Confirmation of proton beam bending in graded Si1−xGex/Si layers using ion channeling

Abstract

A graded composition Si1−xGex/Si [001] layer, which has recently been proposed as a method for bending and extracting protons from high-energy particle accelerators, has been studied by angle-resolved ion channeling analysis using focused MeV proton and He+ beams. Backscattering spectrometry confirms that the composition is linearly graded and a maximum Ge concentration of 0.16 was measured at the epilayer surface. Off-normal planes {111} are curved with respect to the substrate by a total angle of 0.332° and efficient bending of channeled particles along the curved planes and into the substrate is confirmed.

Enhanced beam deflection in bent crystals using multiple volume reflection

“…First, for lower energies a similar approach to that previously used to produce bent layers suitable for bending MeV ions can be produced by growing a graded silicon-germanium epitaxial layer [16], in which the Ge fraction varies from zero at the epilayer interface to a maximum at the surface. The resultant tetragonal strain produces a uniformly curved lattice when viewed along off-normal directions [16][17][18]. 10 µm layers with R ~ 30 mm were recently produced [19], capable of bending ions with energies up to a few GeV/n.…”

Coherent Effects of High-Energy Particles in a GradedSi1−xGexCrystal

“…Si 1Àx Ge x crystals were introduced in the scientific community to achieve broadband optical components for focusing x and rays in a Laue lens [23]. Indeed, the usage of graded Si 1Àx Ge x in channeling experiments is not a novelty [24][25][26]. In those cases, the graded crystal was limited to a film deposited onto a conventional crystalline substrate.…”