Beam bending using graded composition strained layers

Curved crystals are commonly used to bend and extract GeV charged particle beams from high-energy accelerators. There is growing interest in multiturn extraction schemes, whereby the circulating beam makes several passages through the curved crystal, to increase the bending efficiency and also for extending their use to TeV energies. The optimum crystal length in such schemes is typically 5 mm, which imposes difficulties both in accurately aligning and bending such short lengths. This paper examines the use of {Si_1-xGe_x}/{Si} graded composition strained layers to satisfy the optimum crystal dimensions and small bend angles required in such schemes. The use of {Si_1-xGe_x}/{Si} graded layers to bend low-energy charged particles is experimentally demonstrated using 3 MeV protons.