Direct Accelerators

In principle, a direct electron accelerator consists of a high-voltage generator connected to an evacuated acceleration system. The different direct accelerators currently used employ similar methods for electron emission, acceleration, and dispersion the differences are in the design of their voltage generators. 

Secondary windings connected in series feed the high-voltage terminal. The system provides a beam only during the negative half cycle, with a voltage variation between zero and the peak value the machine was designed to deliver. Sulfur hexafluoride gas is used for electrical insulation.  

Low-frequency transformers with iron cores connected to rectifier circuits can generate potentials up to approximately 1 MV. Traditionally, iron core transformers are insulated by oil, but the recent models use sulfur hexafluoride. The energy rating of these generators is in the range from 0.3 and 1 MeV with beam powers up to 100 

ICT machines produced recently have energy ratings from 0.3 to 3.0 MeV and beam power capabilities up to 100 kW. Nearly 180 of these machines, the majority of them rated for less than 1 MeV, have been installed as of the early 1990s. They are used mainly for cross-linking of heat-shrinkable film, plastic tubing, and electric wire.  

Schematic of a direct accelerator (Dynamitron) accelerator. (Courtesy of IBA.) 

---

A direct acceleration of the slow step and thus of the reaction as a whole... 

Early Be and B Observations primaries, while Standard GCR produce secondaries GCR metallicity always the same, originating in SN ejecta or in Superbubbles (SB) Problem with absence of unstable 59Ni in GCR it becomes stable if directly accelerated in SN or continuously accelerated in SB by stellar winds... 

Polarization in the cathodic direction accelerates the cathodic reaction and is called cathodic polarization polarization in the anodic direction accelerates the anodic reaction and is called anodic polarization. In Fig. 7-4 the polarization curve is cathodic at potentials more negative and is anodic at potentials more positive than the equilibrium potential E. In electrode reaction kinetics the magnitude of polarization (the potential change in polarization) is called the overvoltage or overpotential and conventionally expressed by symbol ii, which is negative in cathodic polarization and positive in anodic polarization. 

It is to be expected that reductive dissolution of Fe oxides becomes faster as the electron activity increases, i.e. the lower the redox potential (Eh) of the aqueous system, the faster the dissolution. Fischer (1987) dissolved goethite at pH 3 and RT in an Eh range of between -0.3 and -rO.l V and found that the dissolution rate. Ink, decreased linearly from about 5 to 1 mg Ee " L min (r = 0.96). Organic and inorganic additives that shift the redox potential in a negative direction, accelerate dissolution of iron oxides (Frenier Growcock, 1984). 

Loss of ions occurs via the processes of mutual neutralization, ternary ionic recombination and attachment to aerosol surfaces, processes which urgently need further study in the laboratory. It is an interesting fact that the ion chemistry directly accelerates the loss of ionization from all regions of the atmospheric plasma. Atomic ions are converted into molecular ions, molecular ions into larger cluster ions which recombine more rapidly. The larger ions also act as nucleation sites for the formation of aerosols, thus involving a transition from the molecular to the liquid state. 

Processes are called autocatalytic if the products of a reaction accelerate their own formation. An extreme example would be a chemical explosion. In this case, it is usually not a chemical product that directly accelerates the reaction rather, it is the heat generated by the reaction. The more heat produced, the faster is the reaction and the faster the reaction, the more heat that is produced, etc. 

Chidiac P, Ross EM (1999) Phospholipase C-betal directly accelerates GTP hydrolysis by Galphaq and acceleration is inhibited by... 

In principle, the relativistic winds of newly born magnetars (neutron stars with surface magnetic fields about 1015 G) can directly accelerate particles up to 1021 eV [48], [49] but they are very rare events in the Galaxy. 

Speed, velocity, and acceleration also can be distinguished. The terms velocity and speed are often used interchangeably however, the two quantities are frequently not identical. Velocity means the rate of motion in a particular direction. Acceleration results from a change in velocity over time. General velocity and acceleration measurements are beyond the intent of this chapter. Reaction speed and response speed are other related variables also not considered. 

Turbomolecular pumps are based on the blades of the high speed rotors (50,000 - 90,000 rpm) providing directional acceleration to the gas molecules, moving them away from the chamber that is being evacuated. 

In addition, two further variants, E and N, were synthesized in which residues in the hydrophobic core were replaced with alanine. Even though alanine does not bear any destabilizing side chains, this highly conservative replacement proved to eliminate aU autocatalytic activity. Reactions between E and N as well as E and N did not show any template-directed acceleration on addition of both alanine-modified and native templates. This remarkably high fidelity toward sequence variations was later explored in investigations of more complex systems of interacting replicators. 

The constraints appear to be general.Unlike explosion where feedback leads to direct acceleration of reactant consumption, oscillatory mechanisms are more subtle. According to (7.18) increasing [X] when [Y] is small... 

Acceleration in X direction Acceleration in Z direction Acceleration due to Gravity Internal Energy (Mbar-cc/gram)... 

A significant conclusion of the Gorichev et al. work may be summarized as follows additives, which shift the potential in the negative direction, accelerate the dissolution of iron oxides. 

---