Environmental Engineering Reference
In-Depth Information
The creation and development of sources of electricity determined the devel-
opment of the gas discharge technique. The first type of discharge was an arc
discharge at atmospheric pressure. The subsequent development of the pumping
technique allowed the creation of burned gas discharges of various types. Crookes
tubes [9] were an important development, where on the basis of a mercury vacuum
pump the pressure of the remaining gas in a sealed-off tube may be decreased to
10
7
atm. The gas discharge technique allowed study of various processes involv-
ing electrons and ions in gases, including the cathode rays discovered by J. Plueck-
er (Germany) in 1851. Firstly, they were discovered from the sharp straightforward
boundary of fluorescence resulting from applying a high voltage to electrodes of
the tube with a low gas pressure. Later, it was proved that the gas was excited by
a beam of charged particles that came from the cathode and therefore they were
named cathode rays (
Kathodenstrahlen
) [10, 11]. In reality, cathode rays are electron
beams and they were used subsequently as a specific instrument which became
important in the new physics at the beginning of the twentieth century. For this
technique the creation of an inductive coil by Rumkopf in 1851 was important as
it provided a possibility to obtain high voltages in a simple way. All these develop-
ments allowed various forms of gas discharges to be obtained, including a glow
discharge, and allowed them to be used for various technical applications. Along
with gas discharges, this technique allowed beams of charged particles to be gen-
erated.
The analysis of some results obtained by using the new technique led to a new
understanding of the nature of ionized gases and related physical objects. The un-
derstanding of electricity carriers followed from the electrolysis laws of Michael
Faraday (England) in 1833-1834. The electrolysis laws give the ratio of the charge
of the carrier to its mass. Along with the establishment of the fundamental laws of
electrolysis, Faraday introduced new terms such as “ion” - the electricity carrier -
and “anode” (“way up” fromGreek) and “cathode” (“way down” fromGreek) for the
electrodes involved in electricity transfer. In continuation of these studies, Stoney
(England) suggested the term “electron” for the quantum of elementary charge and
estimated its value in 1874.
The development of electricity sources and gas discharges was a basis for the cre-
ation of the new science branches, such as spectroscopy, atomic physics, and nu-
clear physics, and also led to quantummechanics, the atomic quantum theory, and
nuclear physics at the beginning of the twentieth century. In turn, this new physics
stimulated the subsequent gas discharge development [12, 13]. Finally, understand-
ing the gas discharge phenomenon as a self-consistent one due to the ionization
balance in a gas allowed Townsend to describe the passage of current through a
gas [14-16]. According to I. Langmuir, an ionized gas excited in a gas discharge is
characterized by different spatial regions, and the region adjacent to the walls was
named by him as a “sheath”, whereas a quasineutral ionized gas far from the walls
was called a “plasma” [1-3] by analogy with blood plasma. These terms are used
now [17, 18].
