Acceleration tests of a 3 GHz proton linear accelerator (LIBO) for hadrontherapy

This paper describes the acceleration tests performed at the Catania LNS Laboratory on a 3
GHz linac module of the side coupled type, which boosts the proton energy of a beam extracted from a
cyclotron from 62 to 72 MeV. The output proton energy was measured with two devices: a NaI(Tl)
crystal and a bending magnet. The experimental spectra are in good agreement with the calculated
ones. From their shape it is obtained that (18 ± 3.0)% of the transmitted protons fall in a ± 2 MeV
interval centered around 72 MeV. This result is in good agreement with the 20% value derived from
the simulation of the acceleration process. The measured energy of the accelerated protons was used
to check that the shunt impedance of the structure is equal to the computed one within 3%. This was
the first time that a 3 GHz structure has been used to accelerate protons and the result of the tests have
demonstrated that a high frequency linac can be used as a cyclotron booster.