Performance of different readout topologies of silicon drift detectors in PIXE spectroscopy

PIXE (Particle Induced X-ray Emission) is a very powerful technique for the detection of medium-light elements (down to Z=11 − Na) due to its superior cross-sections in this atomic number region. However, a common problem in all PIXE setups is the backscattering of protons from the target that perturbs the electronic system, causing front-end electronics saturation, increasing the dead-time and deteriorating the energy resolution due to signal-dependent noise. The state-of-the-art detectors for X-ray spectroscopy are silicon drift detectors characterized by a very low output capacitance (of the order of 100 fF) independent of the active area of the device. This feature allows the SDD to reach a lower electronic noise with respect to a conventional silicon diode of equivalent area and thickness. The integration of the first stage of the front-end electronics on the detector chip allows extremely high-resolution spectroscopy even at high counting rates and low energies. We have evaluated the performance of different readout configurations in PIXE spectroscopy (source follower configuration, self-reset charge amplifier configuration, adaptive self-reset charge amplifier configuration, pulsed-reset charge amplifier). The readout topologies have been compared in terms of output waveform, achievable energy resolution, peak shift and maximum count rate.