Hard X Rays from Laser-Wakefield Accelerators in Density Tailored Plasmas

Abstract

Betatron x-ray sources from laser-plasma accelerators combine compactness, high peak brightness, femtosecond pulse duration and broadband spectrum. However, when produced with Terawatt class lasers, their energy was so far restricted to a few kilo-electronvolt (keV), limiting the range of possible applications. Here we present a simple method to increase the energy and the flux by an order of magnitude without increasing the laser energy. The orbits of the relativistic electrons emitting the radiation were controlled using density tailored plasmas so that the efficiency of the Betatron source is significantly improved.

Tomographic characterization of gas jets for laser-plasma acceleration with increased sensitivity

“…The gas jets are essential targets for LPA experiments as they offer the possibility to design different gas density distribution for the focused laser pulse. In particular, the gas jets that are employed as LPA targets include rotationally symmetric gas jet produced by cylindrical nozzles, non-rotationally symmetric jets generated by slit nozzles of various dimensions, jets with tailored shock fronts generated by blades or wires obstructing the gas flow [17], [22]- [25]. The diversity of gas jets results from the significant effect that the gas density spatial distribution has on laser-plasma interaction, e.g.…”

“…These gas jet targets routinely employ complex gas density distributions (e.g. tailored gas density [17]), enabling both the optimization of the electron acceleration and the X-ray generation from the accelerated electron bunches. The rapid advances of laser technology led to a gradual increase in laser pulse energies resulting in a decrease in gas jet dimensions or gas jet densities due to the X-ray generation scaling laws [18].…”

Update on laser-driven X-ray sources at ELI Beamlines

“…As a result, a collimated X-ray beam with bright ultrashort pulses known as plasma betatron radiation is generated [16]- [17]. Recent experimental results on Betatron show that up to 10 11 photons/shot can be routinely delivered [18]- [19], the photon flux can be further enhanced by using the PW class lasers. Furthermore, in the inverse Compton scheme, where the relativistic electrons collide with a counter-propagating intense laser pulse, gamma radiation (100's of keV to the MeV range) can be generated as a result of double Doppler upshift of the scattered laser pulse.…”

Attosecond betatron radiation pulse train

“…This can be done in several ways, e.g. by using a tilted shock front in the acceleration phase 26 , an axially modulated plasma density 27 , off-axis laser alignment to a capillary plasma waveguide 28 , transverse density gradient 29 , 30 , or tailoring the dynamics of the nonlinear plasma wave in a way that electrons find themselves behind its first period (the bubble) for a certain period of time, where their oscillations are amplified due to the opposite polarity of transverse fields 31 . Also, injection of matter by irradiating solid micro-droplets 32 or nanoparticles 33 may provide enhancement of the generated betatron X-ray intensity.…”