Many practical applications of x-rays lie in the important for the society fields of medical imaging, custom, transport inspection and security. Scientific applications besides of fundamental research include material sciences, biomicroscopy, and protein crystallography. Two types of x-ray sources dominate now: conventional tubes and electron accelerators equipped with insertion devices. The first are relatively cheap, robust, and compact but have low brightness and poorly controlled photon spectrum. The second generate low divergent beams with orders of magnitude higher brightness and well-controlled and tunable spectrum, but are very expensive and large in scale. So accelerator based x-ray sources are mainly still used for scientific applications and x-ray tubes - in commercial equipment. The latter motivated by the importance for the society made an impressive progress during last decades mostly due to the fast developments of radiation detectors, computers and software used for image acquisition and processing. At the same time many important problems cannot be solved without radical improvement of the parameters of the x-ray beam that in commercial devices is still provided by conventional x-ray tubes.
Therefore there is a quest now for a compact and relatively cheap source to generate x-ray beam with parameters and controllability approaching synchrotron radiation. Rapid developments of lasers and particle accelerators resulted in implementation of laser plasma x-ray sources and free electron lasers for various experiments requiring high intensity, shrt duration and monochromatic x-ray radiation. Further progress towards practical application is expected from the combination of laser and particle accelerator in a single unit for efficient x-ray generation.