Investigation of planetary ionospheres

Feasibility of using radio sounding techniques to investigate ionospheric properties of planet

Ein analytisches Modell für die Blutdruckübertragungsstrecke der invasiven Blutdruckmessung mit externer Flüssigkeitskopplung

Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.Die invasive Blutdruckmessung spielt in der Anästhesie und in der Intensivmedizin eine wichtige Rolle. Im klinischen Alltag wird vorwiegend das preisgünstige extrakorporale Blutdruckmeßverfahren mit einem externen Einwegtransducer eingesetzt. Die Qualität dieses Verfahrens hängt im wesentlichen von dem Druckübertragungsverhalten der Meßstrecke ab, welche hauptsächlich aus dem Katheter, den Verlängerungsschläuchen, der Flüssigkeitssäule und dem Transducer besteht. Zusätzlich beeinflussen in der Flüssigkeitssäule vorhandene Luftblasen die Druckübertragungsqualität. In diesem Beitrag wird eine analytische Methode zur Bestimmung der Übertragungseigenschaften dieses Blutdruckmeßsystems anhand eines erweiterten neuen Modell vorgestellt. In ihm sind alle wichtigen Bestandteile der Druckübertragungsstrecke hinsichtlich ihrer Geometrie und Materialeigenschaften berücksichtigt

The effect of self-affine fractal roughness of wires on atom chips

Atom chips use current flowing in lithographically patterned wires to produce microscopic magnetic traps for atoms. The density distribution of a trapped cold atom cloud reveals disorder in the trapping potential, which results from meandering current flow in the wire. Roughness in the edges of the wire is usually the main cause of this behaviour. Here, we point out that the edges of microfabricated wires normally exhibit self-affine roughness. We investigate the consequences of this for disorder in atom traps. In particular, we consider how closely the trap can approach the wire when there is a maximum allowable strength of the disorder. We comment on the role of roughness in future atom--surface interaction experiments.Comment: 7 pages, 7 figure

Fabrication of micromirrors with pyramidal shape using anisotropic etching of silicon

Gold micro-mirrors have been formed in silicon in an inverted pyramidal shape. The pyramidal structures are created in the (100) surface of a silicon wafer by anisotropic etching in potassium hydroxide. High quality micro-mirrors are then formed by sputtering gold onto the smooth silicon (111) faces of the pyramids. These mirrors show great promise as high quality optical devices suitable for integration into MOEMS systems

Microfabricated high-finesse optical cavity with open access and small volume

We present a microfabricated optical cavity, which combines a very small mode volume with high finesse. In contrast to other micro-resonators, such as microspheres, the structure we have built gives atoms and molecules direct access to the high-intensity part of the field mode, enabling them to interact strongly with photons in the cavity for the purposes of detection and quantum-coherent manipulation. Light couples directly in and out of the resonator through an optical fiber, avoiding the need for sensitive coupling optics. This renders the cavity particularly attractive as a component of a lab-on-a-chip, and as a node in a quantum network

Atom chip for BEC interferometry

We have fabricated and tested an atom chip that operates as a matter wave interferometer. In this communication we describe the fabrication of the chip by ion-beam milling of gold evaporated onto a silicon substrate. We present data on the quality of the wires, on the current density that can be reached in the wires and on the smoothness of the magnetic traps that are formed. We demonstrate the operation of the interferometer, showing that we can coherently split and recombine a Bose–Einstein condensate with good phase stability

Pyramidal micromirrors for microsystems and atom chips

Concave pyramids are created in the (100) surface of a silicon wafer by anisotropic etching in potassium hydroxide. High quality micromirrors are then formed by sputtering gold onto the smooth silicon (111) faces of the pyramids. These mirrors show great promise as high quality optical devices suitable for integration into micro-optoelectromechanical systems and atom chips. We have shown that structures of this shape can be used to laser-cool and hold atoms in a magneto-optical trap