5,506 research outputs found
Diffraction-contrast imaging of cold atoms
We consider the inverse problem of in-line holography, applied to
minimally-destructive imaging of cold atom clouds. Absorption imaging
near-resonance provides a simple, but destructive measurement of atom column
density. Imaging off resonance greatly reduces heating, and sequential images
may be taken. Under the conditions required for off-resonant imaging, the
generally-intractable inverse problem may be linearized. A
minimally-destructive, quantitative and high-resolution image of the atom cloud
column density is then retrieved from a single diffraction pattern.Comment: 4 pages, 3 figures v2: minor changes in response to referee reports,
mostly additional experimental detail v3: revisions to figure 3: added trace
and changed image. Minor text and referencing changes. Accepted by Phys Rev A
(Rapid Commun
Multi-Color Imaging of Magnetic Co/Pt Multilayers
We demonstrate for the first time the realization of a spatial resolved two color, element-specific imaging experiment at the free-electron laser facility FERMI. Coherent imaging using Fourier transform holography was used to achieve direct real space access to the nanometer length scale of magnetic domains of Co/Pt heterostructures via the element-specific magnetic dichroism in the extreme ultraviolet spectral range. As a first step to implement this technique for studies of ultrafast phenomena we present the spatially resolved response of magnetic domains upon femtosecond laser excitation
Holographic Methods as Local Probes of the Atomic Order in Solids
In the last fifteen years several techniques based on the holographic
principle have been developed for the study of the 3D local order in solids.
These methods use various particles: electrons, hard x-ray photons, gamma
photons, or neutrons to image the atoms. Although the practical realisation of
the various imaging experiments is very different, there is a common thread;
the use of inside reference points for holographic imaging. In this paper we
outline the basics of atomic resolution holography using inside reference
points, especially concentrating to the hard x-ray case. Further, we outline
the experimental requirements and what has been practically realized in the
last decade. At last we give examples of applications and future perspectives.Comment: 14 pages, 6 figure
Resonance testing of space shuttle thermoacoustic structural specimen
The resonance testing of a structural specimen related to the space shuttle vehicle is described. The specimen consisted of a thin aluminum skin reinforced by hat-section stringers and supported by two ribs or bulkheads of corrugated web. A representative section of the space shuttle thermal protection system was bonded to the outer surface of the skin. The tests were completed by using miniature accelerometers to collect vibration data from locations forming a predetermined mesh over the tiles and base structure. The signals were recorded on FM magnetic tape and subsequently analyzed on a modal analysis system
Imaging velocities of a vibrating object by stroboscopic sideband holography
We propose here to combine sideband holography with stroboscopic illumination
synchronized with the vibration of an object. By sweeping the optical frequency
of the reference beam such a way the holographic detection is tuned on the
successive sideband harmonic ranks, we are able to image the instantaneous
velocities of the object. Since the stroboscopic illumination is made with an
electronic device, the method is compatible with fast (up to several MHz)
vibration motions. The method is demonstrated with a vibrating clarinet reed
excited sinusoidally at 2 kHz, and a stroboscopic illumination with cyclic
ratio 0.15. Harmonic rank up to n = 100 are detected, and a movie of the
instantaneous velocities is reported
Applications of holography to vibrations, transient response, and wave propagation
Applications of holography to vibrations, transient response, and wave propagatio
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