Beam quality study for a grating-based dielectric laser-driven accelerator

Abstract

Dielectric laser-driven accelerators (DLAs) based on grating structures are considered to be one of the most promising technologies to reduce the size and cost of future particle accelerators. They offer high accelerating gradients of up to several GV/m in combination with mature lithographic techniques for structure fabrication. This paper numerically investigates the beam quality for acceleration of electrons in a realistic dual-grating DLA. In our simulations, we use beam parameters of the future Compact Linear Accelerator for Research and Applications facility to load an electron bunch into an optimized 100-period dual-grating structure where it interacts with a realistic laser pulse. The emittance, energy spread, and loaded accelerating gradient for modulated electrons are then analyzed in detail. Results from simulations show that an accelerating gradient of up to 1.13 ± 0.15 GV/m with an extremely small emittance growth, 3.6%, can be expected.

Dual-gratings with a Bragg reflector for dielectric laser-driven accelerators

“…Figure 6 shows the bunch energy distribution for those modulated electrons with the laser off and on. It can be seen that the energy sprectrum has a double-peaked profile after laser-bunch interaction due to longer bunch RMS length of 9 µm than laser wavelength, which agrees well with the reported results 11,12,28 . The maximum energy gain is ΔE 2 = 59 ± 4 keV for optimized dual-gratings with a Bragg reflector, while it is ΔE 1 = 32 ± 4 keV for bare dual-gratings.…”

Electron dynamics in grating-type dielectric laser accelerators: Particle transfer function, generalized acceleration/deflection gradients and Panofsky–Wenzel theorem

“…A simple description of the dynamics of a near-resonant particle (time of flight ≈ optical period) traversing a DLA unit cell was presented. The description introduces complex-valued functions G x (x, y), G y (x, y), G z (x, y) which are a natural generalization of acceleration and deflection gradients used in previous DLA literature [11][12][13][14]. The Panofsky-Wenzel theorem implies that G x and G y can be calculated from G z , so both the longitudinal and the transverse dynamics can be derived from a single function G z (x, y), the acceleration gradient.…”

“…The accelaration gradient G acc (= G z ) and deflection gradient G defl (= G x , G y , alternative names: accelerating/deflecting gradients) are defined as the accelerating and deflecting fields (= force per unit charge) acting on a particle, averaged over one DLA unit cell [11][12][13][14], see Fig. 1.…”

“…[7]). Previous publications which use the notions of acceleration and deflection gradients in the context of DLA [11][12][13][14] do not mention the Panofsky-Wenzel theorem. A recent paper by Niedermayer, Egenolf and Boine-Frankenheim [7] is the first article to use the theorem in the context of DLA.…”

“…[7]. The purpose of this Section is to formulate the implications of the Panofsky-Wenzel theorem in terms of acceleration/deflection gradients G x , G y , G z , and thus link the theorem with previous literature that uses acceleration and deflection gradients in the context of DLA [11][12][13][14].…”