CONTACTLESS SUPERCONDUCTING MAGNETIC INSTRUMENT FOR PRECISE POSITIONING IN CRYOGENIC ENVIRONMENTS

摘要

There is an increasing demand of nanotechnology and nano-devices in microelectronics, optics, biomedical and precision engineering industries. In this context, a wide range of applications require micrometer/nanometer positioning within a long range. Ultra precision manufacturing and inspection systems in micro-automating semiconductor fabrication, nanopositioning and nanomeasuring machines (NPM-Machine), development of MEMS and NEMS, copying machines, stepper stages for photolithography, small-scale measuring machines (CMMs) for large area scanning or surface imaging in scanning probe microscopy (SPM) are a few examples of these applications. In some applications, cryogenic environments (temperatures below 120 K) are a desirable or mandatory condition. The sensitivity of a large number of sensors is greatly increased when they are at cryogenics temperatures, like for example, those required for far infrared interferometer spectroscopy. The operating conditions in these environments include very low temperatures but also high vacuum. In this context, it is challenging for mechanisms to overcome all the tribological problems associated with these conditions. In addition very low energy consumption is also desirable in cryogenic environments. The invention here presented is a contactless linear slider that gets benefit of superconducting magnetic levitation to obtain a nanometer resolution within a long stroke (～ 15 mm), minimizing run-outs of the slider (in the micron scale). Moreover, due to self-stable levitation and guidance of the slider, the complexity of the control is significantly reduced and the power consumption minimized (of the order of mW). The linear slider can be divided in two subsystems: the guidance system and the actuating system. The guidance system is composed of a static guideline, made of two superconducting disks and a slider composed of a long permanent magnet. Due to the high translational symmetry of the magnetic field generated by the PM, a contactless sliding kinematic pair is established between the PM and the superconductors in the sliding DoF. Thus, the slider is able to be moved in the sliding direction with very low resistance. However, greater restoring forces appear if the PM is moved in any other direction. Due to the lack of contact between the moving parts is also suitable for operation in clean-room applications, like in semiconductor manufacturing industry. Ultimately, the device was designed, built and tested in a relevant cryogenic environment (15 K and high vacuum) and the results introduced and discussed.