The cyclotron: a particle accelerator for science, medicine and the nuclear industry
The cyclotron has become an essential component in sectors as diverse as medical radioisotope production, particle physics research, and the nuclear industry. This device is behind several real breakthroughs in medical diagnosis, disease treatment, and scientific experimentation.
What is a cyclotron?
This device is not a new concept. It was invented in 1931 by physicist Ernest O. Lawrence and his student M. Stanley Livingston at the University of California, Berkeley. Thanks to this invention, Lawrence won the Nobel Prize in Physics in 1939.
A cyclotron is a particle accelerator that uses magnetic and electric fields to accelerate charged particles and make them collide with materials that convert them into radioisotopes through nuclear reactions. A constant magnetic field curves the path of the charged particles, while an external electric field gives them acceleration impulses each time they pass through the gap between the electrodes.
The cyclotron is a particle accelerator that uses magnetic and electric fields to turn charged particles into radioisotopes through nuclear reactions
How does it work?
The cyclotron accelerates charged particles to high speeds using magnetic and electric fields. This process has several stages:
- An ion source injects charged particles into the center of the device
- Under the influence of a powerful magnet, the particles begin a circular (or expanding spiral) orbit inside the cyclotron chamber. This spiral path allows the particles to pass many times through the acceleration region without requiring extremely high initial voltage
- Each time the particles cross the gap between two "dees" (hollow D-shaped electrodes), they receive an electric field impulse that increases their speed
- As speed increases, the orbit widens until it reaches the desired energy
- The beam of accelerated particles or radioisotopes is extracted for its use
From a physical standpoint, the process relies on two key elements: the magnetic field, which forces the particles to follow curved paths, and the electric field, which incrementally gives them energy. As the particle’s energy grows, it moves into a larger orbit and is finally guided toward the exit (the “beam line”) that directs it onto the intended target.
Using an ion source, the cyclotron generates radioisotope beams with multiple uses for various applications
Main components of a cyclotron
- Proton source – generates the charged particles that are to be accelerated
- Vacuum chamber – allows particles to move without colliding with air molecules
- Electromagnets (north–south) – create a constant magnetic field that curves the trajectory of the protons
- Vertical magnetic field – keeps the particles in a spiral orbit inside the cyclotron
- High-frequency oscillator – produces the alternating electric signal that powers the electrodes
- Dee electrodes – accelerate the particles each time they cross the gap between them
- Beam extraction system – redirects the accelerated protons toward the final target
- Radiological shielding – protects against radiation and secondary neutrons
What differentiates a cyclotron from other particle accelerators?
Cyclotrons accelerate particles along a spiral path, enabling continuous acceleration in a relatively compact space. However, linear accelerators (Linacs) propel particles in a straight line using a sequence of electric fields. Their design is simpler, but they require much more physical space.
Other accelerator types include synchrotrons (such as Alba in Barcelona), which accelerate particles along a circular path using variable fields. The installations are very large and are used for high-energy physics. Rodothrons are also circular accelerators typically used for electrons, operating with a fixed magnetic field and a radiofrequency field synchonized with particle energy.
Different types of particle accelerators
| Type | Particle path | Typical size | Use cases |
| Cyclotron | Spiral | Room-sized | Medical radioisotope production, research |
| Linear accelerator (Lina) | Straight line | Varies | Radiotherapy, physics experiments |
| Synchrotron | Circular (with varying fields) | Massive (multi-building) | High-energy physics |
| Rhodotron electron accelerator machines | Spiral | Compact (industrial scale) | Used for medical radioisotope production |
There are four main types of particle accelerators, including the cyclotron
Areas of applications
The cyclotron has proven its versatility in several areas, most notably nuclear medicine, scientific research and the radioisotope industry.
- Nuclear medicine and radioisotope production
The most prominent application is the production of radioisotopes for imaging or therapy. Many short-lived radionuclides, which cannot easily be produced or transported from distant reactors, are generated in situ using cyclotrons.
For instance, in a Positron Emission Tomography (PET) center, a cyclotron is used to bombard a target and produce a radioisotope, which, after the required chemical processing, is used to label a molecule that is injected into the patient to visualize metabolic functions.
The benefits are numerous: local availability, greater quality control, reduced transport time and better adaptation to the short shelf life of radioisotopes.
- Research and particle science
Although their size and energy do not match those of large synchrotrons or colliders such as CERN, cyclotrons remain valuable tools for ion research, beam production, applied physics, materials science and nuclear technology. In addition, some neutrino projects and high-intensity accelerator programs are exploring "intensive cyclotron" concepts based on advanced cyclotron designs.
- Industry, sterilization and other uses
Cyclotrons are also used to produce radionuclides for industrial applications (thickness gauges, radiotracers) and for the sterilization of materials.
The cyclotron has proven its versatility in several fields, most notably nuclear medicine, scientific research and the radioisotope industry
The cyclotron and the nuclear industry
In the broader ecosystem of the nuclear sector, beyond electricity generation, these types of accelerators are proof that nuclear technology has multiple and strategic applications, especially in medicine. In a context where the demand for radiopharmaceuticals is increasing, personalized medicine is advancing, and research requires particle beams with specific characteristics, cyclotrons hold a significant position in the nuclear technology value chain.
In Spain and the rest of Europe, the cyclotron is a strategic asset for strengthening autonomy in radioisotope production
Panorama en España y retos de futuro
In Spain and the rest of Europe, the cyclotron is a strategic asset for strengthening autonomy in radioisotope production, thereby reducing dependence on imports and reinforcing the medical supply chain. In addition, its technological versatility paves the way for new business models and for the diversification of the nuclear sector beyond electricity generation.
At the global level, the development of cyclotrons and compact accelerators aligns with broader trends in diversifying the peaceful uses of nuclear technology: disease diagnosis and treatment, industrial traceability, and advanced research.
Looking to the future of nuclear innovation, cyclotrons could play a key role in precision medicine (for example, proton or heavy-ion therapy), in the production of customized radionuclides, or in supporting new developments that require specialized ion beams.
Source: OIEA
