Hans M. Hertz

Experimental determination of 2-D flame temperature fields by interferometric tomography

Abstract An optical method for measuring the 2-D temperature distribution in a horizontal plane of an asymmetric diffusion flame is studied. Using a Mach-Zehnder interferometer the method records projections of the index of refraction in the flame from eight different directions. The projection data are detected by a 1024 channel linear diode array and are then transferred to a computer which reconstructs the 2-D distribution of the refractive index and temperature by methods known from computer tomography. All data processing is governed by an interactive computer program. The tomographic reconstruction is performed by the iterative algorithm MART (multiplicative algebraic reconstruction technique), which has been modified to minimize the reconstruction errors for this type of application. The results indicate that it is possible to reconstruct the horizontal temperature field of an asymmetric and moderately hot slot flame using few (i.e. less than 10) projection angles with temperature errors less than ±10%.

Off-axis reflection zone plate for quantitative soft x-ray source characterization

A compact system for high-resolution spectroscopy and quantitative photon flux and brilliance measurements of pulsed soft x-ray sources is described. The calibrated system combines a novel elliptical off-axis reflection zone plate with charge-coupled device detection for simultaneous spectral and spatial measurements. Experiments on a water-window droplet-target laser-plasma source demonstrate λ/Δλ⩾1000 spectral resolution and absolute flux and brilliance measurements.

Trapped particle optical microscopy

Abstract A scanned probe optical microscope allowing nondestructive studies of a wide range of objects and surface is described. The microscope utilizes a noninvasive optical trap to position a microscopic probe light source in immediate proximity to the studied object. We demonstrate the method experimentally and show theoretically its potential for optical imaging with subdiffraction limited resolution of, e.g., biological objects.

Debris-free soft x-ray generation using a liquid droplet laser-plasma target

We describe the use of small liquid droplets as target for laser-plasma soft x-ray and EUV generation. Using a table-top laser, this < 15 micrometers diameter plasma source typically produces line radiation with approximately 1(DOT)1012 photons/ster-line-pulse in the water-window wavelength range. The major adcvantages of the source is that it is practically debris free. We discuss applications of the source to soft x-ray microscopy and lithography.

Scanned Probe Optical Microscopy using a Non-Intrusive Probe

A scanned probe optical microscope allowing non-destructive studies of a wide range of objects and surfaces is described. The microscope utilizes a non-intrusive optical trap to position a microscopic probe light source in immediate proximity to the studied object. Recent theoretical and experimental work aiming at optical imaging with sub-diffraction-limited resolution of, e.g., living biological objects, is discussed.