Thermionic emission from a metal can be explained in terms of Fig. The high-voltage circuit is the subcircuit shown in the upper right portion of Fig. The main advantage of full-wave rectification is that the exposure time can be cut in half due to the doubling in x-ray output compared to half-wave rectification. Extraoral unitsdesigned to provide greater radiation output as required by extraoral procedures; the x-ray beam is larger to accommodate larger anatomic areas under study, 1. Simply understood, the generation of X-rays occurs when electrons are accelerated under a potential difference and turned into electromagnetic radiation. sharing sensitive information, make sure youre on a federal The electric factors that control x-ray production are introduced in this chapter. All of the following are preferred cathode filament materials EXCEPT, 5. The space charge provides the electron source for x-ray production. As explained in Chapter 4, it increases the incoming voltage by the value of the transformer ratio. An advantage of using tungsten is that it has a high melting point, which enables it to last through thousands of exposures. The low barrier at the p- or n-layer is one reason for the poor performance of thick . Characteristic radiation (see Figure 6-4), (1)Can only occur at 70kVp or higher with a tungsten target;2 accounts for a small portion of x-rays produced by dental x-ray machines, (2)Occurs when an electron removes an orbital electron from the target atom, (3)During restabilization of the ionized atom, the hole created by the ejected orbital electron is filled by an outer-shell electron; the movement of the outer-shell electron results in the transference of electron-binding energy into x-ray energy, (4)The energy of the resulting characteristic x-ray photon occurs from the difference in binding energies of the orbital electrons involved, 1. The kinetic energy of the electron is converted into an x-ray photon. When an outer-shell electron drops to fill the hole, a characteristic photon is emitted. -, Seibert JA, Boone JM. Other conventional radiographs, including oral and maxillofacial radiography, constitute 5% of medical exposures, 3. (From Frommer HH, Stabulas-Savage JJ: Radiology for the dental professional, ed 9, St Louis, 2011, Mosby. target angle Bremsstrahlung is a German word that means braking or slowing. This circuit is divided into two parts by the step-down transformer (11 and 12). Simplified diagram of an x-ray circuit. It moves in a pulsating manner from positive to negative at a rate of 60 pulses, or waves, per second and is stated as 60Hz (Fig. The pulsed x-ray output of a full-wave rectified machine occurs 120 times each second compared to 60 times a second for half-wave rectification. See the section on Prevention of Disease Transmission During Radiographic Procedures in Chapter 10. It moves in a pulsating manner from positive to. However, when the foil was given a more positive charge than the filament, negative charge (in the form of electrons) could flow from the filament through the vacuum to the foil. National Council on Radiation Protection and Measurements (NCRP), 3. It includes the x-ray tube (14) and the rectifier unit (15). The electron cloud is called a space charge and is the source of free (in air) electrons for x-ray production. The step-up transformer is also referred to as the. 1997 Jul-Aug;17(4):967-84. doi: 10.1148/radiographics.17.4.9225393. What is thermionic emission radiology? Both the incoming electron and the K-shell electron are removed. high-frequency (HF) They are simply produced by different interactions of the incoming electrons in the anode. Repair and accumulation of radiation effects, a. X-ray production. The interaction of an incident photon passing near an outer-shell electron and being scattered without losing energy, b. These interactions of electrons with tungsten atoms may occur in one of two ways (Box 5-1). This perspective article provides an assessment of the . Each filament is situated in a hollow area in the cathode called a focusing cup (Fig. Current flows in this circuit only during an exposure. This phenomenon is known as, 12. State Bureau of Health and other local agencies, BAssessment of need for radiographic procedures, 1. The number of electrons is measured in the form of milliampere (mA) units, where 1 milliampere is equal to 6.24 x 10^15 electrons/s. The AC power supply (1) is wired into the building, providing electric power from the local power company. 21. effective focal spot By employing four diodes in the circuit, the current can be redirected during the negative half of the electric cycle so that current will flow in the same direction during both the positive and negative halves of the cycle. Note that the arrow direction of the diode symbol indicates the direction of current flow permitted by the diode. Mechanism for transferring information contained in an attenuated remnant x-ray beam into a visible image, 2. Simple x-ray tube. In order to time the x-ray exposure with rapid inspiration on an infant. How many heat units are generated by three (3) exposures of 100 kVp, 400 mA, and 0.01 second using a high frequency generator? The electron cloud is called a space charge and is the source of free (in air) electrons for x-ray production. Chronic effects (long-term or late)effects observed years after original exposure, BUnits of radiation measurementtwo systems used to define radiation measurement: the metric equivalent system, or Systeme Internationale (SI), adopted in 1985, is preferred;3 an older, traditional system may be found in the research literature published prior to 1985, 1. Although the thermionic emission in traditional materials, such as copper and silicon, has been well-explained by a theoretical model put forward by British physicist O. W. Richardson in 1901 . The pulsed x-ray output of a full-wave rectified machine occurs 120 times each second compared to 60 times a second for half-wave rectification. 5-2), a hot cathode tube that was the prototype for modern x-ray tubes. In order to expel the electrons from the system, they need to be given the energy. The base material (polyester) must possess the dimensional stability to withstand processing procedures, 2. The AAPM/RSNA physics tutorial for residents. Radiographics. When a filament like tungsten is heated to a high temperature, some electrons acquire sufficient energy and are able to break away from the surface of the material and go into space. So, the thermionic emission formula is; J = AT2exp(-W/kT) From the above equation, 'j' is the current density of the electron emission (mA/mm^2) 'T' is surface temperature in Kelvin (K) 'A' is the Plank's constant in Amperes/m2/k2 9. They contain two filaments, one large and one small. X-rays created by this interaction are called. Direct imagingexposure of the film by the interaction of the x-ray beam and the photographic emulsion; exposure of a solid-state digital sensor by the interaction of the x-ray beam and a computer chip composed of a grid of x-ray sensitive cells7, b. A Pyrex glass envelope forms the basic structure of the x-ray tube. One positive and negative pulse equals one cycle or 1Hz. A licensed physician or dentist must prescribe radiographic services, 2. All modern general-purpose x-ray machines are full-wave rectified. Although the power supply may be rated at 220V, the actual voltage can vary as much as 5%, depending on the demand for power in the building or the neighborhood. A large step-up transformer supplies the voltage (40 to 125kVp) required for x-ray production. mA selector The autotransformer (3) is a single-coil transformer that serves three functions: it provides the means for kVp selection, it provides compensation for fluctuations in the incoming line voltage, and it supplies power to other parts of the x-ray circuit. As the density, atomic number, or electrons per gram of the material increase, the number of photons passing through the matter decreases, a. What is thermionic emission and field emission? The tube voltage, tube current, and exposure duration (measured in seconds) are adjustable by the user. 6-3. Define effective focal spot and state its significance with respect to the radiographic image As a result, the electron loses energy. This process is called full-wave rectification because it utilizes the entire electric cycle for x-ray production. 25. Filament materials are chosen primarily for their. exposure timer The primary purpose of the filament circuit is to supply a low current to heat the x-ray tube filament for thermionic emission of electrons. At this point, a space charge (cloud of electrons) forms around the . NOTE: Negative phase (X) is eliminated. This transformer has a very high ratio of at least 500:1. 29. As tungsten is heated, electrons in the tungsten atoms orbits spin faster, moving farther from the nucleus. Although the physical mechanism has been known for over a century, it has yet to be consistently realized in a manner practical for large-scale deployment. AC electrical current travels in the copper wire as a sine wave. Particles have both mass and energy b. Because x-ray tubes may be damaged by improper use and are expensive to replace, this chapter provides guidelines for the safe operation of tubes and suggestions for prolonging tube life. The x-rays are pulsating on, off, on, off, and so forth at a rate of 60 pulses per second. Below 70kVp, there are no characteristic photons produced. Thermionic emission is the emission of electrons from a heated filament or substance. When these fast-moving electrons collide with the target, the kinetic energy of their motion is converted into a different form of energy. X-ray transformer tank containing the autotransformer, filament transformer, high-voltage transformer, and rectifier. If an incident photon is scattered, its direction of travel is altered; scattered photons do not aid in the formation of the radiographic image and only increase image density; scattered radiation causes fog (or noise) that degrades image quality, 2. 30 terms. X-rays are produced by the interactions that occur when high-speed electrons strike a target material, 2. FIG. Introduction Metals, as demonstrated by their ability to conduct an electric current, contain mobile electrons. 6-6). There are three ways in which current is rectified: self-rectification, half-wave rectification, and full-wave rectification. Bremsstrahlung and Characteristic Radiation, X-rays are produced when an incoming electron misses all the electrons in the tungsten atom, gets very close to the nucleus, and then suddenly slows down and abruptly changes direction. This is because the binding energy of a K-shell is 69.5 and it takes at least a 70-kVp exposure to eject this electron. When this material is taken in small bites and reviewed as needed, the entire process of creating and controlling x-rays will gradually come into focus. The anode is the positive end of the tube; the target is part of the anode. Use the barrier technique and disposable plastic wrap to cover items likely to become contaminated (e.g., tube head and PID, tube-head support arm, control panel, countertop, treatment chair), c.Obtain radiographic supplies (e.g., image receptors, holding devices) before starting the procedure, d.Disposable intraoral film packet barrier wraps may be used to minimize the possibility of disease transmission during the radiographic procedure and processing, c.Digital sensors should be wiped with an Environmental Protection Agency (EPA)accepted disinfectant before placing the protective sheath barrier and following removal; consult the manufacturers recommendations, 2. Formation of characteristic radiation. There are four essential requirements for the production of x-rays: (1) a vacuum, (2) a source of electrons, (3) a target, and (4) a high potential difference (voltage) between the electron source and the target. These tubes were used in physics laboratories in the late nineteenth century for the investigation of electricity. 6-3. The source of electrons is a filament at one end of the tube. The energy of the electron stream is converted at the anode into heat (>99%) and x-rays (<1%). It is expanded in Fig. Learn. Explain what is meant by a dual-focus tube and describe its advantages This site needs JavaScript to work properly. What are gamma rays? characteristic radiation The high positive electric potential at the target attracts the negatively charged electrons of the space charge, which move rapidly across the tube, forming an electron stream. X-rays created by this interaction are called bremsstrahlung radiation. Electrons in the outermost orbital shells move so far from the nucleus that they are no longer held in orbit but are flung out of the atom, forming an electron cloud around the filament (Fig. All radiographic exposures, both diagnostic and undiagnostic, should be entered sequentially and cumulatively, 3. Which of the following would affect the production of a thermionic cloud? Can only occur at 70kVp or higher with a tungsten target; Occurs when an electron removes an orbital electron from the target atom, During restabilization of the ionized atom, the hole created by the ejected orbital electron is filled by an outer-shell electron; the movement of the outer-shell electron results in the transference of electron-binding energy into x-ray energy, The energy of the resulting characteristic x-ray photon occurs from the difference in binding energies of the orbital electrons involved, Represent a portion of the electromagnetic spectrum, Exist as pure energy without mass or charge, Travel at the speed of light (186,000 miles per second), When x-ray photons interact with matter, they may be either absorbed or scattered, If an incident (initial) photon is absorbed, it ceases to exist, If an incident photon is scattered, its direction of travel is altered; scattered photons do not aid in the formation of the radiographic image and only increase image density; scattered radiation causes fog (or noise) that degrades image quality, Attenuation (removal) of x-ray photons from the beam as they travel through matter (tissue) is determined by the intensity (energy) of the radiation and the density, atomic number, and electrons per gram of the matter, As the energy of the radiation increases, the number of photons passing through the matter increases, As the density, atomic number, or electrons per gram of the material increase, the number of photons passing through the matter decreases, Primary radiationphotons coming directly from the target of the x-ray tube, Secondary radiationradiation resulting from the interaction of primary radiation and matter, Scatter radiationone form of secondary radiation in which the direction of travel has been altered, Refers to the passing of x-ray photons through a material without any alteration of the photon or the material; accounts for approximately 9% of interactions, Photons proceed to strike the image receptor, Results from an incident photon colliding with a tightly bound inner-shell electron, The incident photon ceases to exist; the electron is ejected as a recoil electron (or photoelectron), Ionization of the atom occurs; the ejected electron leaves a vacancy in the shell that must be filled, Low-energy characteristic radiation is produced by the shifting of an outer-shell electron to the inner vacancy, In the energy range used for diagnostic applications, the photoelectric effect accounts for approximately 30% of interactions, Results from an incident photon colliding with a loosely bound outer-shell electron, Incident photon gives up part of its energy in the ejection of the orbiting electron, The direction of travel of the incident photon is changed; its energy is reduced, The scattered photon and the ejected electron may have sufficient energy to undergo many more ionizing interactions before losing their entire energy, Compton-scattered x-radiations may exit the patients tissues and cause image fogging, In the diagnostic energy range, Compton scattering accounts for approximately 60% of interactions, The interaction of an incident photon passing near an outer-shell electron and being scattered without losing energy, The incident photon ceases to exist, and a new photon of identical energy is released from the electron, In the diagnostic energy range, coherent scattering accounts for approximately 8% of total interactions, Image formation and differential attenuation, Radiographic image formation depends on the differential attenuation of x-ray photons from the primary beam by the clients tissues, If all photons exited the clients tissues (no absorption), the image receptor would be totally exposed; if all photons were attenuated (absorbed), the image receptor would be unexposed, As a result of photoelectric, Compton, and coherent interactions, x-ray photons are removed from the beam, Variances in the ability of tissues to absorb x-rays produce radiographic contrast, Generally, as density, atomic number, and electrons per gram of tissue increase, the number of absorbed photons increases; metallic dental restorative materials, enamel, dentin, cementum, and bone absorb photons to a great extent and produce radiopaque images; bone marrow spaces, sinuses, pulp chambers, and periodontal ligament spaces do not attenuate photons and produce radiolucent images, Interactions of Ionizing Radiation with Cells, Tissues, and Organs, Whole-body exposure (total body)each gram of tissue in the entire body absorbs equal amounts of radiation, Specific-area exposure (localized)each gram of body tissue irradiated in the specific area absorbs equal amounts of radiation (e.g., skin exposure from four bitewing radiographs), Direct effecttransfer of energy by ionization mechanism from an x-ray photon to a biologically critical molecule such as deoxyribonucleic acid (DNA), Indirect effecttransfer of energy by the ionization mechanism from an x-ray photon to a noncritical molecule, which, in turn, delivers the energy to the biologically critical molecule, Genetic effectcauses mutations in future generations; results from the exposure of reproductive cells, yielding alterations in genetic coding, Somatic effectinjury in the person being irradiated, Latent periodtime between the exposure and development of the biologic effect, Deterministic effect when the severity of a biological response is dependent on the dose; for example: erythema (redness of the tissue) would be expected to increase in direct proportion to exposure to damaging radiation, Stochastic effecta biologic response that is based on the probability of occurrence rather than its severity; for example: cancer may or may not occur with exposure to damaging radiation, Acute effects (short-term or early)effects that may occur minutes, hours, or weeks after exposure; usually result from high doses of whole-body exposure, Chronic effects (long-term or late)effects observed years after original exposure. 5-5). Thermionic emission occurs in metals that are heated to a very high temperature. 4 THERMIONIC EMISSION He states that at the pressures worked with (about 1 mm.) 1997 Nov-Dec;17(6):1533-57. 5-5). 2004 Sep;32(3):139-47. Thermionic energy conversion (TEC) is the direct conversion of heat into electricity by the mechanism of thermionic emission, the spontaneous ejection of hot electrons from a surface. In the X-ray tube, the purpose of the filament is to provide the free electrons necessary for X-ray production. Bremsstrahlung Radiation Nonthresholdany dose, regardless of its size, is expected to produce a response, 3. Most outpatient facilities have a 220-V power supply going into the x-ray room. 5-3 Simple x-ray tube. Rectifiers use diodes to convert the circuit from AC to DC. This process is called thermionic emission. The AAPM/RSNA physics tutorial for residents. Characteristic Radiation As tungsten is heated, electrons in the tungsten atoms orbits spin faster, moving farther from the nucleus. At the conclusion of this chapter, you will be able to: Explain the x-ray circuit, label the principal parts, and state the function of each, Explain what is meant by rectification and compare the three basic types, Draw the voltage waveform for each of the following types: unrectified, half-wave rectified, full-wave rectified, three-phase rectified, and high frequency, List the primary features of all x-ray control panels and discuss the principal differences between conventional and computerized control consoles, Describe the components of the automatic exposure control system and anatomically programmed exposure system, List five possible causes of x-ray tube failure and describe methods to prevent each, anatomically programmed radiography (APR). control console Although the power supply may be rated at 220V, the actual voltage can vary as much as 5%, depending on the demand for power in the building or the neighborhood. FIG. The shape of the focusing cup and its negative electric charge cause the electrons to be repelled in the direction of a very precise area on the target called the focal spot, Click to share on Twitter (Opens in new window), Click to share on Facebook (Opens in new window), Click to share on Google+ (Opens in new window), Draw a simple x-ray tube and label its parts, Describe both the composition and the function of the basic parts of the x-ray tube, Describe the production of both bremsstrahlung and characteristic radiation, Explain what is meant by a dual-focus tube and describe its advantages, Explain the significance of the target angle with respect to the line focus principle and the maximum field size, Define effective focal spot and state its significance with respect to the radiographic image, Explain the function of a rotating anode and state its purpose, State the effect of changes in milliampere (mA) and kilovolt (kVp) levels on the resulting x-ray beam, Roentgen discovered x-rays while working with a Crookes tube (Fig. This process is called. The various features of the x-ray circuit and the x-ray control panel are discussed. 5-1), a cathode ray tube that was the forerunner of the fluorescent tube and the neon light. autotransformer Significant increase largely arising from the increased use of large-dose medical imaging technologies, Definitionflow of electrons through a wire or other electrical conductor, Direct current (DC)electrons flow in one direction only along an electrical conductor, Alternating current (AC)electrons flow in one direction and then reverse to flow in the opposite direction, Cycleflow of electrons in one direction and then in the opposite direction, Designated as 60-Hz current in most of the Americas (including Canada) (European countries use 50-Hz current), Ampere (A)the number of electrons flowing in an electrical circuit; one milliampere (mA) is equal to, Volt (V)electrical potential or force that moves electrons along an electrical conductor; one kilovolt (kV) is equal to 1000 volts; kilovolt peak (kVp) refers to the peak voltage of an alternating current; dental units usually operate between 60kVp and 100kVp, Power supply to dental x-ray machines is primarily 110 -V, 60-Hz alternating current, Intraoral unitsdesigned to provide sufficient radiation output for standard intraoral bitewing, periapical, and occlusal radiographs, the x-ray beam is restricted to provide exposure of small anatomic sites, Kilovolt peak (kVp) and milliampere (mA) settings may be constant or variable, depending on the manufacturer, Extraoral unitsdesigned to provide greater radiation output as required by extraoral procedures; the x-ray beam is larger to accommodate larger anatomic areas under study, Generatordevice that supplies electrical power to the x-ray tube, Transformerdevice that changes the potential difference of incoming electrical energy to any desired level, Step-up transformerincreases the voltage sufficiently to propel electrons across the vacuum tube circuit to produce x-ray energy, Step-down transformerdecreases the voltage to generate the electrons needed at the filament circuit, Autotransformera special type of self-rectifying transformer designed to supply voltage of varying magnitude to several different circuits of the x-ray machine (e.g., filament circuit and high-voltage tube circuit), Definitionprocess of changing an alternating current into a direct current, Rectifieran electrical device that changes AC to DC, Dental x-ray units are considered to be self-rectified or half-wave rectified, In half-wave rectification, x-rays are generated during the first (positive) half of the electrical cycle; the filament is negative and the target is positive, X-rays are not generated during the second (negative) half of the electrical cycle, With a 60-cycle alternating current, 60 pulses of x-rays are generated per second, with each having a duration of, In full-wave rectification, x-rays are generated during both phases of the alternating current cycle, Solid-state diodes (or vacuum-tube diodes) are used to redirect electrical current so that the filament remains negatively charged and the target remains positively charged for x-ray production, With a 60-cycle AC and full-wave rectification, 120 pulses of x-rays are generated per second, Lead-lined metal casing for the x-ray tube designed to prevent excessive radiation exposure and electrical shock, Limits amount of radiation leakage from unit, Provides mechanical support and protection for the x-ray tube, Oil, gas, or air is sealed within protective housing and surrounds the x-ray tube, The system serves as both a thermal cushion and a lead-lined electrical insulator, Surrounds the electrodes of the x-ray tube to provide a vacuum, The aperture, or window, is a thin segment of the glass that allows maximum emission of x-rays and minimum absorption by the glass, Electrically negative portion of the x-ray tube, Quantity of electrons are boiled off during thermionic emission (when electrical current is passed through a coil of tungsten wire, atoms of the wire absorb thermal energy, and some outer-shell electrons acquire enough energy to move a small distance away, forming an electron cloud), Because like charges repel, the electron beam is directed to a small area on the anode, Electrically positive portion of an x-ray tube, Tungsten target (tungsten is used as the target material because of its high atomic number, which yields higher efficiency in x-ray production plus higher-energy x-ray photons; conducts heat well; has high melting point [3380C]), Copper stemfunctions to conduct heat away from the target, Voltage between the cathode and the anode, Accelerating potential (speed) of electrons, Focal spotportion of a target bombarded by electrons, Process of selectively removing x-rays from the beam, Total filtrationthe result of inherent and added filtration, Inherent filtrationfiltering of a beam by a glass tube, Added filtration occurs by placing metal discs (usually aluminum) in the path of an x-ray beam, Low-energy, nonpenetrating x-rays are filtered from the beam, Federal regulations require 1.5 millimeters (mm) of aluminum-equivalent filtration for units operating below 70kVp and 2.5mm of aluminum-equivalent filtration for units capable of operating above 70kVp, Process of restricting the size and shape of the x-ray beam, Achieved by the use of a lead diaphragm disc with a circular or rectangular opening through which the beam is narrowed, Definitionan open ended, circular or rectangular cone that extends from the tube head to direct the x-ray beam toward the image receptor, Federal regulations limit the size of the intraoral x-ray beam to 7cm (2.75 inches) in diameter, Rectangular PIDs have an exit size of 3.5 4.4cm (1.375 1.75 inches), Available lengths of PIDs are 20cm (8 inches), 30cm (12 inches), and 40cm (16 inches), The longer PID produces an x-ray beam that is less divergent, Descriptionexposure factors (mA, kVp, and exposure time) are set, and electrical circuits are activated by using the controls located there, Most intraoral machines available today have preset mA and kVp, Usually, settings of 5, 7, 10, or 15mA are available; kVp settings range from 60 to 100, Depending on the machine type, the automatic timer is adjusted in impulses (, The exposure switch is depressed to initiate the emission of x-radiation, The emission of x-radiation from the machine is indicated by an audible chirping sound and the glow of an exposure indicator light, The control panel must be located in a protected area and still allow for observation of the client during exposure, Initial process for x-radiation production is achieved by the activation of the onoff switch located on the unit control panel; this process completes the filament circuit, and the filament is heated, Appropriate mA, kV, and exposure time are set by using the controls located on the unit console; if mA and kV are preset by the manufacturer, the control panel will be labeled with the preset values, Milliamperage control, which is connected to the mA-filament circuit (step-down transformer), allows for warming of the cathode filament and determines the number of electrons available for x-ray production; the higher the mA, the hotter the filament becomes, resulting in a greater number of available electrons, Kilovoltage control, which is connected to the high-voltage circuit (step-up transformer), establishes the high voltage needed for x-ray production; this control also provides the condition in which the anode is positively charged and the cathode is negatively charged for the attraction and high-speed acceleration of electrons from the cathode to the anode; the higher the kVp setting, the greater is the speed of acceleration of electrons from the cathode to the anode, The exposure time establishes the time during which electrons are available for the bombardment of target material, X-rays are produced by the interactions that occur when high-speed electrons strike a target material, The phenomenon of x-ray production occurs only when the exposure switch on the console is pressed, which completes the high-voltage circuit, The heated filament provides electrons for x-ray production by thermionic emission, Thermionic emission occurs when electrons absorb sufficient thermal energy (from the mA circuit) to allow for the electrons short movement away from the filament; commonly referred to as a boiling off of electrons; an electron cloud surrounding the filament is formed, The closure of the high-voltage circuit creates an electrical potential difference whereby electrons are attracted from the negative cathode to the positive anode, The one-directional flow of electrons (from the negative cathode to the positive anode) is influenced by the focusing cup of the cathode; electrons are repelled away from the negatively charged focusing cup because like charges repel; this mechanism controls the size and shape of the electron stream, The electron stream is directed at a small portion of the target called the, The actual production of x-radiation occurs by the interaction of accelerating electrons and target atoms, Less than 1% of the kinetic energy leaving the cathode is converted into x-ray energy; just over 99% of the kinetic energy leaving the cathode is converted into heat energy, Two types of interactions for x-ray production, General (braking, or bremsstrahlung) radiation (.
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