Very compact high performance microchannel plate thermal neutron collimators

In most neutron scattering experiments and in boron neutron capture therapy, the angular spread of the neutron beam is defined by the quality of the neutron collimator. A typical collimator consists of a large number of parallel plates coated with neutron absorbing material, and at present these plates are at least few centimeters in length. In order to obtain collimation in both vertical and horizontal planes, two orthogonally aligned collimators are installed in the neutron beam. We present a new type of high performance neutron collimator made with Gd-doped microchannel plates (MCPs). Such collimators are only few millimeters thick and the rocking curve is expected to be even sharper than that of conventional 0.5° collimators. While collimation is performed in two perpendicular planes simultaneously, the geometry of these new collimators can be changed so that the degree of collimation in each direction is controlled independently. The modeling of the proposed collimator indicates that for the existing MCP technology the rocking curve can be made as sharp as 0.2° FWHM, which can be further improved by current developments in the MCP technology. The preliminary experimental evaluation of our first very thin (only 0.6 mm) MCP collimators confirms the accuracy of our numerical model.