Femtosecond Laser Treated 3D Diamond Detectors for Charged Particles

We report on the fabrication and preliminary characterization of novel 3D diamond devices for charged particle detection. Three dimensional detectors present mainly two advantages with respect to conventional planar and sandwich detectors for charge particles: 1) drift distance between electrodes is comparable to mean free path of photogenerated carriers in irradiated device, enabling in this way a faster response (hundreds of ps); 2) lower bias voltages are needed to obtain the electric field values necessary to achieve high charge collection efficiency conditions. A femtosecond laser (Ti:Sapphire, ? = 800 nm, 4 mJ peak energy per pulse) was employed to create arrays of conductive graphitic columns inside the bulk of a single-crystal standard grade CVD diamond. The columns far ends, on top and bottom facets of the samples, were arranged to form metallic strips, then wire-bonded to a dedicated sample holder and connected to the read-out electronics. Preliminary measurements were performed under alpha particle irradiation (241Am radioactive source, 5.5 MeV, 37 kBq), including current transient time-of-flight analysis and energy dispersive spectroscopy. In both cases, significant results were obtained in terms of response speed, time resolution and energy resolution.