Slow Extraction Techniques at the Marburg Ion-Beam Therapy Centre

The Marburg Ion-Beam Therapy Centre offers hadron therapy using proton and carbon beams. The accelerator is based on a 65-m ion synchrotron by Danfysik/Siemens Healthcare. Beam extraction from the synchrotron is driven by a transverse RF knock-out (KO) system featuring Dynamic Intensity Control (DIC) of the spill. DIC allows modulation of the extraction rate by factors up to 30 on millisecond time scales. A fast response of the system to the variable intensity set-point can be obtained by careful adjustment of the RF-KO spectrum relative to the machine tune. Tracking simulations of the extraction phase have been conducted to refine that behaviour. Presently, we investigate how fast machine tune shifts, induced by an air-core quadrupole lens, can be used as a way to further improve the spill quality.