Fast Output Energy Regulation in a Medical Proton Linac
In proton therapy, depth scanning of the irradiated object is performed by changing the Output Energy (OE) of the accelerated beam. In pulsed linear accelerators, adjustment of the OE is usually by changing the amplitude and/or phase of the field in the accelerating elements from one RF pulse to another. The application of non-inertial traveling wave accelerating sections makes it possible to change quickly the phase of the accelerating field during the RF pulse. The phase of the field in the constant gradient section is determined both by the phase of the input RF signal and by the process of wave propagation in the dispersive structure. The calculation results of the traveling wave propagation in the accelerating structure when the phase of the input RF signal changes and the results of simulation the dynamics of particles confirm the change in the linac's OE during the RF pulse. The proposed method for regulation the OE makes it possible to increase in orders the speed of scanning the irradiated object by depth.