Neutron diffraction on microsamples under high pressures

Abstract

The relatively poor intensity of neutron sources and, con-sequently, the large sample volume required by neutron techniques are well known. Whereas the synchrotron sample may measure a few cubic micrometers, the typical neutron sample is about 10-1000 mm3. One can notice that such different sample volumes are responsible for many remarkable differences between X-ray and neutron instruments. There is an-other important consequence, which is less obvious at first sight. Extremeconditions, such as high pressures, high magnetic fields, or extremely high/low temperatures, are much easier to apply to small samples than to large ones. This statement is especially true for high pressures. One can easily apply a pressure of 100 GPa (1 Mbar) to a sample of few cubic micrometers using a diamond anvil cell. The pressure cell will measure a few centimeters and the pressure will be applied by a gentle turning of a small screw or by sending compressed gas to a thin membrane. In contrast, there is no way to apply pressure of 100 GPa to a sample of 1 cm3. Even in the case of modest pressures (∼10 GPa), a pressure setup for a sample of about 1 cm3 may measure I m and weigh several tons. Consequently, it cannot be compatible with any neutron instrumentation.