Short electron bunch generation using single-cycle ultrafast electron guns

Fallahi, Arya; Fakhari, Moein; Yahaghi, Alireza; Arrieta, Miguel; Kärtner, Franz X.

doi:10.1103/physrevaccelbeams.19.081302

Cited by 72 publications

(68 citation statements)

References 37 publications

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“…This is due to the already strong curvature of the bunch longitudinal phase-space at the gun exit (see Figure 1), which limits the compression performances in the linac. This curvature is caused by the high-frequency field (300 GHz) used to accelerate the electron bunch in the gun [3]. The straightforward and most efficient way to reduce it, and therefore to improve the bunch compression in the linac, would be to use lower frequencies in the gun.…”

Section: Resultsmentioning

confidence: 99%

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Beam dynamics in THz dielectric-loaded waveguides for the AXSIS project

Vinatier

Assmann

Dorda

et al. 2017

J. Phys.: Conf. Ser.

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Section: Resultsmentioning

confidence: 99%

“…This is what the AXSIS project [1] aims for. In this project, the electron bunch will be produced by photoemission in a gun driven by single-cycle THz pulses [2,3]. It will then be accelerated in a THz linac structure consisting in a dielectric-loaded waveguide driven by a multicycle THz pulse [4,5,6].…”

Section: Introductionmentioning

confidence: 99%

Beam dynamics in THz dielectric-loaded waveguides for the AXSIS project

Vinatier

Assmann

Dorda

et al. 2017

J. Phys.: Conf. Ser.

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“…First THz guns based on a parallel plate THz waveguide have been reported producing quasi-monochromatic electron bunches with a few percent energy spread around 400 eV mean energy [9]. More advanced THz gun structures driven by either single-cycle or multi-cycle THz pulses have been proposed [10,11]. The single-cycle gun structure is a segmented THz waveguide device composed of arrays of parallel plate waveguides with dielectric fillings to delay the THz pulses in each waveguide, such that when excited with a single high energy THz pulse jointly, a tilted pulse front is created at the interaction point with electrons.…”

Section: Thz Guns and Accelerationmentioning

confidence: 99%

THz Driven Accelerators and X-ray Sources

Kärtner

2018

Conference on Lasers and Electro-Optics

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Approaches towards a linear THz accelerator technology are discussed. Theoretical and first experimental results on laser based high energy THz generation, guns, accelerators as well as compact X-ray sources based on these devices are presented. IntroductionToday, high brightness and highly relativistic electron beams are generated by circular or linear accelerators (LINAC) typically operating with 1-3 GHz accelerating frequencies and approaches towards X-band frequencies in the 10 GHz range are maturing. The achievable accelerating gradients are limited by field emission from cavity walls influenced by pulsed heating to several tens of MV/m in the case of low frequencies and up to 100 MV/m in the case of X-band frequencies. Short electron bunches are typically created by photoemission from the cathode in the presence of a strongly accelerating field followed by bunch compression. Low charge bunches, 1-10 pC, may be compressed to durations down to 3 -10 µm (or 10 -30 fs in pulse duration). At a given accelerating field strength and RF frequency, compression is limited by space charge. With higher operating frequency, higher gradients in the accelerating electric field arise which enhances velocity bunching and leads to the generation of shorter electron bunches. These short electron bunches can be used for ultrafast electron diffraction or intense X-ray production. Choosing an operating frequency of the accelerator in the THz range, i.e. here 0.1 -0.5 THz and using multi-cycle to single-cycle pulses, accelerating fields in the 0.3 to 1 GV/m range are sustainable and bunch compression to the sub-femtosecond level of significant charge on the order of ~1 pC becomes possible. To drive electron guns and accelerators high-energy single-cycle and multi-cylce THz pulses in the mJ and tens of mJ range, respectively, are necessary. Here, we discuss approaches towards this goal and results achieved sofar.

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“…Naturally, an accelerating structure fed by such pulses should be based on new principles, which would allow propagation of ultra-broadband radiation [2][3][4]. We propose an accelerating structure (Fig.…”

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confidence: 99%

Strong terahertz fields: interaction with condensed matter and electron acceleration

et al. 2017

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Recent years witness fast development of the sources of strong single-pulse terahertz radiation, with the record value for terahertz field being about 80 MV/cm [1]. There appeared quite a number of publications where the nonlinear interaction of such strong THz fields with matter was investigated and new effects in intense THz fields were sought for. In this presentation, we will discuss the specific nonlinear properties of graphene in strong electromagnetic fields and propose our approach of using short THz pulses for acceleration of electrons.The first part of the presentation will be devoted to the discussion of the experimental and theoretical results on optical emission from graphene irradiated by a strong (up to 300 kV/cm) short terahertz pulse. The appearance of emission from graphene was observed in experiment in the 350-600 nm spectral range at high THz fields (Fig. 1). We detected the increase of the optical emission by nearly 3 orders of magnitude, while the THz field increased by a factor of 2 only. The spectrum of the optical emission corresponded to Planck's law for the spectral radiance of a black body. We attribute the optical emission to bias-induced spontaneous emission from energetic charge carriers in the graphene. On the basis of the theoretical analysis, we revealed the importance of the dynamic (ballistic) mechanism of electron-hole pair generation induced by an intense terahertz pulse with subsequent spontaneous radiative recombination. In the second part of the presentation we will discuss our results on the generation of the second optical harmonic (SHG) of laser radiation from graphene in the presence of a high power terahertz pulse. We demonstrated essential amplification of SHG under the action of THz field. Polarization characteristics of SHG specific for graphene will be presented together with the dependence of SHG efficiency on optical and THz fields. Detailed theoretical analysis of von Neumann equation allowed us to propose a new mechanism for SHG in graphene under the combined action of optical and THz fields. This mechanism is caused by broadening of the interband resonance due to quasi-particle acceleration by an intense THz field in the process of interband transition. As a result of the "field" interband resonance broadening, the region of electron-hole generation in k-space becomes asymmetric, which leads to the appearance of necessary anisotropy allowing for SHG in the dipole approximation.Intense single-cycle THz pulses produced by rectification of laser radiation are suitable for high gradient acceleration of electrons. Naturally, an accelerating structure fed by such pulses should be based on new principles, which would allow propagation of ultra-broadband radiation [2][3][4]. We propose an accelerating structure (Fig. 2) consisting of a set of waveguides with different adjusted lengths, in which the synchronism of accelerated particles with transversely propagating THz pulse is sustained [3]. A proper mirror shape allows the acceleration of both pre-accelerated parti...

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Short electron bunch generation using single-cycle ultrafast electron guns

Cited by 72 publications

References 37 publications

Beam dynamics in THz dielectric-loaded waveguides for the AXSIS project

Beam dynamics in THz dielectric-loaded waveguides for the AXSIS project

THz Driven Accelerators and X-ray Sources

Strong terahertz fields: interaction with condensed matter and electron acceleration

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