Newsletter July 2015
Dear colleagues and friends of the HI-Jena,
welcome to the summer issue of the HI-Jena newsletter. As usual, below you find the latest research news and announcements from our institute.
We would like to take the opportunity to wish you a nice and stimulating summer conference season, as well as nice and relaxing summer holidays.
Helmholtz Institute Jena
Imaging plasma waves
Due to the extreme electric field strengths available in fully ionized plasmas, the next generation of particle accelerators is likely to use plasmas as the acceleration medium. Nowadays, laser-generated relativistic plasmas can accelerate few-fs electron pulses to multi-GeV electron pulses over centimeter distances only. Here, the laser pulse excites a plasma wave which is associated with electric fields on the order of 100 GeV/m, field strengths which are orders of magnitude higher than in conventional accelerators. As a consequence, laser-driven plasma-accelerators have the potential to be compact alternatives to conventional particle accelerators in the future. The full understanding and further optimization of this acceleration approach, however, requires sophisticated diagnostics to monitor all phases of the acceleration process including the injection of background electrons into the acceleration structure, i.e. the plasma wave driven by a high-intensity laser pulse, and the subsequent acceleration. To be able to resolve the acceleration process diagnostics well-suited for this plasma environment need to be available. Electromagnetic probe pulses with few-fs duration allow for the time-resolved monitoring of the transient accelerating structure in the plasma, i.e. the plasma wave. At the Helmholtz-Institute Jena and the Institute of Optics and Quantum Electronics such a probe beam line was installed at the JETI-40 laser facility. Here, optical probe pulses with a duration of 6 fs only, synchronized to the 30 TW main pulses of JETi 40 are available . These pulse were used in an electron acceleration experiment to monitor the electron acceleration dynamics.
The laser electron accelerator was optimized to produce well-collimated electron bunches with energies up to 180 MeV and a narrow energy spread. The few-cycle probe pulses were used to backlight the interaction and take snap shots at different time delays during the interaction. As the pump pulse enters the gas jet it immediately ionizes the gas and initially drives an almost linear plasma wave. During the further propagation through the plasma, the intensity of the pump increases due to self-focusing and longitudinal pulse compression. As a consequence, the shape of the plasma starts to show characteristic non-linear features, e.g. a curvature caused by the relativistic motion of the electrons associated with the plasma wave. At the point of wavebreaking, characterized by the emission of bright broadband radiation, electrons are injected into the plasma wave and are accelerated by its high-amplitude longitudinal electric fields. Afterwards, the shape of the plasma wave becomes highly nonlinear, which had so far only been observed in high-resolution numerical simulations. The high spatial and temporal resolution of our setup allowed us to measure the length of the first plasma oscillation, i.e. the bubble during the acceleration process. With this unique possibility, we could show for the first time that the bubble starts to expand before the plasma wave breaks, i.e. before electrons are injected. This behavior has up to now only been discussed in theory but it has never been observed in experiments before.
The high resolution of our probing capability allowed us to visualize the full nonlinear evolution of the plasma wave and study the acceleration process with unprecedented precision. Out method can easily be adopted to more complex acceleration geometries or to beam driven acceleration scenarios. Such experiments are planned at SLAC or at DESY, here within the ATHENA project. With our new insight into the injection and acceleration process, laser-driven plasma electron accelerators can be optimized and tuned to become versatile sources of brilliant electron pulses and of ultrashort secondary radiation.
 M. B. Schwab, A. Sävert, O. Jäckel, J. Polz, M. Schnell, T. Rinck, L. Veisz, M. Möller, P. Hansinger, G. G. Paulus and M. C. Kaluza, "Few-cycle optical probe-pulse for investigation of relativistic laser-plasma interactions," Applied Physics Letters 103, 191118 (2013).
 A. Sävert, S.P.D. Mangles, M. Schnell, E. Siminos, J.M. Cole, M. Leier, M. Reuter, M.B. Schwab, M. Möller, K. Poder, O. Jäckel, G. G. Paulus, C. Spielmann, S. Skupin, Z. Najmudin and M. C. Kaluza, "Direct Observation of the Injection Dynamics of a Laser Wakefield Accelerator Using Few-Femtosecond Shadowgraphy," Physical Review Letters 115, 055002 (2015).
News and Announcements
Scientific council of the HI Jena
On June 25th the scientific council of the HI Jena met to assess and discuss the research activities of our institute. We like use to this opportunity to thank all colleagues at our Institute for all their efforts, particularly for preparing the various oral presentations for this event.
Inauguration of JETI 200
To celebrate the inauguration of the new JETI 200 laser, right after the annual meeting of the scientific council of the HI Jena on June 25th the institute members and affiliates were kindly invited to participate in a festive event with barbecue organized in front of the main building of the HI Jena.
Semiannual Palaver of the HI Jena
On July 16th the semi annual palaver of the HI Jena took place. We would like to thank all speakers for their nice presentations as well as all participants for their questions and comments triggering stimulating scientific discussions.
35. Summer student program at GSI/FAIR 2015
For the summer student program 2015 we shall welcome 37 students from 17 countries in Europe and East Asia. During the eight weeks of the program each student is going to work on a small scientific project supervised by a tutor. In addition a lecture series will be held that presents the various research fields and applications at GSI. The program will be complemented by introductory soft skill courses.
More information: https://theory.gsi.de/stud-pro/HGS-HIRe/
Seminar room HI-Jena, Fröbelstieg 3
During the interaction between an intense laser pulse and a plasma medium, energetic particles such as electrons, protons and ions can be accelerated through various acceleration mechanisms. For electron densities close to critical density (ne ≈ nc), laser-plasma interaction is underexplored. Here, it is expected that the laser energy absorbed by the plasma is enhanced due to resonance conditions. Simulations show that this density region can be used for efficient electron and ion acceleration, contrast improvement and pulse shortening.
In order to shed more light into this interaction region, an experiment has been carried out at JETI40, IOQ Jena, where an Argon gas jet is used to produce a near-critical plasma. The interaction region has been imaged using a 2ω probe beam at 90º to the propagation direction. As the focused laser pulse propagates towards the high density regions of the gas jet, Side scattering has been observed to occur preferentially in the upper part of the interaction region. The corresponding plasma densites are measured using interferometry. As the plasma density increases, Side scattering vanishes and laser pulse collapse occurs at the near-critical region followed by ﬁlamentation.
4th International FAIR School
Castiglione della Pescaia, Italy
The 4th International FAIR School, will take place in September in Castiglione della Pescaia in Italy. It is designed for young students with research interests in FAIR physics and is a good start to get an overview on what's happening at FAIR.
Local costs are covered, there is limited support for travel as well. The selection of students will be made early June, the deadline for application is May 31.
More information can be found at: https://hgs-hire.de/program/events/fair-school-2015/index.shtml
12th Topical Workshop of the SPARC Collaboration
Heraklion, Crete, Greece
Please note that hotel conditions at the conference site make an early registration deadline of August 10th necessary.
Further information can be found at apapes.physics.uoc.gr/index_SPARC2015.php.
International Conference on Accelerator Optimization
The oPAC consortium is organizing a 3-day International Conference on Accelerator Optimization in Seville, Spain from 7th to 9th October 2015. The conference will be hosted by oPAC partner University of Seville/Centro Nacional de Aceleradores (CNA).
This International Conference will be an ideal place to present and discuss research advances in beam dynamics, accelerator diagnostics and advanced simulation tools. It will feature talks about the research outcomes from oPAC by fellows and research leaders from across the world. It will also present the opportunity for 15-minute long contributed talks and posters and to discuss future R&D activities in this multi-disciplinary field. Following a peer-review process selected proceedings will be published in a special edition of Physical Review STAB.
To register and/or submit your abstract please visit the conference website: https://indico.cern.ch/event/380975/
Recently finished theses
Two-photon processes in highly charged ions
Direct Observation of the Injection Dynamics of a Laser Wakefield Accelerator Using Few-Femtosecond Shadowgraphy
A. Sävert, S. P. D. Mangles, M. Schnell, E. Siminos, J. M. Cole, M. Leier, M. Reuter, M. B. Schwab, M. Möller, K. Poder, O. Jäckel, G. G. Paulus, C. Spielmann, S. Skupin, Z. Najmudin, and M. C. Kaluza
Phys. Rev. Lett. 115, 055002 (2015)
Towards highest peak intensities for ultra-short MeV-range ion bunches
S. Busold, D. Schumacher, C. Brabetz, D. Jahn, F. Kroll, O. Deppert, U. Schramm, T. Cowan, A. Blazevic, V. Bagnoud, and M. Roth
Sci. Rep. 5, 1 (2015)
Combined linear polarization and angular distribution measurements of x-rays for precise determination of multipole-mixing in characteristic transitions of high- Z systems
G. Weber, H. Bräuning, A. Surzhykov, C. Brandau, S. Fritzsche, S. Geyer, R. E. Grisenti, S. Hagmann, C. Hahn, R. Hess, S. Hess, C. Kozhuharov, M. Kühnel, R. Märtin, N. Petridis, U. Spillmann, S. Trotsenko, D. F. A. Winters, and Th. Stöhlker
J. Phys. B 48, 144031 (2015)
Crystal optics for precision x-ray spectroscopy on highly charged ions—conception and proof
H. F. Beyer, T. Gassner, M. Trassinelli, R. Heß, U. Spillmann, D. Banaś, K.-H. Blumenhagen, F. Bosch, C. Brandau, W. Chen, C. Dimopoulou, E. Förster, R. E. Grisenti, A. Gumberidze, S. Hagmann, P.-M. Hillenbrand, P. Indelicato, P. Jagodzinski, T. Kämpfer, C. Kozhuharov, M. Lestinsky, D. Liesen, Y. A. Litvinov, R. Loetzsch, B. Manil, R. Märtin, F. Nolden, N. Petridis, M. S. Sanjari, K. S. Schulze, M. Schwemlein, A. Simionovici, M. Steck, Th. Stöhlker, C. I. Szabo, S. Trotsenko, I. Uschmann, G. Weber, O. Wehrhan, N. Winckler, D. F. A. Winters, N. Winters, and E. Ziegler
J. Phys. B 48, 144010 (2015)
Ground-state excitation of heavy highly-charged ions
A. Gumberidze, D. B. Thorn, C. J. Fontes, B. Najjari, H. L. Zhang, A. Surzhykov, A. Voitkiv, S. Fritzsche, D. Banaś, H. Beyer, W. Chen, R. D. DuBois, S. Geyer, R. E. Grisenti, S. Hagmann, M. Hegewald, S. Hess, C. Kozhuharov, R. Märtin, N. Petridis, R. Reuschl, A. Simon, U. Spillmann, M. Trassinelli, S. Trotsenko, G. Weber, D. F. A. Winters, N. Winters, D. Yu, and Th. Stöhlker
J. Phys. B 48, 144006 (2015)
Laser spectroscopy of the ground-state hyperfine structure in H-like and Li-like bismuth
J. Vollbrecht, Z. Andelkovic, A. Dax, W. Geithner, C. Geppert, C. Gorges, M. Hammen, V. Hannen, S. Kaufmann, K. König, Y. Litvinov, M. Lochmann, B. Maass, J. Meisner, T. Murboeck, W. Nörtershäuser, R. Sánchez, S. Schmidt, M. Schmidt, M. Steck, T. Stöhlker, R. C. Thompson, J. Ullmann, and C. Weinheimer
J. Phys.: Conf. Ser. 583, 012002 (2015)
Search for inhomogeneous phases in fermionic models
J. Braun, S. Finkbeiner, F. Karbstein, and D. Roscher
Phys. Rev. D 91, 116006 (2015)
Stimulated photon emission from the vacuum
F. Karbstein, and R. Shaisultanov
Phys. Rev. D 91, 113002 (2015)
Long-term operation of surface high-harmonic generation from relativistic oscillating mirrors using a spooling tape
J. Bierbach, M. Yeung, E. Eckner, C. Roedel, S. Kuschel, M. Zepf, and G. G. Paulus
Opt. Express 23, 12321 (2015)
Photon propagation in slowly varying inhomogeneous electromagnetic fields
F. Karbstein, and R. Shaisultanov
Phys. Rev. D 91, 085027 (2015)
Plasma Undulator Based on Laser Excitation of Wakefields in a Plasma Channel
S. Rykovanov, C. Schroeder, E. Esarey, C. Geddes, and W. Leemans
Phys. Rev. Lett. 114, 145003 (2015)
Quantum reflection of photons off spatio-temporal electromagnetic field inhomogeneities
H. Gies, F. Karbstein, and N. Seegert
New J. Phys. 17, 043060 (2015)
Towards a fast calculator for the radiation characteristics of radiative recombination and radiative electron capture
G. Weber, H. Ding, M. O. Herdrich, and A. Surzhykov
J. Phys.: Conf. Ser. 599, 012040 (2015)