Magnetic field electron confinement

The so-called Aharonov-Bohm effect is observed with another experimental setup. A solenoid is placed immediately after the plate, between the slits, and its axis is parallel to the slits, and therefore normal to the beam trajectory beam. If the solenoid is long enough, the magnetic field remains confined in it as a consequence, the magnetic field is shown to have a null value in the region crossed by electrons beamed on either sides of the solenoid. The Lorentz force exerted on the electrons is expected to be null in the absence of any external electrical field. 

Atoms are first stripped of their electrons at very high temperatures this creates a plasma (ionized gas) of positive ions. Then the positive ions must be brought into close enough proximity, so that the strong attractive force between nucleons can overwhelm the Coulomb repulsion between them. Magnetic fields can confine hot plasmas of ions, provided that collective instabilities of these plasmas can be controlled. For a successful nuclear fusion reactor, three requirements must be met (1) The density of the plasma must exceed some critical value p. (2) The plasma confinement time must exceed some critical value t. (3) The temperature of the plasma must exceed some critical value 9... 

The electron bombardment method of ionization has the advantage that no heated surfaces are required, and that propellant materials other than alkali metals may be used. This method utilizes a magnetic field to confine electrons emitted in a chamber through which the propellant is fed. The electrons are extracted from the emitter by a small electric field and move along or around the magnetic field lines with sufficient velocity to ionize atoms with which they collide. The resulting ions are then extracted from the chamber with an electrostatic field, as with other ionization methods. 

End-Hall plasma source (plasma technology) A plasma source that uses a thermoelectron emitter and a magnetic field to confine the electrons so as to impinge on gas molecules exiting an orifice. See also Plasma source. 

Restraining a gaseous plasma from expanding and compressing is also a form of plasma modification. Two reasons for plasma confinement are maintenance of the plasma and exclusion of contaminants. Plasmas may be confined by surrounding material, eg, the technique of wall confinement (23). A second approach to confinement involves the use of magnetic fields. The third class of confinement schemes depends on the inertial tendency of ions and associated electrons to restrain a plasma explosion for a brief but usehil length of time, ie, forces active over finite times are required to produce outward particle velocities. This inertial confinement is usually, but not necessarily, preceded by inward plasma motion and compression. 

An external magnetic field has also been used to confine the plasma [143]. An arrangement where electromagnets are located under the cathode is known as the controlled plasma magnetron method [144]. The diffusion of electrons to the walls is prevented by the magnetic field between cathode and anode. This results in an increase in electron density, and consequently in a faster decomposition of silane and a higher deposition rate. At a deposition rate of 1 nm/s, device quality material is obtained [144]. In addition, a mesh is located near the anode, and the anode can by biased externally, both in order to confine the plasma and in order to control ion bombardment. 

Figure 3 A schematic drawing of a typical ECR ion source. The ions and electrons are confined in the plasma by the magnetic field generated by the solenoid coils and the hexapole magnet.

A flow of argon in which ionisation has been initiated by a tesla discharge passes through an open quartz tube. A water-cooled copper tube is coiled around the quartz tube (Fig. 15.1). The copper tubing is connected to a radiofrequency generator (typically at 27 MHz) with a power of 1 to 2 kilowatts. The variable magnetic field that is created confines the ions and electrons to an annular path (with the appearance of an eddy current). As this environment becomes more and... 

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