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Now showing items 1 - 16 of 8225

  • Thermoluminescence response of X-ray irradiated commercial chalk

    Almugren, K. S.   Sani, S. F. Abdul   Wandira, R.   Wahib, Norfadira   Rozaila, Z. Siti   Khandaker, M. U.   Bradley, D. A.  

    Present research concerns the TL signal stored in chalk of the variety commercially available for writing on blackboards. Samples of this have been subjected to x-ray irradiation, the key dosimetric parameters investigated including dose and energy response, sensitivity, fading and glow curve analysis. Three types of chalk have been investigated, each in five different colours. The samples were annealed at 323 K prior to irradiation. For all three chalk types and all five colours, the dose response has been found linear over the investigated dose range, 0-9 Gy. Regardless of type or colour, photoelectric energy dependency is apparent at the low energy end down to the lowest investigated accelerating potential of 30 kV. Crayola (Yellow) has shown the greatest TL sensitivity, thus selection has been made to limit further analysis to this medium alone, specifically in respect of glow curve and fading study. In addition, elemental compositional and structural change characterizations were made for the same medium, utilizing Energy Dispersive X-Ray (EDX) and Raman spectroscopy, respectively.
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  • Irradiated glass and thermoluminescence yield:Dosimetric utility reviewed

    Bradley, D. A.   Khandaker, M. U.   Alanazi, Abdulaziz  

    With numbers of efforts being made towards harnessing the thermoluminescence yield of doped glass media for dosimetric applications, predominantly in the radiotherapeutic regime, review is provided of the background to this, tracing developments leading to the present day. Included are an examination of the relative strengths of the various TLD currently on offer and that of glass fabrications, commercial Ge-doped optical fibre as well as novel fibres fabricated from Ge-doped glass. The demands that modern radiotherapeutic dose delivery systems are placing upon these passive forms of dosimetry are reviewed together with the various responses arising from current efforts. Also reviewed are the basis of the luminescence yield, citing the defect types occurring in silica, even in the absence of extrinsic dopants.
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  • Environmental monitoring through use of silica-based TLD

    Rozaila, Z. Siti   Khandaker, M. U.   Sani, S. F. Abdul   Sabtu, Siti Norbaini   Amin, Y. M.   Maah, M. J.   Bradley, D. A.  

    The sensitivity of a novel silica-based fibre-form thermoluminescence dosi-meter was tested off-site of a rare-earths processing plant, investigating the potential for obtaining baseline measurements of naturally occurring radioactive materials. The dosimeter, a Ge-doped collapsed photonic crystal fibre (PCFc) co-doped with B, was calibrated against commercially available thermoluminescent dosimetry (TLD) (TLD-200 and TLD-100) using a bremsstrahlung (tube-based) x-ray source. Eight sampling sites within 1 to 20 km of the perimeter of the rare-earth facility were identified, the TLDs (silica-as well as TLD-200 and TLD-100) in each case being buried within the soil at fixed depth, allowing measurements to be obtained, in this case for protracted periods of exposure of between two to eight months. The values of the dose were then compared against values projected on the basis of radioactivity measurements of the associated soils, obtained via high-purity germanium gamma-ray spectrometry. Accord was found in relative terms between the TL evaluations at each site and the associated spectroscopic results. Thus said, in absolute terms, the TL evaluated doses were typically less than those derived from gamma-ray spectroscopy, by similar to 50% in the case of PCFc-Ge. Gamma spectrometry analysis typically provided an upper limit to the projected dose, and the Marinelli beaker contents were formed from sieving to provide a homogenous well-packed medium. However, with the radioactivity per unit mass typically greater for smaller particles, with preferential adsorption on the surface and the surface area per unit volume increasing with decrease in radius, this made for an elevated dose estimate. Prevailing concentrations of key naturally occurring radionuclides in soil, Ra-226, Th-232 and K-40, were also determined, together with radiological dose evaluation. To date, the area under investigation, although including a rare-earth processing facility, gives no cause for concern from radiological impact. The current study reveals the suitability of the optical fibre based microdosimeter for all-weather monitoring of low-level environmental radioactivity.
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  • Dosimetric utility of structural changes in gamma irradiated graphite-rich pencils

    Sani, S. F. Abdul   Ismail, S. S.   Almugren, K. S.   Khandaker, M. U.   Bradley, D. A.  

    9B and H grade carbon-based pencil (carbon concentrations approaching 81 and 62 wt respectively %) have been investigated for radiotherapy dosimetry applications, offering low dependence on photon energy and near soft tissue effective atomic number. Comparison has been made with highly oriented pyrolytic graphite (HOPG), a pure and ordered synthetic form of graphite. The samples were exposed to Co-60 gamma ray doses from 0 to 20 Gy (encompassing the range of doses utilized in fractionated radiotherapy), structural interaction alterations resulting from the radiation doses being observed via Raman and Photoluminescence (PL) spectroscopy and X-ray diffraction (XRD). Among the most prominent features to be observed in Raman spectra are the so-called G and D peaks, appearing at 1578 cm(-1) and 1348 cm(-1) respectively. The intensity ratio I-D/I-G was used for further characterization of the dose-dependent defects produced in the graphitic materials. From PL measurement, sample average energy band gap values are observed to be within the region 1.114-1.116 eV, being considered direct bandgap-like semiconductors. The characteristic XRD crystal plane Miller index (002) peak was observed in order to calculate the atomic spacing, lattice constant and the degree of structural order of the irradiated samples.
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  • Correspondence between phenomenological and IBM-1 models of even isotopes of Yb

    Okhunov, A. A.   Sharrad, F. I.   Al-Sammarraie, Anwer A.   Khandaker, M. U.  

    Energy levels and the reduced probability of E2- transitions for ytterbium isotopes with proton number Z =3D 70 and neutron numbers between 100 and 106 have been calculated through phenomenological (PhM) and interacting boson (IBM-1) models. The predicted low-lying levels (energies, spins and parities) and the reduced probability for E-2 transitions results are reasonably consistent with the available experimental data. The predicted low-lying levels (gr-, beta(1)- and gamma(1)- band) produced in the PhM are in good agreement with the experimental data compared with those by IBM-1 for all nuclei of interest. In addition, the phenomenological model was successful in predicting the beta(2)-, beta(3)-, beta(4)-, gamma(2)- and 1(+)- band while it was a failure with IBM-1. Also, the 3(+)- band is predicted by the IBM-1 model for Yb-172 and Yb-174 nuclei. All calculations are compared with the available experimental data.
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  • Reply to Comment on 'Environmental monitoring through the use of silica-based TLD'

    Rozaila, Z. Siti   Khandaker, M. U.   Sani, S. F. Abdul   Sabtu, Siti Norbaini   Amin, Y. M.   Maah, M. J.   Bradley, D. A.  

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  • Radiometric analysis of construction materials using HPGe gamma-ray spectrometry

    Khandaker, M. U.   Jojo, P. J.   Kassim, H. A.   Amin, Y. M.  

    Concentrations of primordial radionuclides in common construction materials collected from the south-west coastal region of India were determined using a high-purity germanium gamma-ray spectrometer. Average specific activities (Bq kg(-1)) for U-238(Ra-226) in cement, brick, soil and stone samples were obtained as 54 +/- 13, 21 +/- 4, 50 +/- 12 and 46 +/- 8, respectively. Respective values of Th-232 were obtained as 65 +/- 10, 21 +/- 3, 58 +/- 10 and 57 +/- 12. Concentrations of K-40 radionuclide in cement, brick, soil and stone samples were found to be 440 +/- 91, 290 +/- 20, 380 +/- 61 and 432 +/- 64, respectively. To evaluate the radiological hazards, radium equivalent activity, various hazard indices, absorbed dose rate and annual effective dose have been calculated, and compared with the literature values. Obtained data could be used as reference information to assess any radiological contamination due to construction materials in future.
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  • Radiological risks assessment of building materials ingredients:Palm oil clinker and fuel ash

    Karim, M. R.   Khandaker, M. U.   Asaduzzaman, Kh.   Razak, H. A.   Yusoff, S. B.  

    Technical benefits relevant to the use of palm oil clinker (POC) and fuel ash (POFA) in building materials has been well documented. However, the radiological health hazards caused by the incorporation of POC and POFA as an ingredient of building materials have not been studied so far. The radioactivity levels were measured by gamma-ray spectrometry using hyper-pure germanium (HPGe) detector. The activity concentration of Ra-226 and Th-232 in POC and POFA was found to be in the ranges of 5.56 +/- 0.23 to 9.03 +/- 0.21 and 4.21 +/- 0.03 to 7.98 +/- 0.19 Bq kg(-1), respectively, and these values were lower than the world average values of 50 Bq kg(-1) for building materials. The K-40 value was within the range of 413.01 +/- 1.78 to 604.66 +/- 2.18 Bq kg(-1). Several radiological parameters and hazard indices, i.e. radium equivalent activity, absorbed dose rate and annual effective dose etc. were calculated for the evaluation of the potential radiological hazards. The obtained values fall within the recommended limit set by various international organizations. Since the activity levels of Ra-226, Th-232 and K-40 in POC and POFA were significantly lower than the corresponding literature data for other ingredients of building materials, it indicates that POC and POFA are safe to be used in concrete construction.
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  • A comprehensive study of boron nitride nanotubes multiple synthesis from a single precursor

    Ahmad, P.   Khandaker, M. U.   Amin, Y. M.  

    Importance of boron nitride nanotubes due to its applications in the fields of biomedical, microelectronic mechanical systems and solid state neutron detectors has greatly increased the demand for high quality and large scale synthesis of boron nitride nanotubes. The idea of using a single precursor for multiple synthesis has been utilized and boron nitride nanotubes are synthesized from fresh as well as residual material left after first and second experimental runs. For the first time, experimental results are characterized and analyzed for their size, morphology and quality of the final product. Results thus obtained are likely to be steps toward the high yield and large scale synthesis of boron nitride nanotubes.
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  • A simple technique to synthesise vertically aligned boron nitride nanosheets at 1200 degrees C

    Ahmad, P.   Khandaker, M. U.   Amin, Y. M.  

    In order to make the synthesis of boron nitride nanosheets (BNNS) easier and safe, a very simple technique is introduced in the present study. In this technique BNNS are synthesised in a conventional horizontal dual zone quartz tube furnace at 1200 degrees C. Field emission scanning electron microscopy image shows the morphology of synthesised BNNS like spread out cotton packs. Transmission electron microscopy (TEM) images show highly crystalline nature of synthesised nanosheets of boron nitride with an interlayer spacing of 0.34 nm. Raman spectrum shows a major peak at 1366 (cm(-1)) that corresponds to E-2g mode of h-BN. X-ray photon spectroscopy survey shows B 1s (at 191 eV) and N 1s (at 398 eV) peaks that verify the boron and nitrogen contents in synthesised nanosheets.
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  • Cyclotron production of V-48 via Ti-nat(d,x)V-48 nuclear reaction; a promising radionuclide

    Usman, A. R.   Khandaker, M. U.   Haba, H.  

    In this experimental work, we studied the excitation function of nat V-48 via Ti-nat(d,x)V-48 nuclear reactions from 24 MeV down to threshold energy. Natural titanium foils were arranged in the popular stacked-foil method and activated with deuteron beam generated from an AVF cyclotron at RIKEN, Wako, Japan. The emitted. activities from the activated foils were measured using an offline gamma-ray spectrometry. The present results were analyzed, compared with earlier published experimental data and also with the evaluated data of Talys code. Our new measured data agree with some of the earlier reported experimental data while a partial agreement is found with the evaluated theoretical data. In addition to the use of V-48 as a beam intensity monitor, recent studies indicate its potentials as calibrating source in PET cameras and also as a (radioactive) label for medical applications. The results are also expected to further enrich the experimental database and also to play an important role in nuclear reactions model codes design.
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  • Evaluation of Ge-doped silica fibre TLDs for in vivo dosimetry during intraoperative radiotherapy

    Moradi, F.   Ung, N. M.   Mahdiraji, G. A.   Khandaker, M. U.   See, M. H.   Taib, N. A.   Bradley, D. A.  

    Ge-doped silica fibre (GDSF) thermoluminescence dosimeters (TLD) are non-hygroscopic spatially high-resolution radiation sensors with demonstrated potential for radiotherapy dosimetry applications. The INTRABEAM (R) system with spherical applicators, one of a number of recent electronic brachytherapy sources designed for intraoperative radiotherapy (IORT), presents a representative challenging dosimetry situation, with a low keV photon beam and a desired rapid dose-rate fall-off close-up to the applicator surface. In this study, using the INTRABEAM (R) system, investigations were made into the potential application of GDSF TLDs for in vivo IORT dosimetry. The GDSFs were calibrated over the respective dose- and depth-range 1 to 20 Gy and 3 to 45 mm from the x-ray probe. The effect of different sizes of spherical applicator on TL response of the fibres was also investigated. The results show the GDSF TLDs to be applicable for IORT dose assessment, with the important incorporated correction for beam quality effects using different spherical applicator sizes. The total uncertainty in use of this type of GDSF for dosimetry has been found to range between 9.5% to 12.4%. Subsequent in vivo measurement of skin dose for three breast patients undergoing IORT were performed, the measured doses being below the tolerance level for acute radiation toxicity.
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  • Analysis of the energy spectra of ground states of deformed nuclei in the rare-earth region

    Okhunov, A. A.   Turaeva, G. I.   Kassim, H. A.   Khandaker, M. U.   Rosli, Noora B.  

    The Sm-62, Gd-64, 66DY, Yb-70, Hf-72 and W-74 nuclei are classified as deformed nuclei. Low-lying bands are one of the most fundamental excitation modes in the energy spectra of deformed nuclei. In this paper a theoretical analysis of the experimental data within the phenomenological model is presented. The energy spectra of ground states are calculated. It is found that the low-lying spectra of ground band states are in good agreement with the experimental data.
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  • Natural radioactivity levels and radiological assessment of decorative building materials in Bangladesh

    Asaduzzaman, Kh.   Khandaker, M. U.   Amin, Y. M.   Bradley, D. A.  

    The use of building covering media, largely for decorative purposes, presents an associated need for accurate evaluation of naturally occurring radioactive materials, crucial in assessing radiological risk. Radiological risks, assessed through investigation of decorative material samples, have been provided through key quantities, including radium equivalent activity (Ra-eq), external and internal hazard indices, gamma index, indoor and outdoor absorbed dose rates, as well as the corresponding annual effective doses. The concentrations of Th-232 and K-40 in all of the studied samples are higher than the respective world averages whereas for Ra-226, only the clay tiles and a few other samples exceeded the world average value. The values for Ra-eq for all samples were found to be <370Bqk g(-1), recommended as the limiting dose below which safe use of bulk media can be assumed. For most samples, the internal and external hazard indices are well below the recommended limit of 1. The indoor absorbed dose rate has been observed to be higher than the population-weighted world average of 84nGy h(-1), and the corresponding annual effective doses fall below the maximum dose limit of 1mSv y(-1). The activity concentrations presented herein are expected to be useful in assessing the impact of future radiological loadings from use of decorative materials in dwellings.
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  • Raman spectroscopy and X-ray photo-spectroscopy analysis of graphite media irradiated at low doses

    Bradley, D. A.   Rozaila, Z. Siti   Khandaker, M. U.   Almugren, K. S.   Meevasana, Worawat   Sani, S. F. Abdul  

    We explore the utility of controlled low-doses (0.2-100 Gy) of photon irradiation as initiators of structural alteration in carbon-rich materials. To-date our work on carbon has focused on beta-, x- and gamma-irradiations and the monitoring of radiotherapeutic doses (from a few Gy up to some tens of Gy) on the basis of the thermoluminescence (TL) signal, also via Raman and X-ray photo-spectroscopy (XPS), providing analysis of the dose dependence of single-walled carbon nanotubes (SWCNT). The work has been extended herein to investigate possibilities for analysis of structural alterations in graphite-rich mixtures, use being made of two grades of graphite-rich pencil lead, 8H and 2B, both being in the form produced for mechanical pencils (propelling or clutch pencils). 2B has the greater graphite content (approaching 98 wt %), 8H being a mixture of C, O, Al and Si (with respective weight percentages 39.2, 38.2, 9.8 and 12.8). Working on media pre-annealed at 400 degrees C, both have subsequently been irradiated to penetrating photon-mediated doses. Raman spectroscopy analysis has been carried out using a 532 nm laser Raman spectrometer, while for samples irradiated to doses from 1 to 40 Gy, XPS spectra were acquired using Al K-alpha sources (hv similar to 1400 eV); carbon KLL Auger peaks were acquired using 50 eV Pass Energy. At these relatively low doses, alterations in order-disorder are clearly observed, defect generation and internal annealing competing as dominating effects across the dose range.
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  • Experimental determination of proton-induced cross-sections on natural zirconium RID F-5376-2011

    Khandaker, M. U.   Kim, K.   Lee, M. W.   Kim, K. S.   Kim, G. N.   Cho, Y. S.   Lee, Y. O.  

    We measured cross-sections for the formation of (86g.87m.87g)Y, (88.89g)Zr, and (90.92m)Nb radionuclides for proton-induced reactions on natural zirconium by using a conventional stacked-foil activation technique in the energy range between I and 40MeV at the MC-50 cyclotron of the Korea Institute of Radiological and Medical Science. We compared the measured data with the available literature data and the theoretical calculation by the model codes TALYS and ALICE-IPPE. We also deduced the integral yields for thick targets from the measured cross-sections of the produced radionuclides. The optimum production possibility of the medically important (89g)Zr and (86)Y radionuclides were discussed elaborately. (c) 2009 Elsevier Ltd. All rights reserved.
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