The invention relates to a particle therapy system for irradiating a target with a scanning beam technique. The system comprises an irradiation planning device with a planning algorithm configured to associate a particle beam energy E(i) to each spot of the irradiation plan and organize the spots in a sequence of spots according to energy. The system comprises a control system configured for controlling in parallel, from spot to spot, a variation of an output energy of a beam generator, a variation of a magnetic field of one or more electromagnets of a beam transport system and a variation of a magnetic field of the scanning magnet.
