Efficiency of Gas Filled Detector for Beta and Gamma Radiations

Anno, Anno Kare (2006) Efficiency of Gas Filled Detector for Beta and Gamma Radiations. Masters thesis, Addis Ababa University.

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There are many forms of radiation –heat, light, radar, radio waves etc. differ from one another in frequency but not in kind. The so called “kinds” of radiation are characterized by the techniques used to produce and detect them; The classical theory of Maxwell applies to all these radiations and all are ultimately due to the acceleration of electrical charges. Except for differences of frequency, and observation made on one’Kind “of radiation must also be true of all other kinds. Radiation is energy in the form of waves or particles. The great majority of it occurs naturally and we are all exposed to it all of the time .It is all around us-in atmosphere, the earth, our food our bodies and from cosmic rays, from outer space and medical X-rays. Radiation can be produced from a variety of sources. There are two broad types - ionizing and non-ionizing radiation - classified in terms of their effects on matter. Non-ionizing radiation includes some ultra violet light, visible and infrared light, microwaves, radar and radio waves. Ionizing radiation is that which has enough energy to remove an electron from an atom, thereby producing an ion - an electrically charged atom or grouping of atoms. Cosmic rays, x-rays and the radiation emitted by the decay of radioactive substances are examples of ionizing radiation. Although they are types of radiation, alpha and beta particles and neutrons are not parts of the electro-magnetic spectrum because they are particles not waves. We are most affected by ionizing radiation, which deposits some of its energy as a result of electrical interactions when it passes through matter. It can be harmful to the human body in excessive doses because it can damage individual cells, possibly resulting in damage to organs, or other long-term effects. Radiologist discovered that repeated exposure of their hands to X-rays resulted in skin burns. This discovery led to the wide spread use of X-rays in the treatment of cancer. Also it was realized that excessive exposure of the body to radiation could result in radiation different in their biological effect on tissues even when the absorbed dose is the same. This basically depends on ionizing power of radiation. The relative biological effectiveness of electrons and positions are the same. Whereas, heavy ionizing particles such as alpha particles and fission fragments produce much greeter biological effect. However, containing it, shielding against it, moving away from it, or removing the source can gain effective protection from radiation. Radiation has the same effect, whether from natural or man-made sources. Most people receive their greatest exposure to radiation from the naturally occurring radioactive gas radon. It is produced as a result of the decay of uranium - which is present in all rocks and soils. We all breathe it every day and it accounts for about 50 per cent of our total radiation dose. In fact, about 85 per cent of our total dose is the result of naturally occurring radiation. Medical sources, such as x-rays, account for a further 14 per cent. The fall-out from past nuclear weapons tests and incidents such as Chernobyl amount to 0.2 per cent and discharges from the nuclear industry total much less than 0.1 per cent It may be wondered why it is, if the surfaces of all bodies are continually emitting radiant energy, that all bodies do not eventually radiate away all their internal energy and cool down to a temperature of absolute zero. The answer is that they would do so if energy were not supplied to them in some way. In the case of filament of an eclectic lamp, energy is supplied electrically to make up for the energy radiated. As soon as the energy supply is cut off, bodies do, infact, cool down very quickly to room temperature. The reason that they don not cool further is that their surroundings (the walls, and other objects in the room) are also radiating and some of this radiant energy is intercepted, absorbed and converted into internal energy. The same thing is true of all other objects in the room –each is both emitting and absorbing radiant energy simultaneously.

Item Type: Thesis (Masters)
Subjects: Q Science > Q Science (General)
Q Science > QC Physics
Divisions: Africana
Depositing User: Selom Ghislain
Date Deposited: 16 Aug 2018 08:50
Last Modified: 16 Aug 2018 08:50
URI: http://thesisbank.jhia.ac.ke/id/eprint/4797

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