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Cyclotrons

For a fun look at cyclotrons, see this link from the American Institute of Physics (AIP) website, taken from the LBL image library, The Cyclotron, as seen by...

How Cyclotrons Work


Cyclotrons were some of the first particle accelerators used to probe the inner workings of elementary particles. The first cyclotron was invented in 1929 by Ernest Lawrence at the University of California at Berkeley.

Cyclotrons consist of two hollow D-shaped electrodes (dees) sandwiched between a large dipole magnet. Charged particles, usually produced by a radioactive source at the center of the gap between the dees, are then drawn into one of the cavities by an electric field. A charge which moves into a magnetic field with direction perpendicular to the field will follow a semicircular path. That is, the B field provides the centripetal force to curve the charged particle's orbit inside the dees.

In order to accelerate the particles, the two D-shaped cavities must be driven at a constant frequency by a radio frequency (RF) accelerating power source, which essentially switches the charges on the dees back and forth at just the right frequency to accelerate the particles across the gap. It is this switching of polarity at a specific frequency, known as the cyclotron frequency, that accelerates the beam of particles. As the beam spirals out, its frequency does not decrease, and it must continue to accelerate, as it is travelling more distance in the same time.

Eventually, a charged plate at the outer edge of one of the dees deflects the path of the particles and diverts them into a target at their maximum energy.

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Uses for Cyclotrons


For several decades, cyclotrons were the best source of high-energy beams for nuclear physics experiments; several cyclotrons are still in use for this type of research. Cyclotrons can be used to treat cancer. Ion beams from cyclotrons can be used, as in proton therapy, to penetrate the body and kill tumors by radiation damage, while minimizing damage to healthy tissue along their path. Cyclotron beams can be used to bombard other atoms to produce short-lived positron-emitting isotopes suitable for PET imaging.

Our Cyclotron Experiment


We plan on using a cyclotron design to accelerate protons to create a neutrino source, with energies centered at 6.5 MeV for the IsoDAR experiment from the decay of 8Li or up to 52 MeV from pion and muon decay-at-rest (DAR) for DAEδALUS. New low-cost, high-power proton cyclotrons open the opportunity for a novel precision search for sterile neutrinos or CP violation in the neutrino sector. The accelerators can produce decay-at-rest neutrino beams located at multiple distances from a Gd-doped ultra-large water Cerenkov detector in order to search for CP violation in ν(bar)μ → ν(bar)e at short baseline. This new type of search complements presently proposed experiments, providing measurements that could lead to a substantially better exploration of CP violation in the neutrino sector.

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