Characterization of a focusing parabolic guide using neutron radiography method

The aim of the investigation was to test the focusing properties of a new type of focusing neutron guide (trumpet) with parabolically shaped walls. The guide has a length of 431 mm with an entrance area of 16×16 mm2 and an output area of 4×4 mm2. The interior surfaces were coated with a supermirror-surface m = 3 and due to their parabolic shape it was expected that an incident parallel beam can be focused in the focal point of the parabolas. To prove this statement the neutron intensity distribution at different distances behind the guide was recorded by means of a standard, high-resolution radiography detector. The experiments were performed at the V12b instrument at HMI with different levels of beam monochromatization demonstrating maximum intensity gains of about 25. The consideration for using the focusing guide for the purposes of cold neutron radiography will be presented.