Transmission scanning electron microscopical investigation of a gas microjet

Abstract

Expansion flows from different kinds of nozzles (pipe, orifice) into the specimen chamber of a scanning electron microscope (JSM 50A, JEOL, Tokyo) were imaged by means of a transmitted electron detection device using its dark field mode of operation. The experimental videosignal distribution has been numerically transformed in order to get particle number density distributions. Absolute quantification using a thin known foil target yields reasonable particle number densities. The experimental investigation of a nonstationary gaseous microjet ejected from a circular orifice (20 μm in diameter) in the wall of a closed vessel (6 cm3 volume) provides for another estimation of the particle number density at an arbitrarily selected point on the microjet axis.

Imaging and spectrometry of a microscopic gaseous target by SEM and TEM

“…As shown earlier (Wurster 1986), microjets may have mass thicknesses of the order of lpg/cm2. The precise value will depend on the actual diameter of the orifice, the pressure drop, the kind of gas, and the coordinates relative to the jet axis.…”

“…Applying the instmmentation for time-resolved electron microscopy (Bostanjoglo and Tomow 1987) could certainly yield important data on the transient physical state of matter. f) Microscopic gas jets in front of orifice-like or capillary gas-emitting devices provide flexible experimental facilities as to the kind of gases and their particle number densities (Wurster 1986).…”