|
|
Bontoiu, C., Bonatto, A., Apsimon, Ö., Bandiera, L., Cavoto, G., Drebot, I., et al. (2025). Numerical study of self-injected electron acceleration in CNT structured targets driven by an 800 nm laser. Sci Rep, 15(1), 45323–13pp.
Abstract: Laser wakefield acceleration (LWFA) may achieve TeV/m gradients using high-density solid-state plasmas as accelerating media. However, the application of bulk solid materials requires attosecond laser pulses, such as X-ray lasers, to drive wakefields at these high densities. Additionally, the short wakefield wavelengths associated with solid-state plasmas greatly limit the accelerating length. An alternative approach employs 2D carbon-based nanomaterials, like graphene or carbon nanotubes (CNTs), configured into structured targets. These nanostructures are designed with voids or low-density regions to effectively reduce the overall plasma density. This reduction enables the use of longer-wavelength lasers and also extends the plasma wavelength and the acceleration length. In this study, we present, to our knowledge, the first numerical demonstration of electron acceleration via self-injection into a wakefield bubble driven by an infrared laser pulse in structured CNT targets, similar to the behavior observed in gaseous plasmas for LWFA in the nonlinear (or bubble) regime. Using the PIConGPU code, bundles of CNTs are modeled in a 3D geometry as 25 nm-thick carbon tubes with an initial density of 10^22 cm^-3. The carbon plasma is ionized by a three-cycle, 800 nm wavelength laser pulse with a peak intensity of 10^21 W cm^-2, achieving an effective plasma density of 10^20 cm^-3. The same laser also drives the wakefield bubble, responsible for electron self-injection and acceleration. Simulation results indicate that fs-long electron bunches with hundreds of pC charge can be self-injected and accelerated at gradients exceeding 1 TeV/m. Both charge and accelerating gradient figures are unprecedented when compared with LWFA in gaseous plasma.
|
|
|
|
Lei, B. F., Zhang, H., Bontoiu, C., Bonatto, A., Martin-Luna, P., Liu, B., et al. (2025). Leaky surface plasmon-based wakefield acceleration in nanostructured carbon nanotubes. Plasma Phys. Control. Fusion, 67(6), 065036–11pp.
Abstract: Metallic carbon nanotubes (CNTs) can provide ultra-dense, homogeneous plasma capable of sustaining resonant plasma waves-known as plasmons-with ultra-high field amplitudes. These waves can be efficiently driven by either high-intensity laser pulses or high-density relativistic charged particle beams. In this study, we use numerical simulations to propose that electrons and positrons can be accelerated in wakefields generated by the leaky electromagnetic field of surface plasmons. These plasmons are excited when a high-intensity optical laser pulse propagates paraxially through a cylindrical vacuum channel structured within a CNT forest. The wakefield is stably sustained by a non-evanescent longitudinal field with TV m-1-level amplitudes. This mechanism differs significantly from the plasma wakefield generation in uniform gaseous plasmas. Travelling at the speed of light in a vacuum, with phase-matched focusing fields, the wakefield acceleration is highly efficient for both electron and positron beams. We also examine two potential electron injection mechanisms: edge injection and self-injection. Both mechanisms are feasible with current laser facilities, paving the way for experimental realisation. Beyond presenting a novel method toward ultra-compact, high-energy solid-state plasma particle accelerators with ultra-high acceleration gradients, this work also expands the potential of high-energy plasmonics.
|
|
|
|
Martin-Luna, P., Bonatto, A., Bontoiu, C., Lei, B. F., Xia, G. X., & Resta-Lopez, J. (2025). Plasmonic excitations in graphene layers. Chin. J. Phys., 97, 607–624.
Abstract: The interaction of fast charged particles with graphene layers can generate electromagnetic modes. This wake effect has been recently proposed for short-wavelength, high-gradient particle acceleration and for obtaining brilliant radiation sources. In this study, the excitation of wakefields produced by a point-like charged particle moving parallel to a multilayer graphene array (which may be supported by an insulated substrate) is studied using the linearized hydrodynamic theory. General expressions for the excited longitudinal and transverse wakefields have been derived. The dependencies of the wakefields on the positions of the layers and the substrate, the velocity and the surface density have been extensively analyzed. This study provides a deeper understanding of the physical phenomena underlying plasmonic excitations in graphene layers, paving the way for potential applications of these structures in particle acceleration, nanotechnology and materials science.
|
|
|
|
Martin-Luna, P., Bonatto, A., Bontoiu, C., Lei, B. F., Xia, G. X., & Resta-Lopez, J. (2025). Wakefield excitation and stopping power in multi-walled carbon nanotubes: one- and two-fluid model. J. Phys. D, 58(22), 225203–15pp.
Abstract: The motion of charged particles along multi-walled carbon nanotubes (MWCNTs) can induce electromagnetic modes. This wake effect represents an innovative approach for short-wavelength, high-gradient particle acceleration and for producing brilliant radiation sources. This article examines the excitation of wakefields produced by a point-like charge moving parallel to MWCNTs using the linearized hydrodynamic theory. General expressions for the excited longitudinal and transverse wakefields and the stopping power have been derived, relating them to the resonant wavenumbers obtainable from the dispersion relations under the assumption of negligible friction. As the number of walls in MWCNTs increases, they exhibit a richer spectrum of plasmonic excitations, which has been widely studied as a function of the driver velocity in this manuscript. This comprehensive study provides a deeper understanding of the physical phenomena behind plasmonic excitations in MWCNTs, paving the way for potential applications in particle acceleration, nanotechnology, and materials science.
|
|
|
|
Martín-Luna, P., Bonatto, A., Bontoiu, C., Xia, G., & Resta-Lopez, J. (2023). Excitation of wakefields in carbon nanotubes: a hydrodynamic model approach. New J. Phys., 25(12), 123029–12pp.
Abstract: The interactions of charged particles with carbon nanotubes (CNTs) may excite electromagnetic modes in the electron gas produced in the cylindrical graphene shell constituting the nanotube wall. This wake effect has recently been proposed as a potential novel method of short-wavelength high-gradient particle acceleration. In this work, the excitation of these wakefields is studied by means of the linearized hydrodynamic model. In this model, the electronic excitations on the nanotube surface are described treating the electron gas as a 2D plasma with additional contributions to the fluid momentum equation from specific solid-state properties of the gas. General expressions are derived for the excited longitudinal and transverse wakefields. Numerical results are obtained for a charged particle moving within a CNT, paraxially to its axis, showing how the wakefield is affected by parameters such as the particle velocity and its radial position, the nanotube radius, and a friction factor, which can be used as a phenomenological parameter to describe effects from the ionic lattice. Assuming a particle driver propagating on axis at a given velocity, optimal parameters were obtained to maximize the longitudinal wakefield amplitude.
|
|
