Sodium-22 source contribution determination in positron annihilation measurements using GEANT4 (original) (raw)
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Positron Annihilation Spectroscopy (PAS) is a sensitive method dedicated to detection of open-volume type of defects in materials. Nowadays, this technique is of a great interest due to the practical character of obtained results. New devices using monoenergetic positron beams are built. The poster presents progress in this field at LEPTA project at Joint Institute for Nuclear Research in Dubna, present and future directions of works.
Positron Source Simulations using Geant4
2010
The development of an intense polarised positron sources provides a challenge for a new generation of linear colliders. The software framework Geant4, a toolkit for simulation of the passage of particles trough matter, features tracking capabilities of charged particles in electromagnetic fields, and also includes the description of polarisation transfer in scattering processes. Based on Geant4 a novel simulation tool, PPS-Sim*, has been developed to optimise the design and to determine polarisation, beam properties, as well as energy deposition in accelerator components. All source components and their parameters can be chosen easily and flexible. Helical undulator, laser-Compton and coherent Bremsstrahlung in crystals are available as positron production schemes. Target materials and geometry can be adjusted. Flux concentrator, quarter wave transformer and lithium lens are implemented as possible capture devices. Geometry, accelerating components and magnetic field configuration c...
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Physical Review Letters, 2004
Positronium (Ps) produced by 4 to 40 eV positrons colliding with Ne, Ar, Kr, CO 2 , and O 2 is investigated by measuring the ratio of signals of two gamma rays in coincidence resulting from (a) three gamma annihilation of ortho-Ps and (b) two annihilation gamma rays due to para-Ps decay and destruction of ortho-Ps at an aluminum scattering cell surface. These ratios provide evidence that relates to the kinetic energy dependence of ortho-Ps interactions with an aluminum surface, the Ps formation potential at this surface, and the fact that Ps is being formed with inner orbital electrons for CO 2 and O 2 .
Positron implantation profile in kapton
Il Nuovo Cimento D, 1988
The discussion presented in the paper focuses on processes accompanying positron implantation in condensed matter. They finally constitute the positron implantation profile which generally does not exhibit the exponential behavior as it is concluded from the Monte Carlo simulation made using the EGSnrc 4.0 code. The simulation was performed for the kapton and two commonly used positron sources 22 Na and 68 Ge\ 68 Ga. New formula for the implantation profile was proposed.
Experimental Study on the Element-Specic Positron Annihilation Spectroscopy
Journal- Korean Physical Society
Coincidence Doppler-broadening (CDB) and positron annihilation lifetime (PAL) techniques have been applied to study 12 pure elements. The existence of open-type defects was investigated in the elements. The characteristic features of the high-momentum part of the CDB spectra for elemental metals with/without defects were investigated. By normalizing the CDB spectra to the CDB spectrum of well-annealed Ti, ratio-curves are presented. The moment region range (12 ¢ 10 3 moc < PL < 20 ¢ 10 3 moc) was elucidated and provided important information on the elemental specicity. An empirical relation that linked the positron anities and the atomic number to the shape of the high-momentum part of the CDB spectra for 3-d elements was derived. The results imply that elements (closely located in the periodic table) can be identied from an analysis of the CDB spectra.
Analysis of positron profiling data by ROYPROF, VEPFIT, and POSTRAP4 codes: a comparative study
Journal of Theoretical and Applied Physics, 2013
The programs ROYPROF, VEPFIT, and POSTRAP4 are widely used in the field of positron physics. They are mainly employed in analyzing experimental Doppler-broadened data from studying condensed matter samples with variable energy positron beams. A comparative study of analysis results on the same set of data has shown to be consistent. Performance differences are reported. The small differences found may not lead to wrong interpretation of physical results.
Applied Radiation and Isotopes, 2010
The present work describes the methodology for predicting the behavior of extrapolation curves obtained in radionuclide standardization by 4pb-g coincidence measurements, applied to 22 Na, developed at the Laborató rio de Metrologia Nuclear of IPEN-CNEN/SP (LMN-Nuclear Metrology Laboratory). The LMN system consists of a proportional counter (PC) in 4p geometry coupled to a single or a pair of NaI(Tl) scintillation crystals. Two standardization techniques were used: the Sum-Peak and the Nuclear-Peak methods. The theoretical response functions of each detector have been calculated using the MCNPX Monte Carlo code. The code ESQUEMA, developed at LMN, has been used for calculating the extrapolation curve in the 4pb-g coincidence experiment. Modifications were performed in order to include response tables for positrons and coincidences with annihilation photons. From the calibration results it was possible to extract both the activity value and the positron emission probability per decay. The latter was compared with results from the literature.
Positron annihilation spectroscopy techniques applied to the study of an HPGe detector
2013
We measured the Doppler broadening annihilation radiation spectrum in Fe, using 22 NaCl as a positron source, and two Ge detectors in coincidence arrangement. The two-dimensional coincidence energy spectrum was fitted using a model function that included positron annihilation with the conduction band and 3d electrons, 3s and 3p electrons, and in-flight positron annihilation. Detectors response functions included backscattering and a combination of Compton and pulse pileup, ballistic deficit and shaping effects. The core electrons annihilation intensity was measured as 16.4(3) %, with almost all the remainder assigned to the less bound electrons. The obtained results are in agreement with published theoretical values.