Tungsten cathode

A thermal plasma system has been developed for the decomposition of methane. A schematic diagram of the experimental apparatus is shown in Fig. 1. The system consists primarily of D.C. plasma torch, plasma reactor and filter assembly. Plasma was discharged between a tungsten cathode and a copper anode using N2 gas. All the experiments were carried out at atmospheric pressure at 6 kW input electric power and N2 flow rate of 10 to 12 1/min. The feed gas (CH4) flow rates were varied from 3 to 15 1/min depending on the operating conditions, shown in Table. 1. 

A plasma torch is based on arc ignition between a thermionic tungsten cathode and a co-axial copper anode both water-cooled anode and cathode are immersed in an axial magnetic field. Nitrogen is generally chosen as the plasma gas. Air or steam can be injected into the plasma to increase the enthalpy and to produce sub-stoichiometric incineration. The torch is powered by a thyristor-controlled rectifier, which has controls to match the torch impedance. 

Chlorpromazine was determined by diluting 5 mL of a 0.01 M solution with 25 mL of H2O and 20 mL of ethanol, and titrating to a conductimetric endpoint with 0.05N acid or 0.05 N NaOH [63]. Chlorpromazine was determined by titration with KBr03, NaN03, or Ce(S04)2, the determination being made with the use of a molybdenum anode and a graphite, platinum, or tungsten cathode [64]. 

The electron gun consists of a spiral-shaped tungsten cathode and a Wehnelt cylinder. These two components not only constitute the electrodes of the acceleration gap, but also form the optical assembly to control and shape the electron beam. Current signals are linear and have a repetition frequency... 

The electron gun consists of a spiral-shaped tungsten cathode and a Wehnelt cylinder. These two components not only constitute the electrodes of the acceleration gap, but also form the optical assembly to control and shape the electron beam. Current signals are linear and have repetition frequency about 800 Hz. They are used to deflect the electron beam horizontally and vertically over the exit window plane. The scanner can be equipped by two cathodes for maximum output. Then, the width of the exit window is more than double that of a standard unit with a single cathode. The exit window containing the 12-15 prn-thick titanium foil is relatively large to assure an effective cooling of the foil. 

Figure 9 shows an arrangement for measuring secondary electron emission. An electron gun with an incandescent tungsten cathode and the electrodes Bi and Bi is situated in the lower part of the cell. The secondary emitting target P carries the catalyst. A layer of the latter can also be evaporated from Ey or Ei, and deposited on P, which can be heated by radiation or electron bombardment from D. The leads FF of a... 

FLINAK is purified by treatment with the HF released by ammonium bifluoride (NH4HF2) the HF converts oxide impurities in the melt to H20 [7]. In this purification procedure, the fluoride salt mixture is combined with 15 wt% NH4HF2 and heated to about 500°C in a graphite crucible. The molten mixture is poured into a platinum container and heated to 750°C. Hydrogen is passed through the molten mixture for approximately 2 days. Further purification can be achieved by con-trolled-potential electrolysis at an applied potential of about 3 V between a tungsten cathode and glassy carbon anode. 

As the electric discharge passes through the nitrogen, the nitride WN is formed at the hot tungsten cathode. 

The DGP source for spectrochemical excitation has temperatures of 5000-6000 K. It incorporates two graphite anodes and a tungsten cathode in an inverted Y configuration shown in Figure 1 (19), and exhibits the following features (1) It reduces spectral background, (2) it lowers the detection limits, (3) it is stable and reproducible, (4) it reduces chemical interference, and (5) it produces a wide dynamic range. 

In conventional generators, high voltage is applied between a tungsten cathode filament and a metal anode target. The electron bombardment excites a transition of the core electrons in the metal, which... 

An oxide layer is immediately formed during electrolysis of a tungstate solution at a tungsten cathode. The deposits are high molecular oxides, which vary in degree of reduction, depending on the conditions of the electrolyte solution. The acidity and presence of other constituents determine the deposition rate and consequently the layer thickness. 

FIGURE 7.5. Thoriated tungsten cathode (left) and thoriated tungsten anode (right) for xenon short-arc lamps used for wide-angle cinema projection. By courtesy of Plansee AG, Austria. 

Sommerfeld Formula for Thermionic Emission. Using the Sommerfeld formula (2-100), calculate the saturation current densities of thermionic emission for a tungsten cathode at 2500 K. Compare the calculated value of cathode current density with a typical value for the hot thermionic cathodes presented in Table 2-12. 

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