D11+ - Diaphragms

D11 is the only instrument in the world with such a large detection distance. It is therefore particularly sensitive to the arrangement of the collimation elements. A series of motorised diaphragms will be interposed between collimation sections. There is 2 types of diaphragm systems. The first one consists of 4 independent absorbing shutters that can describe a rectangular slit of varying sizes and positions in the beam. The second type of diaphragm is made up of an absorbing plate drilled with apertures of specific shapes and sizes. Each aperture is selected by moving the plate in the 2 directions orthogonal to the beam. The diaphragms are placed between 2 collimation sections. To limit space between these two sections, the diaphragms are designed to be as thin as possible and the thickest components (e.g. motor, encoder) are placed far enough away from the collimation elements to avoid any interaction. The ILL will order : - 4 diaphragms of type 1 - 3 diaphragms of type 2 Most of the parts are made of aluminium. A precise manufacturing is important to ensure the good operation of the diaphragms The commercial or off-the-shelf parts (rails, bearings, ball screws, motors, encoders, switches) are out of the scope of the call for tender. They will be ordered directly by the ILL. The parts made of sintered B₄C (used as absorbent) are out of the scope. The mounting will be of the ILL responsibility. The manufacturer of the diaphragms should be a company specialized in the machining of small series precise parts.