  We report the laser-plasma accelerator-based X-ray sources development at ELI
beamlines. One of the main objectives of ELI Beamlines is to provide beams of
ultrashort particle and complex X-ray sources to users from various research
fields. Two hard X-ray betatron sources with high photon flux based on
laser-plasma acceleration (LPA) are being commissioned. The first source is the
Gammatron beamline located in Experimental Hall E2. It provides X-ray pulses of
energies from 1-100 keV in betatron and up to a MeV in Compton scheme. A novel
X-ray optics has been designed as a focusing optics of these hard X-ray sources
for the user application. The second hard X-ray source based on LPA is being
developed in the ELI plasma physics platform (P3) that will serve as an active
diagnostics HED and Laboratory astrophysics, multi-beam experiments, and
fundamental research. This source is now being commissioned, we will present
the first experimental results. Besides, we have proposed a novel scheme for
enhancing the X-ray flux based on betatron oscillations enhanced from nonlinear
resonances due to interaction with a two-color laser field. In addition, we
will introduce a novel optical probing technique with high sensitivity to
characterize a low-density gas target for a laser-plasma accelerator. It has
been achieved by employing multiple passes of the probe beam through the object
and relay-imaging of the object between the individual passes.
