Three-axis Translation Stage Research Articles

Ground Vacuum Facility to Simulate Low Earth Orbit Plasma Environment

This paper presents a large vacuum facility (6-ft-diameter, 10-ft-long chamber) equipped with a magnetic filter-type low Earth orbit plasma source. A recommended operating envelope for the plasma source was established through single-point measurements by varying the discharge currents of the plasma source and the gas flow rates. A three-axis translation stage was fabricated and tested with 2D and 3D scans of the simulated plasma environment. The measured plasma density during this study was between 1.63×1012−3.1×1012 m−3 for the electrons and 7.54×1012−1.82×1013 m−3 for the ions, whereas the electron and ion temperatures ranged from 0.55 to 2.06 eV and 1 to 3 eV, respectively. The simulated plasma environment compares well with orbital equivalents, specifically the F layers of the ionosphere.

Construction of Tactile Measuring Probes for Coordinate Measurement

Measuring probes are major components of coordinate measuring machines. They contribute to large extend to measurement uncertainty of the CMM. In this paper a number of designs presented, and their static and dynamic behaviours are discussed. The theoretical results are experimentally verified. In the corresponding literature little information can be found about the 3D calibration of these probes.The paper also outlines the construction of a 3D calibration system, discusses it's error sources, their contribution to the measuring uncertainty. This facility has been developed to calibrate measuring probes to an accuracy of 0,02μm. A high precision three-axis translation stage moves the probe stylus, and the position of the stage is determined by three mutually- orthogonal plane mirror laser interferometer transducers. The coordinates indicated by the probe are compared with the coordinates indicated by the interferometers and the errors of the probe are then calculated. The working volume of the calibrator is 100 x 100 x 100μm. The measurement strategy and design considerations are discussed, and results are given to demonstrate its performance.

A three-axis translation stage using opposing wedges with error compensation

We describe the development of a three-axis translation stage using wedges and its motion error compensation. The three-axis stage uses three wedges and is capable of translation in the vertical and longitudinal directions by controlling the horizontal separation of two opposing wedges. An independent linear translation stage is used to achieve displacement along the third axis. Compensation for straightness and positioning errors is achieved using the combined motion of the two opposing wedges and the motion of an independent linear stage. The straightness error in the vertical and horizontal directions through the longitudinal axis was 0.83 μm and 1.65 μm, respectively, before compensation and 0.22 μm and 0.29 μm with error compensation. The positioning error through the longitudinal axis was reduced from 8.96 μm to 0.85 μm.

An in vitro study of femtosecond laser photodisruption in rabbit sclera

To explore the possibility of photodisruption in rabbit sclera by femtosecond (fs) laser and seek appropriate incision techniques and relevant parameters, a fs laser (800 nm/50 fs) with different pulse energies was applied to irradiate rabbit sclera in vitro. By moving a computer-controlled three-axis translation stage to which the sample was attached, the laser achieved three types of incisions: transscleral channel, snake pattern and linear cut. The irradiated samples were observed by light microscopy and scanning electron microscopy (SEM). In comparison with fs laser, Nd:YAG was used as control. The experimental results show that through an objective lens with numerical aperture (NA) of 0.2, the fs laser with power intensity larger than 955 TW/cm2 and pulse energy ranging from 37.5–125 μJ, cutting depths from 30–70 μm may be achieved after linearly scanning in sclera at a translation speed of 0.1 mm/s. However, it failed to make any photodisruption when the power intensity was below 796 TW/cm2 or the pulse energy was less than 31.25 μJ under the same condition. Compared with the Nd:YAG laser, the inner wall of the channel was smoother and the damage to the surrounding tissues was slight with the fs laser. The high precision of intrascleral photodisruption and minimal damage to surrounding tissues by a fs laser display its potential application in the treatment of glaucoma.

A six-circle diffractometer system for synchrotron X-ray studies of surfaces and thin film growth by molecular beam epitaxy

A new ultrahigh vacuum (UHV) surface diffractometer system equipped with molecular beam epitaxy (MBE) capabilities has been developed. It has a versatile 6-circle configuration for defining the diffraction geometry, and a three-axis translation stage for controlling the sample position. Rugged mechanical components are employed in the design to allow accurate diffraction measurements. Sample cooling is facilitated by passing liquid nitrogen into a reservoir in the base of a sample mount. The sample can be heated to very high temperatures by either direct current heating or electron beam bombardment. During film growth and processing, the sample temperature, monitored by thermocouples, can be continuously and rapidly varied between ∼110K to above room temperature. A charge coupled device (CCD) camera, attached to the μ circle, allows rapid reciprocal space mapping for real time studies of sample growth and evolution during deposition and annealing. A beam stop and a baffle are implemented to minimize stray scattered radiation.

Optical measurement of Young's modulus of a micro-beam

This paper presents an optical method based on the interference of light beams of equal path difference for the measurement of the Young's modulus of a micro-beam. An optical wedge which consists of an optical plate and a micro-beam which forms part of a micro-accelerometer is illuminated by a collimated monochromatic sodium light beam. Loading on the micro-beam is accomplished by a loading-pin mounted on a three-axis translation stage and the resulting interference fringe pattern is observed using a CCD camera connected to a computer. Loadings are recorded using a high-sensitive load cell which measures loads of up to 200 g with a resolution of 0.01 g. Test results conducted on micro-beams of different sizes show good repeatability and comparison of the experimental results with theory shows good agreement.

Levitation apparatus for structural studies of high temperature liquids using synchrotron radiation

A new levitation apparatus coupled to a synchrotron-derived x-ray source has been developed to study the structure of liquids at temperatures up to 3000 K. The levitation apparatus employs conical nozzle levitation using aerodynamic forces to stably position solid and liquid specimens at high temperatures. A 270 W CO2 laser was used to heat the specimens to desired temperatures. Two optical pyrometers were used to record the specimen temperature, heating curves, and cooling curves. Three video cameras and a video recorder were employed to obtain and record specimen views in all three dimensions. The levitation assembly was supported on a three-axis translation stage to facilitate precise positioning of the specimen in the synchrotron radiation beam. The levitation system was enclosed in a vacuum chamber with Be windows, connections for vacuum and gas flow, ports for pyrometry, video, and pressure measurements. The vacuum system included automatic pressure control and multi-channel gas flow control. A phosphor screen coupled to a high-resolution video microscope provided images of the x-ray beam and specimen shadow which were used to establish the specimen position. The levitation apparatus was integrated with x-ray diffractometers located at X-6B and X-25 beamlines at the National Synchrotron Light Source. X-ray structural measurements have been obtained on a number of materials including Al2O 3, Ni, Si, Ge, and other metallic and ceramic materials in the liquid state.

Isocontour maps of electron temperature, electron number density and gas kinetic temperature in the Ar inductively coupled plasma obtained by laser-light Thomson and Rayleigh scattering

Isocontour maps of electron temperature ( T c), electron number density ( n c, and gas-kinetic temperture ( T g) in an argon inductively-coupled plasma (ICP), have been constructed for five rf power settings and in the presence and absence of an aqueous aerosol, based on the simultaneous measurement of spatially resolved Thomson and Rayleigh scattering. Each map was assembled from 21 observation heights and 31 radial positions, the location of each point being controlled by a computer-driven three-axis translation stage. The maps demonstrate how T e, n e and T g all increase throughout the plasma as rf power is raised, with the electron number density increasing most rapidly. At greater rf power levels (1.75 kW), the introduction of an aqueous aerosol into the central channel was found to increase n e over the entire plasma. In contrast, at lower applied power (0.75 kW), n c is depressed throughout the discharge upon the introduction of water aerosol. At intermediate rf powers (1.0, 1.25 and 1.5 kW), aerosol introduction raises n c only in the regions near the hot torus, while reducing n c at all other spatial positions, particularly lower in the central channel. Aerosol introduction was found also to thermalize the plasma at all rf power settings by increasing T g in the higher regions and decreasing T e lower in the central channel. In general, T e is substantially higher than T g in the lower regions of the discharge, but the two approach each other in the upper zones.