Semitransparent CVD diamond detectors for in situ synchrotron radiation beam monitoring

Chemically vapour-deposited (CVD) diamond thin films have been used for X-r ay beam monitoring. Advances in experiments using synchrotron light sources have generated a demand for permanent in-line radiation hard X-ray monitor s in the energy range 1.5-25 keV. CVD diamond has two distinct advantages o ver all other detector materials: it has a low atomic number resulting in a low X-ray absorption cross-section and it exhibits a high radiation and te mperature hardness allowing long term operation. This combination enables t hin-film photodetectors to be inserted in the beam line causing only low le vel intensity perturbations downstream. Diamond membranes 20 mu m thick were grown on silicon using the microwave p lasma CVD technique. Four-quadrant position-sensitive devices were fabricat ed on CVD diamond using other low atomic number materials such as graphite and aluminium for contact formation. Positional analysis of 4 keV photons f rom a third generation synchrotron radiation facility (ESRF) under typical operating conditions (10(12)-10(13) photons cm(-2) s(-1)) has demonstrated a spatial resolution of 2 mu m over a 200 mu m x 200 mu m area with 80% tra nsmission remaining. For demanding experiments such as XAFS, this feature a llows real time monitoring of beam instabilities and therefore simultaneous position correction during data acquisition. (C) 1999 Elsevier Science S.A . All rights reserved.