Moein Fakhari

Short electron bunch generation using single-cycle ultrafast electron guns

We introduce a solution for producing ultrashort (

Segmented terahertz electron accelerator and manipulator (STEAM)

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Performance analysis of the prototype THz-driven electron gun for the AXSIS project

fs) high charge (

THz-driven electron streak camera based on a multilayer structure

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Terahertz Accelerator Technology

pC) from ultra-compact guns utilizing single-cycle THz pulses. We show that the readily available THz pulses with energies as low as 20 ?J are sufficient to generate multi-10 keV electron bunches. Moreover, It is demonstrated that THz energies of 2mJ are sufficient to generate relativistic electron bunches with higher than 2 MeV energy. The high acceleration gradients possible in the structures provide 30 fs electron bunches at 30 keV energy and 45 fs bunches at 2 MeV energy. These structures will underpin future devices for strong field THz physics in general and miniaturized electron guns, in which the high fields combined with the short pulse duration enable electron beams with ultrahigh brightness.

Compact Electron Injectors Using Laser Driven THz Cavities

Acceleration and manipulation of electron bunches underlie most electron and X-ray devices used for ultrafast imaging and spectroscopy. New terahertz-driven concepts offer orders-of-magnitude improvements in field strengths, field gradients, laser synchronization and compactness relative to conventional radiofrequency devices, enabling shorter electron bunches and higher resolution with less infrastructure while maintaining high charge capacities (pC), repetition rates (kHz) and stability. We present a segmented terahertz electron accelerator and manipulator (STEAM) capable of performing multiple high-field operations on the six-dimensional phase space of ultrashort electron bunches. With this single device, powered by few-microjoule, single-cycle, 0.3 THz pulses, we demonstrate record terahertz acceleration of >30 keV, streaking with <10 fs resolution, focusing with >2 kT m–1 strength, compression to ~100 fs as well as real-time switching between these modes of operation. The STEAM device demonstrates the feasibility of terahertz-based electron accelerators, manipulators and diagnostic tools, enabling science beyond current resolution frontiers with transformative impact.By sending few-microjoule single-cycle terahertz pulses to a segmented terahertz electron accelerator and manipulator, 70 MV m–1 peak acceleration fields, 2 kT m–1 focusing gradients, 140 µrad fs–1 streaking gradient and bunch compression to 100 fs are achieved.

Thermal Simulation of an Energy Feedback Normal Conducting RF Cavity

Abstract The AXSIS project (Attosecond X-ray Science: Imaging and Spectroscopy) aims to develop a THz-driven compact X-ray source for applications e.g. in chemistry and biology by using ultrafast coherent diffraction imaging and spectroscopy. The key components of AXSIS are the THz-driven electron gun and THz-driven dielectric loaded linear accelerator as well as an inverse Compton scattering scheme for the X-rays production. This paper is focused on the prototype of the THz-driven electron gun which is capable of accelerating electrons up to tens of keV. Such a gun was manufactured and tested at the test-stand at DESY. Due to variations in gun fabrication and generation of THz-fields the gun is not exactly operated at design parameters. Extended simulations have been performed to understand the experimentally observed performance of the gun. A detailed comparison between simulations and experimental measurements is presented in this paper.

Ultrafast Electron Guns for the Efficient Acceleration using Single-Cycle THz Pulses

With the development of modem THz technology [1], which can provide electric fields with GV/m gradients, THz-based control and manipulation of the electron bunches has become possible. THz-driven electron acceleration, compression and streaking have attracted much attention recently [2, 3]. Here, we present a novel THz driven electron streak camera that provides sub-fs temporal resolution using a multilayer structure.

THz cavities and injectors for compact electron acceleration using laser-driven THz sources

The potential of a linear THz accelerator technology is discussed. Theoretical and first experimental results on THz-driven guns and accelerators are presented with a focus on laser based THz generation to drive these devices.

Characterization of the Electron Beam from the Thz Driven Gun for AXSIS

We present ultra-small electron injectors based on cascaded cavities excited by short multi-cycle THz signals. The designed structure is a 3.5 cell normal conducting cavity operating at 300 GHz. This cavity is able to generate pC electron bunches and accelerate them up to 250 keV using less than 1 mJ THz energy. Unlike conventional RF guns, the designed cavity operates in a transient state which, in combination with the high frequency of the driving field, makes it possible to apply accelerating gradients as high as 500 MV/m. Such high accelerating gradients are promising for the generation of high brightness electron beams with transverse emittances in the nm-rad range. The designed cavity can be used as the injector for a compact accelerator of low charge bunches.