Radiation Physics Lecture Notes 2024/2025 PDF

Radiation PHYSICS 4th Year Phys. dep Dr. Nehal Sabry 2024/2025  When neutron from cosmic radiation interacts with atmospheric nitrogen the product is………………………………………………………………… Cosmic radiation are two kinds………………………….  Non-ionizing radiation is a naturally occurring phenomena...

Radiation PHYSICS 4th Year Phys. dep Dr. Nehal Sabry 2024/2025  When neutron from cosmic radiation interacts with atmospheric nitrogen the product is………………………………………………………………… Cosmic radiation are two kinds………………………….  Non-ionizing radiation is a naturally occurring phenomena, and ionizing radiation is only created artificially. (true or false) The dose from cosmic radiation duplicates each……………………from sea level.  The annual dose from cosmic radiation nearly equal……………………… Due to its physical properties, proton is classified as…………………….. …………………………Protect us from cosmic radiation. Lec.2 - Con. Ch. 1 Sources of radiation man-made radiation and natural background radiation Remember X-ray X-ray tube X-ray spectrum X-ray uses  Third According to its sources Natural Background Man-Made Radiation Radiation Cosmic Terrestrial Internal Radiation Radiation Radiation 2-Terrestrial Radiation Terrestrial radiation is emitted by the long-lived radionuclides in rocks and soils some of which become incorporated into the human body through the food and water supply. Important radioactive elements include uranium and thorium and their radioactive decay products which have been present since the earth was formed billions of years ago. The amount of terrestrial radiation varies in different parts of the world due to different concentrations of uranium and thorium in soil. Some radioactive material is ingested with food and water. the most important radioactive elements in the rocks of the earth's crust that contribute to the human radiation dose (Uranium-238), which emits alpha rays and generates 13 radioactive elements that emit alpha, beta and gamma radiation. (Thorium-232), which emits alpha rays and generates 10 radioactive elements that emit alpha, beta and gamma radiation.  Radon gas Rn 222 -Rn 220- Rn219 The most significant impact on the radiation exposure comes from natural sources of gaseous radon and its daughter products. Radon is an odorless and colorless radioactive gas that occurs in nature together with uranium and thorium ores it can diffuse out of the rock and mix into the air where it can be inhaled. Outside its concentration is low because of the dilution in air, but in closed rooms like basements its concentration can be quite large.  It decays by alpha decay and is dangerous in breathing as it causes internal irradiation. One of the radon-problem is therefore mainly due to - bombardment of sensitive lung tissue, which can cause cancer. Radon gas can also dissolve and accumulate in water from underground sources  Rn-222 uranium-238 disintegrates form radium-226 which disintegrates to form radon-222 gas 22286Rn gas is Particularly important a member of the uranium 238 series is commonly found in the environment. It decays by -emission with a half-life of t1/2=3.82 days Once inhaled, the majority of the dose is deposited in the trachea-bronchial region by the decay of the short-lived daughters, 218Po and 214Po, which are both alpha-emitters  Radon-220 the less common isotope radon-220 (thoron) is part of the decay series from thorium-232. its half life time is 56s  Radon-219 is part of the decay series from uranium-235. its half life time is 3.96s 3-Internal Radiation Small traces of many naturally occurring radioactive materials are present in the human body. These come mainly from naturally occurring radioactive nuclides present in the food we eat and in the air we breathe. These isotopes include carbon-14 and potassium-40. Potassium and carbon enter the body through the food chain.  Potassium is an essential mineral for life. Potassium has three naturally occurring isotopes: 39K (93.3%), 40K (0.01%) and 41K (6.7%). 39K and 41K are stable. Potassium 40 has the unusual property of decaying into two different nuclei: Naturally occurring 40K decays to stable 40Ar (10.7%) by electron capture and by positron emission and decays to stable 40Ca (89.3%) by beta negative emission; 40K has a half-life of 1.250 x 109 years.  The reason for this is that protons, like neutrons, like to exist in pairs in a nucleus. Potassium 40 contains odd numbers of both – 19 protons and 21 neutrons. As a result, it has one single proton and one single neutron. In both argon 40 and calcium 40, however, the number of protons and neutrons are even, granting them that extra stability. (potassium-argon dating) The amount of radiation from potassium-40 does not vary much from one person to another. However, radon exposure differs significantly from place to place depending on the amount of uranium in the soil. The outlines of World Population-weighted average annual effective doses (mSv) (UNSCEAR 2008) Source of radiation Effective dose mSv/y Cosmic radiation 0.38 Radiation with terrestrial origin (external) 0.48 Internal contamination 0.30 Radon 222and its daughter products 1.15 Radon 220and its daughter products 0.1 TOTAL 2.41 Man-Made Radiation Sources Although all people are exposed to natural sources of radiation, there are two distinct groups exposed to man-made radiation sources. These two groups are: Members of the public Occupationally exposed individuals Man-made radiation consists of radiation from diagnostic radiology (X-rays) nuclear medicine (radiopharmaceuticals) Radiotherapy fall-out (from nuclear bomb testing between 1945 – 1980) nuclear power plants and nuclear laboratories inhaling radioactivity while smoking  X-rays and medical procedures, are the most significant sources of man-made radiation exposure to the public such as diagnostic X-rays, nuclear medicine, and radiation therapy, Some of the major isotopes would be I-131, Tc-99m, Co-60, Ir-192, Cs-137, and others. consumer products In addition, members of the public are exposed to radiation from consumer products, such as Tobacco , building materials, combustible fuels (gas, coal, etc.), airport X-ray systems, road construction materials, etc.  Of lesser magnitude, members of the public are exposed to radiation from the nuclear fuel cycle NUCLEAR POWER the development of the nuclear power industry and The increasing use of radioisotopes results in increasing quantity of radioactive waste. The annual average dose to a member of the public from nuclear power plants is very low The final sources of exposure to the public would be Fallout from nuclear weapons tests radioactive elements have dispersed in the environment from nuclear weapons tests and accidents  Occupationally exposed individuals, on the other hand, are exposed according to their occupations and to the sources with which they work. Occupationally exposed individuals, however, are monitored for radiation exposure with dosimeters so that their exposures are well documented in comparison to the doses received by members of the public. Some of the isotopes of concern would be uranium and its daughter products, cobalt-60, cesium-137, americium-241, and others.  Note Radiation is used in the manufacturing of many consumer products. It is used to sterilize products such as cosmetics and medical supplies for shrink-wrap packaging. to determine the thickness of materials, how full cans are before sealing them, the quality of welds in structures such as bridges and buildings. This use of radiation can expose workers in the factory, but it does not make the consumer product radioactive Radon 55% Internal Natural 11% sources Terrestrial 8% Cosmic 8% Consumer Man made products sources 3% Nuclear Medicine 4% X-ray  In 1895 Roentgen discovered X-rays almost by accident. While doing some experiments in which he passed an electric current through Crookes tubes (special tubes containing a cathode and electrode from which the air has been removed), Roentgen noticed that photographic plates nearby began to grow fogged https://youtu.be/IsaTx5-KLT8  Filament current applied through tungsten filament at cathode. Heats up filament to produce enough energy to overcome binding energy of electrons (thermionic emission). Electrons released from filament Tube voltage is applied across the x-ray tube. Electrons, therefore, are accelerated towards positively charged anode, which gives them a certain energy.  The electrons strike the anode and the energy released via interaction with the anode atoms produces x-ray photons. These x-ray photons leave the x-ray tube through the window in an x-ray beam towards the patient. They pass through the patient to the film to produce the x-ray image (this section is covered in the next chapter "Interaction with matter"). https://www.youtube.com/watch?v=IsaTx5-KLT8  X-ray spectrum The resulting spectrum of x-ray photon energies released is shown in the graph. At a specific photon energy there are peaks where more x-rays are released. These are at the characteristic radiation energies and are different for different materials. The rest of the graph is mainly Bremsstrahlung, in which photons with a range of energies are produced. Bremsstrahlung - continuous spectrum Bombarding electron approaches the nucleus. Electron is diverted by the electric field of the nucleus. The energy loss from this diversion is released as a photon (Bremsstrahlung radiation).  A bombarding electron knocks a k- shell or l-shell electron out. A higher shell electron moves into the empty space. This movement to a lower energy Characteristic state releases energy in the form of an x-ray photon. radiation The bombarding electron continues on its path but is diverted.  when the fast moving electrons knock off one electron from K-Shell and the vacancy is filled by the nearby electron from the L shell. During this transition, the energy difference is radiated in the form of X-rays of very small wavelength. This corresponds to Kα - line of the series. The frequency ν1 of this line is given by the relation (EK - EL) = hν1. Suppose, the electron from M shell jumps to the K shell, it gives out Kβ line and so on X ray spectrum give reason The tungsten (W) x-ray spectrum at 40KeV is continuous spectrum only. How X-rays are absorbed An X-ray machine sends out a beam of electromagnetic radiation that passes through the body. All materials do not absorb X-rays equally well; if they were, they would not be very useful in diagnosis. As it travels, different parts of the body absorb different amounts of energy. Heavy elements such as calcium are much better absorbers of X-rays than light elements such as carbon, oxygen, and hydrogen, and as a result, structures containing heavy elements, like the bones, stand out clearly.  Dense areas, like bone, block more of the radiation, giving them a white appearance on an X-ray. Fat and muscle absorb less, so they show up in different shades of gray. Tumors often show up as lighter gray than the surrounding tissue. The lungs look black because they are filled with air. After it passes through the body, the X-ray hits a special detector that creates the image on a computer (digital image). Note: The soft tissues-fat, muscles, and are difficult to distinguish from each other on an X-ray image.  Filters in Radiography When the x-ray beam is produced, much energy of photons exists. Many are of such low energies that they will offer nothing to the production of the radiograph. Filtration is required to absorb the lower-energy x-ray photons emitted by the tube before they reach the target (skin) The use of filters reduces the dose received by the patient and nearly not contribute to image quality *This dose reduction is achieved by interposing between the X-ray tube and patient a uniform flat sheet of metal.  Filters for medical radiography are usually made of aluminum (Al) Al (Z = 13) is chosen because it is efficient in removing low-energy x-rays through the photoelectric effect and because it is readily available, Lightweight, inexpensive, and easily shaped. Beryllium is commonly used in mammography (which use low- energy photons) as it provides very little filtration.  There are two types of filtration : Inherent filtration from components in the x-ray tube like housing (glass enveloped) and cooling oil (oil surrounding the tube) Added filtration A thin sheet of metal positioned between the protective x-ray tube housing and the x-ray beam collimator is the usual form of added filtration (Al, Cu, etc.). The thickness of filter materials is dependent on atomic numbers, kilovoltage settings, and the desired filtration factor. Total filtration is the combined effect of inherent and added filtration https://www.jaypeedigit al.com/book/978935152 8548  X-ray applications