The WITCH experiment: Acquiring the first recoil ion spectrum

The standard model of the electroweak interaction describes beta-decay in the well-known V-A form. Nevertheless, the most general Hamiltonian of a beta-decay includes also other possible interaction types, e.g. scalar (S) and tensor (T) contributions, which are not fully ruled out yet experimentally. The WITCH experiment aims to study a possible admixture of these exotic interaction types in nuclear beta-decay by a precise measurement of the shape of the recoil ion energy spectrum. The experimental set-up couples a double Penning trap system and a retardation spectrometer. The set-up is installed in ISOLDE/CERN and was recently shown to be fully operational. The current status of the experiment is presented together with the data acquired during the 2006 campaign, showing the first recoil ion energy spectrum obtained. The data taking procedure and corresponding data acquisition system are described in more detail. Several further technical improvements are briefly reviewed.Comment: 11 pages, 6 figures, conference proceedings EMIS 2007 (http://emis2007.ganil.fr), published also in NIM B: doi:10.1016/j.nimb.2008.05.15

First detection and energy measurement of recoil ions following beta decay in a Penning trap with the WITCH experiment

The WITCH experiment (Weak Interaction Trap for CHarged particles) will search for exotic interactions by investigating the beta-neutrino angular correlation via the measurement of the recoil energy spectrum after beta decay. As a first step the recoil ions from the beta-minus decay of 124In stored in a Penning trap have been detected. The evidence for the detection of recoil ions is shown and the properties of the ion cloud that forms the radioactive source for the experiment in the Penning trap are presented.Comment: 9 pages, 6 figures (9 figure files), submitted to European Physical Journal

Low-temperature anomalous specific heat without tunneling modes: a simulation for a-Si with voids

Using empirical potential molecular dynamics we compute dynamical matrix eigenvalues and eigenvectors for a 4096 atom model of amorphous silicon and a set of models with voids of different size based on it. This information is then employed to study the localization properties of the low-energy vibrational states, calculate the specific heat C(T) and examine the low-temperature properties of our models usually attributed to the presence of tunneling states in amorphous silicon. The results of our calculations for C(T) and "excess specific heat bulge" in the C(T)/T^3 vs. T graph for voidless a-Si appear to be in good agreement with experiment; moreover our investigation shows that the presence of localized low-energy excitations in the vibrational spectrum of our models with voids strongly manifests itself as a sharp peak in C(T)/T^3 dependence at T < 3K. To our knowledge this is the first numerical simulation that provides adequate agreement with experiment for the very low-temperature properties of specific heat in disordered systems within the limits of harmonic approximation.Comment: 5 pages with 2 ps figures, submitted to PR

THE EUROPEAN NUCLEAR EDUCATION NETWORK AND ITS ACTIONS IN FAVOUR OF EDUCATION, TRAINING, INFORMATION AND TRANSFER OF EXPERTISE

The European Nuclear Education Network (ENEN) Association is a non-profit organization established by the consortium of the EU 5th Framework Programme (FP) “ENEN” project in 2003. The ENEN Association started as a network of universities and research centers involved in education and training in nuclear engineering in EU countries and is presently involved in the challenging role of coordinating E&amp;T in the nuclear fields in Europe. The main objective of ENEN is, in fact, the preservation and further development of expertise in the nuclear fields by higher education and training. Its members are now universities, research centers and industrial bodies established in European Countries; in addition, MoUs have been signed with several institutions and networks beyond the borders of European Union, thus reaching the number of more than 60 members. The objective of this paper is to provide an up to date view of the actions and plans of the Association in pursuing its missions

Onderzoek naar de trekvissoorten in het Schelde-estuarium. Voortplantings-en opgroeihabitat van rivierprik en fint

Migratory fish such as river lamprey and twaite shad are important indicators of ecosystem functioning. Over the past century, most migratory fish have disappeared from the river Scheldt due to human impacts. The previous study on migratory fishes in the Scheldt showed however that most species show the first signs of recovery (Stevens et al., 2009). For both river lamprey and twaite shad there are strong indications that they reproduce in the Scheldt. However, the spawning and nursery habitats of both species are unknown and it is unclear whether the preconditions for a sustainable recovery are met. The spawning and nursery habitat of river lamprey can be located through targeted sampling of the larvae in the sediment. Sampling with fyke nets showed that adult river lamprey migrate mainly to the Bovenschelde and Zwalmbeek. In both rivers a number of locations were selected, which are, according to the literature, expected to be suitable habitats for the larvae of river lamprey. Wadable sites were sampled with a specially designed sediment pump and the deeper sites with a Van Veen grab. In neither of these rivers, however, river lamprey larvae could be found and no spawning sites could be identified. Possible reasons for the lack of larvae in the samples are (1) that no suitable larval habitat is present in the studied areas, (2) that the larval density in the investigated habitats is low and hence sampling frequency should be increased, (3) that the River Bovenschelde and the River Zwalm are not the main spawning grounds for river lamprey in the Scheldt. Telemetry of adult river lamprey could be a possible solution to locate the spawning grounds. In order to improve the reproduction and survival of river lamprey in the River Bovenschelde, the migration barriers in the Scheldt and its tributaries should be cleared and sufficient larval habitat should be availability. Larval habitat could be created in the River Zwalm and other tributaries through the restoration of natural banks. In addition, mud and sand banks in the Bovenschelde should be protected as much as possible as potential larval habitat.The population of twaite shad in the Scheldt is too small to identify the critical habitats by sampling in the field. Therefore, a habitat suitability model for spawning and larval shad was constructed based on literature data. Hereto, we first selected the environmental variables that determine habitat suitability. Next, for each variable the tolerance range was determined. Finallly, the variables were combined using fuzzy logic in order to determine the degree of suitability of a habitat. The model predicts the presence of suitable spawning habitat in the Upper Zeeschelde, upstream of the River Durme. Later in the season, when the water temperature rises, suitable spawning habitat is also present in the Rivers Kleine Nete and Grote Nete. Suitable habitat for larval shad is located mainly in the Upper Zeeschelde upstream Rupelmonde and in the River Rupel. Spawning of twaite shad takes place in the main channel and during their ontogeny the larvae migrate to the edges of the main channel and to side channels.Therefore, in areas with suitable spawning and larval habitat, both the main and side channels need protection. In particular mudflats, sand flats and subtidal low dynamic habitats should be safeguarded. Dredging of these habitats thus mortgages the recovery of the twaite shad population in the Scheldt. The oxygen concentration in the estuary has been greatly improved in recent years.However, in summer a low-oxygen zone in the freshwater area persists, comprising the upstream migration of adults and the survival of larvae. Periodic hypoxic conditions should therefore be avoided and a minimum oxygen content of 5 mg / l is essential for both adults and larvae. During the last century, hydrodynamics in the estuary has increased markedly. As a result, larvae have more difficulties in maintaining their position in suitable habitat. Actions that increase the river/tidal flow or eliminate local retention areas should therefore be avoided