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Bremsstrahlung: Acceleration / Deceleration?
Rennhack:
In the process known as Bremsstrahlung, some books say that the electron accelerates, others say it decelerates. Here is a breakdown, which should enlighten us all.
Either way:
Argon National Lab-7291 Radiation Safety Technician Training Course, better known as “Moe study guide.” By H.J. Moe
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When a charged particle is either accelerated or decelerated in an electronic field, electromagnetic radiation may be given off. If an electron passes close to an atom while traversing a substance, the charge Z on the nucleus will exert a force on the electron. This will cause its path to be bent. During this acceleration the electron may radiate energy of any amount from zero up to its total kinetic energy.
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Health Physics, Principals of Radiation Protection. D.J. REES, M.I.T. Press, p. 23, 1967.
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Continuous x-rays, a.k.a. Bremsstrahlung, is due to the acceleration of free electrons or charged particles. Produced by x-ray machines or by stopping of B-rays in an absorber.
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Health Physics, Principals of Radiation Protection. D.J. REES, M.I.T. Press, p. 48, 1967.
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... The continuous spectrium is due to the rapid slowing down of electrons in the target due to interaction the atomic electric field. This radiation is known as 'Bremsstrahlung'. ...
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Accelerated:
Atoms, Radiation and Radiation Protection by James E. Turner
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A beta particle, having little mass, can be accelerated strongly by the electromagnetic force within an atom and thereby emit radiation, called Bremsstrahlung. Bremsstrahlung occurs when a beta particle is deflected in the electric field of a nucleus.
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Introduction to Health Physics by Herman Cember
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Bremsstrahlung consists of X-rays emitted when high-speed charged particles suffer rapid acceleration. When a beta particle passes close to a nucleus, the strong attractive coulomb force causes the beta particle to deviate sharply from its original path. The change in direction is due to radical acceleration, and the beta particle, in accordance with classic theory, loses energy by electromagnetic radiation at a rate proportional to the square of the acceleration.
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Decelerated:
Radiation Protection in Medical Rediography. Ststkiewicz-Sherer, Mosby, p. 374, 1993.
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Ionozing electromagnetic radiation that is nonuniform in energy and wavelength and that is produced when a bombarding beam of electrons in an x-ray tube undergoes deceleration by interaction with the nuclei of the x-ray tube target atoms.
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Bjorken, J. D. and Drell, S. D. "Bremsstrahlung." §7.6 in Relativistic Quantum Mechanics. New York: McGraw-Hill, pp. 120-127, 1964.
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Electromagnetic radiation that occurs when charged particles with energies large compared to their rest energies are decelerated over a very short distance. Since electrons are much lighter than protons, electron bremsstrahlung is the most common. In bremsstrahlung, a continuous spectrum with a characteristic profile and energy cutoff (i.e., wavelength minimum) is produced. In addition, lines can appear super imposed, corresponding to the ejection of K and L shell electrons knocked out of atoms in collisions with the high-energy electrons.
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The Health Physics Fundamentals Study Guide from Combustion Engineering, better known as the “North East Utilities Study Guide”
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When a high energy beta particle passes close to a heavy nucleus it is deflected sharply by the strong electric field. When the beta particle is deflected (and thus slowed down) it emits electromagnetic energy in the form of X-rays.
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Handbook of Health Physics and Radiological Health, better known as the Rad Health Handbook.
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Bremsstrahlung – Secondary electromagnetic radiation (x-rays) produced by the deceleration of charged particles through matter.
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Fundamentals of Radiation Protection by H.F. Henry
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Higher energy electrons also lose energy by their deceleration in the electric field of an atom, with the emission of electromagnetic waves. Such radiation is called Bremsstrahlung.
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Too vague:
US Department of Energy Radiological Control Technician Phase I Core Academic Training Study Guide., better known as the DOE Core study guide
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A high energy beta penetrates the electron cloud surrounding the nucleus of the atom, and experiences the strong electrostatic force of the positively charged nucleus. This results in a change in velocity and the emission of a Bremsstrahlung X-ray.
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Basic Nuclear Physics, Bureau of Naval Personnel, NAVPERS 10786, 1958 pp. 112-113
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When a high-energy beta particle passes close to a heavy nucleus, it is deflected sharply by the strong electric field. In being deflected, a beta particle is found to emit energy in the form of an X-ray. Radiation produced in this way is called bremsstrahlung, which is a german word meaning "breafing radiation". This term arises because a beta is continually slowed down by successive bremsstrahlung processes.
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The Final Word:
Radiation Protection by Jacob Shapiro
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Bremsstrahlung production by acceleration of bombarding electrons. Electrons accelerated (shown here as a change of direction) near the highly charged nucleus of a heavy element may lose all or most of their energy through the emission of photons (called Bremsstrahlung, meaning “breaking radiation”)
The most important mechanism, from the point of view of the use of x-rays in radiography, is through a violent acceleration of the electron, resulting in the sharp deflection, as it interacts with the electrical field around the nucleus. Such acceleration results in the emission of photons of x-radiations. The photons are generally referred to as Bremsstrahlung (breaking radiation), because the electrons lose energy and slow down in the process of emitting the radiation.
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NRRPT Prep Course 1st Edition 1991 RI-Tech Inc.
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Bremsstrahlung is an interaction that produces x rays from the kinetic energy of charged particles. It is predominantly a beta particle interaction. It occurs when a charged particle undergoes a rapid acceleration. (Remember that acceleration is a vector quantity and that it can be either positive or negative in value.) When a beta comes in close proximity to an atom, it will be deflected, which is a negative acceleration. The energy of the photon given off is equal to the loss in kinetic energy of the beta.
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Basic Radiation Protection Technology 4th Edition 2000 by Daniel Gollnick
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Bremsstrahlung is a word of German extraction which translates literally as “breaking radiation”, that is, radiation generated when the charged particle puts on the breaks. The causative agent is again the Coulomb force which produces a deflection in the path of the charged particle. This change in direction is, in the physics sense, a negative acceleration (a de-celeration if you prefer) because the velocity vector changes with the directional change and the speed of the particle is reduced due to the energy loss. The radiation emitted by the particle, the Bremsstrahlung, is electromagnetic in nature.
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Rennhack:
Sounds to me like the Coulumbic force accelerates the electron, causing the energy to be emitted, which then leaves with less kinetic energy, decelerated.
I think some of those books should be a little more complete in their explanation. I remember the last NEU test I took in 2000 had a question about this, and "accelerate" was the answer. However, the NEU study guide never mentions 'accelerate', but does mention 'decelerate'.
--- Quote ---The Health Physics Fundamentals Study Guide from Combustion Engineering, better known as the “North East Utilities Study Guide”
When a high energy beta particle passes close to a heavy nucleus it is deflected sharply by the strong electric field. When the beta particle is deflected (and thus slowed down) it emits electromagnetic energy in the form of X-rays.
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alphadude:
Electromagnetic radiation that occurs when charged particles with energies large compared to their rest energies are decelerated over a very short distance. Since electrons are much lighter than protons, electron bremsstrahlung is the most common. In bremsstrahlung, a continuous spectrum with a characteristic profile and energy cutoff (i.e., wavelength minimum) is produced.
the increase in energy (acceleration) dont make sense when energy is lost at the same time? (photons being produced)
remember how an xray machine works- the electrons are accelerated to increase their effect when they slam (brakes) into the target to produce those wonderful xrays. xrays dont happen when the electrons are in flight or being speeded up- energy should be conserved
SloGlo:
"Radiation Protection by Jacob Shapiro
Quote:
Bremsstrahlung production by acceleration of bombarding electrons. Electrons accelerated (shown here as a change of direction) near the highly charged nucleus of a heavy element may lose all or most of their energy through the emission of photons (called Bremsstrahlung, meaning “breaking radiation”)
The most important mechanism, from the point of view of the use of x-rays in radiography, is through a violent acceleration of the electron, resulting in the sharp deflection, as it interacts with the electrical field around the nucleus. Such acceleration results in the emission of photons of x-radiations. The photons are generally referred to as Bremsstrahlung (breaking radiation), because the electrons lose energy and slow down in the process of emitting the radiation."
interesting choice of quote, mike. i was always under the impression that bremsstrahlung was "braking" radiation. however, the "breaking" radiation terminology mr. shapiro uses would work for both acceleration and deceleration. look at it as radition that is breaking off from the electron as it undergoes velocity changes. hmmm :-?
cool thread, nowz eye gotz sumtin ta think bout twoday.
metalman40:
Acceleration is the rate at which the velocity vector changes Acceleration = change in velocity/time it can be either negative or positive. Decelleration is an undefined term in physics. When the beta interacts with the high Z electron cloud it is accelerated by a negative or positive value.
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