Double focusing HOPG monochromator

The double focussing HOPG monochromator of the SHARP+ instrument is composed by a series of 17 columns supporting each 21 graphite crystals individually. Each crystal is 2 and 3mm thick and can be oriented by means of a dedicated mechanical support and movement in order to focus the neutron beam on the sample position. The horizontal and vertical focussing movements are obtained with dedicated precision mechanics, moved by 2 cams. Each cam is actioned by a motor and its position is detected by an encoder. The dimension of the monochromator active area will be of 212 x 314 mm2, excluding the supporting plates (laterals, top and bottom). Each crystal, and hence its support, must be 12x 14 mm2 (W x H). The gap between each crystal is 0.5 mm in the horizontal direction, and 1 mm in the vertical direction. Supply description The scope of the contract covers the supply of materials, manufacturing, dimensional control, inspections, assembly and tests at all stages of fabrication, and transport to the ILL of the monochromators mechanics. Motors, encoders, B4C pads, crystals and in general al commercial items are not included in the supply and will be provided by the ILL if needed during assembly. The mechanics must be realized in Aluminium (grade AW-5083) in order to reduce as much as possible activation from the transmitted and scattered neutron beam; every crystal support will be covered with a 2 mm thick sintered B4C pad (provided and installed by the ILL). Overall dimensions The overall dimensions should not be modified; if modifications are required they shall be submitted to the ILL in writing for agreement. Excluding motors, encoders and handles, these are the overall dimensions: • Width: 270 mm • Height: 388 mm