Dead layer variation modeling for precise HPGe efficiency calculation of samples in marinelli using MCNP computer code

Authors

10.22052/4.3.11

Abstract

In this research, a method for considering the spatial variation of deal layer (DL) thickness at the lateral and top surfaces of HPGe detectors is presented to achieve a more precise simulation model for efficiency calculation especially in marinelli beaker geometries. As a good approximation, the lateral surface of the detector is divided into 12 segments, assuming each segment covers 30 degrees and the top surface of detector is divided to 25 sections. The detector efficiencies are experimentally measured in each lateral segment and also in 25 points at the top of detector, using Am-241 source at each mentioned positions. The nearest DL thickness for each segment is selected through MCNP calculations of Full Energy Peak Efficiency (FEPE) with different DL thicknesses. Then a proposed detector model with a lateral DL thickness equal to average of selected DL thicknesses on lateral surface and a top DL thickness equal to average of selected DL thicknesses on top surface is used for FEPE calculation of bulk sample geometries such as Marinelli beaker containers. The resulting efficiencies are compared with the experimentally measured efficiencies of a Marinelli beaker containing a set of standard radiation source solution with specified activities. The experimental and simulation results of FEPE show a very good agreement.

Keywords

References

[1] M. Korun, A. Likar, T. Vidmar. Monte-Carlo calculation of the spatial dependence of the coaxial HPGe detector efficiency for point sources. Nucl. Instr. And Meth. A. 390 (1997) 203-208. [2] S. Ashrafi, A. Likar, T. Vidmar. Precise Modelling of a coaxial HPGe detector. Nucl. Instr. And Meth. A. 438 (1999) 421-428. [3] I.O.B Ewa, D. Bodizs, S. Czifrus, Z. Molnar. Monte Carlo determination of full energy peak efficiency for a HPGe detector. Appl. Radiat. Isot. 55 (2001) 103–108. [4] N.L. Maidana, V.R. Vanin, J.A. García-Alvarez, M. Hermida-López. Experimental HPGe coaxial detector response and efficiency compared to Monte Carlo simulations. Appl. Radiat. Isot. 108 (2016) 64-74. [5] N.Q. Huy, D.Q. Binh, V.X. Ana. Study on the increase of inactive germanium layer in a high-purity germanium detector after a long time operation applying MCNP code. Nucl. Instr. and Meth. A. 573 (2007) 384-388. [6] D. Budjas, M. Heisel, W. Maneschg, H. Simgen. Optimisation of the MC-model of a p-type Ge spectrometer for the purpose of efficiency determination. Appl. Radiat. Isot. 67 (2009) 706–710. [7] J. Bosona, G. agren, L. Johansson. A detailed investigation of HPGe detector response for improved Monte Carlo efficiency calculations. Nucl. Instr. and Meth. A. 587 (2008) 304–314. [8] N. Quang Huy. Dead-layer thickness effect for gamma spectra measured in an HPGe p-type detector. Nucl. Instr. and Meth. A. 641 (2011) 101-104. [9] J. Rodenas, A. Pascual, I. Zarza, V. Serradell, J. Ortiz, L. Ballesteros. Analysis of the influence of germanium dead layer on detector calibration simulation for environmental radioactive samples using the Monte Carlo method. Nucl. Instr. and Meth. A. 496 (2003) 390-399. [10] A. Azbouche, M. Belgaid, H. Mazrou. Monte Carlo calculations of the HPGe detector efficiency for radioactivity measurement of large volume environmental samples. J. Environ. Radioact. 146 (2015) 119-124. [11] M.R. Zarea, M. Kamali, Z. Omidi, M. Fallahi Kapourchali. Designing and producing large-volume liquid gamma-ray standard sources for low radioactive pollution measurements of seawater samples by comparison between experimental and simulation results. Measurement (2016). [12] N.L. Maidana, V.R. Vanin, V. Jahnke, J. Fernández-Varea, J.M. Martins. Efficiency calibration of x-ray HPGe detectors for photons with energies above the Ge K binding energy. Nucl. Instrum. Methods A. 729 (2013) 371–380. [13] E. Andreotti, M. Hult, G. Marissens, G. Lutter, A. Garfagnini, S. Hemmer, K. VonSturm. Determination of dead-layer variation in HPGe detectors, Appl. Radiat. Isot. 87 (2014) 331-335. [14] T. Azli, Z. Chaoui. Performance revaluation of a N-type coaxial HPGe detector with front edges crystal using MCNPX. Appl. Radiat. Isot. 97 (2015) 106-112. [15] M.T. Haj-Heidari, M.J. Safari, H. Afarideh, H. Rouhi. Method for developing HPGe detector model in Monte Carlo simulation codes, Rad. Meas. 88 (2016) 1-6. [16] E. Chham, F. Piñero García, T.El Bardouni, M. Angeles Ferro-García, M. Azahra, K. Benaaliloua, M. Krikiz, H. Elyaakoubi, J. El Bakkali, M. Kaddour. Monte Carlo analysis of the influence of germanium DL thickness on the HPGe gamma detector experimental efficiency measured by use of extended sources. Appl. Radiat. Isot. 95 (2015) 30-35. [17] T. Vidmar. EFFTRAN- A Monte Carlo efficiency transfer code for gamma-ray spectrometry. Nucl. Instr. And Meth. A. 550 (2005) 603-608. [18] T. Vidmar, G. Kanisch, G. Vidmar. Calculation of true concidence summing corrections for extended sources with EFFTRAN. Appl. Radiat. Isot. 69 (2011) 908-911.
Journal of Radiation Safety and Measurement
Volume 5, Issue 3 - Serial Number 15
September 2016
Pages 11-20

Files

Share

How to cite

Statistics