Silicon micromachining techniques as a tool to fabricate channeling-based devices

During the last years, because of the low cost, high crystalline perfection and sound knowledge on the handling, the use of bent silicon crystals for applications in accelerators has been intensively investigated. In particular, great attention has been paid towards improving extraction efficiency by the methods used to realize the crystals. For example, 70 GeV protons were extracted from the beam accelerator in Protvino with silicon crystal, obtaining a channeling efficiency close to 85%. The key reason for this successful operation was the use of very short bent crystals. Realization of the short bent crystal devices, as a crystalline undulator, can be difficult by traditional mechanical techniques; a possible alternative method could be the deposition of a high residual stress film onto a Si wafer. We have studied and tested two alternative methods to achieve a uniform curvature of silicon wafers: deposition of both silicon nitride films and thick aluminium films.