Radio-Optically- and Thermally Stimulated Luminescence of Zn(BO2 ) 2 :Tb3+ exposed to Ionizing Radiation

E CRUZ-ZARAGOZA1*, G CEDILLO DEL ROSARIO1,2, M GARCÍA HIPÓLITO2 , J MARCAZZÓ3 , J M HERNÁNDEZ A4 , E CAMARILLO4 AND H MURRIETA S4

1Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, A. P. 70-543, 04510 Ciudad de México, México

2 Posgrado en Ciencia e Ingeniería de Materiales, Instituto de Investigaciones en Materiales-UNAM, A. P. 70-360, 04510 Ciudad de México, México

3 Instituto de Física Arroyo Seco-CIFICEN, CONICET-UNCPBA, Pinto 399, 7000 Tandil, Argentina

4 Instituto de Física, Universidad Nacional Autónoma de México, A. P. 20-364, 01000 Ciudad de México, México

*Email: ecruz@nucleares.unam.mx

Abstract The optical absorption of zinc tetraborate at different concentrations of the terbium impurity (0, 0.5, 1, 2, 4, 8 mol%) was analyzed. The radioluminescence (RL) emission spectra was obtained after beta irradiation of a 90Sr/90Y source. The RL spectrum showed the characteristics bands of Tb3+ with two main emissions at 489 nm and 546 nm which corresponding to the5 D4 →7 F6 and 5 D4 →7 F5 transitions respectively in this ion. The OSL and TL characteristics have been analyzed. The stimulation blue light (497 nm) of a diode laser at 500 mA was used to bleach the thermoluminescent (TL) signals obtained with 5Gy of 60Co source. The two main glow peaks (79 and 161 °C) are sensitives under 497 nm stimulation, and they were shifted to higher temperature values and faded their TL intensities. Similar behavior of TL glow curves before and after OSL stimulation with blue light was observed when the samples were exposed to 30 Gy gamma dose of 137Cs irradiator. The OSL signal response was linear with the dose range of 1-10 Gy and increased their response up to 200 Gy gamma dose. The OSL shows a bleaching sensitive shallow traps and diminishing the intensity of the TL glow curves remaining a complex traps distribution. The RL, TL and OSL properties were investigated in Zn(BO2 )2 :Tb3+ phosphor.

DOI: https://doi.org/10.15415/jnp.2017.51016

LINK: http://dspace.chitkara.edu.in/jspui/bitstream/1/876/1/51016_JNP_%20ECruz-Zaragoza.pdf

Radon Exhalation from Industrial Residues as Suitable Additives for Building Materials

H BARROS1 , * G ESPINOSA2 , W RODRIGUEZ1 AND L SAJO-BOHUS1

1 Universidad Simón Bolívar. Apartado 89000, Caracas 1080 A, Venezuela.

2 Instituto de Física, Universidad Nacional Autónoma de México, Coyoacán, México

 *Email: hbarros@usb.ve

Abstract Radon exhalation from phosphogypsum (PG) and red mud (RM) samples are of environmental concern. The study is oriented to evaluate by different nuclear techniques, industrial materials cumulated in sites at Morón (PG) and Puerto Ordaz (RM) in Venezuela. RM samples and industrial by products are assessed for its potential use as additives in building materials regarding its radiological health risk. Radioactive matter concentration in RM is up to 11.6 kBq.kg-1. Radon concentration range for RM dry powder is between DL and 2.5 kBq.m- ³ and for PG is between 105-340 Bq.m- ³. Results indicate that industrial by product before it can be used as additive; require remedial actions to lower the environmental impact. Experimental values are compared with locally available cement, bricks and gypsum building materials.

DOI: https://doi.org/10.15415/jnp.2017.51011

LINK: http://dspace.chitkara.edu.in/jspui/bitstream/1/871/1/51011_JNP_bannoza.pdf

Radiolysis of Nucleosides: Study of Sedimentary Microenvironment Models for the Protection of Bio-Organic Molecules on Early Earth

E Y AGUILAR-OVANDO1,2* AND A NEGRÓN-MENDOZA1

1 Instituto de Ciencias Nucleares (ICN), Universidad Nacional Autónoma de México (UNAM)

2 Centro de Investigaciones Químicas, Universidad Autónoma del Estado de Morelos (UAEM)

*Email: ellen.aguilar@nucleares.unam.mx

Abstract Nucleic acid bases and their derivatives are important compounds in biological systems. Many efforts have been made to demonstrate the possible prebiotic origin of these molecules, but the abiotic synthesis of these compounds has proved to be very difficult in that conditions. So, if their synthesis actually took place, a study of their stability in prebiotic conditions is quite relevant in chemical evolution studies. In this work, it has been examined and compared the influence of Sodium Montmorillonite on the chemical transformations undergone by two nucleosides (guanosine – purinic– and uridine, –pyrimidinic–) when subjected to conditions simulating the primitive Earth during the period of chemical evolution. The experiments prove the concentration capacity and protective role against external sources of ionizing radiation (specifically γ-ray) that clays can provide to these specific compounds adsorbed on them. By using X-ray diffraction, UVvis spectrophotometry and HPLC for the analysis, it was found that purinic nucleosides (more than pyrimidinic) are quickly adsorbed on clay at low pH values, and the temperature of mineral desiccation applied after adsorption promotes their decomposition into their corresponding nitrogenous bases. In both, purinic and pyrimidinic, desorption occurs in neutral or slightly basic aqueous solutions, and both are protected by clay. Pyrimidinic nucleosides show more resistance to heat, but less resistance towards ionizing radiation, even when adsorbed in clay.

DOI: https://doi.org/10.15415/jnp.2017.51010

LINK: http://dspace.chitkara.edu.in/jspui/bitstream/1/870/1/51010_JNP_Aguilar%20-%20Negron.pdf

Application of a CdTe Detector for Measurements of Mammographic X-ray Spectra

J C SANTOS 1*, A TOMAL2 AND P R COSTA1 .

1 Instituto de Física, Universidade de São Paulo, SP, Brazil

2 Instituto de Física Gleb Wataghin, Universidade Estadual de Campinas, SP, Brazil

*Email: josilene@usp.br

Abstract 
This work aims to characterize mammographic x-ray beams incident and transmitted by breast phantoms (from 0 to 45 mm) composed from known proportion of glandular and adipose tissue-equivalent materials. This study was performed for mammographic x-ray beams generated by a mammography equipment using different target/filter combinations (Mo/Mo, Mo/Rh and W/Rh). It was studied the modification of spectra shape of the beams transmitted through different thicknesses of these materials. It was also evaluated the penetrability of these transmitted beams by its correlations to the HVL, which were experimentally estimated and derived from the x-ray spectra measured using a spectrometry system with a CdTe detector. The x-ray spectra transmitted by the phantom with higher density presented lower intensity than those transmitted by those with lower density, as expected. The differences between the HVL values derived from the spectra and those estimated using air kerma measurements are lesser than 6% for about 88% of the spectra measured in this work. The expected spectra variations with phantom thickness, revealed by the measured transmitted x-ray spectra, were also confirmed by HVL measurements and agree with the estimated attenuation curves. The motivation of the study was related to the robustness of the spectra as a descriptor of radiation beams and the possibility of using these transmitted spectra for dose assessment related to mammographic procedures. We can conclude that developed method is able to characterize mammographic x-ray beams making it possible the use of this kind of data for dose assessment in mammography.

DOI: https://doi.org/10.15415/jnp.2017.51009

LINK: http://dspace.chitkara.edu.in/jspui/bitstream/1/869/1/51009_JNP_Josilene%20Santos%20-%20Brasil.pdf

Characterization Of Structures Of Equivalent Tissue With a Pixel Detector

M.C GRADOS LUYANDO* , B. DE CELIS ALONSO, E. MORENO BARBOSA, M.I. MARTÍNEZ HERNÁNDEZ, J.M. HERNÁNDEZ LÓPEZ AND G. TEJEDA MUÑOZ

1 Benemérita Universidad Autónoma de Puebla

*Email: carminagl87@gmail.com

Abstract 
Research using hybrid pixel detectors in medical physics is on the rise. Timepix detectors have arrays of 256 × 256 pixels with a resolution of 55 µm. Here, and by using Timepix counts instead of Hounsfield units, we present a calibration curve of a Timepix detector analog to those used for CT calibration. Experimentation consisted of the characterization of electron density in 10 different kinds of tissue equivalent samples from a CIRS 062M phantom (lung, 3 kinds of bones, fat, breast, muscle, water and air). Radiation of the detector was performed using an orthodontic X-ray machine at 70 KeV and .06 second of tube current with a purpose-built aluminum collimator. Data acquisition was performed at 1 frame per second and taking 3 frames per phantom. We were able to find a curve whose behavior was similar to others already published. This will lead to the verification of the usage of Timepix for identification of different tissues in an organ.

DOI: https://doi.org/10.15415/jnp.2017.51008

LINK: http://dspace.chitkara.edu.in/jspui/bitstream/1/868/1/51008_JNP_Grados%20-%20Buap.pdf