Measurement of the delayed neutron fraction and correction of small angle scattering data from a pulsed spallation source
Abstract The fraction of delayed neutrons in a moderated beam from the enriched uranium, pulsed spallation source at the intense pulsed neutron source at Argonne National Laboratory has been measured and found to be 0.0283 for 450-MeV protons. Delayed neutrons produce a sample-dependent background in time-of-flight instruments. Because of the distribution of neutron wavelengths in the prompt pulse, the significance of the delayed neutron contribution to the observed scattering profile is strongly dependent on the wavelength and therefore on the magnitude of the momentum transfer. This effect is demonstrated, and a general correction procedure in current use for small angle neutron scattering data is described.
Simulated Fast Neutron Instrument Backgrounds at a MW Spallation Source
Like every megaproject, the European Spallation Source (ESS) currently under construction in Lund, Sweden, has had to make a number of inevitable compromises to remain within budget and on schedule. Some of these compromises carry technical consequences with a potential impact on the operational characteristics of the facility and the neutron scattering instruments in particular. In order to prepare for operation of the facility, it is timely to consider again the sub-jects of instrument backgrounds and shielding from the project design phase. The expected ranges of instrument backgrounds, and the relative strengths of each contributor, are estimated using multiple physics simulations. These are compared with other leading spallation sources. Finally, several suggestions are given to reduce the background contributions in each case, should they prove to be dominant in practice when the commissioning phase of the facility begins.
Balloon assisted translocation of the mitral anterior leaflet to prevent left ventricular outflow obstruction (BATMAN): A novel technique for patients undergoing transcatheter mitral valve replacement
Transcatheter mitral valve replacement (TMVR) is an option for patients at high risk for mitral valve replacement or repair via sternotomy or left thoracotomy approach. TMVR carries up to 22% risk of left ventricular outflow tract (LVOT) obstruction. Severe LVOT obstruction can have devastating hemodynamic and clinical consequences.