Choosing the lens material

Fig. 1. Attenuation of x-rays in lens materials (data from NIST)

Our refractive x-ray lenses can be used in a very wide energy range, roughly from 2 keV to 150 keV. Beryllium is the material of choice up to about 40 keV. Roughly from 40 to 80 keV aluminium is more appropriate. Beyond these energies nickel is used (on request).

In Figure 1 is shown the attenuation of x-rays in these materials, where μ/ρ is the mass attenuation coefficient. The power-law behavior due to photo absorption is limited by Compton scattering that becomes dominant at higher energies. To the right of the knee in the absorption curves the background radiation gets strong. Hence, the lenses should be operated in the energy range to the left of the respective knee.

A comparison of beryllium, aluminium, and nickel with other lens materials such as the resist SU-8 and diamond can be found in our section on frequently asked questions.

Types of refractive x-ray lenses

Our refractive x-ray lenses are available as paraboloids of revolution (2D lenses) and as parabolic cylinders (1D lenses), focusing in both directions or only in one direction, and within a wide range of focal lengths. The 2D lenses have circular frames with a diameter of 12 mm, while the 1D lenses have quadratic frames of 20×20 mm2.

Fig. 2. Geometry of refractive x-ray lenses: 2D lens (left) and 1D lens (right)

In Figure 2, the following notation is used: F frame thickness, D lens thickness, L lens length, d web thickness, R radius of curvature at the apex of the paraboloid, 2R0 geometric aperture. A typical value for the frame thickness F is 2 mm. The lens length L of the 1D lenses usually is 2 mm. The figure shows the typical relative dimensions of x-ray lenses with R = 0.5 mm.

Available refractive x-ray lenses

The following lenses are available from RXOPTICS. Please contact us for more detailed information on available materials (beryllium grades, nickel) and on geometric parameters such as lens thicknesses and geometric apertures. All lenses are UHV compatible.

Radius of curvature
R (mm)
Beryllium
2D lenses
Aluminium
2D lenses
Beryllium
1D lenses
Aluminium
1D lenses
0.05
0.1
0.2
0.3
0.5
1.0
1.5
2.0
2.5
3.0
4.0
5.0