US and Czech scientists collaborate to explore gamma ray production with high power lasers

United States national science foundation (NSF) and the Czech Science Foundation (GACR) finance a new collaborative project of scientists from University of California San Diego in the United States and ELI beamlines (Institute of Physics of the Czech Academy of Sciences) in the Czech Republic, which aims to take advantage of the capabilities of the ELI Beamlines multi-petawatt laser facility. Researchers hope that these experiments can achieve a breakthrough by demonstrating efficient generation of dense gamma ray beams.

Stellar objects like pulsars can create matter and antimatter directly from light due to their extreme energies. In fact, the magnetic field, or “magnetosphere,” of a pulsar is filled with electrons and positrons created by the collision of photons.

Reproducing the same phenomena in a laboratory on Earth is extremely difficult. This requires a dense cloud of photons with energies millions of times greater than visible light, an achievement that has so far eluded scientists working in this field. However, theories suggest that high-powered lasers should be able to produce such a cloud of photons.

As the first international laser research infrastructure dedicated to the application of high power and high intensity lasers, the Extreme Light Infrastructure (ELI ERIC) facilities will enable such research opportunities. The ELI ERIC is a multi-site research infrastructure based on the specialized and complementary facilities ELI Beamlines (Czech Republic) and ELI ALPS (Hungary). ELI’s new capabilities will create the conditions for testing theories in the lab.

Computer simulation of the emission of energetic gamma rays (yellow arrows) by a dense plasma (green) irradiated by a high intensity laser beam (red and blue). The laser propagates from left to right, the emitted photons flying in the same direction. The smooth blue and red regions represent a strong magnetic field generated by the plasma, while the oscillating region corresponds to the magnetic field of the laser.

This project combines the theoretical expertise of University of California San Diego (USA)experimental expertise of ELI beamlinesand the target manufacturing and engineering expertise of General Atomics (USA). The approximately $1,000,000 project, jointly funded by NSF and GACR, will be led by Professor Alexey Arefiev of UC San Diego. Target development for rep deployment will take place at General Atomics, led by Dr. Mario Manuel, while primary experiments will be conducted at ELI Beamlines by a team led by Dr. Florian Condamine and Dr. Stefan Weber.

The concept for the project was developed by Arefiev’s research group at UC San Diego, which specializes in supercomputer simulations of intense light-matter interactions. This project’s approach exploits an effect that occurs when electrons in a plasma are accelerated to near-light speeds by a high-powered laser. This effect is called “relativistic transparency” because it causes previously opaque dense plasma to become transparent to laser light.

In this regime, extremely strong magnetic fields are generated as the laser propagates through the plasma. During this process, the relativistic electrons oscillate in the magnetic field, which in turn causes the emission of gamma rays, mainly in the direction of the laser.

“It is very exciting that we are able to generate the kind of magnetic fields that previously only existed in extreme astrophysical objects, such as neutron stars,” says Arefiev. “The capacity of ELI beamlines lasers to achieve very high intensity on target is the key to achieving this regime.

These experiments will provide the first statistically relevant study of gamma ray generation using high power lasers. The researchers hope that this work will pave the way for secondary sources of high-energy photons that can be used not only for fundamental physics studies, but also for a range of important industrial applications such as materials science, nuclear waste imaging, nuclear fuel analysis, safety, deep high resolution radiography, etc. Such “extreme imaging” requires robust, reproducible and well-controlled gamma-ray sources. This proposal specifically targets the development of such unpublished sources.

Experiments will be greatly aided by another technological advancement. Until recently, high-powered laser installations could execute approximately one shot per hour, which limited the amount of data that could be collected. However, new installations like ELI Beamlines are capable of multiple shots per second. These capabilities allow statistical studies of laser-target interactions in a way that was impossible only a few years ago. This means that a change in the way these experiences are designed and executed is needed to take full advantage of the possibilities.

“The ELI Beamlines P3 facility is a unique and versatile experimental infrastructure for sophisticated high-field experiments and perfectly suited to the planned program”, comments Condamine. Weber notes, “This collaboration between San Diego and ELI Beamlines should be a big step forward in bringing the American community and the ELI team together for joint experiences.”

Thus, an important part of this project is training the next generation of ELI Beamlines scientists to develop techniques that can take full advantage of its proven capabilities. UC San Diego students and postdoctoral researchers will also practice target deployment and data acquisition on General Atomics’ new GALADRIEL laser facility to help improve the efficiency of experiments at ELI Beamlines.

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The P3 (Plasma Physics Platform) facility at ELI Beamlines where the experiments will take place.

“This is the first project funded by the Czech Science Foundation and the US National Science Foundation. I believe that the new collaboration between the agencies will lead to a number of successful projects and that the collaborating scientific teams from the Czech Republic and the United States will benefit from it,” says GACR President Dr. Petr Baldrian.

“We are delighted to work with our counterparts in the Czech Republic to further expand international scientific cooperation in the fields of artificial intelligence, nanotechnology and plasma science research. I am optimistic this will be the first of many collaborative projects between NSF and GACR,says NSF Director Dr. Sethuraman Panchanathan.


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