A new cooling technique for superconducting cavities of particle accelerators
A team of researchers is developing a new method to cool the superconducting cavities of particle accelerators, which could make them more compact.
Particle accelerators are devices used primarily to study matter: the atoms and their particles (protons, neutrons, electrons and quarks). They are used in nuclear physics, atomic physics and physics of materials.
But particle accelerators are also used in other domains: linear accelerators can for example produce rays to be used in radiotherapy. Accelerators are also used in the irradiation of food in some sterilization processes.
However, these are generally large-sized machines. For example, the Orsay synchrocyclotron, used from 1956 to 1990 in nuclear physics and then at the Proton Therapy Center  in Orsay, weighed no less than 900 tons .
Teams of scientists and engineers are looking to reduce the size of these equipment. This is the case of the American laboratory Fermilab, which has recently developed a new technique for cooling the superconducting cavities of accelerators. These cavities are metal enclosures with a magnetic field. The charged particles that enter it receive an electrical impulse that makes them accelerate.
These cavities are metal enclosures with a magnetic field. The charged particles that enter it receive an electrical impulse that makes them accelerate. The superconducting cavities used in large accelerators are generally cooled to around 2 Kelvin (-271.15 ° C). They are traditionally immersed in liquid helium, which is pumped to lower its pressure and temperature. This requires voluminous and complex cryogenic systems, which limits the portability and therefore the possible applications for accelerators.
The method developed by Fermilab uses cryocoolers. Helium, in its gaseous form, is compressed and expanded in a regenerative heat exchanger in a closed cycle. This makes the system more compact than standard equipment using liquid helium.
This type of research could extend the scope of particle accelerators.
 Proton therapy is a form of radiotherapy aimed at destroying cancer cells by irradiating them with a proton beam.
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