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The machines are ephemeral, i.e., they are available for two weeks before being automatically deleted (Figure 143). The machine will also be deleted in case of four days of inactivity, to ensure that sufficient resources remain available for the community of ESRF users.

The service was recently launched for ESRF users, and we are continuously adding new software to satisfy specific beamline users. All feedback to the TID IT Services Helpdesk is welcome.

Fig. 143: VISA user dashboard.

AUTHOR

J.-F. Perrin, ESRF.

Focusing X-rays with diamond lenses

X-ray focusing using beryllium or aluminium lenses has been applied for over 25 years. For some applications, however, diamond is increasingly considered as an alternative lens material. This work presents state-of-the-art polished diamond X-ray lenses machined using laser ablation.

Most X-ray beamlines need a beam size at the sample position that requires upstream focusing, or the signal coming from the sample needs magnification by X-ray optics. Such focusing can be achieved by mirrors, zone plates or lenses. Mirror focusing deviates the optical axis and requires expensive, large and highly polished mirrors. Zone plates have limited efficiency when used at wavelengths below an Angstrom. X-ray lenses [1] maintain the optical axis, are easily aligned and are versatile for focusing of medium to hard X-ray energies. Low-Z (electron number) materials are preferred [2] as this

limits X-ray absorption during the passage of the X-ray beam through the lens. Currently, the most common lens material is beryllium (Be).

Diamond (C*) is an excellent alternative: it has a low Z; is extremely tolerant to incident X-ray beam powers as it features high thermal conductivity, high melting point but low coefficient of thermal expansion; and it can be obtained in single crystalline form. All these characteristics make it the material of choice for many X-ray optical applications [3]. Due to its hardness, however, the machining of C* is complicated. Here, femto-second laser ablation is used to create bi-concave X-ray lenses with highly curved parabolic surfaces (Figure 144).

Machining through ablation uses a laser wavelength of 515 nm, pulse duration of 200 fs and average power of a few milliwatts (depending on the focusing configuration). The as-ablated surface roughness of the lens is 200-500 nm, which is reduced to approximately