Efficiency calibration of x-ray HPGe detectors for photons with energies above the Ge K binding energy

Author(s)

Maidana, Nora L. ^[1] ; Vanin, Vito R. ^[1] ; Jahnke, Viktor ^[1] ; Fernandez-Varea, Jose M. ^{[2, 3]} ; Martins, Marcos N. ^[1] ; Brualla, Lorenzo ^[4]

Affiliation

^[1] Univ Sao Paulo, Inst Fis, BR-05508900 Sao Paulo - Brazil

^[2] Univ Barcelona, Fac Fis, ECM, E-08028 Barcelona - Spain

^[3] Univ Barcelona, Fac Fis, ICC, E-08028 Barcelona - Spain

^[4] Univ Klinikum Essen, NCTeam, Strahlenklin, D-45122 Essen - Germany

• Document type: Journal article
• Source: NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SP; v. 729, p. 371-380, NOV 21 2013.
• Web of Science Citations: 12

Abstract

We report on the efficiency calibration of a HPGe x-ray detector using radioactive sources and an analytical expression taken from the literature, in two different arrangements, with and without a broad angle collimator. The frontal surface of the Ge crystal was scanned with pencil beams of photons. The Ge dead layer was found to be nonuniform, with central and intermediate regions that have thin (pm range) and thick (mm range) dead layers, respectively, surrounded by an insensitive ring. We discuss how this fact explains the observed efficiency curves and generalize the adopted model. We show that changes in the thickness of the Ge-crysLal dead layer affect the efficiency of x-ray detectors, but the use of an appropriate broad beam external collimator limiting the photon flux to the thin dead layer in the central region leads to the expected efficiency dependence with energy and renders the calibration simpler. (C) 2013 Elsevier BM. All rights reserved (AU)

• FAPESP's process: 10/19699-6 - Electron impact inner-shell atomic ionization cross-section measurement
• Grantee: Vito Roberto Vanin
• Support Opportunities: Regular Research Grants
• FAPESP's process: 10/52616-7 - Development of a procedure for hyper-pure germanium detector response calibration combining experimental measurements with Monte Carlo simulations
• Grantee: Nora Lia Maidana
• Support Opportunities: Regular Research Grants