Based on a data sample of (448.1 +/- 2.9) x 10(6) psi(3686) events collected with the BESIII detector at the BEPCII collider, the branching fraction of psi(3686) -> Lambda(Lambda) over bar omega is measured to be (3.30 +/- 0.34(stat) +/- 0.29(syst)) x 10(-5) for the first time. In addition, the Lambda omega (or (Lambda) over bar omega) invariant mass spectra is studied and the potential presence of excited. states has been investigated.
The JET experimental campaign has focused on studies in support of the ITER physics basis. An overview of the results obtained is given for the reference ELMy H mode and advanced scenarios, which in JET are based on internal transport barriers. JET studi
This paper highlights some of the main activities related to fission of the nuclear reactions group at Uppsala University. The group is involved for instance in fission yield experiments at the IGISOL facility, cross-section measurements at the NFS facility, as well as fission dynamics studies at the IRMM JRC-EC. Moreover, work is ongoing on the Total Monte Carlo (TMC) methodology and on including the GEF fission code into the TALYS nuclear reaction code. Selected results from these projects are discussed.
The wall emission (WE) background accompanying observations of fusion plasma neutrons is a limiting factor in high accuracy neutron diagnostics. It is an important issue to solve for envisaged burning plasma experiments such as with ITER. This work repres
The double differential cross section of low momentum kaons (less than or equal to 0.3 GeV/c) from p + C collisions at subthreshold bombarding energies has been for the first time measured by the use of the CLAMSUD magnetic spectrometer installed at the C
Basic properties of minor alloying elements, namely Mo, W, Nb, Ta, V, Mn, Si entering the conventional and reduced-activation structural Fe-(9-12)Cr steels have been analyzed using ab initio calculations. The electronic structure calculations were applied to study the interaction of minor alloying elements with a number of important and well defined lattice structures, such as point defects, the 1/2 < 111 > screw dislocation core, high angle symmetric grain boundaries and free surfaces. The studied elements were classified according to their similarities and discrepancies regarding the interaction with the above mentioned defects. The refractory alloying elements are found to follow the same trend whereas Mn and Si exhibit peculiar behavior with respect to the interaction with both point and extended lattice defects. The obtained results are discussed and compared with previously published ab initio and available experimental data.
Measurement and analysis of the energy distribution of the neutron emission from the nuclear burnup of tritons produced at 1 MeV in d+d --> t+p reactions are reported. The results refer to deuterium plasmas with a strongly pulsed neutron production attain
A series of analytic and numerical models have been developed for the prediction and interpretation of the energy spectrum of the neutron emission from thermonuclear deuteriumtritium (DT) plasmas. The main component of the neutron emission, due to reactions between thermal fuel ions, has been modeled as well as minority components due to the presence of fast (supra-thermal) ions. In particular, the so-called alpha-particle knock-on neutron (AKN) emission has been analyzed and found to carry information on the con- finement of fast alpha particles inside the plasma. The alpha particles carry one fifth of the fusion power generated in the plasma and provide the plasma self-heating. This thesis is devoted to this central endeavor of fusion research and the possibilities for its study in today’s largest magnetic confinement devices, the tokamaks.
The developed models have been used for the interpretation of experimental data taken during the first deuterium-tritium experiment (DTE1) at the Joint European Torus (JET) in 1997. The data were taken with a neutron spectrometer of the magnetic proton recoil (MPR) type developed at the Department of Neutron Research (INF) of Uppsala University. The MPR was used to measure the neutron emission from DT plasmas representing record high fusion power levels of up to 16 MW and correspondingly high quality in the neutron emission observations. These studies in DT plasmas were complemented with theoretical and empirical studies of the 14-MeV triton burn-up neutron (TBN) emission from deuterium plasmas.
The predicted neutron energy spectra were found to be able to describe observations leading to positive identification of previously unobserved spectral features such as the very weak AKN and TBN signature in the neutron emission. In this summary, the developed models are presented as well as the experimental findings. Finally, a discussion is included of the possible application of the presented models and experimental techniques to next-step fusion experiments such as the proposed ITER tokamak.
Trace tritium experiments (TTE) on JET were analysed using Monte Carlo modelling of the neutron emission resulting from the neutral beam injection (NBI) of short (similar to 300 ms) tritium ( T) beam blips into reversed shear, hybrid ELMy H-mode and L-mode deuterium plasmas for a wide range of plasma parameters. The calculated neutron fluxes from deuterium-tritium ( DT) reactions could only be made consistent with all plasmas by applying an artificial reduction of the T beam power in the modelling of between 20% and 40%. A similar discrepancy has previously been observed in both JET (Gorini et al 2004 Proc. 31st EPS Conf. on Plasma Physics ( London, UK) vol 28G (ECA)) and TFTR (Ruskov et al 1999 Phys. Rev. Lett. 82 924), although no mechanism has yet been found that could explain such a difference in the measured T beam power. Applying this correction in the T beam power, good agreement between calculated and measured DT neutron emission profiles was obtained in low to moderate line averaged density ((n(e)) over bar < 4 x 10(19) m(-3)) ELMy H-Mode plasmas assuming that the fast beam ions experience no, or relatively small, anomalous diffusion (D-an << 0.5 m(2) s(-1)). However, the modelled neutron profiles do not agree with measurements in higher density plasmas using the same assumption and the disagreement between the measured and calculated shape of the neutron profile increases with plasma density. In this paper it is demonstrated that large anomalous losses of fast ions have to be assumed in the simulations to improve agreement between experimental and simulated neutron profiles, characterized by the goodness of fit. Various types of fast ion losses are modelled to explain aspects of the data, though further investigation will be required in order to gain a more detailed understanding of the nature of those anomalous losses.
A spectrometer has been designed and built to investigate the dynamics of spontaneous and ion-induced fission processes. It consists of 8 neutron detectors surrounding a low mass scattering chamber containing the fussionable targets and two fission fragme
We present range telescopes for measurements of low energy K+ mesons together with first in-beam results. The hardware trigger, based on the observation of the mu(+) from the K+ --> mu(-) + nu(mu) decay channel, is designed for subthreshold hadron-nucleus
Double-differential cross sections for light charged particle production (up to A=4) were measured in 96 MeV neutron-induced reactions, at the TSL Laboratory Cyclotron in Uppsala (Sweden). Measurements for three targets, Fe, Pb, and U, were performed using two independent devices, SCANDAL and MEDLEY. The data were recorded with low-energy thresholds and for a wide angular range (20°–160°). The normalization procedure used to extract the cross sections is based on the np elastic scattering reaction that we measured and for which we present experimental results. A good control of the systematic uncertainties affecting the results is achieved. Calculations using the exciton model are reported. Two different theoretical approaches proposed to improve its predictive power regarding the complex particle emission are tested. The capabilities of each approach is illustrated by comparison with the 96 MeV data that we measured, and with other experimental results available in the literature.