How Bremsstrahlung Generates X-Rays and Impacts Modern Physics
Bremsstrahlung is the electromagnetic radiation emitted in the form of photons when a charged particle is decelerated upon striking against another charged particle. This radiation gives a continuous X-ray spectrum. This is also known as “braking radiation”. These charged particles are mainly electrons and atomic nuclei of metals. Let us now study bremsstrahlung radiation, its causes, and effects.
In the classical explanation of bremsstrahlung radiation, the quantum effects are neglected and a comparatively simpler approach was considered by Larmor. Bremsstrahlung has its uses in radiation safety equipment and astrophysics. Bremsstrahlung radiation is often considered to be secondary radiation.
Bremsstrahlung Radiation
Bremsstrahlung radiation is a type of electromagnetic radiation emitted when a charged particle upon getting deflected by another charged particle is decelerated. These charged particles are mainly electrons or atomic nuclei. The particles in motion upon clashing lose kinetic energy. The lost energy is emitted as radiation in the form of photons. Thus the law of conservation of energy is also satisfied. This is known as the bremsstrahlung radiation. This bremsstrahlung radiation gives a continuous spectrum. The peak intensities tend to shift towards higher frequencies with the increase in the energy of the decelerated charged articles. This is the bremsstrahlung radiation definition. Bremsstrahlung radiation is of two types namely inner bremsstrahlung and outer bremsstrahlung radiation. We’ll be discussing this later in this article.
Causes of Bremsstrahlung Radiation
Bremsstrahlung can be defined as a process by which some of the energy of the celestial rays is scattered into the atmosphere of Earth. The chromosphere emits solar x-rays in the form of bremsstrahlung radiation. This is generated by fast-moving electrons. However internal bremsstrahlung takes place in case of radioactive disintegration. During beta decay which involves the emission of electrons and positrons, the clash between these charged particles results in the emission of bremsstrahlung radiation. It is mainly caused by the acceleration and deceleration of charged particles such as atomic nuclei and electrons. If the particles emit bremsstrahlung radiation while being accelerated by an external magnetic field it is also known as synchrotron radiation.
Bremsstrahlung X- Rays
The bremsstrahlung x-rays are emitted when electrons get decelerated when fired against a metal target. These charged particles emit bremsstrahlung radiation in the form of photons or bremsstrahlung x-rays. The continuous spectrum formed due to the bombardment of electrons lies in the x-ray region of the electromagnetic spectrum. The energy peaks of the x-ray spectrum tend to shift towards higher frequencies with the increase in energy of the electrons. Often the bombarding electrons also eject electrons from the inner atomic shells of the target metal. The vacancies are quickly filled by dropping electrons from the higher atomic shells. As a result, bremsstrahlung x-rays are emitted.
Inner and Outer Bremsstrahlung
Inner bremsstrahlung and outer bremsstrahlung are the two types of bremsstrahlung radiations.The inner bremsstrahlung is also known as internal bremsstrahlung is caused by the electrons emitted from a radioactive decaying nucleus. This is a feature of beta decay in the nuclei. However, the outer bremsstrahlung is caused when electrons emitted from a separated nucleus are bombarded on other nuclei. The bremsstrahlung decreases constantly with the increase in the energy of the beta particles in the case of electrons and positrons which are emitted by the electron-nuclei pair in case of beta decay. The bremsstrahlung is emitted in case of electron capture without emission of any charged particle. Electron capture requires the energy of a neutrino. The bremsstrahlung radiation is the result of the acceleration of the captured electrons. These types of radiations often have the same frequencies as gamma radiation. These radiations do not exhibit any spectral lines of the gamma radiation and hence can not be considered as gamma decay.
Did You Know?
“ Bremsstrahlung “ is derived from “bremsen” which means “ to break” and “Stahlung” which means “radiation”.
Bremsstrahlung radiation is sometimes emitted from the surface of plasma in the form of free-free radiation.
FAQs on Bremsstrahlung Radiation Explained: Causes and Real-World Uses
1. What is Bremsstrahlung radiation and why is it also called 'braking radiation'?
Bremsstrahlung is a type of electromagnetic radiation produced when a fast-moving charged particle, typically an electron, is deflected and decelerated by the strong electrostatic field of an atomic nucleus. The term 'Bremsstrahlung' is German for 'braking radiation', which aptly describes this process. As the charged particle 'brakes' or slows down, its lost kinetic energy is converted into a photon of radiation, in accordance with the law of conservation of energy.
2. What is the primary cause of Bremsstrahlung radiation inside an X-ray tube?
In an X-ray tube, high-speed electrons are accelerated towards a dense metal target, such as tungsten. The primary cause of Bremsstrahlung is the interaction between these projectile electrons and the nuclei of the target atoms. The powerful positive charge of the nucleus exerts a strong attractive force on the passing electron, causing it to deviate from its path and slow down significantly. This deceleration results in the emission of an X-ray photon, which constitutes Bremsstrahlung radiation.
3. How does Bremsstrahlung radiation differ from Characteristic radiation?
While both are forms of X-ray radiation produced in an X-ray tube, they originate from different atomic interactions:
- Origin: Bremsstrahlung radiation comes from the deceleration of projectile electrons as they interact with the target atom's nucleus. In contrast, Characteristic radiation is produced when a projectile electron ejects an inner-shell electron from a target atom, and an electron from a higher energy shell drops to fill the vacancy.
- Energy Spectrum: Bremsstrahlung results in a continuous spectrum of X-ray energies, as the degree of electron deceleration can vary. Characteristic radiation produces a discrete line spectrum with sharp peaks at specific energies that are unique to the target element's atomic structure.
4. Why does Bremsstrahlung radiation produce a continuous spectrum?
The spectrum of Bremsstrahlung radiation is continuous because the interaction between the projectile electron and the target nucleus is variable. An electron can have multiple interactions, and in each case, it can lose any fraction of its kinetic energy, from a very small amount to its entire energy in a single collision. Since each unique amount of energy lost corresponds to a photon of a specific energy, the result is a broad, continuous range of photon energies rather than fixed, discrete energy levels.
5. How does the accelerating voltage in an X-ray tube affect the resulting Bremsstrahlung spectrum?
The accelerating voltage (tube potential) directly determines the maximum kinetic energy of the electrons striking the target. This has a significant effect on the Bremsstrahlung spectrum. A higher accelerating voltage means the electrons are more energetic, which leads to the production of higher-energy Bremsstrahlung photons. Specifically, it increases the maximum energy (E_max) of the photons in the continuous spectrum, which corresponds to the shortest wavelength, also known as the Duane-Hunt limit. It also increases the overall intensity of the radiation produced.
6. What are some important real-world applications of Bremsstrahlung radiation?
Bremsstrahlung radiation is fundamental to many technologies and scientific fields. Key applications include:
- Medical Imaging: It is the primary source of X-rays used in diagnostic radiography to create images of bones and internal structures.
- Radiation Therapy: High-energy X-rays generated via Bremsstrahlung in linear accelerators are used in radiotherapy to target and destroy cancerous tumours.
- Industrial Inspection: It is employed in non-destructive testing to inspect welds, castings, and machine parts for internal flaws without damaging them.
- Astrophysics: This type of radiation helps astronomers study hot, ionised gases (plasmas) found in celestial objects like solar flares and galaxy clusters.
