Gamma Radiation Source Research Articles

Thermoluminescence characteristics of Ge-doped optical fibers with different dimensions for radiation dosimetry

Important thermoluminescence (TL) properties of five (5) different core sizes Ge-doped optical fibers have been studied to develop new TL material with better response. These are drawn from same preform applying different speed and tension during drawing phase to produce Ge-doped optical fibers with five (5) different core sizes. The results of the investigations are also compared with most commonly used standard TLD-100 chips (LiF:Mg,Ti) and commercial multimode Ge-doped optical fiber (Yangtze Optical Fiber, China). Scanning Electron Microscope (SEM) and EDX analysis of the fibers are also performed to map Ge distribution across the deposited region. Standard Gamma radiation source in Secondary Standard Dosimetry Lab (SSDL) was used for irradiation covering dose range from 1Gy to 10Gy. The essential dosimetric parameters that have been studied are TL linearity, reproducibility and fading. Prior to irradiation all samples ∼0.5cm length are annealed at temperature of 400°C for 1h period to standardize their sensitivities and background. Standard TLD-100 chips are also annealed for 1h at 400°C and subsequently 2h at 100°C to yield the highest sensitivity. TL responses of these fibers show linearity over a wide gamma radiation dose that is an important property for radiation dosimetry. Among all fibers used in this study, 100μm core diameter fiber provides highest response that is 2.6 times than that of smallest core (20μm core) optical fiber. These fiber-samples demonstrate better response than commercial multi-mode optical fiber and also provide low degree of fading about 20% over a period of fifteen days for gamma radiation. Effective atomic number (Zeff) is found in the range (13.25–13.69) which is higher than soft tissue (7.5) however within the range of human-bone (11.6–13.8). All the fibers can also be re-used several times as a detector after annealing. TL properties of the Ge-doped optical fibers indicate promising applications in ionizing radiation dosimetry.

Gamma radiation shielding analysis of lead-flyash concretes

Six samples of lead-flyash concrete were prepared with lead as an admixture and by varying flyash content – 0%, 20%, 30%, 40%, 50% and 60% (by weight) by replacing cement and keeping constant w/c ratio. Different gamma radiation interaction parameters used for radiation shielding design were computed theoretically and measured experimentally at 662keV, 1173keV and 1332keV gamma radiation energy using narrow transmission geometry. The obtained results were compared with ordinary-flyash concretes. The radiation exposure rate of gamma radiation sources used was determined with and without lead-flyash concretes.

Low resistance bakelite RPC study for high rate working capability

This paper presentsseries efforts to lower resistance of bakelite electrode plate to improve the RPC capability under high rate working condition. New bakelite material with alkali metallic ion doping has been manufactured and tested. This bakelite is found unstable under large charge flux and need further investigation. Alternatively, a new structure of carbon-embedded bakelite RPC has been developed, which can reduce the effective resistance of electrode by a factor of 10. The prototype of the carbon-embedded chamber could function well under gamma radiation source at event rate higher than 10 kHz/cm2. The preliminary tests show that this kind of new structure performs as efficiently as traditional RPCs.

Effects of gamma irradiation on electrical parameters of metal–insulator–semiconductor structure with silicon nitride interfacial insulator layer

The effects of gamma irradiation on electrical parameters of Au/Si3N4/n-Si (MIS) structure were investigated by using the capacitance–voltage (C–V) and conductance–voltage (G/ω–V) measurements. The MIS structure was irradiated using gamma-radiation source at a dose rate of 0.69 kGy/h. The C–V and G/ω–V measurements were carried out at a total dose range of 0–100 kGy for five different frequencies (1, 10, 100, 500 and 1000 kHz). The obtained results showed that the C and G/ω values decrease with the increasing radiation dose due to the irradiation-induced defects at the interface. Also, the observed decrease in the C and G/ω values with the increasing frequency was explained on the basis of interface states (Nss). The values of series resistance (Rs) increase with the increasing radiation dose. To obtain the real capacitance and conductance of the capacitor, the measured values of C and G/ω were corrected to eliminate the effect of series resistance. The values of Nss were determined by using the conductance method and were decreased with the increasing radiation dose.

Performance of radiation survey meters in X- and gamma-radiation fields.

The aim of this work was to investigate the different types of radiation detectors commonly used for radiation protection purposes as survey meters. The study was performed on survey meters that use different detectors as ionisation chamber, Geiger Mueller (GM) counter and scintillation detector. For each survey meter, energy dependence and angular response in X- and gamma-radiation fields was tested. The following commercially available survey meters were investigated: ionisation chambers Victoreen 451P, Babyline 31 and VA-J-15A, Geiger counter MRK-M87, 6150 AD6 and FAG FH 40F2 and scintillation counter 6150 ADB. As a source of gamma radiation, (137)Cs and (60)Co were used whereas X-ray radiation fields were generated using an X-ray unit. The radiation characteristics of the survey meters were mostly in compliance with references estimated by standard IEC 1017-2. However, some of them showed larger deviation at lower energies. GM counters exhibit strong energy dependence for low-energy photons.

Dielectric characteristics of gamma irradiated Au/SnO2/n-Si/Au (MOS) capacitor

The dielectric characteristics of gamma irradiated Au/SnO2/n-Si/Au (MOS) capacitor were studied. The MOS capacitor was irradiated by a 60Co gamma radiation source with a dose rate of 0.69kGy/h. The dielectric parameters such as dielectric constant (ε′), dielectric loss (ε″), loss factor (tanδ) and ac electrical conductivity (σac) were calculated from the capacitance–voltage (C–V) and conductance–voltage (G/ω–V) measurements. It is found that the C and G/ω values decrease with the increasing total dose due to the irradiation-induced defects at the interface. Also, the calculated values of ε′, ε″ and σac are found to decrease with an increased radiation dose. This result indicates that the dielectric characteristics of the MOS capacitor are sensitive to gamma-ray dose.

Studies on decontamination for herbal eyebright raw material and product by gamma radiation

Herbal eyebright products and their raw materials have been irradiated with 1, 2, 3 and 5 kGy by Co-60 gamma radiation source at Hanoi Irradiation Center for decontamination. Initial bioburdens were under the limitation levels established for the traditional medicines according to the decree of 16/2011/TT-BYT issued by Vietnam Health Ministry. These values for both bacteria and fungus slightly increased during storage to three months, reach to about 103 and 102 CFU/g for bacteria and molds, respectively. However, there are no microbial colonies that could be observed in the samples irradiated with dose higher than 3 kGy. Results suggested that the dose of 3 kGy was enough for decontamination of eyebright raw powders and products. At dose of 5 kGy, the moisture and vitamin A content of the samples were insignificantly changed. These mean the radiation treatment with low dose did not influenced the quality of eyebright products, and radiation treatment can be applied to prolong the storage of not only eyebright, but also other traditional medicines.

Effects of dose fractionation on the response of alanine dosimetry

Alanine dosimetry is well established as a transfer standard and is becoming more prevalently used in routine dosimetry systems for radiation processing. Many routine measurement applications in radiation processing involve absorbed dose measurements resulting from fractioned exposures to ionizing radiation. Fractioning of absorbed dose is identified as an influence quantity (ISO/ASTM, 2013). This paper reports on study results of absorbed dose fractioning characteristics of alanine for gamma and high energy electron beam radiation sources. The results of this study indicate a radiation response difference due to absorbed dose fractioning in response can be observed after four fractionations for high-energy electron beams and no difference up to seven fractions for gamma rays using an ANOVA evaluation method.

Isodose mapping of terrestrial gamma radiation dose rate of Selangor state, Kuala Lumpur and Putrajaya, Malaysia

A terrestrial gamma radiation survey for the state of Selangor, Kuala Lumpur and Putrajaya was conducted to obtain baseline data for environmental radiological health practices. Based on soil type, geological background and information from airborne survey maps, 95 survey points statistically representing the study area were determined. The measured doses varied according to geological background and soil types. They ranged from 17 nGy h−1 to 500 nGy h−1. The mean terrestrial gamma dose rate in air above the ground was 182 ± 81 nGy h−1. This is two times higher than the average dose rate of terrestrial gamma radiation in Malaysia which is 92 nGy h−1 (UNSCEAR 2000). An isodose map was produced to represent exposure rate from natural sources of terrestrial gamma radiation.

Effect of cobalt-60 gamma irradiation on graphene: Raman and field emission investigations

Electrophoretically deposited graphene (HG) on silicon is irradiated using a cobalt-60 gamma radiation source with the radiation dose up to 22.7 kGy. The effect of gamma irradiation on the field emission current noise behavior of HG is investigated. The power spectra of pristine and irradiated HG exhibit 1/fα type of noise, with α ∼ 0.8. The magnitude of noise power is observed to increase with the radiation dose. The variations in the turn on field and noise power in the emission current are attributed to the structural modifications of HG, as revealed from the field emission scanning electron microscopic and Raman spectroscopic studies.

Decolorization of textile wastewater by gamma irradiation and its reuse in dyeing process

This paper describes the scope of employing high-energy gamma irradiation for textile wastewater treatment and the possibility of using the treated wastewater in the dyeing of knitted cotton fabric. The treatment was carried out in Cobalt-60 gamma radiation source at different irradiation doses (3, 5, 8, and 12 kGy). Then, the irradiated wastewater was used for dyeing of cotton fabric with reactive dye. The performance of the fabric dyed with treated wastewater was compared to that of the fabric dyed with freshwater. Hence, the dyeing performance was evaluated by comparing the depth of shades of both types of dyed fabrics from the analysis of absorption spectrum (K/S value vs. wavelength). The absorption curves of irradiated wastewater dyed fabric in light, medium, and dark shade of three different colors have shown close match to their corresponding freshwater dyed fabric. Variation of shade between the dyed fabrics, representing by ∆E values, were also found within the maximum acceptable limit as it ranges from 0.02 to 0.9. The color fastness of the dyed fabric was also measured with respect to perspiration, rubbing, and washing. In case of fastness, both types of fabrics have shown similar rating (4–5) which lies between “good” to “excellent”.

Spatial brightness distribution of hard X-Ray emission along flare loops

The work is devoted to the simulation of recently discovered hard X-ray and gamma radiation sources localized near the top of solar flare loops. The calculations were performed in the context of a model of a flare magnetic loop inhomogeneous with respect to the magnetic field. Two cases of injection were considered: isotropic and anisotropic along the loop axis. The distributions of electrons along the loop are found by solving the nonstationary relativistic kinetic equation in the Fokker-Planck form. Based on the calculated electron distribution functions, the spatial brightness distribution of hard X-ray and gamma radiation has been calculated. Radiation characteristics are compared for different sets of injection parameters.

A hybrid camera for locating sources of gamma radiation in the environment

We present a new concept for a portable environmentalimaging system, the Compact Hybrid Gamma Camera (CHGC). This combines anoptical and a gamma-photon camera in a co-aligned configuration that offershigh spatial resolution multi-modality imaging for superposition of gammaray and optical images. We report on its potential use for surveying,monitoring and clean-up of radioactive sources in the environment.

Comparison of proton microbeam and gamma irradiation for the radiation hardness testing of silicon PIN diodes

Simple and cost-effective solutions using Si PIN diodes as detectors are presently utilized in various radiation-related applications in which excessive exposure to radiation degrades their charge transport properties. One of the conventional methods for the radiation hardness testing of such devices is time-consuming irradiation with electron beam or gamma-ray irradiation facilities, high-energy proton accelerators, or with neutrons from research reactors. Recently, for the purpose of radiation hardness testing, a much faster nuclear microprobe based approach utilizing proton irradiation has been developed. To compare the two different irradiation techniques, silicon PIN diodes have been irradiated with a Co-60 gamma radiation source and with a 6 MeV proton microbeam. The signal degradation in the silicon PIN diodes for both irradiation conditions has been probed by the IBIC (ion beam induced charge) technique, which can precisely monitor changes in charge collection efficiency. The results presented are reviewed on the basis of displacement damage calculations and NIEL (non-ionizing energy loss) concept.

Comparative study of grafting a polyampholyte in a fluoropolymer membrane by gamma radiation in one or two-steps

Binary graft copolymerization of pH-sensitive monomers (N,N-dimethylaminoethyl methacrylate, (DMAEMA) and acrylic acid (AAc) onto polyvinylidene fluoride (PVDF) membranes with pore sizes of 0.22 and 0.45μm was conducted by one and two-steps grafting using a 60Co gamma radiation source (Gammabeam 651 PT). The DMAEMA and AAc monomers were grafted by an oxidative pre-irradiation method in one-step grafting to obtain PDVF-g-(DMAEMA-co-AAc), and both direct irradiation and an oxidative pre-irradiation method were used to obtain the graft copolymer (PVDF-g-DMAEMA)-g-AAc in two-steps grafting. The optimal conditions, such as reaction time, temperature, solvent, monomer concentration and dose, were studied, the aim of this work was to investigate how these factors affecting the graft percent of DMAEMA and AAc prepared in one and two-steps grafting and their structural differences and also characterize the grafting membrane through analytical techniques.

Gamma radiolytic eradication of methoxychlor in aqueous media: the degradation pathways using HPLC and SPME-GC-MS

Abstract The gamma radiation-induced degradation of environmental pollutant methoxychlor in water was investigated. A 60Co gamma radiation source with a dose rate of 372 Gy h−1 was used for gamma irradiation of 1 mg L−1 and 10 mg L−1 methoxychlor in water with a varied absorbed dose of 1–5 kGy. A single step clean up and pre-concentration procedure based on solid phase micro-extraction was optimized. The extent of radiolytic degradation was monitored by reversed phase HPLC-UV and GC-ECD. The trace and ultra trace level degradation products were identified using GC-MS-SPME by comparing their mass spectra with the NIST 98 m mass spectral library. Most of the generated products for 4 kGy dose are substituted chlorophenols. The reaction pathways of these substituted chlorophenols and benzophenone formation are also proposed. However, generated chlorophenols disappeared along with methoxychlor for an absorbed dose of 5 kGy. The attained degradation of methoxychlor is ∼ 95% that reflects the potential use of ionization radiation for wastewater treatment.

End-to-end calculation of the radiation characteristics of VVER-1000 spent fuel assemblies

The results of end-to-end calculation of the radiation characteristics of VVER-1000 spent nuclear fuel are presented. Details of formation of neutron and gamma-radiation sources are analyzed. Distributed sources of different types of radiation are considered. A comparative analysis of calculated radiation characteristics is performed with the use of nuclear data from different ENDF/B and EAF files and ANSI/ANS and ICRP standards.

Long-term observations of the Seyfert galaxy NGC 1275 at ultrahigh energies by SHALON mirror Cherenkov telescopes

The Seyfert galaxy NGC 1275 is a central dominant galaxy in the Perseus cluster of galaxies. NGC 1275 is known as a powerful source of radio and X-ray radiations. In 1996, in SHALON telescope observations, a new metagalactic source of gamma radiation of ultrahigh energy > 800 GeV was detected. The position of the radiation source detected in our experiment is consistent in its coordinates with the Seyfert Galaxy NGC 1275. The results obtained at high and ultrahigh energies are necessary to understand the radiation generation processes in the entire wide energy range.

Analysis of Total Ionizing Dose Effects on a Pseudo-Static Random Access Memory (PSRAM)

The purpose of this work is to describe the total ionizing dose effects on a commercial ISSI 4Mb pseudo-static random access memory (PSRAM). Experimental results from an irradiation test performed at the Ionizing Radiation Laboratory at Instituto de Estudos Avançados (LRI/IEAv) using a Co-60 gamma-radiation source were analyzed and compared to simulation results of typical memory circuits and typical memory architecture, in order to identify error patterns and failure mechanisms.

Gamma Irradiation Induced Degradation of Orange Peels

In this study, gamma irradiation induced degradation of orange peels (OP) was investigated. The lignocellulosic biomass degradation was carried out at doses of 0 (control), 600, 1800 and 3500 kGy using a Co-60 gamma radiation source. The samples were tested for total and reducing sugars. The concentrations of total sugars ranged from 0.530 g∙g−1 in control sample to 0.382 g∙g−1 of dry weight in the sample which received the highest radiation dose. The reducing sugars content varying from 0.018 to 0.184 g∙g−1 of dry weight with the largest rise occurring in the sample irradiated at 3500 kGy. The concentrations of sucrose, glucose and fructose were determined. The changes generated in physico-chemical properties were determined by Fourier Transform Infrared Spectroscopy (FTIR) and termogravimetric analysis (TG-DTG). The results show that OP was affected, but not significantly, which suggests that lignocellulose and sugars profiles were partially degraded after gamma irradiation.