BlogNCERTImportant Topic of Physics: Cyclotron

Important Topic of Physics: Cyclotron


A cyclotron is a device that accelerates charged atomic or subatomic particles in a magnetic field that is constant. Ernest Orlando Lawrence and M. Stanley Livingston, two American physicists, invented the first particle accelerator of this type in the early 1930s. A cyclotron is made up of two hollow semicircular electrodes, known as dees, that are mounted back to back in an evacuated chamber between the poles of a magnet. A radio-frequency oscillator generates an alternating polarity electric field in the gap. The particles that will be accelerated form in the gap near the center of the device, where the electric field propels them into one of the dees. The magnetic field there directs them in a semicircular path. The electric field has reversed by the time they return to the gap, so they are accelerated into the other dee.

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    Although the speed of the particles and the radius of their orbit increase with each crossing of the gap, as long as the mass of the particles and the strength of the magnetic field remain constant, these crossings occur at a fixed frequency that can be adjusted by the oscillator. This type of cyclotron can accelerate protons to energies of no more than 25 million electron volts. The relativistic increase in the mass of any particle as its speed approaches that of light imposes this limitation. The orbital frequency decreases with increasing mass, and the particles cross the gap when the electric field slows them down. To overcome this limitation, the frequency of the alternating voltage impressed on the dees can be adjusted to match the frequency of the orbiting particles. A device with this feature is known as a synchrocyclotron, and it has been used to achieve energies close to one billion electron volts. Another method is to strengthen the magnetic field near the dees’ periphery and focus the magnetic field by varying its azimuth. Isochronous or azimuthally-varying-field (AVF) cyclotrons are accelerators that operate in this manner.


    A cyclotron is a compact particle accelerator that generates radioactive isotopes for imaging purposes. The cyclotron uses stable, non-radioactive isotopes to accelerate charged particles (protons) to high energy in a magnetic field. When stable isotopes react with the particle beam, a nuclear reaction between the protons and the target atoms occurs, producing radioactive isotopes for nuclear medicine and other applications. Radioisotopes used in medicine do not have a long half-life. As a result, the laboratory must be close to both the cyclotron that generates the isotopes and the end-user – in this case, the nuclear medicine department at Royal University Hospital.

    A cyclotron is a device that accelerates charged particles or ions to extremely high energies. E.O Lawrence and M.S Livingston invented it in 1934 to investigate the nuclear structure. The cyclotron employs both electric and magnetic fields to boost the energy of charged particles. Because both fields are perpendicular to each other, they are referred to as cross fields. Charged particles accelerate outwards from the center of a cyclotron along a spiral path. A static magnetic field keeps these particles on a spiral trajectory, while a rapidly varying electric field accelerates them.

    Working Principle of Cyclotron

    • A cyclotron uses a high-frequency alternating voltage to accelerate a charged particle beam between two hollow “D”-shaped sheet metal electrodes known as the “dees” inside a vacuum chamber.
    • The dees are arranged face to face with a narrow gap between them, forming a cylindrical space within them for particles to move. Particles are injected into the space’s center.
    • Dees are located between the poles of an electromagnet, which generates a perpendicular static magnetic field B to the electrode plane.
    • Due to the Lorentz force perpendicular to the particle’s direction of motion, the magnetic field causes the particle’s path to bend in a circle.
    • Between the dees, an alternating voltage of several thousand volts is applied. The voltage generates an oscillating electric field in the gap between the dees, causing the particles to accelerate.
    • The voltage’s frequency is set so that particles complete one circuit in a single cycle of the voltage. To achieve this condition, the frequency must be set to the cyclotron frequency of the particle.

    Expression for Cyclotron Frequency

    A cyclotron is a type of particle accelerator that accelerates charged particles outwards from the centre along a spiral path. A static magnetic field keeps these particles on a spiral trajectory, while a rapidly varying electric field accelerates them.

    The frequency can be calculated as follows:


    Where q is the particle’s charge, B is the magnetic field used in the cyclotron, and m is the charged particle’s mass.

    Uses of Cyclotron

    In addition to producing imaging isotopes for the RUH’s PET-CT scanner, the laboratory conducts animal and human health imaging and research, as well as crop/plant imaging and research. The facility also houses research into the development of new compounds known as radiopharmaceuticals, which can lead to better detection, diagnosis, and treatment of diseases such as cancer, Alzheimer’s, Parkinson’s, and multiple sclerosis. Scientists can track the processes that can lead to diseases in specific organs by tagging specific biomolecules with radioisotopes, based on how the ‘tagged’ molecules are absorbed. Other areas of study include physics related to the cyclotron’s used in the production of new radioisotopes and the development of more sensitive radiation detectors. Students, faculty, and researchers from a variety of disciplines, as well as industry partners, work together to solve complex problems, and health professionals are trained in the most advanced imaging and treatment protocols. These were the best sources of high-energy beams for nuclear physics experiments for decades. These, however, are still used for this type of research.

    Cancer treatment: Cyclotrons can be used in particle therapy to treat cancer, with ion beams from cyclotrons penetrating the body and killing tumors through radiation damage.

    Also read: Important Topic of Physics: Superposition Principle


    1. What is the cyclotron principle?

    Ans: The cyclotron operates on the principle that a charged particle moving normally to the magnetic field encounters magnetic Lorentz force, causing the particle to follow a circular path.

    2. What exactly is cyclotron motion?

    Ans: It means that q only experiences centripetal acceleration. As a result, the charge undergoes uniform deformation motion in a circle The cyclotron motion of a charged particle in a magnetic field is what it’s called.

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