Direct laser acceleration of non-relativistic electrons at a photonic structure

Abstract

Acceleration of charged particles exploiting the large optical field strength of short laser pulses and the proximity of a dielectric structure has been envisioned to revolutionize particle accelerators [1,2]. Direct acceleration by the optical carrier field of the laser can take place in the vicinity of a grating, also known as the inverse Smith-Purcell effect [3], which has been observed at a metal grating with a terahertz radiation source, however, the acceleration gradient was small (keV/m) [4]. Dielectrics allow much larger acceleration gradients and hence much smaller accelerators due to their orders of magnitude higher damage threshold in the optical regime as compared to metals. Using dielectric gratings as an optical accelerator has been proposed by Plettner et al. [5].We observe direct laser acceleration of non-relativistic 28 keV electrons close to a single fused-silica transmission grating that is illuminated by Titanium:sapphire laser pulses from below (see Fig. 1a-c). Our findings represent the first demonstration of realistically scalable laser acceleration and of the inverse Smith-Purcell effect in the optical regime. The observed maximum acceleration gradient of 25 MeV/m (see Fig. 1d) is already comparable to state-of-the-art linear accelerators operating with radio-frequency fields. Our work represents the decisive step towards an all-optical linear accelerator that may allow building table-top free electron lasers [6] and other electron optical devices.

VOLTAGE SOURCE UP TO 30 kV WITH PULSATION NOT MORE THAN 0.1%

“…A highly stable source with limiting parameters is necessary for accelerating electrons on a periodic dielectric structure using laser radiation from a terawatt femtosecond laser developed at the NSC KIPT [2]. The requirement for the magnitude of the initial electron energy pulsation is smaller due to the fact that the expected acceleration rate is about ∆Е=200 eV [3], which is confirmed by the experimental results presented in [4].…”

Subrelativistic electron source for Dielectric Laser Acceleration, elements of design

“…Before describing our proposal, which is finally similar to that reference, let's explore the possibilities of nano-positioning DLA inside chamber, in link with the best industrial performances. We have analyzed the simple case of aligning the FEA cathode with a standard DLA, for instance a double grating [33]. We have taken for DLA, a standard option of double grating, but any new idea should probably result in similar conclusions.…”

“…The typical DLA length being L DLA = 25µm in [33], the first maximal deflection angle θ is given by tg θ LDLA < 20nm 25µm ∼ 10 −3 , so θ max = 1mrad ∼ 1 20 degree, which is announced as inside performance of rotating piezo components.…”

“…Let's see again the Breuer's work with his notations, equating phase velocity of wave and particle leads (page 19 of [33]) to :…”