Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Snapshots of laser driven electrons

14.03.2011
Physicists of the Laboratory of Attosecond Physics at the Max Planck Institute of Quantum Optics succeeded in the first real-time observation of laser produced electron plasma waves and electron bunches accelerated by them. The physicists describe their results in the scientific journal Nature Physics (March 13th 2011).

Flocking behavior does not only exist among birds, insects or fish; the microcosm offers similar phenomena, too. A team of scientists including Ferenc Krausz and his employees Laszlo Veisz and Alexander Buck of the Laboratory of Attosecond Physics (LAP) at the Max-Planck-Institut für Quantenoptik (MPQ) and the Ludwig-Maximilians-Universität (LMU Munich), in cooperation with colleagues from the Friedrich Schiller University Jena, succeeded in the first observation of laser-accelerated fast electron swarms in conjunction with a plasma wave consisting of positively charged helium ions and slow background electrons.


Artwork depicting laser-driven electron acceleration. An intense light pulse (yellow-orange) produces a plasma wave (white, modulated surface) from oscillating electrons and stationary helium ions. Some electrons leave the plasma wave and fly close to the speed of light as a swarm (red spheres) behind the laser pulse. Graphics: Christian Hackenberger


Helium atoms flowing from a small nozzle are ionized by a laser pulse. Thereby a plasma channel forms from helium ions and free electrons. In this channel the flash of light accelerates a small portion of the electrons almost to the speed of light. Photo: Thorsten Naeser

This way, the physicists managed to observe in real-time how electrons form bunches under the influence of strong laser pulses and how they behave in the slipstream during their flight. The findings facilitate the development of new electron and light sources with which, for example, the structure of atoms and molecules can be explored. In medicine, this knowledge helps the development of new X-ray sources whose resolution will be much higher than current devices allow.

When short laser pulses irradiate e.g. helium atoms their structure is heavily disturbed. If the light is strong enough, electrons are pulled out of the atoms and the helium atoms become ions. This mixture of electrons and ions is called plasma which may support wave structures –the so called electron plasma waves– when exposed to strong light. In laser physics this process and these waves are used under special conditions to rapidly accelerate a small number of the electrons to close to the speed of light and to control them.

A team from the Laboratory of Attosecond Physics at the MPQ and the LMU Munich, in cooperation with the Friedrich Schiller University Jena, succeeded in taking snapshots of both the accelerated electron bunches and the plasma wave produced by the strong laser light that drives them.

In their experiments, the laser physicists focused a laser pulse on a helium gas jet (or flow of helium gas) from a specially designed nozzle. The pulse only lasts a few femtoseconds (one femtosecond corresponds to millionth of a billionth second, 10-15 seconds). The flash of light consists of only a few wave cycles and around one billion billion light particles (photons). Its highest power is focused to a very short moment - the duration of the flash of light - and a tiny area. The high-intensity laser pulse tears out all the electrons from the atoms, leaving behind a plasma composed of free electrons and Helium nuclei. In this cocktail the electrons are much lighter than the helium ions; as a result they are pushed aside. While the laser pulse sweeps across the system the ions remain stationary and the released electrons oscillate around one location. Together the particles form a plasma wave; one oscillation of this structure takes around 20 femtoseconds.

In the plasma wave, gigantic electric fields are formed, which are 1000 times stronger than those generated in the world’s largest particle accelerators. A small number of the electrons take advantage of these fields, fly as a swarm behind the laser pulse in its slipstream and accelerate to close to the speed of light. In this process, every accelerated electron has almost the same energy.

Physicists have long been aware of this phenomenon and it has been demonstrated in earlier experiments. The Japanese laser physicist Toshiki Tajima already described this process in 1970. Today Tajima works as a researcher in the Cluster of excellence "Munich-Centre for Advanced Photonics". However, up to now it has only been possible to individually observe the electron swarm or the whole plasma wave with reduced resolution.

The laser physicists from Garching succeeded in recording both phenomena with a high-resolution image of the plasma wave. The process was documented in snapshots with the same light pulse also responsible for accelerating the electrons. The physicists had previously split the laser pulse so that a small portion of it illuminated the system of free electrons and ions perpendicularly to the electron beam. The periodic structure of the plasma wave refracts and partially deflects the light. ″We observe the deflection and thereby image the plasma wave as a modulation of brightness onto a camera,″ explains Laszlo Veisz, the research-group leader of the LAP team. In doing so the researchers achieve a unique spatial and temporal resolution in the femtosecond range. The electron swarm produces strong magnetic fields that the physicists also record and thus determine its position and duration. Eventually, a film describing the acceleration of the electrons results from the combination of both measurement methods.

″The obtained improved knowledge about laser-driven electron acceleration helps us in the development of new X-ray sources of unprecedented quality, not only for basic research but also for medicine,″ explains Ferenc Krausz.

Original paper:
Alexander Buck, Maria Nicolai, Karl Schmid, Chris M. S. Sears, Alexander Sävert, Julia M. Mikhailova, Ferenc Krausz, Malte C. Kaluza, Laszlo Veisz
Real-time observation of laser-driven electron acceleration
Nature Physics, March 13th 2011, doi : 10.1038/NPHYS1942

Thorsten Naeser | Max-Planck-Institut
Further information:
http://www.munich-photonics.de
http://www.attoworld.de

More articles from Physics and Astronomy:

nachricht Researchers discover link between magnetic field strength and temperature
21.08.2018 | American Institute of Physics

nachricht Smallest transistor worldwide switches current with a single atom in solid electrolyte
17.08.2018 | Karlsruher Institut für Technologie (KIT)

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: It’s All in the Mix: Jülich Researchers are Developing Fast-Charging Solid-State Batteries

There are currently great hopes for solid-state batteries. They contain no liquid parts that could leak or catch fire. For this reason, they do not require cooling and are considered to be much safer, more reliable, and longer lasting than traditional lithium-ion batteries. Jülich scientists have now introduced a new concept that allows currents up to ten times greater during charging and discharging than previously described in the literature. The improvement was achieved by a “clever” choice of materials with a focus on consistently good compatibility. All components were made from phosphate compounds, which are well matched both chemically and mechanically.

The low current is considered one of the biggest hurdles in the development of solid-state batteries. It is the reason why the batteries take a relatively long...

Im Focus: Color effects from transparent 3D-printed nanostructures

New design tool automatically creates nanostructure 3D-print templates for user-given colors
Scientists present work at prestigious SIGGRAPH conference

Most of the objects we see are colored by pigments, but using pigments has disadvantages: such colors can fade, industrial pigments are often toxic, and...

Im Focus: Unraveling the nature of 'whistlers' from space in the lab

A new study sheds light on how ultralow frequency radio waves and plasmas interact

Scientists at the University of California, Los Angeles present new research on a curious cosmic phenomenon known as "whistlers" -- very low frequency packets...

Im Focus: New interactive machine learning tool makes car designs more aerodynamic

Scientists develop first tool to use machine learning methods to compute flow around interactively designable 3D objects. Tool will be presented at this year’s prestigious SIGGRAPH conference.

When engineers or designers want to test the aerodynamic properties of the newly designed shape of a car, airplane, or other object, they would normally model...

Im Focus: Robots as 'pump attendants': TU Graz develops robot-controlled rapid charging system for e-vehicles

Researchers from TU Graz and their industry partners have unveiled a world first: the prototype of a robot-controlled, high-speed combined charging system (CCS) for electric vehicles that enables series charging of cars in various parking positions.

Global demand for electric vehicles is forecast to rise sharply: by 2025, the number of new vehicle registrations is expected to reach 25 million per year....

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

LaserForum 2018 deals with 3D production of components

17.08.2018 | Event News

Within reach of the Universe

08.08.2018 | Event News

A journey through the history of microscopy – new exhibition opens at the MDC

27.07.2018 | Event News

 
Latest News

Air pollution leads to cardiovascular diseases

21.08.2018 | Ecology, The Environment and Conservation

Researchers target protein that protects bacteria's DNA 'recipes'

21.08.2018 | Life Sciences

A paper battery powered by bacteria

21.08.2018 | Power and Electrical Engineering

VideoLinks
Science & Research
Overview of more VideoLinks >>>