  High-intensity X-ray sources are invaluable tools, enabling experiments at
the forefront of our understanding of materials science, chemistry, biology,
and physics. Laser-plasma electron accelerators are sources of high-intensity
X-rays, as electrons accelerated in wakefields emit short-wavelength radiation
due to betatron oscillations. While applications such as phase-contrast imaging
with these betatron sources have already been demonstrated, others would
require higher photon number and would benefit from increased tunability. In
this paper we demonstrate, through detailed 3D simulations, a novel
configuration for a laser-wakefield betatron source that increases the energy
of the X-ray emission and also provides increased flexibility in the tuning of
the X-ray photon energy. This is made by combining two Laguerre-Gaussian pulses
with non-zero net orbital angular momentum, leading to a rotation of the
intensity pattern, and hence, of the driven wakefields. The helical motion
driven by the laser rotation is found to dominate the radiation emission,
rather than the betatron oscillations. Moreover, the radius of this helical
motion can be controlled through the laser spot size and orbital angular
momentum indexes, meaning that the radiation can be tuned fully independently
of the plasma parameters.
