Intensity Dependent Emittance Transfer Studies at the CERN Proton Synchrotron

An intensive study has been undertaken since the year 2002 to understand better the various high-intensity bottlenecks of the CERN Proton Synchrotron machine. One of these limitations comes from the so-called Montague resonance. High-intensity proton synchrotrons, having larger horizontal than vertical emittance, may suffer from this fourth-order coupling resonance driven by space charge only. In particular, such resonance may lead to emittance sharing and, possibly, beam loss due to vertical acceptance limitation. Experimental observations made in the 2002, 2003 and 2004 runs on the Montague resonance are presented and compared with theoretical predictions and 3D particle-in-cell simulation results.