Abstract: A method of providing particle deposition on a semiconductor wafer or other surface first provides a flow of clean gas into a deposition chamber that purges the chamber prior to introduction of the wafer, and after introduction, continues the flow of clean gas. An aerosol is mixed into the clean gas flow for a desired length of time, so that as the combined flow passes through the deposition chamber particles are deposited on the wafer supported in the chamber. After the deposition has continued for either a desired particle count or a length of time, the flow of aerosol is discontinued, and a clean gas flow sheath is provided over the wafer as it is removed from the chamber. The apparatus carries out this method by providing a source of a clean gas, valves for controlling aerosol introduction into the clean gas, and a support for the wafer in the path of gas introduced into the chamber.

Abstract: A diesel particle virtual impactor sampler provides for a total flow through a virtual impactor after the flow passes through a classifier that removes particles substantially larger than the cutoff point of the virtual impactor. The virtual impactor has two outlets, one for minor flow and one for major flow. In a preferred embodiment, filters are used for separately filtering the major and minor flows and collecting the particles carried thereby so that a determination of the concentration of particles above and below the cutoff point can be obtained. Alternately, the major and minor flows and the particles can be passed through particle analyzer instruments for a direct particle measurement of each of the flows.

Abstract: An apparatus for handling exhaust gases, such as diesel exhaust, which cools the exhaust gases as the gases exit a diesel engine, and then filters such gases to remove particulate material. A housing has an inlet pipe with perforations and a filling of a liquid through which gas bubbles as it exits the perforations in the inlet pipe. The gas bubbling through the liquid cools the gases. In order to maintain the bubbles at a desired size, a perforated or porous layer of material is provided in the liquid so that gas moves through the perforated layer before it exits the liquid. Preferably the gas exiting the liquid is then passed through a filter which is maintained in a wet condition by mist carried by the gases that is formed as the gases burst through the surface of the liquid. The fibers of the filter are maintained wetted so that particles of material do not adhere to the fibers and can be flushed therefrom.

Abstract: The present invention relates to a low particle loss cascade impactor with particle collection in externally removable cups for determining the size distribution of particles delivered form an aerosol atomizer. A plurality of downwardly facing cavities formed in the body are arranged from a first end to a second end of the body in a generally zig-zag pattern. Each cavity has a generally cylindrical inner wall surface defining an opening facing in a second direction and a surface facing in a first direction. An entrance passage extends from the outer surface of the body at the first end to a center region of a first cavity. The impaction stage is positioned such that a center line of the impaction stage intersects a center bisecting plane passing through the body at an included angle between about 10.degree. to 80.degree..

Abstract: An aerosol generator used to produce, selectively and rapidly, an aerosol that has a specific particle size and is at a known specific concentration. The generator comprises a plurality of aerosol material atomizers that can be selectively used to obtain different atomized aerosol particles that results in different size when combined with the output of a particle seed atomizer. Particles can be selectively operated to provide, quickly and conveniently, a range of individual particle sizes. The seed atomizer output is mixed with the aerosol atomizer output and passed through a unique, compact heating section for heating the mixture in a manner to provide a high flow rate with low pressure drop. The fluid is passed through a condenser to condense known size particles in the fluid stream, which then can be used as desired, for example to test the efficiency of filters.

Abstract: A volumetric flow controller is used in connection with a virtual impactor classifier to control two separate flows in separate lines from an air pump. Each line has a flow control valve controlled in response to flow signals that are obtained from a pressure transducer that provides an electrical signal proportional to pressure. Pressure changes are sensed and the provided electrical signal is compared with a reference and will actuate a damper motor and move a flow control butterfly valve in the flow line for adjusting the flow when the pressure signal is different from the reference. The circuitry used provides for a dead band, so that changes in the butterfly valve setting will not occur unless the flow varies a selected amount, and also a timer control is used so that the motor operating the damper will be operated only at selected time intervals to prevent "hunting" or continuous operation of the valves. Further, temperature compensation signals can be provided as desired.