Chemical sensitivity in positron annihilation with just one single Ge detector

Abstract

We present a novel method for analyzing the data from momentum distribution measurements employing positron annihilation, using just one single Ge‐detector, but employing a mathematically sufficiently well suited model for background subtraction. For a variety of high purity metals the resulting momentum distributions have exactly the same shapes up to 35 × 10–3 m0c as those obtained with coincidence Doppler broadening of the annihilation radiation using a two‐detector system. This data analysis applies to any positron source without high energy gammas or a slow positron beam system with just a single Ge‐detector and enables the possibility of analysing the chemical surrounding at the positron trapping site without any additional hardware. In particular, in combination with a slow positron microbeam, it allows a spatially resolved measurement of the electron's momentum distribution. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Early precipitation stages of aluminum alloys—The role of quenched-in vacancies

“…1), even though just a rough model, describes the measured data quite well. For a high-momentum analysis (HMA) [15,16] data from consecutive time intervals of 10 h have been summed up to perform the HMA shown in Fig. 3.…”

“…In this state the samples were immediately transferred to the positron spectrometer. There the Doppler broadening of the annihilation radiation (DBAR) has been measured at room temperature (20 8C) with a 68 Ge source [15,16]. One sample aged at room temperature for more than five days has been measured additionally at the synchrotron beamline BN at ELSA Bonn (for details see reference [17]), where all XANES spectra were recorded between 8925 and 9140 eV in fluorescence mode.…”

Spatially resolved deformation studies on carbon steel employing X‐rays and positron annihilation

“…The spectra were taken in a cross-sectional scan along the bending radius in steps of 100 µm. Stabilisation of the electronics and spectral background subtraction was done according to the methods described in [9]. The S-parameter was evaluated in a energy range of ± 1.38 keV around 511 keV.…”

Spatially resolved defect studies on fatigued carbon steel

“…For stabilisation a monitor line ( 7 Be: 477.6 keV) was measured simultaneously. Shifts of the electronics were corrected and the small-angle Compton background was subtracted according to the methods described in [5].…”