X-ray spectroscopic performance of a matrix of silicon drift diodes

Using a 55Fe source we characterized the spectroscopic performance of a matrix of Silicon Drift Diodes (SDDs). The matrix consists of a completely depleted volume of silicon wafer subdivided into five identical hexagonal cells. The back side is composed of five implanted arrays of increasingly negatively biased concentric p + rings. The front side, common to all five cells, is a uniformly implanted p + entrance window. Ionizing radiation impinging the detector bulk generates electrons that drift towards small readout n + pads placed on the back side at the center of each cell. The total sensitive area of the matrix is 135 mm2, the wafer thickness is 450 μ m . We report on the layout of the experimental set-up, as well as the spectroscopic performance measured at different temperatures and bias conditions.