Abstract
We present a general concept to accelerate non-relativistic charged particles. Our concept employs an adiabatically-tapered dielectric-lined waveguide which supports accelerating phase velocities for synchronous acceleration. We propose an ansatz for the transient field equations, show it satisfies Maxwell's equations under an adiabatic approximation and find excellent agreement with a finite-difference time-domain computer simulation. The fields were implemented into the particle-tracking program {\sc astra} and we present beam dynamics results for an accelerating field with a 1-mm-wavelength and peak electric field of 100~MV/m. The numerical simulations indicate that a $\sim 200$-keV electron beam can be accelerated to an energy of $\sim10$~MeV over $\sim 10$~cm. The novel scheme is also found to form electron beams with parameters of interest to a wide range of applications including, e.g., future advanced accelerators, and ultra-fast electron diffraction.
Highlights
High-energy charged-particle accelerators have emerged as invaluable tools to conduct fundamental scientific research
We propose an ansatz for the transient field equations, show it satisfies Maxwell’s equations under an adiabatic approximation and find excellent agreement with a finite-difference timedomain computer simulation
The fields were implemented into the particle-tracking program ASTRA and we present beam dynamics results for an accelerating field with a 1-mm-wavelength and peak electric field of 100 MV=m
Summary
High-energy charged-particle accelerators have emerged as invaluable tools to conduct fundamental scientific research. Power requirements and mechanical breakdowns in accelerating cavities have limited the permissible electric fields to E0 ≲ 50 MV=m, leading to km-scale infrastructures for high-energy accelerators. A key challenge in accelerating low-energy nonrelativistic beams with higher frequencies stems from the difference between the beam’s velocity and accelerating-mode’s phase velocity. This difference leads to “phase slippage” between the beam and the accelerating field which limits the final beam energy and quality. Conventional electron photoinjectors typically operate in a relativistic regime of α ≳ 1; retaining relativistic field strengths while scaling to smaller wavelengths (following E0 ∝ λ−1) is challenging beyond rf frequencies but is routinely attained using high-power infrared lasers in plasmas operating at f ∼ 1 THz. Low-α acceleration with optical wavelengths, i.e., dielectric-laser acceleration (DLA) is interesting due to the foreseen compact footprints, relatively large gradients and high-repetition rates. We especially find that a single derived tapered waveguide can have a versatile range of operation, yielding electron bunches with a broad set of properties of interest for various applications
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