Homogeneous self-standing curved monocrystals, obtained using sandblasting, to be used as manipulators of hard X-rays and charged particle beams

Abstract

A technique to obtain self-standing curved crystals has been developed. The method is based on a sandblasting process capable of producing an amorphized layer on the substrate. It is demonstrated that the amorphized layer behaves as a thin compressive film, causing the curvature of the substrate. This procedure permits the fabrication of homogeneously curved crystals in a fast and economical way. It is shown that a sandblasted crystal can be used as an X-ray optical element for astrophysical or medical applications. A sandblasted bent crystal can also be used as an optical element for steering charged particles in accelerator beamlines. Several samples were manufactured and bent using the sandblasting method at the Sensor and Semiconductor Laboratory of Ferrara, Italy. Their curvature was verified using interferometric profilometry, showing a deformation in agreement with the Stoney formalism. The curvature of the machined samples was also tested using γ-ray diffraction at the Institut Laue-Langevin (ILL), Grenoble, France. A good agreement with the dynamical theory of diffraction was observed. In particular, the experiment showed that the crystalline quality of the bulk was preserved. Moreover, the method allowed curved samples to be obtained free of any additional material. Finally, a crystalline undulator was produced using sandblasting and tested using γ-ray diffraction at the ILL. The crystal showed a precise undulating pattern, so it will be suitable for hard X-ray production

X-ray characterization of self-standing bent Si crystal plates for Large Hadron Collider beam extraction

“…PLSB was bent via the sandblasting method (Camattari et al, 2017), while PLCF was bent by the application of a carbon fibre composite (Camattari et al, 2014). Sandblasting is a mechanical process, which consists in driving a stream of abrasive material against a sample through a pressurized fluid, usually compressed air.…”

“…For both samples the osculating circle lies on the polished side of the crystal (Camattari et al, 2017(Camattari et al, , 2018, i.e. they are bent to the opposite side with respect to the machined surface.…”

“…The techniques used to obtain the self-standing curvature are the sandblasting method (Camattari et al, 2017) and the application of a carbon fibre composite (Camattari et al, 2014): these proved to be efficient methods to maintain the crystal curvature.…”

Laue lens for radiotherapy applications through a focused hard x-ray beam: a feasibility study on requirements and tolerances

“…CDP crystals have been simulated. In order to obtain crystals featuring CDPs, a promising technique could be the sandblasting method (Camattari et al 2017). Indeed, it was demonstrated that sandblasting a crystal through a flux of abrasive material produces on the surface of the crystal itself a thin damaged layer that behaves as a tensile film, allowing the precise curvature of the substrate.…”

Silicon crystalline undulator prototypes: Manufacturing and x-ray characterization

“…Another technique consisted of patterning a thin film of strained silicon nitride on a silicon monocrystal to generate an undulated structure [13]. Another technique consisted on sandblasting the two major surfaces of a crystal to produce a patterned amorphized layer capable of undulating the sample [14]. Sandblasting is a mechanical process consisting in driving a stream of abrasive material against a sample through a pressurized fluid, usually compressed air.…”