Newsletter May 2018
Dear colleagues and friends of the HI Jena,
welcome to the May 2018 issue of the HI Jena newsletter.
Below you find informations and news about recent activities of our institute.
Helmholtz Institute Jena
High resolution without particle accelerator*
A visit to the optometrist often involves optical coherence tomography. This imaging process uses infrared radiation to penetrate the layers of the retina and examine it more closely in three dimensions, without having to touch the eye at all. This allows eye specialists to diagnose diseases such as glaucoma without any physical intervention.
However, this method would have even greater potential for science if shorter wavelengths were used, thus allowing a higher resolution of the image. With ultrashort X-ray pulses, processes and structures can be resolved down to the nanometre range. Physicists at the Helmholtz-Institute Jena and the Friedrich Schiller University Jena are therefore developing »handy« laser systems, which enable ultrashort X-ray pulses at laboratory scale and thus allow a wide variety of applications in the lab.
For the first time, the physicists used extreme ultraviolet radiation (XUV) for this process, which was generated in their own laboratory, and they were thus able to perform the first XUV coherence tomography at laboratory scale. This radiation has a wavelength of between 20 and 40 nanometres - from which it is therefore just a small step to the X-ray range. »Large-scale equipment, that is to say particle accelerators such as the German Elektronen-Synchotron in Hamburg, are usually necessary for generating XUV radiation,« says Silvio Fuchs of the Helmholtz-Institute Jena. »This makes such a research method very complex and costly, and only available to a few researchers.« The physicists have already demonstrated this method at large research facilities, but they have now found a possibility for applying it at a smaller scale.
In this approach, they focus an ultrashort, very intense infrared laser in a noble gas, for example argon or neon. »The electrons in the gas are accelerated by means of an ionisation process,« explains Fuchs. »They then emit the XUV radiation.« It is true that this method is very inefficient, as only a millionth part of the laser radiation is actually transformed from infrared into the extreme ultraviolet range, but this loss can be offset by the use of very powerful laser sources.
The advantage of XUV coherence tomography is that, in addition to the very high resolution, the radiation interacts strongly with the sample, because different substances react differently to light. Some absorb more light and others less. This produces strong contrasts in the images, which provide the researchers with important information, for example regarding the material composition of the object being examined. »For example, we have created three-dimensional images of silicon chips, in a non-destructive way, on which we can distinguish the substrate clearly from structures consisting of other materials,« adds Silvio Fuchs. »If this procedure were applied in biology - for investigating cells, for example, which is one of our aims - it would not be necessary to colour samples, as is normal practice in other high-resolution microscopy methods. Elements such as carbon, oxygen and nitrogen would themselves provide the contrast.«
Before that is possible, however, the physicists still have some work to do. »With the light sources we have at the moment, we can achieve a depth resolution down to 24 nanometres. Although this is sufficient for producing images of small structures, for example in semiconductors, the structure sizes of current chips are in some cases already smaller. However, with new, even more powerful lasers, it should be possible in future to achieve a depth resolution of as little as three nanometres with this method,« notes Fuchs. »We have shown in principle that it is possible to use this method at laboratory scale.«
The long-term aim could ultimately be to develop a cost-effective and user-friendly device combining the laser with the microscope, which would enable the semiconductor industry or biological laboratories to use this imaging technique with ease.
(*Original text by Sebastian Hollstein for “Lichtgedanken”-magazine of the Friedrich Schiller University Jena.)
S. Fuchs, M. Wünsche, J. Nathanael, J. J. Abel, C. Rödel, J. Biedermann, J. Reinhard, U. Hübner, and G. G. Paulus
Optical coherence tomography with nanoscale axial resolution using a laser-driven high-harmonic source,
Optica 4, 903-906 (2017).
News and Announcements
New targets greatly improve the performance of laser-driven particle acceleration
The use of nanostructured targets enables the PHELIX laser to accelerate considerably more particles to substantially higher energies. The experiment with the high-performance laser was conducted at the GSI/FAIR campus by scientists from GSI and FAIR as well as from Goethe University Frankfurt and the Helmholtz Institute Jena. The innovative nano target was created at GSI’s Materials Research department. The results give laser-driven particle acceleration a boost, and also harbor considerable potential for future plasma research at the FAIR accelerator facility.
One of Germany’s strongest lasers is located on the campus of GSI and FAIR: the Petawatt High-Energy Laser for Ion Experiments (PHELIX). By focusing all of the light energy into a hair-thin beam, plasma physicists can use the laser to study states of matter under conditions that are similar to those inside stars and giant planets. However, they also test possible applications such as laser-driven particle acceleration. To do this, scientists shoot the laser at a target to study how the ultra-powerful pulse of light affects the material. Now, scientists have, for the first time, tested a target with a nanowire surface instead of one with a smooth surface. “In the new surface, extremely thin nanowires are located close to one another like tall tree trunks in a dense forest that is bombarded from above by a laser,” explains Paul Neumayer, a plasma physicist at GSI and the director of the experiment. Nanotargets are extremely fragile structures. Until recently, laser pulses would destroy such targets before fully reaching them. In cooperation with the Helmholtz Institute Jena, the scientists at FAIR have greatly improved PHELIX’s temporal contrast, which means the laser pulse is now extremely “cleanly” delineated in terms of time. As a result, the wires are immediately hit by the laser’s full energy density, thus stripping off the electrons from the target atoms at one blow. This creates an electrostatic field, which, in turn, can accelerate lightweight particles.
“The new target enabled us to accelerate 30 times more particles than with the normally employed smooth foil targets under the same conditions,” says Neumayer. “Moreover, we increased the energy of the accelerated particles by 2 to 2.5 times.” There are two reasons for this improvement. First, a nanotarget has a much higher surface area than a smooth one, thus intensifying the laser’s interaction with the material. Second, the laser pulse can penetrate deep into the target’s structure in the spaces between the wires. As a result, the laser energy can be deposited with much higher densities than would normally be achievable with the laser light.
In addition to making laser-driven particle acceleration more efficient, the new targets have another benefit: they greatly increase the X-ray emissions of the hot plasma. “This is not only a huge advantage for the measurement of exotic plasmas, but also opens up interesting prospects for the development of extremely intense short-pulsed X-ray sources for future FAIR experiments,” explains Neumayer.
The innovative nanotargets were developed by Dimitri Khaghani as part of his doctoral dissertation. Khaghani is a laser and plasma physicist who earned his doctorate at Goethe University Frankfurt. For his dissertation, he worked together very closely with GSI’s Materials Research department, which has been researching and producing nanowires for years. Nanowires grow in tiny channels in plastic foils. To create these channels, researchers first bombard the foils with heavy ions from a linear accelerator. The areas damaged along the ions’ path are then chemically etched to turn them into open channels that are subsequently filled using an electrochemical method. “This process enabled us to test nanowires made of different materials and of various lengths and diameters so that we could find out when laser acceleration is most efficient,” says Khaghani, who received the Giersch Excellence Grant and the Giersch Award for Outstanding Doctoral Thesis for his research with nanotargets. “The synergy effect achieved through the close cooperation between the Plasma Physics and Materials Research departments on the campus certainly contributed to the success of the experiments and enabled us to take a big step forward,” says Khaghani, who is now a postdoc at the Helmholtz Institute Jena.
Another Award for Start-up Class 5 Photonics
Class 5 Photonics, a spin-off from Helmholtz-Institut Jena, a branch of GSI, and from Deutsches Elektronen-Synchrotron DESY specialized in high-performance laser technology, is the proud Gold Winner of the Laser Focus World Innovators Award 2018 in the laser category with its Supernova OPCPA product. The Laser Focus World Innovators award recognizes companies that have made major contributions to advancing the field of optics and photonics through recently launched products or services and is awarded yearly during the CLEO conference and tradeshow in San Jose, California.
The novel Laser systems from Class 5 Photonics are deployed worldwide in leading research laboratories. The Supernova OPCPA already received the PRISM AWARD in the category of Lasers in January of this year. This Laser system allows researchers to conduct experiments ten times faster.
CEO Robert Riedel is pleased about the double recognition: “We are really proud having won this award. The Supernova has shown its’ strengths now for the second time against many other excellent competitors – it really proves that this laser system is a highly desired product. The Laser Focus World Innovators Award is a great incentive for us to continue our work and deliver outstanding products.
The spin-off company was founded in 2014 in Hamburg. The scientists from Helmholtz Institute Jena and DESY are developing high power lasers with pulses in the femtosecond range. One femtosecond is a quadrillionth of a second. Shorter laser pulses allow more precise working of materials, for instance. Also, such short laser pulses open up new innovative applications like 3D nanostructuring. For science, the technology is of great importance.
Further informations: http://www.class5photonics.com/
Seminar room HI-Jena, Fröbelstieg 3
High harmonic generation on solid targets is considered a promising route towards compact sources for intense and ultrashort XUV and X-Ray pulses. Understanding the influence of laser and target parameters is crucial to maximize the efficiency and to control the temporal structure of the generated radiation. In this talk I will explain, using analytical calculations and Particle-In-Cell simulations, different mechanisms to isolate single attosecond XUV pulses in time and space.
Seminar room HI-Jena, Fröbelstieg 3
For more than 100 years, X-rays have been used to determine the structure of crystals and molecules via coherent diffraction methods. These techniques rely on coherent scattering where incoherence due to wavefront distortions or incoherent fluorescence emission is considered as detrimental. Here we show that methods from quantum imaging, i.e., exploiting higher order intensity correlations, can be used to image the arrangement of sources that scatter incoherent X- ray radiation. We present the method of Incoherent Diffraction Imaging (IDI) and discuss a number of properties that are conceptually superior to those of conventional coherent X-ray structure determination. We also report an experimental demonstration in the soft x-ray domain, where higher-order intensity correlations are used to achieve higher fidelities in the image reconstruction and potentially a sub-Abbe resolution, and discuss recent experiments aiming at full 3D reconstruction of different samples with atomic resolution using hard x-rays.
Seminar room HI-Jena, Fröbelstieg 3
Seminar room HI-Jena, Fröbelstieg 3
High harmonic generation on solid targets is considered a promising route towards compact sources for intense and ultrashort XUV and X-Ray pulses. The intensity of emitted harmonic radiation usually reduces with increasing harmonic order. In contrast, we report the enhancement of individual harmonics generated at an ultra-steep plasma vacuum interface. Theory and simulations show that the enhancement of selected harmonics can be described by the reflection of the incident laser pulse at a relativistic mirror oscillating at both the laser and the plasma frequency.
19th international Conference on Physics of Highly Charge Ions (HCI 2018)
Caparica, Lisbon (Portugal)
The abstract submission for the 19th international Conference on Physics of Highly Charge Ions (HCI 2018), to be held in Caparica, Lisbon (Portugal), is open. The abstract submission should be done via the HCI 2018 website: http://hci2018.pt/
Abstracts can be submitted in the following topics:
- Fundamental Aspects, Structure and Spectroscopy
- Collisions with Electrons, Ions, Atoms and Molecules
- Interaction with Clusters, Surfaces and Solids
- Interactions with Photons and Plasmas
- Strong Field and Ultrafast Processes
- Production, Experimental Developments and Applications
The deadline for abstract submission is 15 April 2018.
Doctoral students conference on optics DoKDoK 2018
Take part in the 7th DoKDoK! The conference provides a great opportunity for young researchers, academicians and industry players working in Optics and Photonics to present their newest findings, share experience, and network in a friendly and collegial atmosphere. The conference is held entirely in English and has an international focus.
PhD students are cordially invited to submit their original contributions. The technical program will include invited talks from academicians and industry representatives.
Abstract submission deadline: 30th June 2018
Recently finished theses
Erzeugung dichter Elektronenpulse mit Laser-Plasma-Beschleunigern für QED-Experimente in hohen Feldern
Entwicklung und Aufbau eines Teilchendetektors für erste Experimente am Ionenspeicherring CRYRING
Cryogenic Current Comparators for Larger Beamlines
P. Seidel, V. Tympel, R. Neubert, J. Golm, M. Schmelz, R. Stolz, V. Zakosarenko, T. Sieber, M. Schwickert, F. Kurian, F. Schmidl, and T. Stöhlker
IEEE Trans. Appl. Supercond. 28, 1 (2018)
Analysis of angular momentum properties of photons emitted in fundamental atomic processes
V. A. Zaytsev, A. S. Surzhykov, V. M. Shabaev, and Th. Stöhlker
Phys. Rev. A 97, 043808 (2018)
Lifetimes of relativistic heavy-ion beams in the High Energy Storage Ring of FAIR
V. Shevelko, Yu. A. Litvinov, Th. Stöhlker, and I. Yu. Tolstikhina
Nucl. Instr. Meth. Phys. Res. B 421, 45 (2018)
Photon-photon scattering at the high-intensity frontier
H. Gies, F. Karbstein, C. Kohlfürst, and N. Seegert
Phys. Rev. D 97, 076002 (2018)
Ring-like spatial distribution of laser accelerated protons in the ultra-high-contrast TNSA-regime
G. A. Becker, S. Tietze, S. Keppler, J. Reislöhner, J. H. Bin, L. Bock, F.-E. Brack, J. Hein, M. Hellwing, P. Hilz, M. Hornung, A. Kessler, S. D. Kraft, S. Kuschel, H. Liebetrau, W. Ma, J. Polz, H.-P. Schlenvoigt, F. Schorcht, M. B. Schwab, A. Seidel, K. Zeil, U. Schramm, M. Zepf, J. Schreiber, S. Rykovanov, and M. C. Kaluza
Plasma Phys. Contr. F. 60, 055010 (2018)
K-shell ionization of heavy hydrogenlike ions
O. Novak, R. Kholodov, A. Surzhykov, A. N. Artemyev, and Th. Stöhlker
Phys. Rev. A 97, 032518 (2018)
A sensitive EUV Schwarzschild microscope for plasma studies with sub-micrometer resolution
U. Zastrau, C. Rödel, M. Nakatsutsumi, T. Feigl, K. Appel, B. Chen, T. Döppner, T. Fennel, T. Fiedler, L. B. Fletcher, E. Förster, E. Gamboa, D. O. Gericke, S. Göde, C. Grote-Fortmann, V. Hilbert, L. Kazak, T. Laarmann, H. J. Lee, P. Mabey, F. Martinez, K.-H. Meiwes-Broer, H. Pauer, M. Perske, A. Przystawik, S. Roling, S. Skruszewicz, M. Shihab, J. Tiggesbäumker, S. Toleikis, M. Wünsche, H. Zacharias, S. H. Glenzer, and G. Gregori
Rev. Sci. Instrum. 89, 023703 (2018)
Quantum interference in laser spectroscopy of highly charged lithiumlike ions
P. Amaro, U. Loureiro, L. Safari, F. Fratini, P. Indelicato, T. Stöhlker, and J. Santos
Phys. Rev. A 97, 022510 (2018)
Spatio-Temporal Characterization of Pump-Induced Wavefront Aberrations in Yb3 + -Doped Materials
I. Tamer, S. Keppler, M. Hornung, J. Körner, J. Hein, and M. C. Kaluza
Laser Photon. Rev. 12, 1700211 (2018)
Using the focal phase to control attosecond processes
D. Hoff, M. Krüger, L. Maisenbacher, G. Paulus, P. Hommelhoff, and A. Sayler
J. Opt. 19, 124007 (2017)
Velocity map imaging of scattering dynamics in orthogonal two-color fields
D. Würzler, N. Eicke, M. Möller, D. Seipt, A. M. Sayler, S. Fritzsche, M. Lein, and G. G. Paulus
J. Phys. B 51, 015001 (2017)
Spectral and spatial characterisation of laser-driven positron beams
G. Sarri, J. Warwick, W. Schumaker, K. Poder, J. Cole, D. Doria, T. Dzelzainis, K. Krushelnick, S. Kuschel, S. P. D. Mangles, Z. Najmudin, L. Romagnani, G. M. Samarin, D. Symes, A. G. R. Thomas, M. Yeung, and M. Zepf
Plasma Phys. Contr. F. 59, 014015 (2017)