CNAO’s ‘High Technology’ components consist of a set of accelerators and transport lines of particle beams. The beams are generated by sources that produce carbon ions and protons. The most important accelerator machine is the Synchrotron. The synchrotron at CNAO is a prototype resulting from the research in high energy physics made possible through the collaboration of the Istituto Nazionale di Fisica Nucleare (INFN), CERN (Switzerland), GSI (Germany), LPSC (France) and of the University of Pavia University (Italy). It is based mostly on Italian technology.
The synchrotron is a “donut” 80 meters long with a diameter of 25 meters. In two areas inside the circumference the beams of particles are created in devices called “sources”, which contain plasma formed by the gas atoms that have lost their electrons. Using magnetic fields and radio frequency pulses, these atoms are extracted and the protons and carbon ions are selected. In this way “packages” composed of beams -each one containing billions of particles- are formed.
These packages are pre- accelerated and sent to the synchrotron where, initially, they travel at about 30,000 kilometers per second. Subsequently they are accelerated to kinetic energies of 250 MeV for protons and 480 MeV for carbon ions (the MeV, equivalent to one million electron volts, is the unit of energy used in nuclear and atomic scale phenomena).
The particle beam is accelerated in the synchrotron and travels about 30,000 kilometers in a half second to reach the desired energy. The beams are then sent to one of the three treatment rooms. Above this station there is a magnet of 150 tons which bends 90 degrees the particle beam and directs it from above to the person to be healed.
The beam that strikes the cells of the tumor is like a “brush” that moves in a manner similar to that of electrons in a TV and acts with a precision of 200 micrometers (two tenths of a millimeter).
This accuracy is achieved by means of:
Constant monitoring of the patient to follow any movements of the body (breathing, for example) that can change the location of the tumor, using infrared cameras to measure movement in a three-dimensional way
Two scanning magnets that, based on feedback of the beam monitoring system, move the “brush” along the outline of the tumor
In this way, section by section, the tumor is destroyed. The transition from one section to another deeper section is achieved by increasing the beam energy. The entire radiation lasts a few minutes.