A compact dual atom interferometer gyroscope based on laser-cooled rubidium

We present a compact and transportable inertial sensor for precision sensing of rotations and accelerations. The sensor consists of a dual atom interferometer operated with laser-cooled ⁸⁷Rb. Raman processes are employed to coherently manipulate the matter waves. We describe and characterize the experimental apparatus. A method for passing from a compact geometry to an extended interferometer with three independent atom-light interaction zones is proposed and investigated. The extended geometry will enhance the sensitivity by more than two orders of magnitude which is necessary to achieve sensitivities better than 10^-8rad/s/.     

Theory of radiation-induced self-organization of defect structures

During high-dose electron irradiation of thin Ni foils at 520 K, groups of about 10 Stacking-Fault Tetrahedra (SFT) are formed, which are referred to as patches. Within the patches the SFT occupy the sites of a square lattice whose sides are parallel to the two 100 directions of the crystalline host lattice in the foil plane. A theory of this planar square lattice of SFT is the subject matter of the preceding paper (Part I). The patches themselves are arranged in a planar face-centred cubic lattice that also shares its orientation with the host lattice. In the present paper (Part II) a mesoscopic theory is presented that accounts for this ordering of SFT-lattice patches in terms of an instability of disordered patch arrangements that results from a point-defect-mediated dynamic patch-patch interaction. This interaction arises from the competition of SFT-lattice patches for static crowdions migrating one-dimensionally along close-packed host lattice directions and for three-dimensionally diffusing vacancies and dumbbell interstitials. The so far exclusive occurrence of ordered SFT-lattice patches in Ni is related to the low packing density of this material, which leads to a high stability of the static crowdions and thus to a long range of the dynamic interaction between SFT-lattice patches.     

Dislocation dynamics in cyclic plastic deformation

The paper presents a theoretical investigation of the slip avalanches (so-called strain bursts) which occur in single-glide-orientated face-centered cubic or hexagonal close-packed metals during stress-amplitude-controlled cyclic plastic deformation. The study is based on a model of the dynamics of dislocations that has been developed in a companion paper (Part I). It is shown that this model allows for a quantitative treatment of the strain-burst phenomenon. In particular, the scaling relations between different strain-burst-characteristic parameters which have been found by experiment are connected to the evolution of the dislocation microstructure and thus find a natural explanation.     

Self-affine surface morphology of plastically deformed metals

We analyze the surface morphology of metals after plastic deformation over a range of scales from 10 nm to 2 mm using atomic force microscopy and scanning white-light interferometry. We demonstrate that an initially smooth surface during deformation develops self-affine roughness over almost 4 orders of magnitude in scale. The Hurst exponent H of one-dimensional surface profiles initially decreases with increasing strain and then stabilizes at H approximately 0.75. We show that the profiles can be mathematically modeled as graphs of a fractional Brownian motion. Our findings can be understood in terms of a fractal distribution of plastic strain within the deformed samples.     

Narrow bandwidth interference filter-stabilized diode laser systems for the manipulation of neutral atoms

We present and investigate different external cavity diode laser (ECDL) configurations for the manipulation of neutral atoms, wavelength-stabilized by a narrow-band high transmission interference filter. A novel diode laser, providing high output power of more than 1 W, with a linewidth of less than 85 kHz, based on a self-seeded tapered amplifier chip has been developed. Additionally, we compare the optical and spectral properties of two laser systems based on common laser diodes, differing in their coating, as well as one, based on a distributed-feedback (DFB) diode. The linear cavity setup in all these systems combines a robust and compact design with a high wavelength tunability and an improved stability of the optical feedback compared to diode laser setups using diffraction gratings for wavelength discrimination.