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The cryogenic positioning system for a magnetic microscope

2000; Taylor & Francis; Volume: 80; Issue: 5 Linguagem: Inglês

10.1080/01418630008221959

1463-6417

R. Vaccarone, Andrea Bevilacqua, P. Musico, A. Pozzo, P. Ottonello,

Mechanical and Optical Resonators

Abstract We are developing a magnetic microscope, based on a micro SQUID sensor, with an integrated coil of 10 μm diameter. We present here the new features of this system. The scanning stage of the microscope is completely contained in a cryogenic environment and is activated by piezoelectric actuators of the bimorph type. A capacitive transducer of new design which has been designed and constructed in our laboratory, monitors the movement of the scanning stage. The capacitive transducer detects the position of the moving stage by the change in the capacitance of two sliding electrodes. The x and y measurements are integrated in a single device. The electronic capacitance monitor is based on a nuli capacitance bridge with fast-acting digital feedback. In the measurement of variable capacitance, we obtain a 14 bit resolution with a bandwidth larger than 750 Hz by using a XSP56001 digital signal processor (DSP), fast analogue-to-digital converters and multiplying digital-to-analogue converters. The DSP controls the scanning stage by driving the piezoelectric actuators, monitoring the capacitance change due to the movements of the sample platform and correcting accordingly its position.