User:Bfilseth/Sandbox

Compound refractive lens (CRL) is a series of individual lenses arranged in a linear array in order to achieve focusing of X-rays in the energy range of 5-40 keV.

Because the refraction index for X-rays is close to 1 for all materials the focusing achieved by using a conventional lens is extremely small. Together with strong absorption in the lens material this has made conventional lenses for X-ray focusing inappropriate. A CRL overcomes this by using a series of lenses made from materials with relatively low absorbption such as aluminium or beryllium.

CRLs were first developed by a group of scientists at ESRF by drilling cylindrical holes in an aluminium block. Since the index of refraction is generally slightly below 1 for X-rays a concave lens will be converging the X-rays. This is opposite to visible light where a convex lens is used for convergence. The walls between the cylindrical holes act as concave lenses when X-rays are incoming in the plane made up by the axis of the drilled cylinders.