Multiturn extraction based on trapping in stable islands

For some applications an intermediate extraction mode between fast (one turn) and slow (several thousand turns) is needed. This is the case of the five-turn extraction used to transfer the proton beam from the CERN Proton Synchrotron (PS) to the Super Proton Synchrotron (SPS). Unavoidable losses and poor betatronic matching with the receiving machine affect the present approach, which is based on beam slicing by means of an electrostatic septum. These features are rather serious obstacles to an intensity upgrade of the PS/SPS Complex. To overcome these difficulties, a novel extraction technique was proposed recently. By using nonlinear magnetic elements, stable islands can be generated in the transverse phase space. Furthermore, provided the linear tune is varied slowly, it is possible to trap the charged particles inside the stable islands in order to split the beam into different beamlets. Once generated, the distance between these beamlets can be tailored to the extraction needs by simply increasing the distance of the tune from the resonance value. The results of numerical simulations for the novel technique are presented and discussed in detail together with the outcome of the intense experimental studies performed to assess the validity of this approach.