  In multi-electrode detectors, the motion of excess carriers generated by
ionizing radiation induces charge pulses at the electrodes, whose intensities
and polarities depend on the geometrical, electrostatic and carriers transport
properties of the device. The resulting charge sharing effects may lead to
bipolar currents, pulse height defects and anomalous polarity signals affecting
the response of the device to ionizing radiation. This latter effect has
recently attracted attention in commonly used detector materials, but different
interpretations have been suggested, depending on the material, the geometry of
the device and the nature of the ionizing radiation. In this letter, we report
on the investigation in the formation of anomalous polarity pulses in a
multi-electrode diamond detector with buried graphitic electrodes. In
particular, we propose a purely electrostatic model based on the
Shockley-Ramo-Gunn theory, providing a satisfactory description of anomalous
pulses observed in charge collection efficiency maps measured by means of Ion
Beam Induced Charge (IBIC) microscopy, and suitable for a general application
in multi-electrode devices and detectors.
