Evacuation technology

The next paper, Evacuation technology for ceramic extrusion , by Mark Redmann, explores the various types of vacuum pumps that are suitable for use in extruding ceramic compounds. 

The prevacuum technique, as its name implies, eliminates air by creating a vacuum. This procedure faciUtates steam penetration and permits more rapid steam penetration. Consequendy this results in shorter cycle times. Prevacuum cycles employ either a vacuum pump/steam (or air) ejector combination to reduce air residuals in the chamber or rely on the pulse-vacuum technique of alternating steam injection and evacuation until the air residuals have been removed. Pulse-vacuum techniques are generally more economical vacuum pumps or vacuum-pump—condenser combinations may be employed. The vacuum pumps used in these systems are water-seal or water-ring types, because of the problems created by mixing oil and steam. Prevacuum cycles are used for fabric loads and wrapped or unwrapped instmments (see Vacuum technology). 

Vacuum Tubes. In the manufacture of vacuum tubes for use in polarized ion sources, vaporized cesium is used as a getter for residual gaseous impurities in the tube and as a coating to reduce the work function of the tungsten filaments or cathodes of the tube. The cesium vapor is generated by firing, at about 850°C within the sealed and evacuated tube, a cesium chromate pellet and zirconium (12) (see Vacuum technology). 

A slow response to a smoldering mix of chemicals at the Napp Technologies plant in Lodi, NJ is blamed for an April 21,1995 explosion and fire that killed four workers and injured dozens of others. The blast destroyed more than 70% of the plant, which made pharmaceutical and cosmetic iiuerniediate products, and employed 110 workers. The explosion wrecked several stores housed in (he Napp building, damaged nearby buildings, and forced evacuation of 400 residents for about 13 hours. Chemicals leaked into a nearby river, killing hundreds of fish. 

A peculiar characteristic of vacuum technologies as applied to cryogenics is that vacuum equipments are built and tested at room temperature, then evacuated and cooled. Defects that may develop cannot be fixed at low temperature. Moreover, some problems that occur at low temperatures disappear when the equipment has been warmed up again hence, they cannot be easily located. 

The evacuation of a distributed volume can be described only through much more complex formulas (see for example ref. [9], p. 84), and this is beyond the scope of this short introduction to the vacuum technology. 

In April 1995, an explosion and fire at Napp Technologies, in Lodi, New Jersey, killed five employees, injured several others, destroyed a majority of the facility, significantly damaged nearby businesses, and resulted in the evacuation of 300 residents from their homes and a school (USEPA-OSHA, 1997). Additionally, firefighting generated chemically contaminated water that ran off into a river. The property damage exceeded 20 million. 

The PIMMS-elements can be divided in the fields of fluidic, plasma physics, electrostatic, and high frequency technology. The fluidic part covers the supply with plasma and sample gas, their distribution inside, and their evacuation out of the system. By means of plasma physics both the ionization of the plasma gas by the microwave field and the ionization of the sample gas by impact ionization are described. Electrostatic theory governs to design the elements for acceleration, focusing, and deflection of the plasma electrons and the sample gas ions. Electromagnetic wave theory describes the creation of a microwave-field inside the plasma chamber. 

Co45Fe45Zrio)x(Al203)ioo-x films with thicknesses from 3 to 6 pm were fabricated by ion-beam sputtering in a chamber evacuated and then filled with pure argon to the pressure 6.67-10 Pa using the technological procedures and experimental techniques described in [1-4]. 

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