A cyclotron is a type of particle accelerator in which charged particles are propelled by an alternating electric field and constant magnetic field. It is also used to produce radioactive isotopes that can be used for imaging procedures and nuclear medicine applications. The particles are injected at the center of the magnet and spiral outward as their power increases. In a typical cyclotron, a charged particle (usually injected at the center of the magnet) is accelerated along a spiral path under the action of a static magnetic field and an alternating electric field. The energies of the accelerated particles are usually in excess of 10 MeV. In this article, we discuss some applications and limitations of cyclotrons.
Uses of cyclotron
Uses of Cyclotrons in cancer therapy
- A cyclotron is used for proton therapy(where a beam of focussed protons is aimed at a tumor site). Proton therapy is common among pediatric patients. It is also can be used for various types of cancers like treating spine tumors, breast cancer, sarcoma, brain tumors, and prostate cancer. The cyclotron sends a high-energy beam of protons through the skin toward the tumor.
- Cyclotron is also capable of generating radioisotopes which are widely used in medicine and imaging purposes.
Uses of Cyclotron in scientific research
- Cyclotron-produced radiopharmaceuticals are very studied due to their ability in detecting various cancers. Early detection of tumors is key in cancer research and this will improve the efficiency of the therapeutic process.
- Scientists use cyclotrons for nuclear physics experiments in which they use accelerated charged particles to bombard atomic nuclei.
- Cyclotrons can also be used to change the nuclear structure.
- It is used in research settings to measure the is used to measure properties of isotopes (especially short-lived radioactive isotopes) like half-life, mass, interaction cross-sections, and decay schemes. [Read more]
Working principle of the cyclotron
- Cyclotron works on the principle of Lorentz force law.
- Any charged particle moving normally to a magnetic field experiences a force that depends on the magnetic field.
- The particle experiences acceleration and goes into a curved trajectory.
- The particle emits radiation and in turn, loses energy.
- The static magnetic field allows it to maintain the spiral path and the alternative current accelerates the particle.
The formula for cyclotron frequency
The cyclotron frequency is the frequency of an accelerated particle (like an electron) with charge q(in Columb) and mass m(in Kg) in a magnetic field B(measured in Gauss)
The cyclotron frequency can be derived by equating the formula for Lorentz force with centrifugal force. This calculation though does not take into account the relativistic effects. If you want to do an exercise you can derive the formula for cyclotron frequency and add relativistic effects to it to derive the exact formula.
Limitations of cyclotron
While cyclotron has a lot of uses there are a few limitations to their practical application. The limitations of a cyclotron are given as follows:
- The mass of an object varies when it is comparable to the speed of light. This was not counted in the above formula. So there is a limitation to the maximum energy a particle can be accelerated.
- The radioisotopes that are generated by cyclotrons are not very stable and hence the place of application has to be very close to the cyclotron.
- A cyclotron can only accelerate charged particles (like protons, deuterons, and alpha particles). It cannot accelerate uncharged particles.
- There is also a limit on the beam intensity. As the number of particles in the beam increases, the electrostatic repulsion grows stronger and can disrupt the neighboring particle orbits.
- Cyclotrons cannot accelerate particles with very high masses.
