Very compact high performance microchannel plate neutron collimators

The angular spread of a neutron beam is usually defined by the quality of neutron collimators used in most neutron scattering experiments as well as in boron capture therapy. 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 should be installed in the neutron beam. We present a new type of high performance neutron collimator made with ¹⁵⁷Gd-doped microchannel plates (MCPs). The thickness of such collimators is on the scale of only few millimeters 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.