Numerical investigation of space charge effects on the positions of beamlets for transversely split beams

Abstract

The use of transversely split beams was proposed some years ago as a means to perform extraction from a circular particle accelerator over multiple turns. In the course of studies carried out to increase understanding of the beam behavior, space charge effects have been probed. The experimental results showed a dependence of the beamlets' positions on the total beam intensity. In this paper detailed numerical simulations studies are reported, which clearly indicate that the observed behavior is due to indirect space charge effects. The analysis includes configurations, which have not yet been experimentally probed, in order to better understand the complex interplay between nonlinear single-particle and intensity-dependent effects.

Advancing the CERN proton synchrotron multiturn extraction towards the high-intensity proton beams frontier

“…This last point is important to be addressed as indirect space charge effects generate a shift of the transverse position of the beamlets at extraction [12]. This phenomenon was investigated in and confirmed by numerical simulations [13].…”

“…While a linear shift with intensity of the time of the peak losses is clearly observed for the island, no shift is visible for the core. This effect is linked with the transverse displacement of the fixed-point positions as a function of intensity as reported in [12], which was understood to be caused by indirect space charge effects as discussed in [13]. The experimental observations are in agreement with expectations: the distance of the fixed-point position from the origin increases proportionally to the beam intensity and the position of the loss peak therefore decreases with intensity, as particles at larger amplitude will be intercepted earlier by the septum.…”

“…Therefore, in light of these potential needs, an extended experimental campaign was carried out in 2017 to assess in great detail the MTE performance for high-intensity beams. Intensity-dependent effects had been observed with MTE already during its infancy [12], while their theoretical explanation, based on the analysis of indirect space charge effects, has been provided only recently [13]. Hence, the results of these high-intensity tests are an important milestone as, for the first time ever, they imply the capability of mastering complicated phenomena stemming from the interplay between external nonlinearities and space-charge (direct or indirect) effects.…”

On the adiabaticity of emittance exchange due to crossing of the coupling resonance

“…In recent years, there has been intense theoretical efforts to study in detail the phenomenon of resonance crossing in one degree-of-freedom (1DoF) Hamiltonian systems in view of devising novel beam manipulations [4,5,6,7,8,9]. This culminated with the proposal and final implementation of the CERN PS Multi-Turn Extraction (MTE) as an operational means to provide an optimized extraction technique based on nonlinear beam dynamics [10,11,12,13,14,15,16].…”

Barrier bucket and transversely split beams for loss-free multi-turn extraction in synchrotrons

“…Compared to the conventional debunching, the longitudinal distribution is only altered close to the barriers. Furthermore, clear intensity-dependent effects (see, e.g., [20,21] for the case of transverse splitting) have been observed in the past, but in spite of this, the novel technique has provided excellent results independently of the beam intensity used. Thanks to the new scheme, new options become viable for future operation of fixed-target beams in the CERN accelerator chain.…”