Characterization of a quadrant diamond transmission X‐ray detector including a precise determination of the mean electron–hole pair creation energy

Precise monitoring of the incoming photon flux is crucial for many experiments using synchrotron radiation. For photon energies above a few keV, thin semiconductor photodiodes can be operated in transmission for this purpose. Diamond is a particularly attractive material as a result of its low absorption. The responsivity of a state‐of‐the art diamond quadrant transmission detector has been determined, with relative uncertainties below 1% by direct calibration against an electrical substitution radiometer. From these data and the measured transmittance, the thickness of the involved layers as well as the mean electron–hole pair creation energy were determined, the latter with an unprecedented relative uncertainty of 1%. The linearity and X‐ray scattering properties of the device are also described.