Search arXiv⌕ Search
Home/Archive/arXiv

arXiv · 2610.29094

Oscillation modes, Decoherence, Beam Transfer Functions, and Instabilities for a Beam Subjected to Space-Charge Forces

Kazuhito Ohmi·Liangsheng Huang·Hanyang Liu·Li Rao·Renjun Yang·Sheng Wang·Mingyang Huang
View original source ↗Read source document ↗Export metadata ↓

Abstract

Based on the oscillation modes of a bunch subject to the space-charge force, we discuss the decoherence of the dipole oscillation, the beam transfer function, and the beam instability. The longitudinal phase space is discretized into \(n_l\times n_J\) grids in the azimuthal and radial directions, respectively. The transverse dipole moment in the longitudinal phase space is represented by a vector of length \(n_l n_J\), and the transformation given by the Vlasov equation is represented by a matrix transformation of size \(n_l n_J\times n_l n_J\). Solving the eigenvalue problem of this matrix gives the \(n_l n_J\) eigen-oscillation modes of the bunch. Using the resulting eigenvectors within a standard linear-algebraic treatment, we analyze these three phenomena. The analysis was performed for the Rapid Cycling Synchrotron (RCS) of the China Spallation Neutron Source (CSNS) using \(n_l=41\) and \(n_J=40\), and it visualizes the features related to the continuous distribution of the tune, Landau damping, and isolated modes separated from the continuous tune region.

Explore related subjects

physics.acc-ph

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Kazuhito Ohmi, Liangsheng Huang, Hanyang Liu, Li Rao, Renjun Yang, Sheng Wang, Mingyang Huang. 2026-10-21. Oscillation modes, Decoherence, Beam Transfer Functions, and Instabilities for a Beam Subjected to Space-Charge Forces. https://arxiv.org/abs/2610.29094

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

Evaluation of Transverse Incoherent Tune Shifts in the Electron-Ion Collider

Achieving the Electron-Ion Collider (EIC) peak luminosity goal of 10 to the power of 34 per square centimeter per second requires high average currents, flat beams, non-circular vacuum chambers, and large transverse orbit offsets in the Hadron Storage Ring (HSR) and Electron Storage Ring (ESR). These conditions can generate collective effects and incoherent tune spreads that drive particles across low-order betatron resonances, causing emittance growth, halo formation, and reduced beam lifetime. We quantitatively evaluate incoherent transverse betatron tune shifts from beam-beam interactions, direct space charge, and beam-environment interactions associated with image forces and vacuum chamber geometry. Xsuite and PyHEADTAIL simulations validate the analytical calculations for beam-beam and direct space-charge effects, respectively. For indirect space-charge effects, we review and compare several analytical formalisms and apply the Laslett image-charge formulation to rectangular vacuum chambers with off-axis beams. The analysis accounts for transverse orbit offsets of up to 20 mm in the HSR and 10 mm in the ESR. The results establish baseline parameters and provide quantitative guidance for EIC design, optimization, and operation. The comparison of indirect space-charge formalisms also offers an accessible reference and methodology for studies of high-intensity beam dynamics.

physics.acc-ph↗
arXiv2026

Physics-constrained graph closures and working-point conditioning for a fast surrogate of linac beam dynamics

When a graph neural network estimates a physical quantity, its frame, edge direction, aggregation and feature normalization decide which laws it can break. Wrong choices leave systematic errors the loss never registers. We build a linac beam-dynamics surrogate on this observation. Space charge, short-range wakefields and coherent synchrotron radiation enter as bounded closures on analytic kernels, on graphs whose frame and direction follow the interaction and whose symmetry makes the net space-charge self-force vanish for any weights. Verified without training, with randomized weights, the invariants break by five to eight orders of magnitude once the responsible feature is inverted. Per-working-point models constrained by the rms envelope equation are distilled into one model conditioned on 15 machine settings. On the 18.4~m L0+L1 section of the Shanghai soft x-ray free-electron laser linac, this model predicts the transverse beam envelope at 50 unseen settings to about $7\%$, with the centroid trajectory and emittance, in 0.38~s on a single Quadro RTX 6000 GPU. Training is instead dominated by a normalization choice, a data-derived output range for the beam size: at all 16 working points it lowers the starting error 2.2- to 8.5-fold and fixes the convergence speed. The remaining accuracy differences between hybrid and data-driven architectures vary with the working point and with the density of observation. The held-out error scales roughly as $N^{-0.6}$ with the corpus size $N$. Whether the physics pays off where collective effects are strong, as in a magnetic bunch compressor, is in the next phase of our study.

physics.acc-ph↗
arXiv2026

Development of a Prototype Superconducting Radio-Frequency Multicell Cavity for Compact, Conduction-Cooled Accelerators

Jefferson Lab and General Atomics are jointly advancing compact, high-power irradiation systems capable of delivering electron-beam powers in the hundreds of kilowatts based on superconducting radio-frequency (SRF) technology. A critical step toward deploying SRF accelerators in industrial environments is replacing traditional liquid-helium cryogenic systems with conduction-cooled cryomodules powered by commercial cryocoolers. This paper reports recent progress in the design, fabrication, and testing of a prototype three-cell SRF cavity developed at Jefferson Lab and evaluated in a dedicated horizontal test cryostat at General Atomics. Peak surface magnetic fields up to 18.4\,mT, corresponding to accelerating gradients of approximately 4.3\,MV/m, were achieved in one of the cells. The results provide key insights into cavity preparation, thin-film coating, mechanical robustness, and cryogenic integration, offering guidance for the continued maturation of compact, conduction-cooled SRF accelerators for industrial irradiation applications.

physics.acc-ph↗