Space charge dominated beam instabilities in high intensity superconducting LINAC

The strong nonlinear space charge of high intensity proton beams may lead to beam instabilities or resonances in the cavity. For the superconducting structures that are operated from medium to high β range, such resonances may lead to beam loss further leading to the radio-activation of the cavity. Here we use the envelope equation to analyze the linear stability criterion of so-called mismatch perturbations about the matched envelope in periodic solenoidal transport lattices. A Gaussian core is used to study the effects of sudden and adiabatic perturbations. We also perform fully three-dimensional PIC simulations to obtain various order transverse resonance modes that are excited in the structure and locate the regions of tune depression over which the linac should be operated to avoid these modes. (author)