excited state. It was expected that there should be an effect like resonance absorption, or resonance fluorescence, to be detected in the atomic nucleus, but it took decades to measure and give proof of the process, because the photons involved in this process are at much higher energy levels: They emit gamma rays. (orig./CB)