plasma accelerators driven by particle beams
- June 23rd, 2016 - An international team involving a scientist from LOA has published two studies in the journal Nature Communications, improving the capabilities and the understanding of plasma accelerators driven by particle beams.
In the first study [Nat. Commun. 7, 11785 (2016)], the researchers were able to create a new type of plasma accelerator, taking the form of a hollow plasma channel – a tube of plasma with neutral gas on the inside. With this particular geometry, particles flying in the tube won’t experience transverse forces that can be detrimental to the quality of the beam. This is critical for the positron, the antimatter sibling of the electron, whose acceleration in plasma is extremely challenging. By sending a beam of positrons into the tube, the authors were able to excite a wakefield that can be used for the acceleration of positrons, and that is free of unwanted transverse forces.
In the second study [Nat. Commun. 7, 11898 (2016)] lead by Sebastien Corde from LOA, the scientists have investigated the dynamics and interaction of an electron beam with self-produced plasma. In this case, the plasma is directly generated by the ionization of a gas by the electron beam itself. When the beam travels through a high-ionization-potential gas (such as argon), as in the reported experiment, the conditions are expected to be strongly unfavorable for plasma acceleration and very small gain of energy (sub-GeV) was anticipated. Instead, surprisingly large energy gains, up to 27 GeV, were experimentally observed, in disagreement with expectations.
The results have revealed two key phenomenons that are taking place and make this very high-field acceleration possible. First, the beam undergoes self-focusing: its beam size is rapidly reduced and then maintained at its minimum value so that the beam becomes very dense and can drive high-field plasma wakes (see figure). Second, such a beam does not undergo continuous head erosion, because the particles at the head of the bunch have very low divergence and they provide an onset of ionization sufficient to provide guidance for the rest of the beam.
These unexpected and surprising results provide a more complete understanding of the interaction between beams and plasmas, which will certainly guide future optimizations of beam-driven plasma accelerators.
S. Gessner et al., Nat. Commun. 7, 11785 (2016) - http://dx.doi.org/10.1038/ncomms11785
S. Corde et al., Nat. Commun. 7, 11898 (2016) - http://dx.doi.org/10.1038/ncomms11898
2016 E. Fabre prize awaeded to J. Faure
The prize “Edouard Fabre 2016” for contributions to the physics of laser-driven inertial confinement fusion and laser-produced plasmas has been assigned to Jerome Faure, LOA. The Prize is especially addressed to researchers in full activity, within about 15 years after obtaining their Ph.D.
In 2003, J. Faure obtained a CNRS position at Laboratoire d’Optique Appliquée where he performed remarkable experimental work in developing laser-plasma accelerators, demonstrating the possibility of using laser-plasma interaction to accelerate electrons in extremely short distances and producing high quality electron beam. In 2012, he got an ERC Starting grant to produce with a kHz laser system, femtosecond electron bunches and to apply them for the study of ultra fast phenomena using electron diffraction with femtosecond time resolution. In parallel Jerome Faure teaches quantum physics and statistical physics as Associated Professor at Ecole Polytechnique. He is now a CNRS research director and the head of the APPLI research group at LOA (Application of ultrafast sources to solid state physics).
more information here
First ENSTA-ParisTech MOOC
- February 9th, 2016 - The first MOOC of ENSTA-ParisTech was posted on February 4, 2016 in FUN, the French e-learning platform. Davide Boschetto, researcher at LOA laboratory, offers a first course on the Introduction to Quantum Physics. 5 days following its launch, more than 600 e-students have already registered. The course will start April 25th, 2016. FUN includes more than 50 partners in France and around the world, among with ENSTA-ParisTech.
Vacuum laser acceleration of relativistic electron
- December 21st, 2015 - Two teams from CEA LIDYL and Laboratory for Applied Optics (LOA) at ENSTA-ParisTech - Ecole Polytechnique - CNRS were able to demonstrate for the first time the vacuum acceleration of electrons to relativistic energies by an intense laser beam. These results are published in Nature Physics (december 2015). This observation shows that it is possible to take benefit of the very strong amplitudes of the electric field of femtosecond laser pulses that are used today to accelerate high-energy particles over short distances.
By concentrating the light over periods of femtoseconds (10-15 s) durations, the laser pulses can reach very high instantaneous light powers (~ 1 PW or 1015 W) and hence extremely high amplitudes of the associated electric field (~ 10 TéraV/m or 1013 V/m).
Like the large sea waves off the coast that can not move ships, this oscillating field can not accelerate at very high energy charged particles. But like the surfer who is at first providing speed on its own to catch the wave and then continuously enjoy its slope, the injection of relativistic electrons in the laser beam (with a speed very close to that of light) can theoretically enable its acceleration, taking the full advantage of extremely high electric fields associated with the ultrashort laser pulse.
Many teams around the world have tried to demonstrate this phenomenon, without being able to provide convincing proof up to now. LOA and LYDIL researchers show that the interaction of the laser pulse with a solid target (plasma mirror) provides the ideal electron injection conditions. Electrons have been accelerated to about 10 MeV energies over a distance of 80 micrometers. This experiment paves the way to realize ultra-compact electron accelerators of very high energies.
Caption: Electron beam profile from the plasma mirror. The colors reflect the number of electrons emitted in a given direction. Deflected due to the acceleration of 1.5 MeV to 10 MeV over a distance of 80 microns by the laser pulse, the high energy electron beam is visible at the center of the figure (red spot), while very few electrons are emitted in the direction of the reflected light beam (white spot). © F. Quéré (CEA) - J. Faure (CNRS).
Femtosecond x-ray laser
- November 16th, 2015 - For over a decade, the duration of flashes of XUV laser radiation generated from laser-plasma interaction was limited to a few picoseconds, reducing access to many pioneering and innovative applications in the ultrafast range. A team of the Laboratory of Applied Optics (LOA) led by Stéphane Sebban has just published in the journal Nature Photonics results demonstrating, for the first time, that intense femtosecond pulse duration can be obtained. The amplifying medium is a plasma of nickelloïd krypton emitting at 32.8 nm which was injected by a source of high-order harmonics obtained in argon. Laboratory-size applications previously limited to large infrastructures such as synchrotrons or free electron lasers become feasible. This work was carried out in cooperation with the LPGP (University Orsay), the ELI-Beamlines Project (Prague), the APRI Laboratory (Gwangju, South Korea) and LULI (Ecole Polytechnique, Palaiseau).
More information :
- Article : Table-top femtosecond soft X-ray laser by collisional ionization gating, A. Depresseux et al., Nature Photonics, Published online 16 November 2015
- Press release
- Nature, S. Corde et al, august 27th, 2015 - For several years, plasma accelerators have shown their tremendous ability to accelerate particle beams. One objective is to downsize the experimental facilities and to allow the generation of very high energies while keeping the infrastructures within achievable size. To date, plasmas created by laser based on the interaction of an intense femtosecond laser with the matter or plasmas created by electron beams generated from RF accelerators, have accelerated energetic electrons with remarkable properties like ultrafast pulse duration, charge, energy or compactness in the case of lasers.
Sébastien Corde, researcher at LOA, has this time shown (Nature on August 27, 2015) with an international team working on the SLAC-FACET infrastructure at Stanford (USA), how these plasmas can be used to accelerate an other type of particles, the positrons. A positron beam with an initial energy of 20 GeV could gain 5 GeV by capturing about 30% of the energy of the plasma. These results are an important step toward the realisation of the next generation of particle colliders.
- Illustration: Weiming An (UCLA)
- More information:
laser-plasma accelerators at LOA
Victor Malka, CNRS Research Director at LOA (Laboratoire d’Optique Appliquée - École polytechnique, ENSTA Paris-Tech, CNRS) presents in this "Labshot" his work on the laser-plasma accelerators.
Laser-plasma accelerators have potential applications in radiotherapy, in medical imaging and in materials’ science.
Medical X-ray imaging at LOA
A European FET OPEN program on medical x-ray imaging has been awarded to LOA early in March 2015. The project, called VOXEL (Volumetric medical X-ray imaging at extremely low dose) is part of the European framework programme Horizon 2020 on Research and Innovation actions for Future and Emerging Technologies. Coordinated by IST (Portugal), the project gathers research teams from France (LOA, Imagine Optic, LIDyL), Netherland (CWI), Italy (CNR) and Spain (UPM).
Abstract of the project:
Computerized Tomography (CT) has been one of the greatest achievements in medical imaging, but at the cost of a high, potentially harmful, X-ray irradiation dose. The ultimate goal of VOXEL is to provide an alternative to tomography with a disruptive technology enabling 3D X-ray imaging at very low dose. VOXEL aims at prototyping new cameras working in the soft and hard X-rays (< 10 keV) that will combine the X-ray penetration and nanometre spatial resolution, easiness to use, afforded by avoiding the rotation of the source or the sample, and extremely low dose for maximum impact on medicine and biology.
VOXEL relies on the integration of trans-disciplinary fields in medical imaging, optics, X-ray physics, applied mathematics and value to society through foreseeable commercialization. VOXEL aims at prototyping in parallel a soft X-ray “water window” microscope and a hard X-ray 3D camera for medical applications (< 10 keV). While both cameras need groundbreaking development in the underlying physics, only hard X-ray camera has high technological risk (and high societal impact). VOXEL will benefit from the soft X-ray camera thanks to its Biological applications in nano-tomography but also as a test platform for our physical and mathematical models.
The VOXEL team members are leaders in X-ray metrology, wavefront sensing, atomic physic, mathematical computing and 3D medical imaging; with VOXEL we are uniquely positioned to succeed, and to raise the competitiveness of Europe. Doing so by basing the research lead in Portugal with a woman coordinator will be exemplary: beyond the scientific and technological success, thanks to our focus in science and its valorisation, VOXEL will be transformative for scientifically emerging countries.
New ERC Proof of Concept grant at LOA
January 22th, 2015 - An ERC grant Proof of Concept (POC) has been awarded to LOA (V. Malka) on the development of innovative technologies for cancer detection at an early stage. The project includes the scientific developments of several LOA researchers like K. Ta Phuoc, C. Thaury and S. Corde. The most advanced electron beams produced by laser plasma accelerators will be used to radiate a bright, tunable X ray beam to significantly improve the spatial resolution of the imaging technique of low contrast biological objects.
ERC POC grants support high-risk/high-gain research at the frontiers of knowledge to generate unexpected or new opportunities for commercial and societal applications. It helps ERC grant-holders (Advanced grant in this case) to bridge the gap between research and the earliest stage of a marketable innovation.
This is the fifth ERC grant awaded to LOA researchers.
E. Fabre prize for LOA
Stéphane Sebban, CNRS researcher at LOA, won the E. Fabre international award for his pioneering work on X-ray laser developments using intense femtosecond lasers and plasmas. The prize was delivered at the 17th International Congress on Plasma Physics (ICPP 2014) held in Lisbon, Portugal, and is awarded to experienced international researchers having a research activity of less than 15 years after their PhD.