On the double peak structure of avalanche photodiode response to monoenergetic x-rays at various temperatures and bias voltages

C. M.B. Monteiro, F. D. Amaro, M. S. Sousa, M. Abdou-Ahmed, P. Amaro, F. Biraben, T. Chen, D. S. Covita, A. J. Dax, M. Diepold, L. M.P. Fernandes, B. Franke, S. Galtier, A. L. Gouvea, J. Götzfried, T. Graf, T. W. Hänsch, M. Hildebrandt, P. Indelicato, L. JulienK. Kirch, A. Knecht, F. Kottmann, J. J. Krauth, Y. Liu, J. Machado, F. Mulhauser, B. Naar, T. Nebel, F. Nez, R. Pohl, J. P. Santos, J. M.F.Dos Santos*, K. Schuhmann, C. I. Szabo, D. Taqqu, J. F.C.A. Veloso, A. Antognini

*Corresponding author for this work

Research output: Contribution to JournalArticleAcademicpeer-review


The double response of a large area avalanche photodiode, a planar RMD model S1315, to 6-keV x-rays was investigated as a function of APD biasing voltage and for different operating temperatures. Our data are consistent with the interpretation that the dissimilar APD response is due to x-ray interactions in the different APD-layer structures; interactions in the APD entrance layer just below the front electrode, where the electric field intensity is very low lead to pulses with higher risetime and lower amplitudes, when compared with interactions in the deeper layers where the electric field is more intense. Average pulse risetime values of 14 and 7 ns have been measured in our setup, the slower pulses presenting average amplitudes which are around 20% lower than those of the faster pulses. While the fast risetime does not depend significantly on APD biasing voltage and on temperature, the slow risetime presents a slight decrease with increasing bias voltage and decreasing temperature, a behaviour that is consistent with the increase of the electric field as a result of the increase in the APD biasing voltage. The fraction of the slow pulses reduces from 60% to 40% as the APD biasing increases from about 1.58 to 1.64 kV, indicating a reduction in the thickness, from 25 to 15 μm, in the weak-electric-field entrance layer.

Original languageEnglish
Article numberC01033
JournalJournal of Instrumentation
Issue number1
Publication statusPublished - 1 Jan 2018


M.D., B.F., J.J.K., and R.P. acknowledge support from the European Research Council (ERC) through StG. #279765. A.A. acknowledges support from the European Research Council (ERC) through CoG. #725039. F.D.A., L.M.P.F, A.L.G., C.M.B.M. and J.M.F.S. acknowledge support from FEDER, through COMPETE, and from FCT (Lisbon), in the frame of projects PTDC/FIS-NUC/1534/2014 and LIBPhys — R&D Unit 4559. C.M.B.M., F.D.A., P.A. and J.M. acknowledge the support of FCT contracts SFRH/BPD/76842/2011, SFRH/BPD/74775/2010, SFRH/BPD/92329/2013, SFRH/BD/52332/2013. A.A, K.K. and K.S. acknowledge support from SNF project 200021_165854. T.G., A.V., B.W. and M.A.A. acknowledge support of DFG GR

FundersFunder number
Horizon 2020 Framework Programme725039
European Research Council279765
Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung200021_165854
Fundação para a Ciência e a TecnologiaSFRH/BD/52332/2013, SFRH/BPD/76842/2011, SFRH/BPD/74775/2010, SFRH/BPD/92329/2013, PTDC/FIS-NUC/1534/2014
CANDU Owners Group
European Regional Development Fund
Programa Operacional Temático Factores de Competitividade


    • Charge transport and multiplication in solid media
    • Solid state detectors
    • X-ray detectors


    Dive into the research topics of 'On the double peak structure of avalanche photodiode response to monoenergetic x-rays at various temperatures and bias voltages'. Together they form a unique fingerprint.

    Cite this