kGy Range Research Articles

Investigation on various types of silica fibre as thermoluminescent sensors for ultra-high dose radiation dosimetry

With high-dose applications lacking the benefit of an economic yet versatile dosimeter that provides for a wide dynamic dose range, ongoing research is seeking to introduce suitable thermoluminescent (TL) material for such needs. Acknowledging the high potential of silica fibres, as developed by members of this group over the past few years, in present work evaluation has been made of 13 types of fibre, differing in dopant, dopant concentration and diameter including P−, Al−, Er−, Ge− and Al-Tm-doped fibres, ultra-high numerical aperture and borosilicate fibre, and two non-doped fibres, quartz and suprasil F300. Evaluation is made in terms of TL response to photon and electron irradiations with the objective of determining a TL material that can offer sensitive yet extended dose capability, saturating only above the few tens of kGy range. The various silica fibres that have been investigated were found to show saturation levels from 5 kGy for Ge-doped fibre (4 mol %) to 80 kGy for 2 mol % Al−doped silica fibre. Borosilicate fibres demonstrated the greatest potential for high dose dosimetry, maintaining a highly-linear response, any tendency towards saturation only being indicated to beyond receipt of doses of 100 kGy. For this fibre type detailed TL characterizations were conducted, including glow curve analysis, reproducibility and fading tests. The results suggest borosilicate fibre to be suitable for high dose TL dosimetry, providing sufficient sensitivity and appropriate dosimetric characteristics.

EFFECT OF GAMMA RADIATION ON A MIXED DYE FILM AND ITS POSSIBLE USE AS A RADIATION DOSIMETER

Dyed poly vinyl alcohol (PVA) films prepared by a simple technique of casting aqueous PVA solution incorporating a mixture of two dyes namely chlorophenol red (CPR) and Quinaldine Red (QR) on a horizontal glass plate are useful as high dose dosimeter in the dose range 2-30 kGy range. The colour of these films change from deep red to yellow when exposed to gamma radiation. Chloral hydrate was added with different concentrations. The response of the prepared films can be modified either by change of chloral hydrate concentration or ratio of the two dyes. As a result, these films can be used as a dosimeter in two dose ranges. The dosimetric parameters, e.g.; dose response, effect of relative humidity on response as well as pre- and post-irradiation stability of these films were investigated.

Some novel features of post-500°C heating blue stimulated OSL emission of fired natural quartz

Abstract In this study, some novel features of the post 500°C blue stimulated optically stimulated luminescence (OSL) of fired geological quartz are reported. Different observations (i) pulse annealing and (ii) impact of bleaching on high temperature TL glow peak suggested 510°C (heating rate of 2°C/s) TL peak trap to be responsible for the observed emission. The dosimetric properties of this emission were seen to make its applicability for dose assessment till kGy range. The signal was seen to be easily bleachable, reaching background value within 100 s with blue light at 125°C. The signal qualified all the tests (i) reproducibility, (ii) negligible recuperation and (iii) accuracy of dose recovery needed for reliable assessment of the radiation dose with modified Single aliquot regenerative (SAR) protocol. Considering the bleachability and high dynamic dose range of this signal, it has the potential to stretch the upper dose limit of dating by one order of magnitude than possible with conventional OSL, corresponding to 325°C TL trap. So, combining all the results, the signal reported here could be very useful for dosimetric applications involving measurement of high radiation dose, like dating.

Facile preparation of new polystyrene leucomalachite green thick films and study of their radiochromic behavior for low doses of gamma radiation

Colourless polystyrene-leucomalachite green (PS-LMG) thick films containing a suitable chloroalkane were prepared by a fast and facile casting method, and were investigated for their radio chromic response behavior under the influence of 1.25 MeV γ-radiation. Their gamma response was studied in the 0.05 kGy to 10 kGy range to evaluate their suitability for potential use as the dosimeter in the radiation processing industries. The films were found to undergo a visibly distinct green coloration in the studied range, with the colour intensity increasing with an increase in the total dose. The radiochromic response of these films when investigated as a function of film thickness showed that the colour development as well as the linearity of the response was markedly affected by the thickness of the films. The effect of dye loading and the chloroalkane concentration on the radiochromic response of these films were also investigated. Depending upon the film thickness and reactant concentrations, the films were found to be capable of visually detecting gamma radiation doses as low as few tens of grays.

Analysis of TL and OSL kinetics in lithium magnesium phosphate crystals

Within this work the samples of the LiMgPO4 compound have been crystallized using a micro pulling down crystal growth method. The measured TL and OSL response was investigated in order to evaluate basic kinetic parameters. Collected data were analyzed using Tm-Tstop, deconvolution and variable heating rate methods. It was found that both the TL and OSL response of the LiMgPO4 samples can be expressed in the form of a linear combination of several first order components. The obtained results suggest that luminescence processes in the studied material may follow a first order kinetics, as the measured TL glow curves do not shift with increasing dose. Increasing the dose of beta radiation up to kGy range, a linear response was measured for all the studied LiMgPO4 samples. The obtained values of kinetic parameters evaluated with Tm-Tstop method remain in agreement with those obtained by deconvolution for low-temperature peaks. In turn, for peaks located at higher temperatures the results obtained by variable heating rate method are close to those of deconvolution. This implies that more detailed analysis is needed to achieve a compatibility between the applied modes of data analysis and to achieve the accurate values of kinetic parameters. By calculating a decrease in the area under the whole LMP glow curve for the two weeks fading time, using the estimated trapping parameters, and comparing the results with previous work one may conclude that Tm-Tstop method combined with the initial rise analysis gives the most reliable values of kinetic parameters.

Influence of Branching Density in Ethylene-Octene Copolymers on Electron Beam Crosslinkability

Two ethylene-octene copolymers (EOC) with the same melt flow index (MFI = 3 g/10 min) but different octene contents, being 20 and 35 wt % (EOC-20 and EOC-35), were compared with regard to sensitivity to electron beam crosslinking. Dynamic mechanical analysis (DMA) revealed a large influence of the octene content on the storage modulus and the glass transition temperature (Tg) but a smaller influence of irradiation on the properties below melting point (Tm). Rheology at 150 °C pointed out large differences in samples crosslinked in the 0–60 kGy range and at lower frequencies (0.1–1 Hz). The loss factor tanδ confirmed that before irradiation the two copolymers were very similar, while after irradiation to 120 kGy, the EOC-35 had considerably lower tanδ than EOC-20, which corresponds to a better elasticity (or a higher level of crosslinking). A high-temperature creep test showed a considerably lower creep for EOC with a higher octene content. An analysis of the insoluble gel content exhibited higher values for EOC-35 confirming a higher level of crosslinking. Analysis according to the Charlesby-Pinner equation revealed increased crosslinking-to-scission ratio, G(X)/G(S), for EOC-35. While the G(X) value changed only slightly, a significant decrease in the G(S) value was discovered.

Bacterial Diversity in Buffalo Meat and Bowel from Traditional Market and the Sensitivity of Some Bacteria to Irradiation and Antibiotics

The population of buffaloes in Indonesia was 1.37 million in 2012, representing an increase of 5.5 % over its population the previous year. Buffaloes have been in Indonesia for such a long time, they have become a part of the lives of the majority of the Indonesian society. Research has been conducted to know the bacteria diversity in domestic buffalo meat and bowels from traditional markets in Pandeglang, Banten, in order to ascertain their safety based on their initial contamination and also to study the sensitivity of several of the bacteria to irradiation and antibiotics. The total bacterial was assessed by total plate count method as index of quality. The buffalo meat and bowel samples were taken from livers, intestines, lymph, lungs and tripe. Results showed that the contaminating bacteria were aerobic bacteria, coliform bacteria including Escherichia coli ( E. coli ), and Staphylococcus spp. in buffalo meat and bowel. The numbers of aerobic bacteria were in the 1.7×10 5 - 2.3×10 6 CFU/g range, while the total coliform bacteria were in the 2.0×10 3 - 6.8×10 4 CFU/g range. The total number of E. coli was in the 2.0×10 3 - 6.0×10 4 CFU/g range, and Staphylococcus spp. was in the 2.0×10 4 - 2.7×10 5 CFU/g range. No Salmonella was detected in any of the samples observed. The total coliform bacteria, E. coli , and Staphylococcus spp. in all buffalo meat and bowel samples exceeded the maximum numbers of microbes permitted by the Indonesian National Standard (SNI). The maximum of total coliform, E. coli, and Staphylococcus spp. permitted by SNI are 1.0×102, 1.0×10 and 1.0×10 2 CFU/g, respectively. The D 10 values of S. aureus were in the 0.13 - 0.23 kGy range, while for E. coli they were in the 0.07 - 0.13 kGy range. The isolate of S. aureus from the lungs was the most resistant to cefoxitin, tetracycline, and amoxicillin antibiotics. The isolate of E. coli from buffalo bowels were almost sensitive to cefoxitin, tetracycline, and amoxicillin antibiotics. Received: 4 October 2014; Revised: 24 April 2015; Accepted: 11 May 2015

Luminescence Properties of CaF2 Nanostructure Activated by Different Elements

Nanostructures of calcium fluoride (CaF2) doped with Eu, Tb, Dy, Cu, and Ag were synthesized by the coprecipitation method and studied for their thermoluminescence (TL) and photoluminescence (PL) properties. The PL emission spectrum of pure CaF2 nanostructure has a broad band in the 370–550 nm range. Similar spectra were observed in case of doped samples, beside extra bands related to these impurities. The maximum PL intensity was observed in Eu doped sample. The TL results of Eu, Cu, Ag, and Tb doped samples show weak glow peaks below 125°C, whereas Dy doped one is found to be highly sensitive with a prominent peak at 165°C. This sample was further exposed to a wide range of gamma rays exposures from 137Cs source. The response curve is linear in the 100 Gy‐10 kGy range. It is also observed that the particle size of CaF2 nanostructure was significantly reduced by increasing Dy concentration. These results showed that Dy is a proper activator in the host of CaF2 nanostructure, providing a highly sensitive dosimeter in a wide range of exposures and also plays a role as a controlling agent for particle size growth.

Dosimeter Film Based on Ethyl Violet-Bromophenol Blue Dyed Poly(Vinyl Alcohol)

Dyed poly(vinyl alcohol) (PVA) films, prepared by a simple technique of casting aqueous solutions of PVA containing a mixture of Ethyl violet and bromophenol blue (EV-BPB) on a horizontal glass plate, are useful as routine high-dose dosimeter in the 1 - 30 kGy range. The color of films changes from violet to yellow when exposed to gamma radiation. The response of this dosimeter depends up on the concentration of chloral hydrate (CH) in the polymer material. The radiation chemical yield (G-value) of PVA dyed film was calculated and found to increase by increasing concentration of chloral hydrate. Post-irradiation storage on the response of the films are discussed. The overall combined uncertainty (at 2σ) associated with measurement of response (ΔA mm-1) at 600 nm for dose range 1 - 15 kGy is 5.6%.

Dosimeter Film Based on Ethyl Violet-Bromophenol Blue Dyed Poly (vinyl alcohol)

DYED POLY(VINYL ALCOHOL) (PVA) films, prepared by a simple technique of casting aqueous solutions of PVA containing a mixture of ethyl violet and bromophenol blue (EV-BPB) on a horizontal glass plate, are useful as routine high-dose dosimeter in the 1-30 kGy range. The colour of films changes from violet to yellow when exposed to gamma radiation. The response of this dosimeter depends up on the concentration of chloral hydrate (CH) in the polymer material. The radiation chemical yield (G-value) of PVA dyed film was calculated and found to increase by increasing concentration of chloral hydrate. Post-irradiation storage on the response of the films are discussed.

Gamma Dosimetry Using Some Dyes in Organic Solvents Solutions at 295 and 77 K

The aim of this work is to study the behavior under irradiation of different dyes (green malachite, methyl orange, red cresol, and bromothymol blue) in organic solvents (acetone and methanol) at different gamma doses and different temperatures to propose them as possible dosimeters for low-temperature applications. For this purpose, organic dissolutions were irradiated with gamma rays in the kiloGray (kGy) range at 77 and 295 K, and the color bleaching of the solutions was followed spectrophotometrically (UV-Vis range). The response curves at different temperatures show the linear range interval from 10 to 40 kGy with correlation coefficients of 0.999 and 0.998 for some systems. This is the main reason to continue carrying out studies that allow the proposal of these systems as chemical dosimeters.

Study of the Thermoluminescent Characteristics of Ceramic Roof Tiles Exposed to Beta Radiation

ABSTRACTIn this work, thermoluminescence (TL) characteristics of roof tile ceramic samples previously exposed to beta radiation are reported for the very first time. TL measurements were carried out using powdered samples obtained by the the fine-grained method, with grain size ranged from 300 nm to 5 μm. Characteristic thermoluminescence glow curves showed a complex structure with a dosimetric maximum located at ~ 200 °C. TL response of roof tile samples increases as the radiation dose increases in the 25 Gy to 1.6 kGy range. One response showed a linear behaviour, with no evidence of saturation within the dose interval investigated. The entire TL glow curve exhibited a remarkable reusability during 10 consecutive irradiation-TL readout cycles. The total TL signal showed a very low fading and remained almost constant after 3 h of irradiation and the corresponding TL readout. TL dosimetry features of powdered roof tile place it as a promising material in retrospective dosimetry as well as in possible TL dating applications.

Characterization of the optical properties and stability of Presage™ following irradiation with photons and carbon ions

Background. The on-going development of both intensity-modulated radiotherapy (IMRT), including the more recent intensity-modulated arc therapy, as well as particle beam therapy, has created a clear need for accurate verification of dose distributions in three dimensions (3D). Presage™ is a new 3D dosimetry material that exhibits a radiochromic response when exposed to ionizing radiation. In this study we have 1) developed an improved optical set-up for measurements of changes in OD of Presage™ point dosimeters, 2) investigated the dose response of Presage™ for photons and carbon ions in the therapy range, 3) investigated the dose response of Presage™ for photons in the kGy range and 4) investigated the fading (i.e. bleaching) of Presage™ postirradiation. Materials and methods. Presage™ was examined in 1 × 1 × 4.5 cm3 optical cuvettes; a cuvette holder assured accurate repositioning, and the optical setup included a reference detector to take into account laser intensity fluctuations. The cuvettes were measured pre- and postirradiation for a two week period. Results. A linear response was observed between dose and optical response between 0 Gy and 100 Gy for γ-radiation from Co-60 and for carbon ions (both plateau and SOBP) from 0 to 20 Gy. The dosimeter was found to have a saturation dose of approximately 100 Gy for photons. A linear energy transfer (LET) effect was not observed in the dose response of different LET radiation. The postirradiation change in optical fading was found to be 0.5% ΔOD/day. Conclusions. Our study shows that Presage™ remains a dosimeter of interest for radiation therapy with other particles as well as photons in the therapy dose range.

Comparison of the Performance of Synthesized Nano-structure Hydroxyapatite with Bovine Bones and Alanine Samples for EPR Dosimetry

Radiation dosimetry was done by measuring free radicals induced in synthetic nano-structure hydroxyapatite (HAP) using EPR method. The HAP samples were synthesized via fluid body simulated method and were irradiated at different dose intervals and subsequently subjected to the EPR measurement. The effects of some EPR parameters were investigated as well. Variations of EPR signal intensities were constructed as peak-to-peak signal amplitude and were compared with alanine and bovine bone samples for two different dose ranges of Gy and kGy from dosimetric point of view. The results were shown that the HAP samples were more practical for doses in Gy range. At kGy range doses the bone sample and alanine dosimeter shows a better EPR responses.

Identification of irradiated oysters by EPR measurements on shells

Abstract In this paper the EPR spectra of the radicals induced in oyster shells after irradiation to (0.5–2) kGy ionizing radiation doses are analyzed. EPR spectra of irradiated shells showed the complex radical composition of biocarbonates, characterized by the presence of SO 2 − , SO 3 − and CO 2 − radicals with different symmetries. In particular, the radiation-induced line at g = 2.0038, due to the g x component of the orthorhombic SO 3 − , was well distinguishable from the rest of the spectrum. The g x component of the orthorhombic SO 3 − was found to be intense and stable enough to allow the identification at least for the whole shelf life of the oyster. Furthermore, it is still well visible at low microwave powers for which the other signals are weak or non-visible and has a linear dose response in the (0.5–2) kGy range. A possible procedure protocol for the identification of irradiated oysters, can be based on acquisitions of the spectrum at low microwave power values (tenths of milliWatt) and low modulation amplitude values (0.03–0.05 mT) and on the identification of the g = 2.0038 signal as a proof of the ionizing radiation treatment performed on the sample.

Electron paramagnetic resonance study of rare-earth related centres in K 2YF 5:Tb 3+ thermoluminescence phosphors

Rare-earth related centres have been investigated in K 2YF 5:Tb 3+ crystals, exhibiting thermoluminescence (TL) below and above room temperature (RT), using electron paramagnetic resonance (EPR) spectroscopy at Q (34 GHz) and W-band (94 GHz). The spectra have been studied prior to irradiation, after exposure in the kGy range to X-rays at 77 K and subsequent pulse annealing up to 570 K. In addition to Gd 3+, previously studied in detail, we identified Er 3+ and Yb 3+ centres as accidental impurities in as-grown crystals and determined their effective g tensors. The EPR spectra of irradiated and annealed crystals provide evidence for the production of at least three distinct Tb-related trapped hole centres, two of which could definitely be identified as Tb 4+. Hence, we prove that the Tb 3+ activator ions also act as hole traps in K 2YF 5. Pulse annealing experiments indicate that the TL above RT results from thermal release of electrons, recombining at these Tb 4+ ions.

Modification of etching properties of a newly developed nuclear track detector called allyl bis-(2-nitroxy-ethyl) carbomate (ABNEC)–allyl diglycol carbonate (ADC) copolymer [ABNEC:ADC (1:9)] by gamma irradiation

The gamma irradiation effects on the bulk etch rate, V b of an indigenously prepared new nuclear track detector which is a copolymer of allyl bis-(2-nitroxy-ethyl) carbomate (ABNEC) and allyl diglycol carbonate (ADC) [ABNEC:ADC (1:9)] were studied in the dose range of 25.0–250.0 kGy and etching temperature range of 60–80 °C. The bulk etch rates increase and the activation energy values for bulk etching of gamma-irradiated detectors decrease with the increase in gamma dose indicating the scission of the detector. UV–visible spectra of the unirradiated and the irradiated films were also taken to explore the possibility of using this new detector for gamma dose measurements.

Characteristics of gamma-ray response of Radix W dosimeter in several kGy range

Characteristics of gamma-ray response of Radix W dosimeter in several kGy range

A New Electron Paramagnetic Resonance Method to Identify Irradiated Soybean

Low-dose gamma irradiation causes minimal changes in food matrix making identification of radiation-processed foods a challenging task. In the present study, soybean samples were irradiated with commercially permitted gamma radiation dose in the 0.25 to 1.0 kGy range for insect disinfestations of food. Immediately after irradiation electron paramagnetic resonance (EPR) spectrum of the skin part of soybean showed a triplet signal (g = 2.0046, hyperfine coupling constant hfcc = 3.0 mT) superimposed on naturally present singlet. These signals were characterized as cellulose and phenoxyl radicals using EPR spectrum simulation technique. Kernel part of the samples exhibited a short-lived, radiation-induced singlet of carbon-centered radical superimposed on naturally present sextet signal of Mn2+. A detailed study on relaxation and thermal behavior of induced radicals in skin part was carried out using EPR spectroscopy. These findings revealed that progressive saturation and thermal characteristics of the induced radicals may be the most suitable parameters to distinguish soybean subjected to radiation dose as low as 0.25 kGy from thermally treated and nonirradiated samples, even after a prolonged period of storage.

Detection of irradiated chestnuts: preliminary study using three analytical techniques

Irradiation of chestnuts has recently been considered as an alternative treatment to fumigation to reduce the considerable amount of the product normally lost during post-harvest period. The treatment is allowed in countries such as Korea and, in view of a possible extension to European countries, to permit the legal controls as required by the directive 1999/2/EC [ European Parliament and Council Directive, 1999/2/EC, on the approximation of the laws of the Member States concerning foods and food ingredients treated with ionising radiation. Official Journal of the European Communities. L 66/16 of 13.3.1999] and meet consumer consensus, reliable methods for detecting irradiated chestnuts have to be proposed. The aim of the present work was to test the efficacy of the European Standard EN 13751, EN 1788, EN 1787 and EN 13708 in detecting irradiated chestnuts. For this purpose, six sets of “Montella” chestnuts, a typical Italian variety recognized as a PGI (protected geographical indication), non-irradiated and irradiated at different doses in the 0.1–1 kGy range, were analysed by thermoluminescence (TL), photo-stimulated luminescence (PSL) (screening and calibrated PSL) and ESR techniques. PSL and TL analysis results revealed the low luminescence sensitivity of the chestnuts. Nevertheless, PSL screening data were in the intermediate band above the negative threshold (at all doses except at the lowest one) and TL analysis led to correct positive classifications even at the lowest dose tested (0.15 Gy). On the contrary, no radio-induced ESR signal could be registered with the irradiated samples of chestnut shell or pulp.