A tabletop laser-driven X-ray source--FemtoX II

IntroductionsBy matching large femtosecond laser equipment with special design target chamber, Top-Unistar brings normal laboratory with FemtoX II, which has less than 100fs x-ray pulse. Meanwhile, ac

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By matching large femtosecond laser equipment with special design target chamber, Top-Unistar brings normal laboratory with FemtoX II, which has less than 100fs x-ray pulse. Meanwhile, according to the customer requirements, Top-Unistar will design and provide the customer with complete solutions and diagnostic devices.

After nearly two decades development, laser-driven x-ray sources have been widely used in top laboratories in the world. In addition, they showed super fine, super bright, high signal-to-noise ratio and high stability. Laser-driven x-ray sources have important roles in the study of ultrafast process of materials and fine resolution imaging studying. Due to its low cost, laser-driven x-ray source have become an effective complement in the ultrafast field to synchrotron facilities.

In particular, the current third generation synchrotron have time resolution of only hundreds picoseconds (ps), which could not be used to study events occurs in the sub-ps as well as rapid changes process in femtoseconds, such as chemical bond breaking and bond, lattice vibration and so on. For the chemical reaction and phase transitions which are caused by the atomic motion, their time scales is in the sub-ps, traditional ultrafast spectroscopy can provide the information of electronic state transition, but cannot provide the structure changes which lead to transition of these electronic state. However, laser-driven x-ray become an effect way to obtain this information. Since femtosecond laser have two characters, one is several tens fs pulse width, other one is high pulse energy. The x-ray generated by laser-driven x-ray source have equivalent pulse width, besides the x-ray and the laser have natural time synchronization, so FemtoX II could be used in pump probe experiments, which could have sub-ps or even fs time resolution of physical dynamic analysis.

In addition, the spot size of FemtoX II is depended largely on the spot size of the laser. In the current system, if the spot size of the laser is 5 microns (FWHM), the spot size of the x-ray could be obtained on the order of 10 microns. And because its excitation mechanism is different from conventional x-ray tube, laser-driven x-ray source could achieve ultrafine spot size and higher x-ray output power, which have important application prospect in x-ray imaging and phase contrast imaging.



  • Kα pulse width with less than 100fs

  • More than 1011ph/s photon flux

  •  Focal spot with 10 microns

  • Radiation protection chamber design

  •  Complete fine adjustment device

  • Flexible coupling optics




Pumping laser*

Laser engergy



Repetition rate



Laser pulse duration


Spot size (FWHM)


Laser intensity

~1018 W/cm²




X-ray pulse duration


Emitted photons**


X-ray source dimension***

~10 µm (FWHM)

X-ray optics(multilayer mirror)

X-ray spot size on sample***


Kα photons on sample***

~108 ph/s

No x-ray optics

Min.source-object distance(SOD)


Beam angle


* Top-Unistar could provide an integrated solution based on the customer’s own laser equipment, but the technical parameters need to be verified.

**Cu target 6 X 1011ph/sin 2π);

***This parameter is related to multilayer mirror


Fig.1 Overview of FemtoX II (top); overview of target chamber (left); schematic view of the optical path (right).



A.    Ultra-fine x-ray static imaging, spatial resolution better than 2µm, which can be applied for phase contrast imaging, colorful imaging, low dose imaging.

Fig.2 (a) image of shrimp, (b) the intensity of x-ray on a red dotted line distribution, (c) image of fish.



B.    Ultrafast x-ray diffraction, time resolution 0.05~1ps, structural changes in analytical ability 0.01 Å


Fig.3 Schematic view of the optical path of pumping probe experiment (top);SrRuO3/SrTiO3 superlattice oszillations of Bragg reflection, time resolution~150fs (bottom).


C.     Ultrafast x-ray absorption spectroscopy, time resolution 0.1~1ps, structural changes in analytical ability 0.01 Å


Fig.4 Dispersive ultrafast X-ray absorption spectrometer. Reproduction with permission(top);EXAFS spectra recorded at -20 ps (before excitation, solid) and +25 ps (after excitation, dot) for Fe(III)(C2O4)33-(bottom).

From J. Phys. Chem. A 111, 9326–9335 (2007).

D.     Ultrafast X-ray dynamic imaging: time resolution 0.05-1ps, spatial resolution better than 3μm.


 Fig.5 schematic view of the optical path of laser-driven high-energy Betatron radiation