Capacitive long-range position sensor for microactuators

Design, fabrication and measurements for a capacitive long-range position sensor for microactuators are presented. The sensor consists of two periodic geometries (period ≈ 8-16 µm) on resp. a slider and a sense-structure with minimal gap-distance of ~ 1 µm. A relative displacement between the two results in a periodic change in capacitance. In open-loop operation the change in capacitance vs. slider displacement is measured using synchronous detection. Adjusting the minimal gap-distance with additional sense-actuators increases the capacitance. In closed-loop operation the position of the sense-structure is controlled to keep the sensor-capacitance at a larger constant value. Our results indicate that the position precision is increased to 18 nm in closed-loop operation compared to 70 nm in open-loop operation

Micromachined capacitive long-range displacement sensor

First measurement results are presented for a surface-micromachined long-range (50– 100 μm) periodic capacitive position sensor. The sensor consists of two periodic geometries (period = 10 μm) sliding along each other with minimum spacing of about 1.5 μm. The relative displacement between the two, results in a periodic change in capacitance. An electrostatic comb-drive actuator is employed to generate displacements. Measured maximum capacitance change ΔC=0.72 fF corresponds to simulation results but needs better shielding from external noise sources. The results show this sensorconcept can potentially lead towards long-range nano-positioning control of microactuator systems

Micromachined capacitive displacement sensor for long-range nano-positioning

Integrated long-range position sensing with high accuracy will be of paramount importance for high-potential applications in a.o. future probe-based datastorage and microscopy applications [1], provided that nm position accuracy can be obtained over a range of tens of micrometers or more. This work presents the design, fabrication and measurements for an integrated incremental capacitive long-range position sensor for nano-positioning of microactuators. For compactness, economical viability and optimal performance, the aim has been to fully integrate sensor and actuator through micromachining technology, without additional micro-assembly. Two related concepts are presented and evaluated through analysis, 2D-Finite-Element Simulations and experimental assessment. The sensors consist of two periodic geometries (period ≈ 8-16μm) on resp. a slider, movable in x-direction, and sense-structures, movable in y-direction, at both sides of the slider, Fig. 1. In ICMM the displacement of the slider is measured by measuring the periodic change in capacitance ΔCs(x) with a charge-amplifier and synchronous detection technique [2]. Using sense-actuators, the gap-distance between sense-structures and slider is made smaller than is possible with standard available photo-lithography (< 2 μm), thus increasing the capacitance and the S-N Ratio

Towards embedded control for resonant scanning MEMS micromirror

This paper describes the design and realization of an electrostatic actuated MEMS mirror operating at a resonance frequency of 23.5 KHz with a PLL feedback loop. The design is based upon a thorough understanding of the (non-linear) dynamical behavior of the mirror. Using an external position sensitive device (PSD) the proper working of the PLL is demonstrated. Next we study the possibility to replace the PSD sensor with an embedded capacitive phase-angle sensor. We show measurements of capacitance changes with large parasitic influences while actuating the mirror in a feed forward mode. This demonstrates the feasibility of a fully embedded control for a resonant scanning MEMS mirror. Keywords: MEMS micromirror; laser display; raster scanning, capacitive tilt-angle sensor; PLL\ud \u

Physics of Solar Prominences: II - Magnetic Structure and Dynamics

Observations and models of solar prominences are reviewed. We focus on non-eruptive prominences, and describe recent progress in four areas of prominence research: (1) magnetic structure deduced from observations and models, (2) the dynamics of prominence plasmas (formation and flows), (3) Magneto-hydrodynamic (MHD) waves in prominences and (4) the formation and large-scale patterns of the filament channels in which prominences are located. Finally, several outstanding issues in prominence research are discussed, along with observations and models required to resolve them.Comment: 75 pages, 31 pictures, review pape

Measurement of the Atmospheric Muon Spectrum from 20 to 3000 GeV

The absolute muon flux between 20 GeV and 3000 GeV is measured with the L3 magnetic muon spectrometer for zenith angles ranging from 0 degree to 58 degree. Due to the large exposure of about 150 m2 sr d, and the excellent momentum resolution of the L3 muon chambers, a precision of 2.3 % at 150 GeV in the vertical direction is achieved. The ratio of positive to negative muons is studied between 20 GeV and 500 GeV, and the average vertical muon charge ratio is found to be 1.285 +- 0.003 (stat.) +- 0.019 (syst.).Comment: Total 32 pages, 9Figure

Anisotropy studies around the galactic centre at EeV energies with the Auger Observatory

Data from the Pierre Auger Observatory are analyzed to search for anisotropies near the direction of the Galactic Centre at EeV energies. The exposure of the surface array in this part of the sky is already significantly larger than that of the fore-runner experiments. Our results do not support previous findings of localized excesses in the AGASA and SUGAR data. We set an upper bound on a point-like flux of cosmic rays arriving from the Galactic Centre which excludes several scenarios predicting sources of EeV neutrons from Sagittarius $A$. Also the events detected simultaneously by the surface and fluorescence detectors (the `hybrid' data set), which have better pointing accuracy but are less numerous than those of the surface array alone, do not show any significant localized excess from this direction.Comment: Matches published versio

Hypoxic regulation of neutrophil function and consequences for Staphylococcus aureus infection.

Staphylococcal infection and neutrophilic inflammation can act in concert to establish a profoundly hypoxic environment. In this review we summarise how neutrophils and Staphylococcus aureus are adapted to function under hypoxic conditions, with a particular focus on the impaired ability of hypoxic neutrophils to effect Staphylococcus aureus killing.This work was supported by a Wellcome Trust Research Training Fellowship awarded to K.M.L, Papworth Hospital Research and Development Department and the NIHR Cambridge Biomedical Research Centre