The double sheath on cathodes of discharges burning in cathode vapour

International audienceThe model of a collisionless near-cathode space-charge sheath with ionization of atoms emitted by the cathode surface is considered. Numerical calculations showed that the mathematical problem is solvable and its solution is unique. In the framework of this model, the sheath represents a double layer with a potential maximum, with the ions which are produced before the maximum returning to the cathode surface and those produced after the maximum escaping into the plasma. Numerical results are given in a form to be readily applicable in analysis of discharges burning in cathode vapor, such as vacuum arcs. In particular, the results indicate that the ion backflow coefficient in such discharges is at least 53%, in agreement with values extracted from the experiment

The Russian-American gallium experiment (SAGE) Cr neutrino source measurement

No description supplie

Substrate rocks of Fe-Mn crusts on the IOAN and Dalmorgeologiya Guyots

Substratum of cobalt-manganese crusts penetrated by numerous deep-sea drill holes on the IOAN and Dalmorgeologiya Guyots of Magellan Seamounts in the Pacific Ocean has been studied. Rocks have been characterized, and ferromanganese manifestations developed in the substratum in different forms have been studied in detail. They are considered to be products of deposition of water fluids arising in the volcanic pedestal and unloading on the guyot's periphery when penetrating into top parts of rocks to different degree phosphatized mainly by replacement. It is demonstrated by numerous substratum relicts and remains of organisms in them

Chemical composition of phosphorites, Fe-Mn nodules and crusts, and basalts from the West Pacific

The monograph gives the first systematic description of ore-bearing guyots from the West Pacific. It is mostly based on data obtained in numerous expeditions of Russian vessels during 1984-1992. Ore deposits located on upper parts of all slopes and tops of the guyots include phosphorites associated with cobalt- and platinum-rich ferromanganese crusts. Location, origin and prospecting of mineral deposits are discussed on the base of new data on metallogenic factors (geodynamics, tectonics, magmatism, sedimentation and morphostructures)