Electrons with a velocity close to the speed of light are hard to control. Using them as a tool for applications at the frontier of ultrafast physics requires them to be packed into extremely short pulses with tunable energy.
Figure caption: A laser pulse (red) hits helium atoms (blue), streaming from a nozzle with supersonic velocity. A very compact and controlled difference in density (dark blue ray) develops due to the partial obscuring of the nozzle by a razor blade. Precisely at this difference in density, the laser pulse hits the helium atoms, separates the electrons and accelerates them to nearly the speed of light. Since the electrons are all separated at the same location and same time from the atoms, they nearly gain the same energy. Figure: Thorsten Naeser
A team around Laboratory for Attosecond Physics (LAP) group leaders Dr. Laszlo Veisz and Prof. Stefan Karsch, both based at the Max-Planck-Institute of Quantum Optics (MPQ) has now achieved that feat by using a laser-driven accelerator. They created electron pulses with few-femtosecond duration, whose many individual particles all have nearly the same, but widely tunable energy.
These monochromatic electron pulses can be used to create ultrashort flashes of light in the extreme ultra-violet or even X-ray range, who in turn are a versatile tool for probing fast processes in the microcosm. (Physical Review Letters, May 02, 2013).
Bunches made up of electrons travelling close to the speed of light have a great potential in medicine or probing the microcosm, if their properties can be well controlled. Usually such pulses are provided by conventional radio-frequency (RF) accelerator systems, which are on one hand large and costly and on the other hand can only provide ultrashort particle bunches with even more costly tricks and great particle losses.
Accelerating particle bunches with a laser might become a viable workaround for these problems. Its main problem, however, has always been the difficulty of giving the same energy to all particles in a bunch, and hence creating “cool” bunches. Once this issue can be overcome, it would allow a much better control of the bunch properties and their adaptation to the application in mind.
A conventional RF-accelerator always contains a particle source defining the number of particles in a bunch, its pulse duration and energy width, and an acceleration section defining the final energy. In a laser accelerator, a defined particle source has been missing so far, and the electrons to accelerate were trapped randomly along the acceleration distance. This causes their energy distribution to become broad. The team around Laszlo Veisz and Stefan Karsch has now shown how to integrate a particle source into a laser accelerator and use it to create bunches whose individual particles all have nearly the same energy.
Dr. Olivia Meyer-Streng | Max-Planck-Institut
Significantly more productivity in USP lasers
06.12.2016 | Fraunhofer-Institut für Lasertechnik ILT
Shape matters when light meets atom
05.12.2016 | Centre for Quantum Technologies at the National University of Singapore
In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.
Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...
Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...
A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.
Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...
In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.
“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...
The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.
The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...
16.11.2016 | Event News
01.11.2016 | Event News
14.10.2016 | Event News
06.12.2016 | Materials Sciences
06.12.2016 | Medical Engineering
06.12.2016 | Power and Electrical Engineering