Few-Cycle Laser-Driven Electron Acceleration

Electron acceleration by laser-driven plasma waves 1,2 is capable of producing ultra-relativistic, quasi-monoenergetic electron bunches 3-5 with orders of magnitude higher accelerating gradients and much shorter electron pulses than state-of-the-art radio-frequency accelerators. Recent developments have shown peak energies reaching into the GeV range 6 and improved stability and control over the energy spectrum and charge 7 . Future applications, such as the development of laboratory X-ray sources with unprecedented peak brilliance 8,9 or ultrafast time-resolved measurements 10 critically rely on a temporal characterization of the acceleration process and the electron bunch. Here, we report the first real-time observation of the accelerated electron pulse and the accelerating plasma wave. Our time-resolved study allows a single-shot measurement of the 5.8 +1.9 −2.1 fs electron bunch duration full-width at half-maximum (2.5 +0.8 −0.9 fs root mean square) as well as the plasma wave with a density-dependent period of 12-22 fs and reveals the evolution of the bunch, its position in the surrounding plasma wave and the wake dynamics. The results afford promise for brilliant, sub-ångström-wavelength ultrafast electron and photon sources for diffraction imaging with atomic resolution in space and time 11 .The recent development in laser wakefield acceleration (LWFA) is made feasible by transverse breaking of the plasma wave 12 , which results in self-injection and trapping of electrons in the accelerating structure 2,13,14 . Whereas beam parameters such as the energy spectrum, accelerated charge, beam divergence and pointing are now being measured routinely with methods adopted from conventional accelerator technology, the duration of electron bunches arising from LWFA has so far defied accurate determination. Bunch duration measurements up to now have relied on techniques using THz radiation emitted by the electrons, yielding upper limits for the electron pulse length corresponding to the temporal resolution of ≥30 fs (refs 15-18). The plasma wave has been observed so far in single-shot, yet time-integrating schemes 19,20 . Thus, the measurements were incapable of providing insight into the relevant plasma wave dynamics and of timing the accelerated electron bunch with respect to the plasma wave.In this work we present snapshots of the magnetic field generated by the accelerated electron bunch and-simultaneously-of the plasma wave by the combination of two techniques: time-resolved polarimetry 21,22 and plasma shadowgraphy 23 . The novelty in our experimental investigation is the few-cycle duration of our laser pulses, which is even shorter than half of the plasma period. This, in combination with a high spatial resolution, allows

show abstract

“…30. These statistics were calculated with all 2,300 shots from one electron run; error bars are one standard deviation (s.d.…”

Section: Methodsmentioning

confidence: 99%

Real-time observation of laser-driven electron acceleration

et al. 2011

View full text Add to dashboard Cite

show abstract

“…Electrons from a conventional accelerator can be injected into the wakefield, but matching the beam properties to the wakefield size is difficult leading to low efficiency of particle trapping [32]. A number of advanced techniques have been proposed and demonstrated that use density modification [33][34][35], secondary laser beams [36][37][38] or ionization [39][40][41] to greatly simplify injection into the wakefield. But, perhaps the easiest way of injecting high charge beams into the wakefield is through the use of self-injection [24][25][26].…”

Section: Laser Wakefield Accelerationmentioning

confidence: 99%

Compact laser accelerators for X-ray phase-contrast imaging

Najmudin

Kneip

Bloom

et al. 2014

Phil. Trans. R. Soc. A.

View full text Add to dashboard Cite

Advances in X-ray imaging techniques have been driven by advances in novel X-ray sources. The latest fourth-generation X-ray sources can boast large photon fluxes at unprecedented brightness. However, the large size of these facilities means that these sources are not available for everyday applications. With advances in laser plasma acceleration, electron beams can now be generated at energies comparable to those used in light sources, but in university-sized laboratories. By making use of the strong transverse focusing of plasma accelerators, bright sources of betatron radiation have been produced. Here, we demonstrate phase-contrast imaging of a biological sample for the first time by radiation generated by GeV electron beams produced by a laser accelerator. The work was performed using a greater than 300 TW laser, which allowed the energy of the synchrotron source to be extended to the 10–100 keV range.

show abstract

“…The high amplification gain reached by the parametric amplification has led to the generation of sub-10-fs optical pulses with terawatt peak powers [5,6]. Such a highly intense pulse has been applied to initiate the relativistic light-matter interaction generating monoenergetic electrons [7].…”

Section: Introductionmentioning

confidence: 99%

Four-Wave Optical Parametric Amplification in a Raman-Active Gas

Kida

Imasaka

2015

Photonics

View full text Add to dashboard Cite

Four-wave optical parametric amplification (FWOPA) in a Raman-active medium is experimentally investigated by use of an air-filled hollow fiber. A femtosecond pump pulse shorter than the period of molecular motion excites the coherent molecular motion of the Raman-active molecules during the parametric amplification of a signal pulse. The excited coherent motion modulates the frequency of the signal pulse during the parametric amplification, and shifts it to lower frequencies. The magnitude of the frequency redshift depends on the pump intensity, resulting in intensity-dependent spectral characteristics that are different from those in the FWOPA induced in a noble-gas-filled hollow fiber.

show abstract

Few-Cycle Laser-Driven Electron Acceleration

Cited by 115 publications

References 21 publications

Real-time observation of laser-driven electron acceleration

Real-time observation of laser-driven electron acceleration

Compact laser accelerators for X-ray phase-contrast imaging

Four-Wave Optical Parametric Amplification in a Raman-Active Gas

Contact Info

Product

Resources

About