The nano-focus at the diffraction endstation is created by a fixed KB-mirror system. The two mirrors with matching numerical aperture create a symmetric diffraction limited focus in the shape of two crossed one-dimensional sinc functions.

Beam size and intensity

The coherent properties, the size and the intensity of the focused beam depending on the used photon energy have been studied extensively by Björling et al. (2020) and by Johansson et al. (2021).

Graph of photon flux at NanoMAX
Photon flux measured in the focus of the diffraction endstation at 300 mA ring current. Data were collected 2021. Below the red curve are measured focal sizes (FWHM) in nano-meters and corresponding setting of the secondary source aperture, in um.

Hardware

The design parameters of the two mirrors have been published by Johansson et al. (2021).

Vertical (M1 – upstream)Horizontal (M2 – downstream)
Mirror materialSingle crystal siliconSingle crystal silicon
Substrate shapeElliptical cylinderElliptical cylinder
Source to mirror center46.69 m46.82 m
Mirror center to focal point0.31 m0.18 m
Incidence angle at mirror center2.7 mrad2.5 mrad
Reflection directionDownwardRightward
Substrate size (L x W x H)150 x 30 x 50 mm100 x 30 x 50 mm
Active optical surface (L  W)140 x 8 mm90 x 8 mm
Figure error (tangential)<1.0 nm PV<1.0 nm PV
Micro roughness<0.15 nm RMS<0.15 nm RMS
Sagittal radius>10 km>10 km
Reflective coatingPt, 40–50 nmPt, 40–50 nm
Numerical aperture6.1 x 10^-46.2 x 10^-4
Beam divergence1.22 mrad1.25 mrad
Geometrical demagnification150.6260.1
Beam acceptance aperture378 um225 um