Temporal characterization of ultrashort linearly chirped electron bunches generated from a laser wakefield accelerator

Relativistic wakes produced by intense laser or particle beams propagating through plasmas are being considered as accelerators 1, 2 for next generation of colliders and coherent light sources 3 . Such wakes have been shown to accelerate electrons and positrons to several gigaelectronvolts (GeV) 4-10 , with a few percent energy spread 8-10 and a high wake-to-beam energy transfer efficiency 7 . However, complete mapping of electric field structure of the wakes has proven elusive. Here we show that a high-energy electron bunch can be used to probe the fields of such light-speed wakes with femtosecond resolution. The highly transient, microscopic wakefield is reconstructed from the density modulated ultra-short probe bunch

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“…The divergence of the probe is 2 mrad (root-mean-square, rms). The pulse length of the probe is measured to be 1-3 fs rms [26].…”

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confidence: 99%

Femtosecond Probing of Plasma Wakefields and Observation of the Plasma Wake Reversal Using a Relativistic Electron Bunch

et al. 2017

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“…However, RF cavities cannot resolve ∆E/E| slice of few-fs LWFA bunches. New approaches employing light fields (Zhang et al, 2016a) or plasma wakefields (Dornmair et al, 2016) as transverse deflectors are now emerging. Since these methods are closely connected with bunch duration measurement, we discuss them in Sec.…”

Section: Slice Energy Spreadmentioning

confidence: 99%

“…Measurement of such short bunch durations, and their internal profiles, is one of the greatest new, ongoing diagnostic challenges that plasma electron accelerators have posed. Some researchers have addressed this challenge with creative extensions of time-domain TDS (Zhang et al, 2016a) and EO (Debus et al, 2010a;van Tilborg et al, 2006) methods. (Buck et al, 2011) introduced a time-domain magneto-optic (MO) method to resolve LWFA bunch durations in the few-fs range (Secs.…”

Section: Bunch Length Measurementmentioning

confidence: 99%

“…The problem of characterizing few-fs LWFA bunches has spurred the proposal (Bettoni et al, 2016;Dornmair et al, 2016;Xiang and Huang, 2007) and laboratory demonstration (Bettoni et al, 2016;Zhang et al, 2016a) of new TDS configurations that use near-IR light fields (Xiang and Huang, 2007;Zhang et al, 2016a) or wake fields (Bettoni et al, 2016;Dornmair et al, 2016) with few-fs periods to deflect electrons, instead of microwaves with ns periods. (Bettoni et al, 2016) proposed and demonstrated a passive deflector based on the selftransverse wakefield interaction of the bunch passing offaxis through a dielectric-lined or corrugated waveguide.…”

Section: A Transverse Deflecting Structuresmentioning

confidence: 99%

“…The technique could equally well be implemented with a separate probe pulse overlapping and co-propagating with the accelerating bunch. (Zhang et al, 2016a) relied on energy chirp within the accelerating bunch to map longitudinal position within the bunch onto energy. Thus when the modulated bunch exited the accelerator, and passed through a slit that blocked its most deflected parts (Fig.…”

Section: A Transverse Deflecting Structuresmentioning

confidence: 99%

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Diagnostics for plasma-based electron accelerators

et al. 2018

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Plasma-based accelerators that impart energy gain as high as several GeV to electrons or positrons within a few centimeters have engendered a new class of diagnostic techniques very different from those used in connection with conventional radio-frequency (RF) accelerators. The need for new diagnostics stems from the micrometer scale and transient, dynamic structure of plasma accelerators, which contrasts with the meter scale and static structure of conventional accelerators. Because of this micrometer source size, plasma-accelerated electron bunches can emerge with smaller normalized transverse emittance (n < 0.1 mm mrad) and shorter duration (τ b ∼ 1 fs) than bunches from RF linacs. We review single-shot diagnostics that determine such small n and τ b non-invasively and with high resolution from wide-bandwdith spectral measurement of electromagnetic radiation the electrons emit: n from x-rays emitted as electrons interact with transverse internal fields of the plasma accelerator or with external optical fields or undulators; τ b from THz to optical coherent transition radiation emitted upon traversing interfaces. The duration of ∼ 1 fs bunches can also be measured by sampling individual cycles of a co-propagating optical pulse or by measuring the associated magnetic field using a transverse probe pulse. Because of their luminal velocity and micrometer size, the evolving structure of plasma accelerators, the key determinant of accelerator performance, is exceptionally challenging to visualize in the laboratory. Here we review a new generation of laboratory diagnostics that yield snapshots, or even movies, of laser-and particle-beam-generated plasma accelerator structures based on their phase modulation or deflection of femtosecond electromagnetic or electron probe pulses. We discuss spatiotemporal resolution limits of these imaging techniques, along with insights into plasma-based acceleration physics that have emerged from analyzing the images, and comparing them to simulated plasma structures. CONTENTS I.Introduction 1 II. Properties of plasma accelerator structures and beams 3 A. General properties of plasma electron accelerators 3 1. Frequency-domain holography 41 2. Longitudinal optical shadowgraphy 45 3. Transverse optical probing 46 4. Electron radiography 48 D. "Movies" of wake evolution 49 1. Multi-shot transverse probes 49 2. Single-shot frequency-domain streak camera 50 3. Single-shot imaging of meter-long wakes 52 E. Scaling of wake probes with plasma density 54 V. Conclusion 55 References 58

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Femtosecond electron microscopy of relativistic electron bunches

et al. 2023

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The development of plasma-based accelerators has enabled the generation of very high brightness electron bunches of femtosecond duration, micrometer size and ultralow emittance, crucial for emerging applications including ultrafast detection in material science, laboratory-scale free-electron lasers and compact colliders for high-energy physics. The precise characterization of the initial bunch parameters is critical to the ability to manipulate the beam properties for downstream applications. Proper diagnostic of such ultra-short and high charge density laser-plasma accelerated bunches, however, remains very challenging. Here we address this challenge with a novel technique we name as femtosecond ultrarelativistic electron microscopy, which utilizes an electron bunch from another laser-plasma accelerator as a probe. In contrast to conventional microscopy of using very low-energy electrons, the femtosecond duration and high electron energy of such a probe beam enable it to capture the ultra-intense space-charge fields of the investigated bunch and to reconstruct the charge distribution with very high spatiotemporal resolution, all in a single shot. In the experiment presented here we have used this technique to study the shape of a laser-plasma accelerated electron beam, its asymmetry due to the drive laser polarization, and its beam evolution as it exits the plasma. We anticipate that this method will significantly advance the understanding of complex beam-plasma dynamics and will also provide a powerful new tool for real-time optimization of plasma accelerators.

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Temporal characterization of ultrashort linearly chirped electron bunches generated from a laser wakefield accelerator

Cited by 14 publications

References 24 publications

Femtosecond Probing of Plasma Wakefields and Observation of the Plasma Wake Reversal Using a Relativistic Electron Bunch

Femtosecond Probing of Plasma Wakefields and Observation of the Plasma Wake Reversal Using a Relativistic Electron Bunch

Diagnostics for plasma-based electron accelerators

Femtosecond electron microscopy of relativistic electron bunches

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