Michael M. Shahin

Nature of charge carriers in positive and negative corona discharges

The identification of the nature of the stable charge carriers in corona discharges in atmospheric gases is of importance in several fields. In electrography, both positive and negative coronas are used as ion generators for electrostatic charging of various photoreceptors as well as other functions that involve electrostatic forces. The mechanism of the interaction of these charged carriers with various surfaces, including the photoconductors, depends primarily on their molecular structure inasmuch as it may influence the ion-electron recombination energy (R. E.) of these species.1 In this work,2–5 the results of mass spectrometric sampling of charge carriers that emerge from both positive and negative corona discharges will be discussed, and the measurements made on various ion-molecule reactions that occur while the primary ionic species traverse the electrode gas will be described. The discharge tube chosen for this study contained coaxial electrodes which ensured stability at a wide range of pressures. With such an electrode geometry, the ionization of gas molecules occurs primarily in the vicinity of the central wire as the electrons gain sufficient energy from the field only at small distances from the wire. Thus, at low currents, the system may be assumed to be similar to a line source for the continuous generation of positiveions. These ions will then move through the gas perpendicular tothe axis, undergoing various interactions with the gas molecules before reaching the cathode, where they are continuously sampled through a small orifice and analyzed by a quadrupole mass spectrometer. A schematic diagram of the apparatus is shown in Figure 1. The quadrupole mass spectrometer used in conjunction with the discharge tube is essentially similar to that described previously.2, 3

Future of laser electrophotographic technology for color document printing

Recent years have witnessed the development of laser electrophotography as one of the major technologies for document printing, serving a wide range of market applications. With the evolution of color and market demand for color hard copy, electrophotography is again taking center stage to serve the customer need in quality, cost and convenience. Today, electrophotographic technology is used to offer products for color document printing for desktop, mid-volume and high-speed applications. Total cost of ownership, convenience and quality today favor the use of this technology over alternatives in many applications. Development of higher speed color electrophotographic engines demands very high speed, Raster Input Processors and pre-press applications that are expected to become available in the market during the next five years. This presentation will cover the changing environment of office communication and the continuing role of electrophotography in color document printing.