Drive-Witness Acceleration Scheme Based on Corrugated Dielectric mm-Scale Capillary (original) (raw)
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Experimental and numerical studies of dielectric Wakefield acceleration devices
Proceedings of the 2003 Bipolar/BiCMOS Circuits and Technology Meeting (IEEE Cat. No.03CH37440)
Results are reported from experiments, and numerical analysis of wake fields set up by electron bunches passing through a cylindrical dielectric liner made of alumina. The bunches excite many TM-modes, and the Ez component of wake field is sharply localized on the axis periodically behind the bunches. The experiment is at ATF Brookhaven, and uses up to three 50 MeV bunches spaced by one wake field period (21 cm) to study the superposition of wake fields by measuring the energy loss of each bunch after it passes through the 53-cm long dielectric element. The millimeter-wave spectrum of radiation excited by the passage of bunches is of interest too. The numerical analysis was aimed not only to simulate the behaviour of our device, but in general to predict dielectric wake field accelerator (DWA) parameters. It is shown that one needs to match the radius of dielectric channel with the bunch longitudinal rmslength to achieve optimal performance.
Enhanced stability of laser wakefield acceleration using dielectric capillary tubes
Physical Review Special Topics - Accelerators and Beams, 2014
The stability of beams of laser wakefield accelerated electrons in dielectric capillary tubes is experimentally investigated. These beams are found to be more stable in charge and pointing than the corresponding beams of electrons accelerated in a gas jet. Electron beams with an average charge of 43 pC and a standard deviation of 14% are generated. The fluctuations in charge are partly correlated to fluctuations in laser pulse energy. The pointing scatter of the electron beams is measured to be as low as 0.8 mrad (rms). High laser beam pointing stability improved the stability of the electron beams.
ANALYSIS OF A RECTANGULAR DIELECTRIC-LINED ACCELERATING STRUCTURE WITH AN ANISOTROPIC LOADING
Analysis of Cherenkov radiation generated by high current relativistic electron bunch passing through a rectangular waveguide with anisotropic dielectric loading has been carried out. Some of the materials used for the waveguide loading of accelerating structures (sapphire) possess significant anisotropic properties. In turn, it can influence excitation parameters of the wakefields generated by an electron beam. Using orthogonal eigenmode decomposition for the rectangular dielectric waveguide, the analytical expressions for the wakefields have been obtained. Numerical modelling of the longitudinal and transverse (deflecting) wakefields has been carried out as well. It is shown that the dielectric anisotropy causes frequency shift in comparison to the dielectric-lined waveguide with the isotropic dielectric loading.
We report on a collinear wakefield experiment using the first tunable dielectric loaded accelerating structure. By introducing an extra layer of nonlinear ferroelectric, which has a dielectric constant sensitive to temperature and dc bias, the frequency of a dielectric loaded accelerating structure can be tuned. During the experiment, the energy of a witness bunch at a fixed delay with respect to the drive beam was measured while the temperature of the structure was scanned over a 50 C range. The energy change corresponded to a change of more than half of the nominal structure wavelength.
2017
Dielectric lined waveguides are under extensive study as accelerating structures that can be excited by electron beams. Rectangular dielectric structures are used both in proof of principle experiments for new accelerating schemes and for studying the electronic properties of the structure loading material. Analysis of Cherenkov radiation generated by high current relativistic electron bunch passing through a rectangular waveguide with transversal isotropic dielectric loading has been carried out. Some of the materials used for the waveguide loading of accelerating structures (sapphire, ceramic films) possess significant anisotropic properties. In turn, it can influence excitation parameters of the wakefields generated by an electron beam. General solutions for the fields generated by a relativistic electron beam propagating in a rectangular dielectric waveguide have been derived using the orthogonal eigenmode decomposition method for the transverse operators of the Helmholtz equati...
Physical Review Special Topics - Accelerators and Beams
Experimental results are reported for test beam acceleration and deflection in a two-channel, cm-scale, rectangular dielectric-lined wakefield accelerator structure energized by a 14-MeV drive beam. The dominant waveguide mode of the structure is at 30GHz,andthestructureisconfiguredtoexhibitahightransformerratio(30 GHz, and the structure is configured to exhibit a high transformer ratio (30GHz,andthestructureisconfiguredtoexhibitahightransformerratio(12:1). Accelerated bunches in the narrow secondary channel of the structure are continuously energized via Cherenkov radiation that is emitted by a drive bunch moving in the wider primary channel. Observed energy gains and losses, transverse deflections, and changes in the test bunch charge distribution compare favorably with predictions of theory.
Resonant Excitation of Accelerating Field in Dielectric
2018
Beam driven dielectric wakefield accelerators (DWAs) [1] typically operate in the terahertz frequency range, which pushes the plasma breakdown threshold for surface electric fields into the multi GV/m range. DWA technique allows to accommodate a significant amount of charge per bunch, and opens access to conventional fabrication techniques for the accelerating structures. Resonant excitation of coherent Cerenkov radiation in DWA by a multi-bunch beam was used for selective resonant mode excitation [2] and enhancement of accelerating wakefield [3]. We investigate the resonant excitation of Cerenkov Smith-Purcell radiation [4] in a corrugated cylindrical waveguide by a multi-bunch electron beam. The accelerating field is calculated using Particle in Cell simulations and some basic post-processing is done in order to estimate the possible enhancement of the accelerating field. The aim of this work is to investigate regimes of the resonant excitation that can potentially produce acceler...
2017
Dielectric waveguide structures are a basis for development of new generation of accelerators on the basis of a wakefield method of the charged particle acceleration, beam manipulation, and also free electron lasers. A self-coordinated dynamics of relativistic particle beams in a single layer cylindrical waveguide with dielectric filling is investigated. The computer code is developed based on mathematical expressions for the analysis of the radial dynamics. The possibility of modeling interaction of different types of particles in a bunch is realized. Influence of both own wake fields and external fields of focusing and deflection systems on bunch dynamics are analyzed.
Tracking with wakefields in dielectric laser acceleration grating structures
Physical Review Accelerators and Beams, 2020
Due to the tiny apertures of dielectric laser acceleration grating structures within the range of the optical wavelength, wakefields limit the bunch charge for relativistic electrons to a few femtocoulomb. In this paper, we present a wakefield upgrade of our six-dimensional tracking scheme DLAtrack6D in order to analyze these limitations. Simulations with CST Studio Suite provide the wake functions to calculate the kicks within each tracking step. Scaling laws and the dependency of the wake on geometrical changes are calculated. The tracking with wakefields is applied to beam and structure parameters following recently performed and planned experiments. We compare the results to analytical models and identify intensity limits due to the transverse beam breakup and strong headtail instability. Furthermore, we reconstruct phase advance spectrograms and use them to analyze possible stabilization mechanisms.