Jorge Vieira

 

 

Light Sources

 

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Sources of coherent intense beams of radiation are important for imaging, probing, and controlling matter. High frequency x-rays, for example, can provide direct access to the time-scales of biological and chemical processes. X-rays can also penetrate deeply in high density matter, and be used to probe matter under extreme temperatures and pressures, such as in the interior of planets and stars. Most advanced x-ray sources today rely on large electron accelerators to produce relativistic electron beams. Bending the trajectories of these electrons can lead to intense bursts of x-rays. The LCLS, at SLAC, for example, uses a 3 Km long linear electron accelerator to produce multi-10 GeV electron bunches. These electrons are sent into an undulator to produce the brightness bursts of temporally x-rays ever produced on earth [lcls].

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The interaction of relativistic electrons with intense lasers and plasmas can potentially reduce the size of current x-ray sources. There are many configurations leading to the generation of x-rays in plasma, including relativistic plasma mirrors [lichters'96], Compton/Thomson backscattering [esarey'93], and betatron radiation sources [whittum'90]. These sources can thus provide intense beams of radiation that are already useful in the fields of material science, biology, and high energy density physics. These sources, are, however, not as bright as conventional ones.

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We are interested in building advanced tools to capture radiation in kinetic plasma simulations and to use these tools to explore new radiation emission regimes in laser plasma interactions, including plasma accelerators and Thomson/Compton backscattering. For example, we developed an advanced radiation diagnostic that captures radiation emission at run time in particle-in-cell codes [pardal'18]. This tool solves the radiated electric and magnetic fields in space and in time and therefore includes built-in temporal and spatial coherence effects. This feature gives access to the spatio-temporal radiation profile from a collection of many light emitting particles. These features yield much interesting, exciting and important physics, which is nevertheless yet to be explored and understood.

RaDiO is particularly useful in capturing the radiation from relativistic particles because this limit maximizes the disparity between the radiated frequency and the typical time-scale for the particle trajectories. We can thus capture radiation emission in this limit by only resolving the typical time-scales for the particle motion in particle-in-cell simulations.

See below a demonstration of how it works.