Thin planar epitaxial silicon detector for synchrotron X-rays

The silicon PN junction offers some advantages in contrast with ion chamber ; high quantum efficiency, very large dynamic range, good linearity, vacuum and cryogenically compatibility. This in particular in experiments using synchrotron radiation such EXAFS in absorption or in fluorescence mode. We use a 30 μm thin ion implanted and passivated silicon detector as a beam monitor and another planar diode of 200 μm to measure the photon flux behind the sample. These two detectors are working in the photovoltaic mode at room temperature. Currents are amplified in a low input impedance current preamplifier and are typically ten times greater than with an ion chamber for the same absorption. Thus the contribution of the electronic to the total noise is significantly less compared to the other system and faster rise time become possible. We have done in particular the copper foil EXAFS in 1 minute against 15 minutes in the conventional step by step mode.