Coupled beam hose and self-modulation instabilities in overdense plasma

Schroeder, C. B.; Benedetti, C.; Esarey, E.; Grüner, F.; Wp, Leemans

doi:10.1103/physreve.86.026402

Cited by 39 publications

(20 citation statements)

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“…The simulations were performed with the spectral quasi-cylindrical code FBPIC [26] using the azimuthal modes m = 0 and m = 1. (This is sufficient because the fields of the unperturbed, symmetrical beam are entirely contained in the mode m = 0, and because the perturbations due to the small offset x c create additional contributions in the modes m > 0 with a typical amplitude (x c /r b ) m [6]. Thus, if x c is small compared to r b , the relevant physics can be captured by the leading order, i.e.…”

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confidence: 99%

Saturation of the Hosing Instability in Quasilinear Plasma Accelerators

et al. 2017

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The beam hosing instability is analyzed theoretically for a witness beam in the quasi-linear regime of plasma accelerators. In this regime, the hosing instability saturates, even for a monoenergetic bunch, at a level much less than standard scalings predict. Analytic expressions are derived for the saturation distance and amplitude and are in agreement with numerical results. Saturation is due to the natural head-to-tail variations in the focusing force, including the self-consistent transverse beam loading.PACS numbers: 41.75.Jv,52.38.Kd The beam hosing instability is a major concern for both conventional accelerators and plasma-based accelerators. In both cases, this instability can exponentially amplify the small misalignments between the beam and the accelerating structure, and potentially lead to a strong degradation of the beam emittance, or even to complete disruption of the beam. Thus the hosing instability (which is related to the well-known beam-breakup instability) has been actively studied in its various regimes [1]. This includes the long-bunch, weakly-coupled regime [2,3] applicable to low-current bunches in conventional accelerators, as well as the long-bunch [4-6] and short-bunch [7-12] strongly-coupled regimes, which are of interest for beams propagating in plasmas or ion channels.In particular, the short-bunch, strongly-coupled regime is relevant to the evolution of the witness beam in plasma-wakefield acceleration (both for the beam-driven and laser-driven scheme). In this case, the exponential growth of the hosing instability as a function of the acceleration distance has raised concerns regarding the feasibility of a plasma-based particle collider [13]. However, these predictions have been made in the context of the blow-out (or bubble) wakefield regime, i.e. when the driver (beam or laser) is strong enough to expell all the plasma electrons, forming a co-moving ion cavity [14][15][16][17][18]. Plasma accelerators may also operate in the quasi-linear regime, where the driver excites a plasma density perturbation that is a fraction of the background plasma density [19]. In this Letter, we show that the sustained exponential growth of the hosing instability, which indeed applies for monoenergetic beams in the blow-out regime, does not occur in the quasi-linear regime. Instead, in the quasi-linear regime, the instability can rapidly saturate, and leads only to a moderate amplification of the beam misalignment.This early saturation is due to the head-to-tail spread in betatron frequency that naturally occurs across the bunch in the quasi-linear regime. It is indeed well-known that a head-to-tail spread in betatron frequency can mitigate the hosing instability [1,20]. However, in the blowout regime, the focusing force of the wakefield is independent of the longitudinal coordinate, and thus any head-to-tail spread in betatron frequency necessarily requires an energy spread in the bunch. Owing to the typically large beam-loading for high efficiency, large energy spreads (e.g. a few percents [11]...

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Saturation of the Hosing Instability in Quasilinear Plasma Accelerators

et al. 2017

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“…5 Hosing is also a challenge for long-beam PWFAs. 6 Of specific interest for short-beam PWFAs is the nonlinear blowout regime, 7 for which essentially all electrons are expelled from the vicinity of the drive beam and a co-propagating ion cavity is formed. The focusing fields in this regime are linear and the accelerating field enhanced.…”

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Accurate modeling of the hose instability in plasma wakefield accelerators

et al. 2018

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Hosing is a major challenge for the applicability of plasma wakefield accelerators and its modeling is therefore of fundamental importance to facilitate future stable and compact plasma-based particle accelerators. In this contribution, we present a new model for the evolution of the plasma centroid, which enables the accurate investigation of the hose instability in the nonlinear blowout regime. It paves the road for more precise and comprehensive studies of hosing, e.g., with drive and witness beams, which were not possible with previous models.

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“…The values of a set of proton bunch parameters are varied independently and the respective simulations compared to a baseline simulation with parameters similar to those of AWAKE. We note here that the hose instability, which can possibly compete with the SMI [18], is not described in 2D axisymmetric geometry. We therefore assume in this work that the seed for the self-modulation process is large enough to prevent the growth of the hose instability [9,19].…”

Section: Introductionmentioning

confidence: 76%

Influence of proton bunch parameters on a proton-driven plasma wakefield acceleration experiment

Moreira

Vieira

Muggli

2019

Phys. Rev. Accel. Beams

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We use particle-in-cell (PIC) simulations to study the effects of variations of the incoming 400 GeV proton bunch parameters on the amplitude and phase of the wakefields resulting from a seeded selfmodulation (SSM) process. We find that these effects are largest during the growth of the SSM, i.e. over the first five to six meters of plasma with an electron density of 7 × 10 14 cm −3 . However, for variations of any single parameter by ±5%, effects after the SSM saturation point are small. In particular, the phase variations correspond to much less than a quarter wakefield period, making deterministic injection of electrons (or positrons) into the accelerating and focusing phase of the wakefields in principle possible. We use the wakefields from the simulations and a simple test electron model to estimate the same effects on the maximum final energies of electrons injected along the plasma, which are found to be below the initial variations of ±5%. This analysis includes the dephasing of the electrons with respect to the wakefields that is expected during the growth of the SSM. Based on a PIC simulation, we also determine the injection position along the bunch and along the plasma leading to the largest energy gain. For the parameters taken here (ratio of peak beam density to plasma density n b0 /n0 ≈ 0.003), we find that the optimum position along the proton bunch is at ξ ≈ −1.5 σ zb , and that the optimal range for injection along the plasma (for a highest final energy of ∼1.6 GeV after 10 m) is 5-6 m.

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Coupled beam hose and self-modulation instabilities in overdense plasma

Cited by 39 publications

References 20 publications

Saturation of the Hosing Instability in Quasilinear Plasma Accelerators

Saturation of the Hosing Instability in Quasilinear Plasma Accelerators

Accurate modeling of the hose instability in plasma wakefield accelerators

Influence of proton bunch parameters on a proton-driven plasma wakefield acceleration experiment

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