XI-th Collaboration MeetingJune26, ROPOSAL: BEAM TEST SCENARIO OF THE LOI IN THE ISIS SYNCHROTRON Yoshiro Irie, JAEA/KEK for the LOI/SH collaboration

XI-th Collaboration Meeting June26, 2 WHY THE LOI ? beam loading is very heavy at the early acceleration stage. if the loading is not cancelled properly in the second harmonic system, beam will undergo dipole oscillations, AND the bunch shape becomes rather sharp, almost losing the meaning of the SH. assumed criterion if the instability criterion (F Pedersen, 75) is applied to the second harmonic system.

XI-th Collaboration Meeting June26, 3 WHAT CAN BE DONE BY ONLY ONE LOI SYSTEM ? if the LOI can provide the necessary voltage per turn, it will be possible to use the LOI alone as a second harmonic cavity at the period, t ≤ 0.4msec. the required voltage is ~13kV per gap (C Prior, 1995), and the achieved voltage is 12.6kV (August 2005). required RF voltage to the second harmonic cavity (C Prior, 1995)

XI-th Collaboration Meeting June26, 4 WHAT CAN BE DONE BY ONLY ONE LOI SYSTEM ? -cont’d- synchrotron frequency at t = 0.3msec is calculated for the fundamental voltage with V = 40 KV and  s = 21.9 ˚, giving 5.7kHz. so, during 0~0.4msec, significant difference in beam shape will be expected between with and without LOI.

XI-th Collaboration Meeting June26, 5 PHASE SPACE MOTIONS matched case (simplified calculations) V(t), , ,  s : given in C Prior (1995)

XI-th Collaboration Meeting June26, 6 PHASE SPACE MOTIONS mismatched case if the second harmonic cavity phase (  ) is modulated by the beam loading, the synchronous phase (  s ) will also be changed. beam then starts oscillations around the new synchronous phase. beam shape is also changed with deteriorated bunching factor. phase shift (  = 0.1 rad) is assumed for the mismatching.

XI-th Collaboration Meeting June26, 7 CONCLUSIONS At the initial acceleration stage, the LOI can barely provide the necessary voltage. Synchrotron frequency at t = 0.3msec is calculated for the fundamental voltage with V = 40 KV and  s = 21.9 ˚, giving 5.7kHz. So, during 0~0.4msec, significant difference in beam shape will be expected between with and without LOI.