Impact of stochastic fluctuations on proton beams under space-charge effects

Transient electric-current fluctuations arising from power supplies can be translated into magnetic-field perturbations during particle-accelerator operations. As speculated over the past decades, it is probable such inevitable machine imperfection leads to emittance growths, beam-halo formation, and consequential beam losses.With robust experimental evidence of transient coloured noise and its real-time Fast-Fourier-Transform analysis, the ripple currents were modelled on the Ornstein-Uhlenbeck process via parameterisation. For investigating the conjectured effects on intense beams, the first-ever, data-driven stochastic noise model—equipped with the wide-spectrum noise generator and a suite of beam-diagnostic calculations—was formulated with massive realism; i.e., tracking a huge number of macroparticles propagating through focusing channels in the face of power-supply noise and space charge. With uniform charge-density distributions at injection, the power-supply ripples and collective effects due to space charge conspire to yield fractional growths of r.m.s. emittances as large as 8 ∼ 9 % in both transverse planes over a 2.2-ms period, prior to accelerating beams. It was thus concluded that fluctuating power-supply currents, when coupled to space charge and impinging upon intense proton beams, can substantially escalate the insidious process of degrading beam properties during the full injection period. This article concerns the systematised methodology of a hybrid of empirical datasets and a numerical model created and developed for quantitatively assessing the impact of frequency-dependent noise on beams and attendant ramifications engendered in its space-charge-dominated sphere. * Author Email:  philyoon@proton.me