Systems and methods for generating tunable x-ray emissions including a tunable x-ray source that includes a driver, such as a laser, configured to generate one or more driver pulses, such as one or more laser pulses, and a target source configured to emit a target material. The target source is arranged so that the emitted target material intersects a propagation axis of the driver pulse(s) and the target source may be configured so that the emitted target material has a tailored density profile along the propagation axis of the driver pulse(s), the tailored density profile along the propagation axis having a first density peak region followed by a lower density region followed by a second density peak region, e.g., in an “M” shape.
