Enhancement of x-rays generated by a guided laser wakefield accelerator inside capillary tubes

Abstract

Electrons accelerated in the nonlinear regime in a laser wakefield accelerator experience transverse oscillations inside the plasma cavity, giving rise to ultra-short pulsed x-rays, also called the betatron radiation. We show that the fluence of x-ray can be enhanced by more than one order of magnitude when the laser is guided by a 10 mm long capillary tube instead of interacting with a 2 mm gas jet. X-rays with a synchrotron-like spectrum and associated critical energy ∼5 keV, with a peak brightness of ∼1×1021 ph/s/mm2/mrad2/0.1%BW, were achieved by employing 16 TW laser pulses.

Very Compact Linear Colliders Comprising Seamless Multistage Laser-Plasma Accelerators

“…The pulsed discharge capillaries relying on collisional plasma processes have some difficulties in plasma densities less than 10 17 cm À3 and the temporal and spatial stabilities of the density channel properties for the operation at a high repletion rate such as 10 kHz [5,29]. In contrast to pulsed discharge plasma waveguides, metallic or dielectric capillary waveguides filled with gas [18,30] will be revisited for a large-scale laser-plasma accelerator operated at a practically higher-repetition rate than 10 kHz, because of the passive optical guiding of laser pulses, the propagating electromagnetic fields of which are simply determined the boundary conditions on a static solid wall of the waveguide unless the laser intensity is high enough to cause the material breakdown on a capillary wall [20,21]. Furthermore, the modal nature of electromagnetic fields arising from the boundary conditions on a solid wall allows us to conceive a novel scheme that can overcome a drawback of LPAs, referred to as dephasing of accelerated electron beams from a correct acceleration phase in laser wakefields.…”

3D printing of gas jet nozzles for laser-plasma accelerators

“…However, in the past the complexity of the discharge target has lead to stability issues. Dielectric capillary tubes work as waveguides and therefore provide additional guiding of outer Airy laser modes [20]. Gas cells have a similar design, but provide no additional guiding capabilities.…”

Electron beams and X ray radiation generated by laser wakefield in capillary tubes

“…In this case, electrons accelerated to energies as high as 300 MeV, and photons with a critical energy of ∼ 5 keV and a fluence of ∼ 10 5 ph/mrad 2 [16] were measured. These values are higher than those observed in the case shown above.…”

“…For the peak X-ray fluence measured in the capillary tube, 5.7 10 4 ph/mrad 2 achieved for n e = 8 × 10 18 cm −3 , the corresponding critical energy E c is 5.4 keV and the electron × mean energy Ē e 88 MeV. Assuming X-rays are emitted with a synchrotron like spectrum, an X-ray source radius r β of 2 μm can be deduced using the definition of the critical energy [16]. Using the duration of X-ray emission of 40 fs calculated from simulations, the peak brightness obtained with the capillary tube is estimated to be ∼ 1×10 21 ph/s/mm 2 /mrad 2 /0.1%BW, which is nearly 2 orders of magnitude higher than the one achieved with the gas jet of ∼3×10 19 ph/s/mm 2 /mrad 2 /0.1%BW.…”

“…In this paper, we report on the study of electrons self-injection in long plasmas produced inside capillary tubes for two values of input laser intensities [13,15,16]. The influence of the plasma density and of the capillary tube parameters on the non-linear evolution of the laser pulse and electron trapping are characterized using the measured electrons and X-ray beams properties.…”