Science & Technology

Science & Technology

Secondary Sources Division

Head of Division: Dr. Subhendu Kahaly (Leading Scientist)

(subhendu.kahaly @


The main mission of the Secondary Sources Division is to generate XUV attosecond pulses, coherent x-ray beams, charge particle and THz beams at the highest possible repetition rate and pulse energy – and some of their combinations – with cutting-edge parameters for user experiments as well as for scientific and industrial applications in various fields of ultrafast and attosecond sciences. The capacities offered are complemented with advanced, state-of-the-art experimental end-stations such as a NanoEsca, two reaction microscopes, a liquid jet end-station, a VMI end-station, several radiation and particle spectrometers and surface science apparatuses.

Furthermore, the division pursues active research to enhance the capabilities of the ultrafast radiation pulses and particle sources beyond the state of the art; develop relevant diagnostics, define associated metrology and guide applications; and to address challenging scientific questions on laser driven XUV high-harmonics, coherent X-rays, THz radiation generation; charge particle acceleration and their optimal spatio-temporal control.

Technologies offered
  • The SYLOS COMPACT 1 kHz gas target attosecond beamline with three different focusing options to select the optimal generation conditions in conjunction with the gas medium for the targeted photon energy to be used in XUV-XUV pump-probe or XUV-IR pump-probe studies. The beamline currently emits APT with 400 nJ pulse energy during pulse generation in the 10–65 eV spectral region.
  • The SYLOS LONG 1 kHz gas target attosecond beamline, which can be optimized to specific user requests through its continuously adjustable focusing arrangement paired with 16 sections of a target cell that can be individually addressed. The XUV pulses can be used in combination with up to three other, arbitrarily delayed pulses from the IR/VIS/VUV/XUV spectral range. The pulses are available through a CAMP chamber end-station interface.
  • Both the COMPACT and LONG 1 kHz attosecond beamlines are challenging XUV pulse energies capable of inducing nonlinear effects at a 100-fold increased repetition rate and an unprecedented cut-off photon energy.
  • The HR (100 kHz) gas target attosecond beamline for GAS phase experiments, which currently provides APT with 395 attosecond long pulses and 50 pJ energy on the user’s target in the 20–65 eV spectral range.
  • The HR (100 kHz) gas target attosecond beamline for CONDENSED phase experiments. This beamline uses the same generation geometry as the gas phase experiments, and is dedicated to experiments on solid or liquid phase targets. The source incorporates a time-compensated monochromator to provide the possibility of selecting different XUV photon energy regions.
  • A Velocity-map Imaging Spectrometer (VMIS) end-station for gas phase, angularly/energy resolved photoelectron spectroscopy.
  • Two Reaction Microscope (ReMi) end-stations for kinematically complete gas phase experiments with attosecond or femtosecond temporal resolution.
  • A NanoEsca end-station equipped with CM and a surface science end-station providing a PEEM, a double hemispherical electrostatic energy analyzer, a TOF energy analyzer, a unique gold layer on an Ir(001) spin filter and a sample preparation chamber (with LEED, XPS, sample manipulators) for real and k-space band structure mapping, spin diagnostics, magnetic imaging, plasmonics, ARPES with few tens of meV energy, nm spatial and fs/as temporal resolution.
  • In-house diagnostic instruments including TOF and MBES spectrometers with standard and high resolution, XUV and VUV flat-field photon spectrometers, an XUV CCD and an XUV wavefront sensor. In addition, a cold particle source is also available.
  • The SHHG SYLOS beamline, which provides a versatile, few-cycle intense laser plasma interaction station and a tunable surface plasma based charge particle and attosource (initially aiming at 1–10 µJ@8–60 eV) driven by state-of-the-art 100 mJ, 1 kHz, CEP stabilized, <2.2-cycle SYLOS laser. It includes the options of laser-solid or laser-liquid interactions at relativistic intensity either in the reflection or in the transmission mode, with plasma mirror based temporal contrast cleaning and adaptive optics based wavefront correction (3-6 µm FWHM focal spot with a peak intensity of ~ 1018 – 1020 W/cm2 in the interaction plane). Ref: JOSA B 35, A93-A102 (2018)
  • The SHHG HF beamline, which provides a versatile pump-probe multi-cycle intense laser plasma interaction station and a controllable surface plasma based charge particle and attosource (aiming at 0.7–7 mJ@100–200 eV) driven by state-of-the-art 2 PW, 10 Hz HF laser. It includes options for laser-solid or laser-foil interaction at relativistic intensity either in the reflection or in the transmission mode, with plasma mirror based temporal contrast cleaning and adaptive optics based wavefront correction (2–4.5 µm FWHM focal spot with a peak intensity of ~ 1021 – 1022 W/cm2 in the interaction plane). Ref: JOSA B 35, A93-A102 (2018)
  • The eSYLOS beamline, which provides high-charge (10 pC+) relativistic (30 MeV+) laser-driven electron beams and high brightness XUV/X-ray photon source (0.2–10 keV) at 10 Hz and 1 kHz repetition rates, generated by the laser wakefield acceleration mechanism, and driven by the SYLOS2 and the SEA lasers. The LWFA process inherently ensures a compact, few-μm, sub-10 fs soft (0.2–10 keV) X-ray source with a peak brightness that compares favourably with 3rd generation synchrotron light sources.
  • The eSYLOS end-station for the direct application of the generated electron beams (e.g. for radiobiology) generated by eSYLOS, and the application of X-rays for structural and ultrafast time-resolved pump-probe studies. This end-station is envisioned to operate as a user facility.
  • The SPWe source and SPWX end-station, which provides compact, high-brightness, ultrashort hard X-ray (20+ keV) source generated by a 10 Hz GeV+ laser wakefield electron accelerator driven by the HF-PW laser. Main applications targeted are high-resolution radiography and 3D microscopy (computed tomography).
  • The Nonlinear Terahertz Spectroscopy Facility (NLTSF), which consists of a multi-mJ, fs pump laser and a THz pump–THz probe system. It enables time-resolved studies of THz-induced phenomena by using a strong THz pulse to initiate changes in the sample and a weaker THz pulse to detect them. This instrument is operated as a user facility.
  • The High-Energy Terahertz Beamline (HE-THz) which will provide >1 mJ Terahertz pulse energy in single-cycle waveform for unique strong-field control experiments.

The NLTSF and the HE-THz beamlines offer a broad range of possibilities for THz nonlinear spectroscopy and strong-field control of materials. THz pulses with up to 0.5 MV/cm peak electric field are available at the NLTSF. At HE-THz, >1 mJ pulse energy will be available with a peak electric field strength up to 5–10 MV/cm.

The NLTSF has already been commissioned. Most of the GHHG beamlines and several end-stations are in the commissioning phase. Other beamlines and instruments are either upcoming or planned.


The main research area is Atomic, Molecular and Optical physics (AMO physics) or the study of electronic structure and dynamics in atoms, molecules and plasmas. The special parameters of the beamlines will permit the application of a novel approach to these physical systems based on XUV-XUV pump-probe techniques. In general, researchers apply IR-XUV pump-probe schemes due to the lack of sufficiently powerful XUV sources. However, the strong IR field may significantly perturb the dynamics under study and compromise the information content of such measurements unless additional data treatment is applied to precisely model the interaction. XUV-XUV pump-probe methods interact with the system under study perturbatively and thereby provide direct access to the undisturbed dynamics. Moreover, the extended photon energies will provide access to inner valence shell electrons which, together with the attosecond pulse durations, open the path to study electronic correlations. Notably, the short and powerful XUV pulses of the SYLOS HHG beamlines will provide an entry point to a mostly unexplored field of AMO physics: nonlinear multiphoton interactions which are deemed to play a central role in molecular relaxation processes and chemistry. Due to the high pulse repetition rate, some of the experiments can be extended to the single particle level in a correlated manner thereby significantly increasing the information content obtainable about those processes.

Other research topics addressed by the division include ultrafast dynamics on surfaces and in the liquid phase, high repetition rate, laser-driven particle acceleration and relevant radiation sources from plasma targets, radiobiology with high repetition rate laser-driven particle/X-ray sources, X-ray imaging of soft and hard materials, 3D microtomography of soft and hard materials/samples, nonlinear terahertz spectroscopy and strong-THz-field control of materials.



  • A major challenge in the past decade has been the experimental realization of a benchmarking experiment on electron correlations that would permit the evaluation of the plethora of theories that have been put forward about this intriguing process. To keep things simple and clear, the model system should be the simplest three-body system available: helium. Realizing the two-photon double ionization of He and performing a kinematically complete measurement of the photoreaction would be a major breakthrough for this significant question. ELI-ALPS has established collaborations with the University of Freiburg and the University of Heidelberg to advance this experiment that promises to be feasible with the pulse parameters of the SYLOS GHHG beamlines for the first time.
  • The HR GHHG beamlines would allow for low count rate coincidence measurements with high statistics, enabling XUV-IR pump-probe experiments on both gas and condensed phase systems. The unique capability of the beamlines is to use a newly designed water-cooled gas cell that is necessary to sustain the heat load delivered at such high repetition rate by the HR laser. The gas cell can support multiple gas types (argon, krypton, xenon, neon and helium etc.). The beamline is under continuous upgrade and optimization, and can currently provide up to 50 pJ XUV APTs on target within the 20–65 eV photon energy range, delivering the highest XUV flux in this parameter range, at 100 kHz (for before upgrade parameters see details in 
  • SHHG SYLOS and SHHG HF both would be unique in the world and would contribute significantly by bringing the plasma physicists, astrophysicists, strong field scientists, ultrafast optics and the imaging community together under the same platform. No attosecond beamline with such parameters using relativistic laser interaction with surface plasma was neverhas been offered for user experiments before. Furthermore, such a combination of state-of-the-art beam shaping, beam diagnostics and charged particle diagnostics in laser plasma experiments can also be considered as unique. The novelty the projects bring to the field areis mainly three-fold: (i) allow subcycle dynamical studies in intense relativistic laser-matter physics with the highest possible spatio-temporal resolution; (ii) allow attosecond (as) experiments to accumulate the largest possible data statistics (nonexistent at such high power) and (iii) achieve unprecedented reproducibility of relativistic interaction and experimental conditions, not available anywhere at present.
  • 1 kHz laser-driven relativistic electron and X-ray source (eSYLOS) with bespoke end-stations for scientific and industrial user access. 10 Hz laser-driven ultrarelativistic electron (2 GeV+) and hard X-ray source (20 keV+) (SPWe and SPWX) with bespoke end-station for X-ray imaging (μ-CT) of soft and hard materials/samples.
  • Planned facilities at the HE-THz beamline include (i) a pump-probe user end-station with THz and optical pulses, and (ii) a THz pump-XUV probe user end-station.


HR Attosources Group

SYLOS Attosources Group

Surface Plasma Attosource Group

Laser Plasma Physics Group

Particle Acceleration and THz Sources Subdivision

Particle Acceleration Group

Terahertz Group