Controlled Electron-Beam Injection into Plasma Waves for Tailored Betatron-Radiation Generation
Particle accelerators constitute a key technology for the study of the structure of matter. They are driving synchrotrons and free-electron lasers for research in molecular physics, medicine, biology and material science. Moreover, they allow for the construction of particle colliders for high-energy physics to reveal the secrets of the universe at its most fundamental level. Unfortunately, such accelerators are kilometre-scale, billion Euro machines, which severely limits their availability and proliferation.
The acceleration of charged particles in strong plasma wakes, a potential alternative technology, which is orders-of-magnitude more compact than standard accelerators, has seen remarkable progress both in experiment and theory in recent years. Nowadays, acceleration gradients of more than 10 GV/m can be readily achieved using either ultra-short and intense laser pulses  or particle beams as wake drivers . With the demonstration of first GeV electron beams from laser-plasma accelerators  and a general trend towards higher reproducibility  and improved control [5-7] over the involved plasma processes, plasma-acceleration techniques are starting to draw considerable interest and are raising hopes for their use in user-facility environments in the not too distant future, e.g. at photon sources  and eventually in high-energy particle colliders .
The studies of a team of scientists from DESY, Hamburg (Germany), and IST, Lisbon (Portugal), concentrate on the controlled injection of few-femtosecond, phase-space-tailored electron bunches into a plasma wakefield. This is achieved by means of external injection of conventionally accelerated electron beams or by controlled-injection techniques (e.g. ). In contrast to common wakefield methods relying on electron self-injection, these sophisticated processes allow for a controlled and tailored population of 6D phase space in such a way that electron bunches may be forced to undergo controlled transverse betatron oscillations inside the strongly focussing transverse plasma fields. These oscillations are the source of synchrotron radiation (betatron radiation), which is of interest for applications in phase-contrast imaging , the structural investigation of biological samples , and material science. In addition, controlled external injection is of high importance and directly linked to the staging of multiple acceleration modules in series  with the goal of applications at the energy frontier.
This phenomenologically rich field of physics at the intersection of relativistic laser, plasma, and accelerator science can only be captured and theoretically fully understood by means of computationally highly demanding particle-in-cell codes. The research team is utilising the code OSIRIS . OSIRIS is a state-of-the-art massively parallel particle-in-cell code highly optimised for a wide range of architectures.
Jens Osterhoff1 (PI), Alberto Martinez de la Ossa1, Julia Grebenyuk1, Timon Mehrling1, Jorge Vieira2, Joana L. Martins2, Ricardo A. Fonseca2, Luís O. Silva2
1Deutsches Elektronen-Synchrotron DESY, Hamburg (Germany)
2Instituto Superior Técnico, Universidade Técnica de Lisboa (Portugal)
Dr. Jens Osterhoff
Deutsches Elektronen-Synchrotron DESY
22607 Hamburg, Germany
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