A charged particle irradiation device (10) and method for irradiating a target volume (50), adapted for receiving a treatment plan (70) defining a series of prescribed irradiation points (140) having each a prescribed dose to be delivered, comprising an irradiation unit (40) having at least one scanning magnet (100 110), and at least one beam position monitor (130) installed in between the said scanning magnet (100 1 10) and said target volume (50). A controller (80) comprises means for calculating for any said prescribed irradiation point corresponding nominal magnetic settings of the scanning magnet such that a beam (90) is pointing to said prescribed irradiation point when corresponding magnetic settings are applied, and for calculating corresponding expected position at said beam position monitor (130) The controller (80) further comprises a) means for selecting a tuning reference point from said series of prescribed irradiation points b) means for specifying a prescribed tuning dose to be given to said selected tuning reference point, said prescribed tuning dose being equal or smaller than the said prescribed dose at said selected tuning reference point c) means for comparing a beam position provided by the beam position monitor (130) and the expected position at said beam position monitor (130) for said selected tuning reference point d) means for computing a first correction to be applied to said nominal magnetic settings of the scanning magnet (100 110) in order to align the beam position provided by the beam position monitor to the expected position at said beam position monitor (130) for said selected tuning reference point e) means for correcting the nominal magnetic settings of the scanning magnet for all said prescribed irradiation points according to said first correction.Linvention porte sur un dispositif dirradiation de particules chargées (10) et sur un procédé pour lirradiation dun volume cible (50), conçus pour recevoir un plan de traitement (70)
