Test and first application of artificial sapphire sensors

Samples of monocrystalline sapphire sensors of 10×10 mm² area and 0.5 mm thickness with the initial charge collection efficiency of about 2% have been studied in electron beams. The response as a function of the absorbed dose revealed excellent radiation hardness. The signal size dropped smoothly with the absorbed dose approaching 30% of the signal of non-irradiated sensors after the dose of 12 MGy. Four sapphire sensors have been installed, together with four pCVD diamond sensors, as a beam halo monitor of the FLASH facility. A report on the commissioning and operation experience is given.