Advances in neutron detection
The term "neutron scattering" encompasses several techniques involving the interaction of the neutron with an atom. When a neutron beam falls on a nucleus, scattering of the wave occurs. Neutrons can penetrate deep into matter, therefore, they are most often used as structural probes. Thermal neutron wavelengths and energies are well matched to inter-atomic distances and excitation energies in condensed matter and thus can be used to study condensed matter. Both light and heavy elements can be studied. It is also possible to distinguish isotopes. Small Angle Neutron Scattering (SANS) involves directing a monochromatic beam of neutrons onto a solid sample containing nanometer-sized particles. The transmitted beam shows a broadening proportional to the average size of the particles. A size range of about 10-1000 Angstrom can be studied with minimum resolution. Detection involves the conversion of the neutrons into charged particles that are then registered by a counter. In proportional counters for example, the protons penetrate an x-ray transparent window and pass into the gas inside where interactions with the gas inside produce ions, which are detected. Apart from size, shape and orientation of some component of the sample may also be studied. Models, pore diameters and pore spacing can be arrived at for a variety of materials. More intense neutron scattering sources have resulted in the need for more efficient neutron detectors since current detectors are unable to process the information produced. This has resulted in the development of the multi PSPC, a very fast 2D neutron detector for small angle scattering devices. It is made up of 128 Neutron Position Sensitive Proportional Counters (PSPC) mounted side by side over a 1 m² detection area. It has a greater count rate capability than Multi Wire Proportional chambers, MWPCs, without compromising efficiency and resolution. It can easily replace traditional MWPCs traditionally used in small angle scattering applications, and is cheaper and faster.
