Room temperature CVD diamond X-ray and charged particle microdetectors

Hot filament chemical vapour deposition technique is particularly suitable for the realisation of diamond tip and wire detectors working in a coaxial geometry with a built-in internal metal electrode. By using tungsten wires of different diameters and by controlling the shape of the tip by an electr ochemical etch, it is possible to obtain various kinds of microdetectors, w ith diameters ranging from 50 to 300 mu m. The response of these diamond ti p and wire detectors has been tested at low X-ray energies (50-250 keV) and at relatively high energies (6-15 Mev) both in terms of sensitivity (colle cted charge with respect to the absorbed dose) and of Linearity as a functi on of X-ray fluence. Sensitivities larger than 2 nC/Gy are achieved, with a good linearity in the dose rate range used in applications. Such microprob es have been proved to be suitable as narrow X-ray beam profilers and as su rface or in vivo microdosimeters for on-line monitoring of radiotherapy pla ns. Such detectors have also been used as nuclear micro detectors by measur ing the response to alpha particles from an Am-241 source and from a proton beam (2.4 MeV energy) produced by a van de Graaff accelerator. In this cas e the estimated collection efficiency is higher than 20% for wires and 50% for tips. (C) 1999 Elsevier Science B.V. All rights reserved.