Intense pulsed neutron source

ISIS is only one pulsed source available for the study of liquids. Both the USA and Japan have facilities similar to SANDALS and GEM for studying liquids, but with slightly lower neutron intensity in the forms of the IPNS (Intense Pulsed Neutron Source) at the Argonne National Eab. on the instrument GEAD, and the KEK Neutron Scattering Eacility (KENS) on the instrument ELit II, respectively. 

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. 

Figure 2. Schematic diagram of the QENS spectrometer at the Intense Pulsed Neutron Source (IPNS), Argonne National Laboratory.

We thank those who have contributed to our own TINS and QENS studies R. A. Beyerlein, S. K. Sinha, D. E. W. Vaughan, and the staff of the Intense Pulsed Neutron Source at Argonne National Laboratoiy. (This work supported in part by the U.S. Department of Energy, BES-Materials Sciences, contract W-31-109-ENG-38.)... 

Intense Pulsed Neutron Source/Advanced Photon Source, Argonne National Laboratory, Argonne, IE, USA Institut Laue-Langevin, Grenoble, France... 

Acknowledgment This research is supported by a grant from Materials Science Division of US Department of Energy. We are grateful to the Intense Pulse Neutron Source Division of Argonne National Laboratory for neutron beam time at the SAND Low-Angle Diffractometer and to Dr. Chwan-Yuan Ku for technical assistance. 

The moderator at an accelerator-based neutron source is used to slow the neutrons down so that they have suitable wavelengths for neutron diffraction, in the same way as for a reactor neutron sovuce. However, in order that the moderation process does not broaden the pulsed time structure of the neutron flux too much, the moderator must be relatively small. (Also note that, unlike a reactor, the process of moderation plays no role in the production of neutrons at an accelerator-based sovuce.) This has the consequence that the neutrons produced by an accelerator-based source are undermoderated and there are many more epithermal neutrons than for a reactor source. Figure 1 also shows the neutron flux for a moderator at the world s most intense pulsed neutron source, the ISIS spallation neutron source at the Rutherford Appleton Laboratory, UK (see Figure 3). 

High-intensity pulsed-neutron sources provide a powerful tool in nuclear physics generally, and in reactor physics in particular. Basically, the pulse technique consists of observing the transient behavior of neutron intensity following a burst of neutrons injected into the medium under study. Using pulsed-neutron techniques, one can determine neutron spectra, flux densities, capture and scattering cross sections, diffusion constants, neutron lifetime, neutron age, and reactivity. 

---