Beam dynamics
Background
Most particle accelerators increase the energy of charged particles in several steps. In circular accelerators — such as cyclotrons, and synchrotrons — the particles are guided in approximately circular orbits and forced to pass by the same radio frequency (RF) high voltage system many times. At every pass by the RF system, the energy of the particle is increased. In linear accelerators, multiple RF systems are lined up one behind the other to provide an energy boost to the particles that traverse them only once. In all cases, it is necessary to manipulate the beam to keep it from increasing in size and hitting the wall of the vacuum pipe in which it moves. Special care must be taken to keep the beam in phase with the accelerating RF field. When intense beams are accelerated, the internal forces between the beam particles (space charge forces) can become important since particles of the same electric charge will repel and tend to increase the size of the beam. Beam dynamics is the study of all these effects.
The Role of NSCL
NSCL has been a leading institution in the study of beam dynamics in cyclotrons since 1960 when our first high precision cyclotron for nuclear physics research was being designed. Several computer codes have been developed in our laboratory to help in the design and analysis of beam dynamics in cyclotrons. These codes are being used all over the world. The use of superconducting magnets to produce high intensity magnetic fields (100,000 times the earth’s magnetic field) decreases the size of the magnets needed to guide the particles and, consequently, their cost. Our laboratory developed a small cyclotron that produces neutrons for cancer therapy and is mounted on a gantry that rotates around the patient. Precise calculation of the beam behavior is needed to design such a compact accelerator.
In more recent times we have been involved in the study of high intensity beams in accelerators. This effort comprises the development of numerical methods to calculate the effects due to space charge forces and the development of small accelerators to study experimentally whether our predictions are accurate. The interest in high intensity accelerators has increased enormously as scientists need more intense beams for their cutting-edge research. In addition, high intensities would be needed for some possible applications, such as contraband and explosive detection, energy generation in accelerator driven nuclear power plants, or the transmutation of the waste products from nuclear reactors.
