Laser-Photofield Emission from Needle Cathodes for Low-Emittance Electron Beams

Ganter, R.; Bakker, R.J.; Gough, C.; Leemann, Simon; Paraliev, M.; Pedrozzi, M.; Pimpec, F. Le; Schlott, V.; Rivkin, L.; Wrulich, A.

doi:10.1103/physrevlett.100.064801

Cited by 69 publications

(61 citation statements)

References 20 publications

(19 reference statements)

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“…Ganter et al (2008) have performed photo-field emission tests from a single ZrC needle. With 16 ps long laser pulses at 266 nm, they have obtained electron pulses with up to 150 pC and a peak current of 2.9 A at 60 keV in pulsed high-voltage operation, at a repetition rate of 30 Hz and a tip radius r ≈ 50 µm.…”

Section: Current Status Of Tip-based and Tip Array-based Approachesmentioning

confidence: 99%

Dielectric laser accelerators

England¹,

Noble²,

Bane³

et al. 2014

Rev. Mod. Phys.

331

184

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The use of infrared lasers to power optical-scale lithographically fabricated particle accelerators is a developing area of research that has garnered increasing interest in recent years. We review the physics and technology of this approach, which we refer to as dielectric laser acceleration (DLA). In the DLA scheme operating at typical laser pulse lengths of 0.1 to 1 ps, the laser damage fluences for robust dielectric materials correspond to peak surface electric fields in the GV/m regime. The corresponding accelerating field enhancement represents a potential reduction in active length of the accelerator between 1 and 2 orders of magnitude. Power sources for DLA-based accelerators (lasers) are less costly than microwave sources (klystrons) for equivalent average power levels due to wider availability and private sector investment. Due to the high laser-to-particle coupling efficiency, required pulse energies are consistent with tabletop microJoule class lasers. Combined with the very high (MHz) repetition rates these lasers can provide, the DLA approach appears promising for a variety of applications, including future high energy physics colliders, compact light sources, and portable medical scanners and radiative therapy machines.

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Section: Current Status Of Tip-based and Tip Array-based Approachesmentioning

confidence: 99%

Dielectric laser accelerators

England¹,

Noble²,

Bane³

et al. 2014

Rev. Mod. Phys.

331

184

View full text Add to dashboard Cite

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“…Despite the low bunch charge (∼fC) supported by DLAs, successful FEL operation appears feasible [26]; source development is needed, as in other FEL approaches [18,27]. Moreover, the realization of accelerating, deflecting, focusing and bunching elements for non-relativistic electrons could lead to a new generation of electron optics with applications in ultrafast electron diffraction experiments and time-resolved electron microscopy.…”

mentioning

confidence: 99%

“…Due to their micron-scale size, DLA structures require and support electron beams with normalized emittance values in the nm-range [23]. Therefore, a nonrelativistic DLA section in combination with an ultralow emittance electron source, such as a laser-triggered needle cathode with an intrinsic emittance of ∼50 nm [18], is crucial for the injection of high-quality electron beams into the relativistic section of the DLA. A common laser source, amplified in various sections, can be used to drive the electron gun, the non-relativistic and the relativistic DLA.…”

mentioning

confidence: 99%

“…However, the excellent beam control of a standard SEM outweighs the low expected count rate in this proofof-concept experiment. With a pulsed electron source, which will be implemented in future experiments, I eff will be many orders of magnitude higher; 3 A peak current have been shown with a pulsed source, 10 12 times as large as I b in our experiment [18]. After passing the grating, the electrons enter an electrostatic filter lens spectrometer [19], which blocks all unaccelerated electrons.…”

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confidence: 99%

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Laser-Based Acceleration of Nonrelativistic Electrons at a Dielectric Structure

2013

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A proof-of-principle experiment demonstrating dielectric laser acceleration of non-relativistic electrons in the vicinity of a fused-silica grating is reported. The grating structure is utilized to generate an electromagnetic surface wave that travels synchronously with and efficiently imparts momentum on 28 keV electrons. We observe a maximum acceleration gradient of 25 MeV/m. We investigate in detail the parameter dependencies and find excellent agreement with numerical simulations. With the availability of compact and efficient fiber laser technology, these findings may pave the way towards an all-optical compact particle accelerator. This work also represents the demonstration of the inverse Smith-Purcell effect in the optical regime.The acceleration gradients of linear accelerators are limited by breakdown phenomena at the accelerating structures under the influence of large surface fields. Today's accelerators, which are based on metal structures driven by radio frequency fields, operate at acceleration gradients of ∼20-50 MeV/m. The upper limit in future radio frequency accelerators, such as the discussed CLIC and ILC, is ∼100 MeV/m, given by the damage threshold of the metal surfaces [1][2][3]. At optical frequencies dielectric materials withstand roughly two orders of magnitude larger field amplitudes than metals [4]. Together with the large optical field strength attainable with short laser pulses, dielectric laser accelerators (DLAs) hence may support acceleration gradients in the multi-GeV/m range [5]. With this technology lab-size accelerators, providing particle beams with energies currently only available at km-long facilities, seem feasible. Here we demonstrate the efficacy of the concept.Charged particle acceleration with oscillating fields requires an electromagnetic wave with a phase speed equal to the particle's velocity and an electric field component parallel to the particle's trajectory. So far, laserbased particle acceleration schemes employ the longitudinal electric field component of a plasma wave [6][7][8] or of a tightly focused laser beam [9], but in both schemes the accelerating mode has a phase velocity that does not match the speed of light. Therefore, relativistic particles can only be accelerated over short distances and the maximum attainable energies of these devices are limited. Exploiting the near-field of periodic structures, for example of optical gratings, offers the possibility to continuously accelerate non-relativistic as well as relativistic particles. In essence, the effect of the grating is to rectify the oscillating field in the frame co-moving with the electron, conceptually similar to conventional radio frequency devices. Single gratings can only be used to accelerate non-relativistic electrons, an effect also known as the inverse Smith-Purcell effect [10][11][12]. However, double grating structures, in which electrons propagate in a channel between two gratings facing each other, support a longitudinal, accelerating speed-of-light eigenmode that can be used to a...

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“…To combat this issue, enhanced local fields in the vicinity of metallic nano-structures and longer wavelength drivers can be exploited to significantly reduce the optical intensities required to induce emission and accelerate electrons to high energies. Indeed, during the last decade, numerous studies have explored strong-field physics by coupling femtosecond laser pulses to nanostructured solids, particularly metallic nano-tips [140][141][142][143][144][145][146][147][148][149][150][151][152][153][154]. The results of those investigations demonstrated that, with proper modification, much of the basic physics underlying laser induced ionization of atomic and molecular gases also applies to laser-induced electron emission from solids.…”

Section: Chapter 5 High-energy Electron Emission From Metallic Nano-mentioning

confidence: 99%

Field Ionization and Field Emission with Intense Single-cycle THz Pulses

Li¹

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This dissertation focuses on light-matter interactions in the strong-field, lowfrequency, single-cycle regime in both gas-phase and solid-state systems through the investigation of field ionization of Rydberg atoms and field emission from metallic nano-tips exposed to intense, single-cycle THz pulses. Field ionization/emission mechanism, as well as post-ionization/emission energy transfer dynamics, have been studied.In the experiments, single-cycle THz pulses with a central frequency f ∼0.2 THz and peak field amplitude F m ∼0.5 MV/cm are used to explore: 1) Field ionization of excited atoms (Na Rydberg states of nd, n = 6−15) in the long-pulse/low-frequency regime. A F ∝ n −3 over-the-barrier ionization threshold scaling behavior is observed, reflecting the suppression of core-scattering during the ionization pulse and, more importantly, the extended times required for Rydberg electrons to escape over the field-dressed Coulomb potential barrier. We have also examined energy transfer in the single-cycle limit and showed that in contrast to ionization by multi-cycle pulses, electrons that are ionized near the field extrema of a single-cycle pulse acquire substantial energies (∼ 2U p ), and those ionized near the zero-crossing can obtain much larger energies (> 6U p ), even in the absence of rescattering.2) Field ionization of oriented atoms (Na Rydberg-Stark states in an n-manifold, n = 10−12). The ionization threshold fields are found to be orientation-dependent, due to both diabatic population transfer between "uphill" and "downhill" oriented states and an asymmetry in the single-cycle THz waveform.3) High-energy field-electron-emission from W nano-tips having different cone angles and tip radii, 10 nm < R < 1 µm. Electrons with energies easily exceeding iii 5 keV are observed. The maximum electron energies are proportional to the peak THz field and are roughly independent of the tip radius. These observations can be attributed to the large field enhancement and spatial localization of the enhanced field in the vicinity of the nano-tips. At low-frequencies/long-wavelengths, such near-field characteristics can fundamentally change the energy transfer process as compared to that which occurs following the ionization of gas-phase atoms or molecules, and allow for the creation of very high energy electrons.iv

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Laser-Photofield Emission from Needle Cathodes for Low-Emittance Electron Beams

Cited by 69 publications

References 20 publications

Dielectric laser accelerators

Dielectric laser accelerators

Laser-Based Acceleration of Nonrelativistic Electrons at a Dielectric Structure

Field Ionization and Field Emission with Intense Single-cycle THz Pulses

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