COLLOQUIUM - "Smart*Light: a compact and tunable Compton x-ray source", Jom Luiten (TUE)

Friday 24 Apr 2026, 11:00 → 12:00 Europe/Amsterdam

Colloquium (Nikhef)

In the Smart*Light project at Eindhoven University of Technology (TU/e) an X-band LINAC-based Compton scattering x-ray source is being developed, providing narrowband x-rays with photon energies continuously tunable over a wide range. The source is compact, fitting on a single optical table. The beamline features a robust 100 keV DC photoinjector and a novel 50-cell X-band LINAC, in which electrons can be accelerated up to ~20 MeV. The electron bunches with bunch charges up to 10 pC, are focused to a ~20 mm spot, where they collide with 10 mJ, 800 nm femtosecond laser pulses at a maximum rep rate of 500 Hz.

In September 2024 the first x-rays were generated [1,2]. At present, x-rays with energies ranging from a few keV up to 18 keV can be generated with 4% bandwidth. By using the second harmonic of the 800 nm interaction laser, photon energies up to ~40 keV come within reach. It has been experimentally verified that the x-ray polarization can be varied continuously by simply changing the laser polarization. Efforts are underway to focus the electron beam to a spot size of ~5 mm, which will result in a significant increase of the x-ray flux and coherence. Combined with 500 Hz rep rate, this should result in an average brilliance of at least 10⁸ photons/mm²/mrad²/0.1% BW, i.e., comparable to state-of-the-art x-ray tubes. We are investigating the possibility of increasing the average brilliance by 2-3 orders of magnitude by burst mode operation.

In parallel to improving the source further, we are performing demo x-ray experiments, such as K-edge subtraction imaging and phase contrast imaging. We have installed Fresnel zone plate lenses, which allow us to either focus or collimate the x-ray beam. In collaboration with industry, we are now preparing Critical Dimension Small Angle X-ray Scattering (CD-SAXS) experiments in transmission on silicon wafers for semiconductor metrology.

 

[1] Van Elk et al., Opt. Express 33, 47498 (2025)

[2] Stragier et al., Eur. Phys. J. Spec. Top. https://doi.org/10.1140/epjs/s11734-025-01819-1