Measurement and modelling of anomalous polarity pulses in a multi-electrode diamond detector

¹ Physics Department, NIS Centre and CNISM, University of Torino; INFN sez. Torino - via P. Giuria 1, 10125 Torino, Italy
² Ruđemer Bošković Institute - Bijenička cesta 54, P.O. Box 180, 10002 Zagreb, Croatia
³ Department of Industrial Engineering, University of Roma “Tor Vergata” - 00133 Roma, Italy

Received: 15 September 2013
Accepted: 28 October 2013

Abstract

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.