Life and Work of Rolf Wideröe by © Pedro Waloschek,     => Contents

Box 2:  Cyclotrons and Synchrocyclotrons

Cyclotrons became the working tools of nuclear physics. Many were built throughout the world. They made it possible to smash atomic nuclei, just as Wideröe had dreamt in his youth; but they could also be used to produce useful quantities of new isotopes and for much fundamental research work. The energy of the accelerated protons (cyclotrons are not well suited for electrons) could easily reach 40 MeV, and it also became possible to accelerate heavier atomic nuclei. Of particular importance was the high number of particles (also called `intensity') which could be accelerated with cyclotrons.

Subsequent attempts to achieve higher energies with cyclotrons were problematic because classical mechanical equations were no longer applicable; it became necessary to refer to the more precise formulae of Einstein's relativistic mechanics. However, this meant that Lawrence's original constant frequency idea no longer worked. As the particle paths' radii increased in size, the frequency had to be changed, it had to be adapted to the particles' relativistic speed.

Although this is possible in principle, it means that the frequency had to be changed during the acceleration process. It is therefore possible only to accelerate relatively small bunches of particles and the frequency has to be precisely adjusted in the process. The total number of particles thus accelerated is reduced by a factor of about one hundred. Yet this was accepted in order to achieve higher energies. These machines were called `synchrocyclotrons'. Many of them were constructed later on and they reached energies of several hundred MeV.

The synchrocyclotron in Dubna (previously USSR) for example, which was first operated in 1954, achieved an energy of 680MeV and was fitted with a gigantic magnet weighing 7,200tons. However, there were also many smaller synchrocyclotrons with which important research work was undertaken.

With these machines it became possible to systematically investigate artificially produced `mesons', whereby the field of nuclear physics was left behind and the next step forward, particle physics, was taken. The CERN synchrocyclotron (`SC') in Geneva became operational in 1958 and served several generations of particle and nuclear physicists.