We present a new method of characterising bright X-ray beams such as betatron radiation from laser wakefield accelerators. This method provides a non-destructive route to measuring the spectrum and divergence on a single shot basis, which could be particularly useful for sources which have significant shot-to-shot variation. We show, through Monte-Carlo simulation, the feasibility of applying this method for broad-band, synchroton-like radiation.
It is well known that plasma accelerators can generate bright, energetic X-ray beams via transverse betatron oscillations of the accelerating electron bunch. Many of the applications of betatron radiation require the radiation to be well characterized, but this is difficult owing to large shot-to-shot fluctuations, especially in cases where the injection of electrons is uncontrolled. It is therefore desirable to develop single-shot, non-invasive methods for characterizing broad-band X-ray beams.
The method, which we call XCERP diffraction, is based on energy-resolved diffraction from a thin powdered target. This can be achieved through single photon detection in a CCD which requires, on average, fewer than one X-ray detected on each pixel site. Since the diffracted X-rays are detected off-axis, the undiffracted portion of the beam can be used in applications. Our simulations show that existing betatron sources have sufficient photons to be accurately characterised by this method.
We show, via numerical simulations, that the spectrum and divergence of the radiation can be retrieved using XCERP diffraction from a single shot without apriori assumptions of the form of the spectrum. This contrasts with alternative approaches, such as recording the transmission of X-rays through various filters.
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