Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Focused Laser Power Boosts Ion Acceleration


An international team of physicists has used carbon nanotubes to enhance the efficiency of laser-driven particle acceleration. This significant advance brings compact sources of ionizing radiation for medical purposes closer to reality.

The interaction of high-intensity laser light with solid targets could someday serve as the basis of table-top sources of high-energy ions for medical applications. An international team led by physicists of the LMU affiliated with the Munich-Centre for Advanced Photonics (MAP), a Cluster of Excellence based in Munich, and in cooperation with scientists from the Max Planck Institute of Quantum Optics, has taken another step towards this goal.

A laser beam shines on an ultrathin diamond-like carbon foil coated on one side with a layer of nanotubes. The impact of the laser beam ejects high-energy ions from the unc

Isabella Cortrie

They have done so by boosting the efficiency of a technique that uses extremely intense pulses of laser light to eject packets of high-energy ions from diamond-like carbon foils. In their experiment, the researchers coated one side of the foil with carbon nanotubes.

Upon laser irradiation, the layer acts like a lens to focus and concentrate the light energy on the foil, which results in the production of much more energetic ion beams. This makes experiments with high-energy carbon ions on cells feasible for the first time, and brings light-driven generation of ionizing radiation closer to practical application.

Light is an enormously powerful and versatile source of energy. When high-intensity pulses of laser light are fired at ultrathin diamond-like carbon (DLC) foils, they punch through the foil, stripping electrons from the atoms. The negatively charged electron cloud then drags a stream of positively carbon ions along, accelerating them to speeds of up to 10% of the speed of light.

The bursts of carbon ions produced by the radiation pressure exerted on the foil by ultrashort laser pulses could be used to treat tumors, provided the ions pack sufficient energy. At present, the only machines capable of producing such high-energy ion beams are large and highly expensive particle accelerators. Laser-based technologies are as yet unable to generate beams of comparable quality. However, light-driven approaches offer a possible route to much more compact and far less costly ion sources for medical applications in the future.

To reach this goal, laser physicists need to increase pulse intensities, and find ways to ensure that much more of the incident light energy is delivered in concentrated form to the carbon foil target. MAP physicists have now taken a significant step toward the latter objective. Each laser pulse fired at the target lasts for 50 femtoseconds (a femtosecond equals a millionth of a billionth of a second), and consists of about 20 oscillations of the optical field.

This means that not all of the electromagnetic energy associated with the optical pulse reaches the target at the same time. It arrives in dispersed form, so that the radiation pressure acting on the target atoms rises gradually to a maximum, then drops off again. Since only the peak energy is sufficiently high to rip ions from the foil, the process is not terribly efficient.

Ultrathin foils of diamond-like carbon were first used in studies of radiation pressure acceleration five years ago. For the latest experiments, technicians at the MAP Service Centre used vapor deposition to coat the front of each foil with carbon nanotubes. The nanotubes come to lie on the surface in a higgledy-piggledy fashion, like blades of grass in a haystack. But the plasma formed when the laser pulse impinges on the nanotube coating effectively acts like a lens.

As a result, the power of the incident pulse is concentrated sufficiently to permit immediate ionization of the underlying carbon foil. In addition, the nanotube coating focuses the light pulse onto a very small area of the target.

These two effects together enhance the energy of the carbon ions ejected from the foil to around 200 MeV (mega electron volts) – significantly higher than was previously attainable. In a collaborative effort involving researchers from Germany, the UK, Spain and China, the experiments were carried out with the ASTRA-Gemini laser at the Rutherford Appleton Laboratory in Didcot (UK), as part of the Laserlab Europe Program.

The higher energies now available make it possible, for the first time, to carry out experiments on cells with beams of carbon ions. However, because the radiation must pass through healthy tissue before it reaches a tumor, energies of at least one GeV (gigaelectronvolt) will be required for clinically relevant applications, about five times higher than that attained in the latest experiments.

But boosting power output to this level is not an impossible dream. On the basis of the expertise available at the Munich-Centre for Advanced Photonics, a new Centre for Advanced Laser Applications (CALA) is now being built on the High-Tech Campus in Garching.

CALA will house a novel ultrashort pulse system, called ATLAS 3000, which is designed to provide laser pulses with powers of up to three petawatt. In combination with the energy enhancement made possible by the nanotube-coated carbon foils, this system promises to bring the era of light-based sources of ionizing radiation a lot closer.

Original Publication
J. H. Bin, W. J. Ma, H. Y. Wang, M. J. V. Streeter, C. Kreuzer, D. Kiefer, M. Yeung, S. Cousens, P. S. Foster, B. Dromey, X. Q. Yan, R. Ramis, J. Meyer-ter-Vehn, M. Zepf, and J. Schreiber
Ion Acceleration Using Relativistic Pulse Shaping in Near-Critical-Density Plasmas.
Phys. Rev. Lett. 115, 064801 (2015), 3 August 2015
doi: 10.1103/PhysRevLett.115.064801

For further information, please contact:
Prof. Jörg Schreiber
Ludwig-Maximilians-Universität München (LMU)
Fakultät für Physik, Lehrstuhl für Experimentalphysik - Medizinische Physik
Am Coulombwall 1, 85748 Garching, Germany
Tel.: +49 (0) 89 289-54025

Karolina Schneider | idw - Informationsdienst Wissenschaft
Further information:

More articles from Physics and Astronomy:

nachricht Sharpening the X-ray view of the nanocosm
23.03.2018 | Changchun Institute of Optics, Fine Mechanics and Physics

nachricht Drug or duplicate?
23.03.2018 | Fraunhofer-Institut für Angewandte Festkörperphysik IAF

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: Space observation with radar to secure Germany's space infrastructure

Satellites in near-Earth orbit are at risk due to the steady increase in space debris. But their mission in the areas of telecommunications, navigation or weather forecasts is essential for society. Fraunhofer FHR therefore develops radar-based systems which allow the detection, tracking and cataloging of even the smallest particles of debris. Satellite operators who have access to our data are in a better position to plan evasive maneuvers and prevent destructive collisions. From April, 25-29 2018, Fraunhofer FHR and its partners will exhibit the complementary radar systems TIRA and GESTRA as well as the latest radar techniques for space observation across three stands at the ILA Berlin.

The "traffic situation" in space is very tense: the Earth is currently being orbited not only by countless satellites but also by a large volume of space...

Im Focus: Researchers Discover New Anti-Cancer Protein

An international team of researchers has discovered a new anti-cancer protein. The protein, called LHPP, prevents the uncontrolled proliferation of cancer cells in the liver. The researchers led by Prof. Michael N. Hall from the Biozentrum, University of Basel, report in “Nature” that LHPP can also serve as a biomarker for the diagnosis and prognosis of liver cancer.

The incidence of liver cancer, also known as hepatocellular carcinoma, is steadily increasing. In the last twenty years, the number of cases has almost doubled...

Im Focus: Researchers at Fraunhofer monitor re-entry of Chinese space station Tiangong-1

In just a few weeks from now, the Chinese space station Tiangong-1 will re-enter the Earth's atmosphere where it will to a large extent burn up. It is possible that some debris will reach the Earth's surface. Tiangong-1 is orbiting the Earth uncontrolled at a speed of approx. 29,000 km/h.Currently the prognosis relating to the time of impact currently lies within a window of several days. The scientists at Fraunhofer FHR have already been monitoring Tiangong-1 for a number of weeks with their TIRA system, one of the most powerful space observation radars in the world, with a view to supporting the German Space Situational Awareness Center and the ESA with their re-entry forecasts.

Following the loss of radio contact with Tiangong-1 in 2016 and due to the low orbital height, it is now inevitable that the Chinese space station will...

Im Focus: Alliance „OLED Licht Forum“ – Key partner for OLED lighting solutions

Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP, provider of research and development services for OLED lighting solutions, announces the founding of the “OLED Licht Forum” and presents latest OLED design and lighting solutions during light+building, from March 18th – 23rd, 2018 in Frankfurt a.M./Germany, at booth no. F91 in Hall 4.0.

They are united in their passion for OLED (organic light emitting diodes) lighting with all of its unique facets and application possibilities. Thus experts in...

Im Focus: Mars' oceans formed early, possibly aided by massive volcanic eruptions

Oceans formed before Tharsis and evolved together, shaping climate history of Mars

A new scenario seeking to explain how Mars' putative oceans came and went over the last 4 billion years implies that the oceans formed several hundred million...

All Focus news of the innovation-report >>>



Industry & Economy
Event News

New solar solutions for sustainable buildings and cities

23.03.2018 | Event News

Virtual reality conference comes to Reutlingen

19.03.2018 | Event News

Ultrafast Wireless and Chip Design at the DATE Conference in Dresden

16.03.2018 | Event News

Latest News

For graphite pellets, just add elbow grease

23.03.2018 | Materials Sciences

Unique communication strategy discovered in stem cell pathway controlling plant growth

23.03.2018 | Agricultural and Forestry Science

Sharpening the X-ray view of the nanocosm

23.03.2018 | Physics and Astronomy

Science & Research
Overview of more VideoLinks >>>