Microwave linear accelerators

A standing wave (SW) microwave linear accelerator consists of a linear array of resonant cavities that are energized by a common source of microwave power. These cavities are nearly isolated by webs with small-diameter apertures, and the high-energy electron beam passes through these apertures. However, they are coupled through intermediate cavities, which stabilize the microwave phase relationship between the accelerating cavities. 

Schematic of a microwave linear accelerator or linac The three most common designs of industrial low-energy electron accelerators...

The technique of pulse radiolysis (1) has found extensive application in the study of fast free radical reactions with compounds of biological interest (2), The high energy, electron pulse of short duration (typically 0.2 ys) produced by a microwave linear accelerator forms products, including free radical species, from the radiolysis of water ... 

Linear accelerator A device that uses microwave technology to accelerate electrons in a highly focused beam to deliver targeted radiation to tumor sites. 

A rapid reaction kinetic technique (time scale = 10-1000 ps) that typically uses a Van de Graff accelerator or a microwave linear electron accelerator to promptly generate a pulse of electrons at sufficient power levels for excitation and ionization of target substances by electron impact. The technique is the direct radiation chemical analog of flash photolysis and the ensuing kinetic measurements are accomplished optically by IR/visible/UV adsorption spectroscopy or by fluorescence spectroscopy. 

There are two major mechanisms by which the microwave electric field is converted to heat within a food. The first, the ionic interaction, comes from the linear acceleration of ions by the field. These ions are primarily from various salts within the product. The second interaction is molecular rotation of polar molecules, primarily water, as well as weaker interactions with carbohydrates and fats. 

So far the microwave electron linear accelerator is the most suitable for this purpose. In this accelerator electrons are injected into an evacuated cylindrical waveguide in which pulsed radiofrequency of several megawatts from a klystron oscillator travels. Electrons enter the radiofrequency field at the correct phase are accelerated to a velocity close to that of light. By means of gun control, electrons are injected only during the radiofrequency pulse, and thus the electron pulses of several nanosecond duration, useful for conventional nanosecond or microsecond pulse radiolysis, are produced. 

With the aid of a subharmonic prebunching cavity operated at a few tenths of the main accelerating microwave frequency, the electron linear accelerator is... 

Two types of electron accelerator machine exist, the electrostatic accelerator and the microwave linear... 

To see that, let us focus on a couple of factors that mainly determine the economy of the EB remediation process i.e. a high power (by which high volumes of water can be rehabilitated daily), and the efficiency (which establishes the transfer rate ofthe accelerator nominal power into useful energy). To this respect, it is instructive to learn from Table 2 that DC and UHF machines (Chapter 2) best match with these requirements. In the DC type machines, electrons are accelerated by a direct-current field, while in the UHF type, acceleration occurs across an electromagnetic field oscillating at few hundreds MHz. These accelerators achieve high powers coupled with moderately-high efficiencies, and therefore represent the best choice for wastewater treatment. At present, the linear accelerators, which are based on a microwave field, show efficiencies and power below the others, such that they are not suitable for environmental purposes. 

Water (1.51) was brought in a storage vessel and 200 pg of each of scandium and samarium were added as nitrate solution to serve as internal standards. The sample was then irradiated with 30 MeV bremsstrah-lung (mean electron beam current 150 pA) from an electron linear accelerator for 5h in a 0.7-1 flow-chamber under slow continuous cyclic flow. Thereafter, the components of interest (Sc, Cr, Mn, Co, Ni, Cu, Zn, As, Y, Zr, Nb, Mo, Cd, Sn, Sb, I, Ba, Tl, Pb, and U) were separated by a sulfur-substituted cellulose-based sorbant filter switched into the flow cycle after activation. This sorbant was then dried in a microwave furnace and pressed to a thin (1mm thick) pellet. Product activities were counted with a large coaxial germanium detector (where was... 

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