Luminous arc

Figure 2.15 Luminous arc located near the galaxy cluster 2242-02. (Reproduced from photos by courtesy of NASA)...

Luminous arc An apparent arc of light around a massive object that is causing a gravitational lensed image of galaxies behind. Can be hundreds of light-years in length. 

According to Violle,1 the temperature of the positive carbon point and of the carbon particles in the voltaic arc equals the evaporation temperature of carbon. This was determined by breaking off the incandescent tip of the carbon and dropping it into a calorimeter. One gram carbon requires 1600 cal. to heat it from 0° up to its evaporation temperature. As 300 cal. are necessary to heat it from 0° to 1000°, 1300 cal. remain for raising the temperature from 1000° to x°, if x is the evaporation temperature of carbon. If we take the specific heat of carbon at 0.52, then 1300 cal. represent 2500° more, so that the evaporation temperature of carbon, x and the hottest parts of the luminous arc, equal 35000.2... 

The degree of decomposition by the voltaic arc depends of course, to a great extent upon the chemical nature of the liquids and vapors in which the luminous arc is produced While ether, methyl alcohol, ethyl alcohol, glacial acetic acid, and other aliphatic fluids and their vapors are subject to decompositions with very trifling charring, and give products which are chemically closely related to the products started with, benzene, toluene, nitrobenzene, aniline, naphthalene, phenol, and other members of the aromatic series are destroyed, and considerable charring results. 

For this reason the method worked out and employed by Lob,1 replacing the luminous arc by metallic and carbon re-... 

As already mentioned in the introduction, the enormously high temperature of the luminous arc is only applicable in certain cases to organic compounds. 

Dealing strictly with facts will eliminate the misinterpretations of perceptions. In our example, it would be easy to verify that a fire was actually burning versus an electrical short that was arcing, or the simple refraction of light from a luminous surface by going to the location of the incident and visually inspecting the area in question. 

The word photography is derived from two Greek Words signifying to delineate by light. It has been objected to this term, that the luminous raj s arc not those which effect the chemical changes that result in the production of an impression upon the sensitive tablet on which the image is received, but rather the violet rays of the spectrum, so that the word photography is a... 

I will now take such a flame as 1 had a moment since, and set free from it the particles of carbon. Here is some camphine, which will burn with a smoke but if I send these particles of smoke through this pipe into the hydrogen flame, you will see they will burn and become luminous, because we heat them a second time. There they are. Those are the particles of carbon re-ignited a second time. They arc those particles which you can easily see by holding a piece of paper behind them, and which, whilst they are in the flame, arc ignited by the heat produced, and, when so ignited, produce this brightness. When the particles are not separated, you get no... 

The luminous gas phase created by a special mode of DC discharge recognized as the low-pressure cascade arc torch (LPCAT) provides an especially important case for understanding the fundamental aspects of the luminous gas phase. The luminous gas phase in form of luminous gas jet stream or torch are created by blowing out DC discharge into an expansion chamber in vacuum. The luminous gas jet of Ar mainly consists of photon-emitting excited neutral species of Ar, which is certainly not the plasma of classical definition. The core of LPCAT is the tip of injection nozzle however, it is not the core of electrical discharge. 

The existence of the dissociation glow in DC discharge strongly suggests that the creation of chemically reactive species in LCVD involves different mechanism than those in the electron impact ionization. However, in DC discharge, electron impact and ion impact reactions cannot be eliminated. Low-pressure cascade arc torch (LPCAT) provides a unique opportunity to investigate the formation of chemically reactive species with minimal influence of ions and electrons. That is, the creation of chemically reactive species from an organic molecule by the luminous... 

The formation and the dissipation of luminous gas phase of organic vapor by excited Ar neutrals in the cascade arc polymerization could be described as follows. A fraction of photon-emitting Ar neutrals (Ar ), expressed by nA, interacts with the monomer (ABH), and causes the dissociation of the monomer yielding fragmented photon-emitting species (A and B ) and hydrogen atom (H) according to the scheme described by Eq. (4.2). 

In low-pressure cascade arc torch (LPCAT), the electrical power is applied in the cascade arc generator, in which only carrier gas, generally Ar, is activated to create luminous gas. The luminous gas created in the cascade arc generator is blown into the second expansion chamber, in which the monomer is introduced. Thus, the luminous gas of Ar neutrals primarily creates polymerizable species, and following these two steps should treat the deposition kinetics. Principles described in this chapter apply to each of the two steps. Details of deposition kinetics in LPCAT are described in Chapter 16. 

A single monoatomic gas, e.g., argon or helium, is used as the carrier gas of the cascade arc discharge. When the luminous gas is injected into an expansion chamber under low pressure, e.g., 1 torr or less, the flame extends a significant length (e.g., 1 m), which depends on the fiow rate, input power, diameter of the nozzle, and pressure of the expansion chamber. This mode of cascade arc torch is termed low-pressure cascade arc torch (LPCAT), which is useful in the surface modification by means of low-pressure cascade arc torch treatment and low-pressure cascade arc torch polymerization. 

The relative motion of substrate with respect to the luminous gas jet is more or less mandatory for the uniform treatment. Figure 16.4 depicts a reactor equipped with three cascade arc generators, of which two are used to treat substrates placed on a rotating plate. 

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