An optimization procedure for designing a ceramic tensile creep specimen to minimize stress concentration is carried out using a finite element method. The effect of pin loading and the specimen geometry are considered in the stress distribution calculations. A growing contact zone between the pin and the specimen has been incorporated into the problem solution scheme as the load is increased t...

We report an experiment to demonstrate the crucial effect of the so-called background reservoir during the propagation of femtosecond laser pulses in air. The background reservoir was blocked by allowing only the filament to pass through a pinhole generated by the filament itself in an aluminum foil. We observed that the filamentation process is terminated immediately after the pinhole. Consequ...

Emission at 13.2 nm from the 4d S0 -4p P1 laser transition of Ni-like Cd was observed in a cadmium vapor plasma column excited by a high-current capillary discharge. The dynamics of the plasma were studied using time-resolved soft x-ray pinhole images and hydrodynamic simulations. The pinhole images show that the plasma column maintains a good symmetry up to the time of maximum compression. Fif...

A new micro-XRF instrument was developed in combination with an atomic force microscope (AFM). A small pinhole of 5 or 10 μm was made on the AFM cantilever. The center of the micro X-ray beam generated by a polycapillary X-ray lens was passed through the pinhole. The present experiment demonstrated that the size of the original X-ray beam of 48 μm produced by the polycapillary lens was reduced ...

We experimentally demonstrate an all-diffractive optical setup for digital lensless holographic microscopy with easy wavelength line selection and micrometric resolution. In the proposed system, an ultrashort laser pulse is focused with a diffractive lens (DL) onto a pinhole of diameter close to its central wavelength to achieve a highly spatially coherent illumination cone as well as a spectra...

Tantalum-178 is a short-lived radionuclide (Tm = 9.3 min.) and emits primarily 56to 64-keV characteristic x-rays. We have determined the imaging characteristics with this radionuclide and a large-field-of-view Anger camera. With a pinhole collimator, good spatial resolution is possible with Ta-178, although the image quality is superior with Tc-99m under comparable conditions. Spatial resolutio...

Charge exchange collisions between highly charged Mg ions in colliding laserproduced magnesium plasmas are studied. Pinhole photography and XUV spectroscopy are used as diagnostic tools. XUV pinhole pictures taken at early stages give more insight into the expansion dynamics of the colliding magnesium plasmas. Spectroscopic studies show selective population of the n = 3 levels of Mg IX ions whi...

The robustness and prolongation of multiple filamentation (MF) for femtosecond laser propagation in air are investigated experimentally and numerically. It is shown that the number, pattern, propagation distance, and spatial stability of MF can be controlled by a variable-aperture on-axis pinhole. The random MF pattern can be optimized to a deterministic pattern. In our numerical simulations, w...