Neutron radial collimator using Zr–Gd alloy foil as collimating blade for engineering material diffractometer

In this study, 50-μm-thick Zr–Gd alloy foil was used as the collimating blade for a neutron radial collimator. Very thin Zr–Gd alloy foil presents excellent mechanical properties and low neutron transmission compared with a Mylar foil blade coated with gadolinium oxide (Gd2O3). The tensile strength of the 50-μm Zr–80Gd alloy foil is 135 MPa with a 4% thick tolerance, whereas the tensile strength for the 100-μm Mylar foil blade is 50 MPa with a 10% thick tolerance. The neutron transmission for 50-μm-thick Zr–80Gd alloy foil is 35.352% (1-Å neutron), which performs better than the Mylar foil blade because of the high content of gadolinium. Considering the blade thickness, the gauge volume width for different blade thicknesses was calculated analytically and optimized using McStas. The neutronic properties of a 2-mm gauge volume radial collimator with 240 blades of 50-μm Zr–80Gd alloy foils were simulated using MCNPX. The neutron-to-gamma ratio at the detector surface of the Zr–Gd alloy was higher than that of the Mylar foil blade. The transmission of the radial collimator was 93.6%, and a 2-mm gauge volume was simulated. The construction of a radial collimator using the Zr–Gd alloy blades is in progress. This shows that the Zr–Gd alloy foil provides a new type of high-quality neutron radial collimator blade.