Tham khảo tài liệu 'modern developments in x-ray and neutron optics episode 9', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 19 Reflective Optical Arrays 313 Fig. . An MOA consisting of an arrangement of 1D strips to give a 2D focus whatever the radial distance. Additionally in practice many more channels would be used compared to the number shown in the schematic diagram typically channels would be 10 pm wide with walls of comparable thickness over areas of a few square millimetres. Flexing may be carried out either mechanically or by coating piezo material on for example the spokes shown in Fig. . By controlling each piece of piezo independently the X-ray beam could be further manipulated for example to reduce aberrations in an adaptive or active way. The two-dimensional focusing capabilities of such arrays could be simulated by making a series of 1D strips as shown schematically in Fig. . As well as being technically less challenging to manufacture each strip could also be flexed independently. Other arrangements designed for specific applications would also be possible. Computer Simulations Modelling the performances of MOAs even in the simplest way is challenging. It requires both finite element analysis FEA to determine the effect of flexing on the channel walls and ray tracing to characterise the optical performances. More sophisticated analyses will require wavefront propagation and studies of the effects of diffraction. FEA and ray tracing are both complicated for such optics as the effects of many channels have to be taken into account. For FEA this means that the number of elements to be analysed is very large leading to problems with mesh sizes while ray tracing has to be carried out non-sequentially as at most two optical surfaces out of many hundreds will be encountered by an individual array. So far only rudimentary FEA studies have been carried out but many characteristics of the optical performances have been investigated using the optical design software ZEMAX . Recently ray-tracing analysis has been carried out using the much more flexible and .
