Spallation Neutron Source SNS

Following the decline of nuclear energy, the AMSBs could remain and act as neutron sources for transmutation (incineration) of the remaining nuclear materials, for materials research and development, and for medical use (proton irradiation). The same goals are being pursued by the Spallation Neutron Source (SNS) project in the USA or the Japan Proton Accelerator Research Complex (J-PARC) project in Japan, which are the projects of experimental facilities of intense spallation neutron sources driven by proton accelerators. 

The maximum neutron flux from research reactors Is limited by heat dissipation in the moderator. The optimum performance of a moderator assembly can therefore be Improved by pulsed neutron methods. The first phase in the development of pulsed neutron sources was based on electron linear accelerators which produce fast neutrons in a heavy metal target by (Y,n) and (y>f) processes C3 ] The problems of heat dissipation again limit the flux but the use of an incident proton beam overcomes this difficulty. The Spallation Neutron Source (SNS) C35] Is based on a 800 MeV proton... 

Figure 3 Schematic diagram of the TOPAZ single-crystal diffractometer to be completed at the SNS (spallation neutron source, Oak Ridge, Tennessee) by 2009. (Image downloaded in 2006 from http //neutrons.oml.gov/instrument ystems/beamline 12 topaz/ index.shtml. US Government)...

CCD = charge-coupled device IHIs = interligand hypervalent interactions ILL = Institut Lane-Langevin INS = inelastic neutron scattering IPNS = intense pulsed neutron source LINAC = linear accelerator MaNDi=macro-molecular neutron diffractometer NiMH=nickel-metal OPAL = open pool Australian light-water reactor hydride SANS = small-angle neutron scattering SNS = spallation neutron source. 

One of the brightest operational pulsed neutron sources (ISIS) is located in the UK (http //www.isis.rl.ac.uk/). In the US, the construction of the spallation source at the Oak Ridge National Laboratory (http //www.sns.gov/) is scheduled for completion in 2006. 

Stream of new pulsed neutron sources in Japan (J-PARC), the United States (SNS), and the proposed new European spallation source (ESS). 

Reactor sources are much more common than spallation sources there are around 20 reactors that produce core fluxes >10 cm s. To generate the proton beam needed for a spallation source requires considerable infrastructure and by 2004 there were only five spallation sources world-wide ISIS [8], IPNS (Argonne, USA) [12], LANSCE (Los Alamos, USA) [13], KENS (Tsukuba, Japan) [14] and SINQ (Villigen, Switzerland) [11] with two more under construction, SNS (Oak Ridge, USA) [9] and J-PARC (Tokai, Japan) [10]. Reactor sources are also much more developed, the first neutron experiments were carried out in the 1950s and the ILL opened in 1975. In contrast the first spallation user facility, opened only in 1980, with ISIS in 1985. 

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