Speaker
Description
The design betatron tune of the Rapid Cycling Synchrotron (RCS) of China Spallation Neutron Source (CSNS) is (4.86, 4.80), which allows for incoherent tune shifts to avoid serious systematic betatron resonances. However, at the design tune, severe horizontal beam instability and vertical beam loss induced by half-integer resonance under space charge detuning were observed when the beam intensity exceeded 50% of the design value. Simulations and experiments have shown that space charge-induced beam loss reduces as the tunes move up and away from half-integer resonance lines. However, experimental observations have shown that instability growth rates increase rapidly as the tune approaches integer from below. The tune requirements for reducing the beam loss caused by space charge effects and suppressing beam instability are distinct at the RCS of CSNS. The tunes over the whole acceleration process are optimized based on space charge effects and beam instability. The optimized tune pattern has proven highly effective in controlling beam loss caused by these two factors.