Cup-shaped electrode

In spark sources, electrical discharges are used to desorb and ionize the analytes from solid samples [98]. As shown in Figure 1.42, this source consists of a vacuum chamber in which two electrodes are mounted. A pulsed 1 MHz radio-frequency (RF) voltage of several kilovolts is applied in short pulses across a small gap between these two electrodes and produces electrical discharges. If the sample is a metal it can serve as one of the two electrodes, otherwise it can be mixed with graphite and placed in a cup-shaped electrode. 

In the hollow cathode discharge (HCD), as the name implies, the cathode is no longer a simple planar electrode. It is typically either a cup-shaped electrode or a cyUndrical electrode with both ends open, as shown in Figure 3.7. The shape of the anode in such a device is... 

Carbone primary cell. This device uses a porous, cup-shaped carbon element as the positive electrode and a zinc ring as the negative. The electrolyte is a caustic-soda solution with a special mineral oil floating on its surface. The oil prevents evaporation of the electrolyte. 

The ion source with the extraction system is connected to the accelerator or directly to the target through a transport system. The transport system consists of several elements. After the extraction optics, an active beam-focusing tool is usually applied (electrostatic einzel lens or solenoid) followed by a charge separator. Diagnostics units are installed in the beam line to measure the beam quality. The most important beam parameters are the ion current, beam profile, and emittance. The beam current is measured by a special cup-shaped metal electrodes (Faraday cups) that convert the intensity of the stopped ion beam into electrical current. The beam profile and emittance can be diagnosed by several methods. The detailed description of different transport systems can be found in the ion source handbooks (Wolf 1995 Brown 2004). 

Many electrodes qualify as recessed electrodes. A metal recording electrode linked by a salt bridge to a potential source is a recessed electrode. Recessed skin-surface electrodes are generally cup-shaped. The gap between the skin surface and the metallic cup electrode is filled with electrode paste or some other electrolyte to maintain good electrical contact between the electrode and the surface which it contacts. The advantage of this type of... 

The hearth cavity is filled with high-purity NbjOj powder and Nb metal rod or powder in appropriate proportions. The entire assembly is flushed with argon gettered over Ti chips or foil at 900° to remove any Oj, Nj, or hydrocarbons. A continuous argon flow of approximately 2 L/min is maintained during operation to carry the volatile impurities out of the chamber. The arc is struck by touching the electrode momentarily to the hearth. The electrode is then raised and swiveled until the arc plasma bathes the mixed powders. As the metal melts and reacts with the oxide powder, the material sinks into the crucible and the piston is continuously raised to keep the melt in view. If a simple cup-shaped hearth is employed in place of the piston hearth, the electrode is lowered in the course of the reaction. 

If the platinum wire is to be used as an electrode it may be preferable not to flatten and shape it as in the Housekeeper method, but to use a mercury cup on the outside of the apparatus (Figure 42, III). The fine wire is fused into a constricted part of a narrow bore tube and the... 

The most widely used spectral line source for atomic absorption spectroscopy is the hollow cathode lamp. An illustration of this lamp is shown in Figure 9.5. The internal atoms mentioned above are contained in a cathode, a negative electrode. This cathode is a hollowed cup, pictured with a C shape in the figure. The internal excitation and emission process occurs inside this cup when the lamp is on and the anode (positive electrode) and cathode are connected to a high voltage. The light is emitted as shown. 

The detector of the PIMMS is a U-shaped Faraday cup surrounded by guard electrodes. 

The field at the edges can be reduced by shaping the dielectric into the form of two cups as shown in Fig. 5.14(b). This shape ensures that the electrode edges are... 

The cell consists of a small beaker with a top that will accommodate two electrodes as shown in Fig. 1. The cadmium electrode is made by plating cadmium onto a platinum wire that is sealed through the bottom of a small glass tube. The amalgam electrode is made by placing a small quantity of the cadmium amalgam in the cup of a special J-shaped glass tube with a platinum wire sealed into it. Electrical contacts are made by copper wires spot-welded to the platinum lead wires. 

Yoon and coworkers152 have also observed large (5-10 pm diameter) pores on the electrode side of PPy films prepared on unpolished platinum electrodes. Well-ordered microstructures have been formed on electrode services by using gas bubbles as templates. Thus, microscale shapes in the form of cups, bowls, and bottles have been formed from PPy doped with camphorsulfonic acid.157... 

In this paper we describe a model of a cup plater with a peripheral continuous contact and passive elements that shape the potential field. The model takes into account the ohmic drop in the electrolyte, the charge-transfer overpotential at the electrode surface, the ohmic drop within the seed layer, and the transient effect of the growing metal film as it plates up (treated as a series of pseudo-steady time steps). Comparison of experimental plated thickness profiles with thickness profile evolution predicted by the model is shown. Tool scale-up for 300 mm wafers was also simulated and compared with results from a dimensionless analysis. 

In a later version [14] shown in Fig. 3, the two capillaries terminated in a cup which could be filled with electrolyte in which the electrode could be immersed. The Pt electrode was then a parallelopiped shaped like the rhom-bohedral primitive unit cell of the f.c.c. system having all six faces equivalent to (111) orientation or a rectangular solid having all six faces equivalent to (100) orientation. This type of crystal was then used in a transfer... 

Electrodes of many shapes and sizes have been used and almost any shape of electrode can be made if desired. Figure 5-20 shows some of the basic electrode types and shapes. A simple cup, such as shown in Figure 5-20a, is often used for powder samples. The sample is placed in the cup and an arc struck between the cup and a counter electrode. The sample is vaporized and excited in the arc. In Figure 5-20b the cup is undercut. The temperature of the cup rises more rapidly in this case. Often the sample and cup are both volatilized into the arc. A porous cup electrode is shown in Figure 5-20c. The cup is filled with liquid and passes slowly through the porous bottom end of the electrode. An arc or spark is struck to a lower counter electrode to excite the sample. Another technique useful for liquids uses a disk electrode, as shown in Figure 5-20d. The disk rotates and feeds liquid into the arc or spark gap for excitation. Another method to introduce a liquid sample into the arc or spark is to use a cored electrode as shown in Figure 5-20e. The solution enters the electrode gap by capillary action in the core. 

Since a wide variety of sample types is likely, it follows that sample preparation will differ markedly from one type of sample to another. Metals can be formed into self-electrodes, as previously mentioned, or into flat disks. Metal alloys may need to be remelted to obtain homogeneity and also to be formed into a suitable shape. Metal powders can be pressed into pellets and placed in cupped graphite or carbon electrodes. Metals also may be converted into ionic solutions by proper treatment with acids or other chemical agents. 

Lower electrode The anode, a cupped, undercut graphite electrode [ASTM (1968) shape S-4]... 

During the process, arc stability is needed (using the methodology of the arc plasma discharge it is possible to obtain a self-sustained arc with an improvement in the synthesis of carbon nanotubes). This can be obtained by accurate control of the electrode gaps (usually an electronic controller is used), and also by using a specific shape of the electrode surfaces exposed to the arc (typically flat or cupped for the cathode, and conical for the anode). 

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