Analysis Of A Linear Accelerator

Analysis Of A Linear Accelerator Nowadays patient with cancer are treated by radiation, surgery, chemotherapy or with a combination of these options. The radiotherapy treatment unit used to deliver radiation to cancerous cells and tissues is the linear accelerator, also known as linac. The linear accelerator has been defined by Khan F. M. (2003) as a device that uses high-frequency electromagnetic waves to accelerate electrons, to high energies through a linear tube. The electron beam itself can be used for treating superficial toumors, or it can strike a target to produce x-rays for treating deep-seated toumors. The energy used for the radiotherapy treatment of deep situated tissues varies from 6-15 MV (photons) and the treatment of superficial toumors (less than 5cm deep) is between 6-20MeV. (Khan, 2003) The purpose of this essay is to describe a linear accelerator, analyse its components in the stand and the gantry of the linac, and explain the principles of operation and then discuss why it is best situated to the task for which it was designed. Some advantages and disadvantages of the linac will also be included in the discussion part of the essay. Main body: Figure 1:http://www.cerebromente.org.br/ As you can see from the schematic picture above, the major components of a linac are: Klystron: source of microwave power Electron gun: source of electrons. Waveguide (feed and accelerating waveguide): microwaves travel through the feed waveguide and then to the accelerating waveguide, where electrons are accelerated from the electron gun. Circulator: a device that prevents microwaves of being reflected back from the accelerator. Cooling water system: cools the components of the linac. Bending magnet: â€Å"A bending magnet is used to change the direction of the accelerated electron beam from horizontal to vertical.† (Hendee et al, 2005) X-ray target: electrons hit the target and produce x-rays. Flattening filter: even out the intensity of the beam. Ionisation chambers: they control th e dose leaving the head of the linac. Beam collimation: shape the radiation beam to a certain size Klystron: There are two types of microwave power. The klystron and the magnetron. Magnetrons are used for lower energy linacs. In the high energy linear accelerator klystron is used. All modern linacs have klystrons. Both klystron and magnetron are special types of evacuated tubes that are used to produce microwave power to accelerate electrons. (Karzmark and Morton, 1998). â€Å"The tube requires a low-power radiofrequency oscillator to supply radiofrequency power to the first cavity called the buncher.† (Hendee et al, 2005) In the bunching cavity, electrons produced from the electron gun, are bunched together to regulate their speed. The microwave frequency is thousands times higher than ordinary radio wave frequency. For a linac to work, the microwave frequency needed is 3 billion cycles per second. (3000MHz) (Karzmark and Morton, 1998) Electron gun: The electron gun is part of the klystron. Here, electrons are produced and then accelerated to radiofrequency cavities. The source of electrons is a directly heated filament made from tungsten, which will release electrons by thermionic emission. (Bomford, 2003) Tungsten is used because it is a good thermionic emitter with high atomic number, providing a good source of electrons. Klystrons usually have 3-5 cavities, used to bunch electrons together and increase microwave power amplification.

HEALTH ECONOMIC Assignment Example | Topics and Well Written Essays - 250 words

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Reconstruction Essay Example | Topics and Well Written Essays - 1500 words

Reconstruction - Essay Example The rise was initiated by various factors that included social, economic, legal, and political. The big business era was a source of wealth and capitalization for many Americans most of who were involved in various national corporations that controlled markets (Wilson 214). Sufficient resources such as oil, coal, and iron were foundations for the building of the states after the war. Adequate iron led to the production of iron and steel that were part of inputs in the big businesses. Steel was used to make railroads and cars that were used in the transportation of various products ranging from coal, ores, and agricultural produce from a state to another (Symonds). Oil was a precious good after its discovery, which was used in homes and to power machinery in some of the industries. Coal powered factories were efficient compared to water-powered; hence, the discovery of coal-fueled the increase of steel mills in the U.S. There was a rise in the number of immigrants to Southern States that provided a foundation for investors, investors, and labor. The immigrants worked in the big businesses and agricultural sector; hence, providing cheap labor. The high population required enhanced transportation methods leading to the increase in railroad networks. The increased demand led to a change in the social life of some of the citizens due to enhanced wealth sources. The banks offered loans that were sources of investment capital. Investors in the big businesses would seek assistance from banks to set up steel mills and railroads as part of the reconstruction. Stock markets were used by trusts such as Rockefeller’s to trade shares and purchase other corporations. The Federal Government did not regulate the operations and establishment of businesses. They were free to pool and set cartels that would increase competition opportunities. However, this factor led to the growth of monopolies in the