PARTICLE  ACCELERATOR

The particle accelerator, great ,and  even kilometer-long machines, are tools for investigation of matter that allow to accelerate, through electromagnetic fields, electrically charged particles (such as protons and electrons) and ions, to collide with each other or to target appropriate targets for the purpose of studying the atom's nucleus and the particles that make up the structure of matter and its interactions. The energy produced by the collision can also give rise to new particles of extremely short life, which do not exist in normal conditions. Subsequently, they were found to be fundamental for both biology and medical applications (oncology therapies, diagnosis). Accelerators are generally classified according to the acceleration system and trajectory followed by the beam. Those in which the trajectory is straight are the linear accelerators, which are used to accelerate protons, electrons, α and ions particles: they consist of successively increasing length tubes inserted into a linear structure in which the particles are accelerated by Electric fields alternate and sent to the target. The most powerful linear accelerator is the SLC (Stanford Linear Collider) in the United States, which reaches more than 100 GeVs. In the circular accelerators (cyclotron, betatrone, synchrotron etc.) the trajectory of the particles is bent by the so-called Lorentz force generated by a magnetic field and acceleration is imprinted by variable electric or magnetic fields, unlike the linear accelerator, where the energy that can reach is limited by the overall length of the cavity system the circular one allows to increase the final energy. One of the most powerful circular accelerators is the Geneva CERN's Large Electron-Positron Accelerator (LEP). The LEP is a 27km long ring of accumulation that operates on two particle bundles (in this case electrons and positrons) travelling in opposite directions making them face to face. The LEP reaches 200 GeV energies, but on its ring is currently under construction a new and more powerful accelerator, the LHC (Large Hadron Collider), with extremely powerful magnets that will allow energy to reach 14 TeV (teraelettronvolt = 1012 eV).

 The main difference between the two categories is that in the first particles are accelerated by an electrostatic potential difference or oscillating electric fields, while the latter also utilize transverse magnetic fields. This concept can be summarized by saying that the motion of charged particles in an accelerator is determined by Lorentz's strength - so called by the name of Dutch physicist Hendrik Antoon Lorentz, winner of the 1902 Nobel Prize in Physics.

Lorentz's strength is mathematically described by the formula: