A new type of high performance and compact neutron collimator can be manufactured from Gd- or B-doped microchannel plates (MCPs). Structures only a few mm thick have very narrow rocking curves and high out-of-angle rejection ratios, as observed previously with a cold neutron beam. We present the results of measurements with a collimated (L/D ratio ~280:1) thermal neutron beam. MCP collimators doped with 3 mole % of natGd2O3 as well as doped with 10 mole % of 10B2O3 were calibrated for transmission versus tilt angle. The MCPs used in this study were only 0.6 and 0.8 mm thick with ~8.5 m circular pores on 11.5 5m centers. All the measured rocking curves agree well with the theoretically predicted performance. Both experimental and modeling results indicate that very efficient MCP collimators (with <0.1 wide rocking curves and a rejection ratio exceeding 103) can be built with the existing technology. The possibility to manufacture collimators with very large L/D ratios exceeding 1000:1 is also discussed for the case of unetched MCPs. The peak transmission of such devices with very sharp rocking curves will be limited to ~40% by the transmission of the undoped glass. Application of MCP collimators for scatter rejection in neutron radiography is also considered in terms of possible image distortions, which are shown to occur only for the systems with detector spatial resolution better than 20 m FWHM.
Citation: IEEE Transactions on Nuclear Science
Pub Type: Journals
collimators, neutron optics, neutron scattering