Γ-ray Irradiation Research Articles

Influence of Ambient Light on the Radiation-Induced Attenuation of Germanosilicate Optical Fibers in the Visible and Near-Infrared Domains

We investigated the influence of the ambient light on the Radiation-Induced Attenuation (RIA) of Ge-doped optical fibers measured at the telecommunication wavelengths when exposed to a <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">60</sup> Co source, and in the visible and Near-InfraRed (NIR) domains when exposed to X-rays. From our results, it is possible to observe that this class of optical fibers are sensitive to the ambient light. Indeed, in all cases, their RIA value changes depending on the illumination conditions. In particular, the γ-ray irradiations revealed jumps in the measured RIA when changing the lamp of the irradiation chamber, whereas the X-ray irradiations reported that the relative photobleaching effect caused by the ambient light increases with the wavelength, up to ~1300 nm. The spectral study revealed no direct correlation between the absorption bands of the known Ge-related point defects and the external photobleaching phenomenon.

Effect of Recombinant Human Thrombopoietin (rhTPO) on Long-term Hematopoietic Recovery in Mice with Acute Radiation Sickness and Relative Mechanism

To investigate the effect and relative mechanism of Recombinant Human Thrombopoietin (rhTPO) on long-term hematopoietic recovery in mice with acute radiation sickness. Mice were intramuscularly injected with rhTPO (100 μg/kg) 2 hours after total body irradiation with 60Co γ-rays (6.5 Gy). Moreover, six months after irradiation, peripheral blood, hematopoietic stem cells (HSC) ratio, competitive transplantation survival rate and chimerization rate, senescence rate of c-kit+ HSC, and p16 and p38 mRNA expression of c-kit+ HSC were detected. Six months after 6.5 Gy γ-ray irradiation, there were no differences in peripheral blood white blood cells, red blood cells, platelets, neutrophils and bone marrow nucleated cells in normal group, irradiated group and rhTPO group (P>0.05). The proportion of hematopoietic stem cells and multipotent progenitor cells in mice of irradiated group was significantly decreased after irradiation (P<0.05), but there was no significant changes in rhTPO group (P>0.05). The counts of CFU-MK and BFU-E in irradiated group were significantly lower than that in normal group, and rhTPO group was higher than that of the irradiated group(P<0.05). The 70 day survival rate of recipient mice in normal group and rhTPO group was 100%, and all mice died in irradiation group. The senescence positive rates of c-kit+ HSC in normal group, irradiation group and rhTPO group were 6.11%, 9.54% and 6.01%, respectively (P<0.01). Compared with the normal group, the p16 and p38 mRNA expression of c-kit+ HSC in the irradiated mice were significantly increased (P<0.01), and it was markedly decreased after rhTPO administration (P<0.01). The hematopoietic function of mice is still decreased 6 months after 6.5 Gy γ-ray irradiation, suggesting that there may be long-term damage. High-dose administration of rhTPO in the treatment of acute radiation sickness can reduce the senescence of HSC through p38-p16 pathway and improve the long-term damage of hematopoietic function in mice with acute radiation sickness.

Feasibility and equivalence analysis of transient dose rate effect simulation by pulsed laser in level-shifting transceiver and TCAD simulation on its ESD circuits

Compared to linear accelerators, pulsed lasers have the characteristics of high efficiency, low cost, stable pulse output, and low environment interference for researching the transient dose rate effect (TDRE) on semiconductor devices. In this paper, pulsed laser radiation experiments are performed on a level-shifting transceiver. The experimental results are consistent with the results of the transient γ-ray radiation experiment, demonstrating the feasibility of using the pulsed laser in TDRE research on the level-shifting transceiver. This paper obtains theoretical and experimental conversion factors (CFs) through theoretical analysis and equivalency of the peak photocurrents, which are measured in pulsed laser and transient γ-ray radiation experiments. The CF results from the two approaches are within 7% of each other. In pulsed laser radiation experiments, an uncommon phenomenon is found. At the I/O (Input/Output) ports of the level-shifting transceiver, a trend of a positive photocurrent followed by a negative pulse is observed. A hypothesis is proposed that this photocurrent is produced by the turn-on and turn-off of the parasitic PNP (Positive-Negative-Positive) transistors in electrostatic discharge circuits at the level-shifting transceiver I/O ports. In addition, this hypothesis is verified by TCAD (Technology Computer Aided Design) simulations.

Optical spectroscopy assessment of the impact of γ-ray irradiation on Gd3+-doped phosphate glass

The effects of γ-ray irradiation (10, 100 kGy) on Gd3+-doped phosphate glass were evaluated. Glass irradiated at 100 kGy was characterized alongside the pristine by differential scanning calorimetry, Fourier transform-infrared spectroscopy and Raman scattering, wherein a lack of alteration in thermal and structural properties was supported. Yet, absorption bands developed around 500 nm with γ-ray dose indicating phosphorus oxygen hole center defects. Optical band gap and Urbach energies exhibited decreasing and increasing trends, respectively, reflecting the influence of trapped electrons and increased disorder/defects. By exciting γ-irradiated samples at 265 nm, blue radio-photoluminescence was observed where intensity increased with dose. Decay curves measured monitoring 415 nm emission showed first-order kinetics suggested to arise from phosphorus electron centers. Emission from Gd3+ was quenched with gamma-ray dose while the 6P7/2 emitting state lifetimes decreased. Correlations between Gd3+ emission intensities and lifetimes with optical band gaps suggest electron center defects perform as ‘energy sinks’.

Comparison of the dosimetric response of two Sr salts irradiated with 60Co γ-rays and synchrotron X-rays at ultra-high dose rate

As part of the development of innovative radiotherapy techniques using X-ray synchrotron sources, namely FLASH-radiotherapy and microbeam radiation therapy (MRT), two rod dosimeters based on strontium sulfate (SrSO4) and strontium carbonate (SrCO3) were developed and irradiated at the ESRF-ID17 Biomedical beamline to investigate new solid-state dosimeters.The radiation-induced defect in Sr-based dosimeters was detected by means of an electron paramagnetic resonance (EPR) spectrometer. For the study, the EPR response of the dosimeters irradiated with synchrotron X-rays in the 30–600 keV range and dose rate of 11.6 kGy/s was compared with the response after irradiation with a 60Co γ-ray source with a dose rate of 0.288 Gy/s.Both Sr dosimeters show an increased intensity of the EPR signal in the case of irradiation at the synchrotron with respect to the case of 60Co γ-ray irradiation. The measured enhancement of the delivered dose is explained by the fact that Sr shows an increased photoelectric interaction at orthovoltage X-ray energies, producing an increased number of free radicals.The experimental relative response rESRF of the EPR signals between samples irradiated at the ID17 beamline and the 60Co beam quality was found to be 9.66 for SrSO4 and 11.19 for SrCO3. Meanwhile, the theoritical relative responses rμen/ρESRF calculated as the ratio of mass energy absorption coefficients (μen/ρ) of the dosimeters to that for water at the ID17 with respect to the 60Co beam was found to be 11.85 for SrSO4 and 13.31 for SrCO3.The increased EPR response of Sr salt dosimeters irradiated with photons in the keV range proved that these detectors type could be a good candidate for the development of very sensible detectors for radiotherapy applications.

The sex pheromone heptacosane enhances the mating competitiveness of sterile Aedes aegypti males

BackgroundAedes aegypti is a vector that transmits various viral diseases, including dengue and Zika. The radiation-based sterile insect technique (SIT) has a limited effect on mosquito control because of the difficulty in irradiating males without reducing their mating competitiveness. In this study, the insect sex pheromone heptacosane was applied to Ae. aegypti males to investigate whether it could enhance the mating competitiveness of irradiated males.MethodsHeptacosane was smeared on the abdomens of Ae. aegypti males that were allowed to mate with untreated virgin females. The insemination rate was used to assess the attractiveness of heptacosane-treated males to females. The pupae were irradiated with different doses of X-rays and γ-rays, and the emergence, survival time, egg number, and hatch rate were detected to find the optimal dose of X-ray and γ-ray radiation. The males irradiated at the optimal dose were smeared with heptacosane, released in different ratios with untreated males, and mated with females. The effect of heptacosane on the mating competitiveness of irradiated mosquitoes was then evaluated by the hatch rate, induced sterility, and mating competitiveness index.ResultsApplying heptacosane to Ae. aegypti males significantly increased the insemination rate of females by 20%. Pupal radiation did not affect egg number but significantly reduced survival time and hatch rate. The emergence of the pupae was not affected by X-ray radiation but was affected by γ-ray radiation. Pupae exposed to 60 Gy X-rays and 40 Gy γ-rays were selected for subsequent experiments. After 60 Gy X-ray irradiation or 40 Gy γ-ray irradiation, the average hatch rate was less than 0.1%, and the average survival time was more than 15 days. Moreover, at the same release ratio, the hatch rate of the irradiated group perfumed with heptacosane was lower than that of the group without heptacosane. Conversely, the male sterility and male mating competitiveness index were significantly increased due to the use of heptacosane.ConclusionsThe sex pheromone heptacosane enhanced the interaction between Ae. aegypti males and females. Perfuming males irradiated by X-rays or γ-rays with heptacosane led to a significant increase in mating competitiveness. This study provided a new idea for improving the application effect of SIT.Graphical

An effective way to control the radical reaction and its mechanism in EPDM under γ-ray irradiation

The effects of a compound that contains a xanthate group named DIP on the radical reactions and structural evolution of the ethylene propylene diene monomer (EPDM) were investigated. It was found that the structural evolution and long-term stability of the EPDM can be realized by controlling the radical reaction in the matrixes of EPDM during γ-ray irradiation. The results show that the DIP can prevent EPDM deterioration, when the γ-ray irradiation dose reaches 450 kGy, the retention rate of the elongation at break and tensile strength of the EPDM samples containing 1 wt% DIP could remain about 90% and 160%, while those of additive-free EPDM are only about 33% and 70%. On the other hand, the thermal stability of the EPDM samples decreases markedly with the dose increasing under γ-ray irradiation. However, the thermal decomposition temperature of the EPDM samples containing DIP remains basically unchanged after irradiation, and DIP can also improve the oxidation resistance of the EPDM. Electron spin resonance studies reveal that DIP can effectively control the radical reactions inside the EPDM during γ-ray irradiation. Rheology results show that the structural evolution of the EPDM can be well controlled under γ-ray irradiation owing to the presence of DIP in the EPDM matrixes. Density functional theory calculations indicate that the reversible radical reactions inside EPDM/DIP systems are crucial in realizing the long-term stability and controllable structural evolution of the EPDM under γ-ray irradiation.

Study on the enzymatic hydrolysis performances of carbohydrates, proteins and oils after γ-ray irradiation

Study on the enzymatic hydrolysis performances of carbohydrates, proteins and oils after γ-ray irradiation

Mechanisms of the Device Property Alteration Generated by the Proton Irradiation in GaN-Based MIS-HEMTs Using Extremely Thin Gate Insulator

Recently, we reported that device performance degradation mechanisms, which are generated by the γ-ray irradiation in GaN-based metal-insulator-semiconductor high electron mobility transistors (MIS-HEMTs), use extremely thin gate insulators. When the γ-ray was radiated, the total ionizing dose (TID) effects were generated and the device performance deteriorated. In this work, we investigated the device property alteration and its mechanisms, which were caused by the proton irradiation in GaN-based MIS-HEMTs for the 5 nm-thick Si3N4 and HfO2 gate insulator. The device property, such as threshold voltage, drain current, and transconductance varied by the proton irradiation. When the 5 nm-thick HfO2 layer was employed for the gate insulator, the threshold voltage shift was larger than that of the 5 nm-thick Si3N4 gate insulator, despite the HfO2 gate insulator exhibiting better radiation resistance compared to the Si3N4 gate insulator. On the other hand, the drain current and transconductance degradation were less for the 5 nm-thick HfO2 gate insulator. Unlike the γ-ray irradiation, our systematic research included pulse-mode stress measurements and carrier mobility extraction and revealed that the TID and displacement damage (DD) effects were simultaneously generated by the proton irradiation in GaN-based MIS-HEMTs. The degree of the device property alteration was determined by the competition or superposition of the TID and DD effects for the threshold voltage shift and drain current and transconductance deterioration, respectively. The device property alteration was diminished due to the reduction of the linear energy transfer with increasing irradiated proton energy. We also studied the frequency performance degradation that corresponded to the irradiated proton energy in GaN-based MIS-HEMTs using an extremely thin gate insulator.

Radiolytic Water Splitting Sensitized by Nanoscale Metal-Organic Frameworks.

High-energy radiation that is compatible with renewable energy sources enables direct H2 production from water for fuels; however, the challenge is to convert it as efficiently as possible, and the existing strategies have limited success. Herein, we report the use of Zr/Hf-based nanoscale UiO-66 metal-organic frameworks as highly effective and stable radiation sensitizers for purified and natural water splitting under γ-ray irradiation. Scavenging and pulse radiolysis experiments with Monte Carlo simulations show that the combination of 3D arrays of ultrasmall metal-oxo clusters and high porosity affords unprecedented effective scattering between secondary electrons and confined water, generating increased precursors of solvated electrons and excited states of water, which are the main species responsible for H2 production enhancement. The use of a small quantity (<80 mmol/L) of UiO-66-Hf-OH can achieve a γ-rays-to-hydrogen conversion efficiency exceeding 10% that significantly outperforms Zr-/Hf-oxide nanoparticles and the existing radiolytic H2 promoters. Our work highlights the feasibility and merit of MOF-assisted radiolytic water splitting and promises a competitive method for creating a green H2 economy.

Radiation-induced scintillation properties of Ce-doped lutetium aluminosilicate glasses doped with cerium prepared by using a xenon image furnace

Ce-doped Lu2O3–Al2O3–SiO2 glasses were prepared using a xenon image furnace and their physical, optical, and scintillation properties were investigated. The photoluminescence (PL) properties were discussed based on the variations in the coordination environment of the different glass compositions. The characteristic shifts of PL spectra were explained in terms of (i) effects of crystal field due to the presence of different coordination environments which Ce3+ can take and (ii) effects of self-absorption due to the increase in Ce4+ based on the results of Raman spectra, transmission spectra, and PL lifetimes. The PL quantum yield (QY) tends to be higher for specimens with the emission peak located on the relatively shorter wavelength side, i.e., those with significant Ce3+ in the 6-coordinated environment and low Ce4+ content. This tendency also affects scintillation properties, with both scintillation spectral intensity and light yield under γ-ray irradiation showing characteristics that correlate positively with PL QY.

Raman and optical spectroscopy study of iron-bearing bio-relevant phosphate glasses: Assessment of γ-ray irradiation effects

Glasses with 50P2O5-30CaO-(20 – x)Na2O-xFe2O3 (x = 0.1, 1, 5, 10 mol%) compositions were prepared by melting, and characterized by X-ray diffraction, Raman scattering, and optical spectroscopy. The glasses were subjected to γ-ray irradiation and structural and optical properties evaluated via Raman, absorption, and photoluminescence spectroscopy. The pristine glasses were X-ray amorphous, whereas Raman spectroscopy indicated Fe2O3 depolymerizes glass structure. Absorption spectroscopy showed that iron occurred largely as Fe3+ with Fe2+ revealed at high iron contents. Following γ-ray irradiation, the Raman features were preserved supporting lack of structural alteration. Radiation-induced defects were detected optically for 0.1 mol% Fe2O3 but prevented at higher concentrations. Bluish luminescence ascribed to electron centers was detected under 265 nm excitation for 0.1 mol% Fe2O3 similar to the irradiated host exhibiting ms-scale decay. The optical properties of γ-irradiated glasses at higher iron contents were like the pristine, supporting an increase in glass network resistance against gamma radiation.

Effect of nano-Ag proportion on the structure of Ag– TiO2–Bi2WO6 photocatalyst and its antibacterial property on Escherichia coli

In this study, TiO2–Bi2WO6 (TB) heterojunctions were synthesized by solvothermal method, nano-Ag was reduced by γ-ray irradiation, and a series of Ag–TiO2–Bi2WO6 (ATB) composite photocatalysts with different nano-Ag usage were constructed by chemical deposition and freeze-dried. The microstructure, crystalline phase composition, chemical composition, and light absorption properties of ATB were characterized, and its photocatalytic bacterial inhibition performance was analyzed against Escherichia coli. The results showed that the proportion of nano-Ag significantly improved the photocatalytic inhibition performance of ATB against E. coli, and the highest inhibition rate of ATB against E. coli (52.5%) was achieved when the Ag proportion was 15%, which was 2.5 times higher than that of TB. The improved photocatalytic inhibition performance of ATB was attributed to the combination of the interlaced heterostructure, SPR effect, and Schottky barriers, which narrowed the forbidden bandwidth, promoted the separation of electron-hole pairs, and generated a large number of reactive radicals such as h+, •O2-, and •OH under visible light. Influenced by this, the microbial cell structure was broken and inducted into the E. coli apoptosis. The results provided a novel photocatalyst in photocatalytic antibacterial research.

Effect of Trapped Charge Induced by Total Ionizing Dose Radiation on the Top-Gate Carbon Nanotube Field Effect Transistors

The excellent performance and radiation-hardness potential of carbon nanotube (CNT) field effect transistors (CNTFETs) have attracted wide attention. However, top-gate structure CNTFETs, which are often used to make high-performance devices, have not been studied enough. In this paper, the total ionizing dose (TID) effect of the top-gate structure CNTFETs and the influence of the substrate on top-gate during irradiation are studied. The parameter degradation caused by the irradiation- and radiation-damage mechanisms of the top-gate P-type CNTFET were obtained by performing a Co-60 γ-ray irradiation test. The results indicate that the transfer curves of the top-gate P-type CNTFETs shift negatively, the threshold voltage and the transconductance decrease when TID increases, and the subthreshold swing decreases first and then increases with the increase in TID. The back-gate transistor is constructed by using the substrate as a back-gate, and the influence of back-gate bias on the characteristics of the top-gate transistor is tested. We also test the influence of TID irradiation on the characteristics of back-gate transistors, and reveal the effect of trapped charge introduced by radiation on the characteristics of top-gate transistors. In addition, the CNTFETs that we used have obvious hysteresis characteristics. After irradiation, the radiation-induced trapped charges generated in oxide and the OH groups generated by ionization of the CNT adsorbates aggravate the hysteresis characteristics of CNTFET, and the hysteresis window increases with the increase in TID.

Simulation of a ring oscillator operation during γ-ray irradiation using the TID response model of MOSFETs and its experimental verification

The response of N-type MOSFET characteristics to TID (Total Ionizing Dose) effects caused by γ-ray irradiation was modeled as a sum of two exponential functions which expresses the charge accumulation of the oxide traps and the interface traps respectively. This model was applied to the circuit simulation of a ring oscillator operation. It was shown that the simulation result reproduces the variation in the measured oscillation frequency experimentally. The simulation also showed that there is an optimum size ratio between N-type MOSFET and P-type MOSFET which can minimize the variation in oscillation frequency due to TID effects. These obtained results verified that the proposed method can be applied to the prediction of response in a dynamic operation circuit to TID effects.

Development of Tl-doped KI single crystal scintillators

Tl-doped (0.1, 0.3, 1, and 3%) KI single crystals were synthesized, and photoluminescence and scintillation characteristics of KI:Tl were evaluated. An emission peak at ∼420 nm was observed under ∼300 nm excitation in all the samples. All the synthesized samples exhibited a peak at 420–440 nm and a tail emission at ∼350 nm under X-ray irradiation. These origins would be 3P1→1S0 transitions of Tl+ (420–440 nm) and the off-center configuration of the self-trapped excitons (∼350 nm), respectively. According to pulse height spectra under γ-ray irradiation, scintillation light yield (LY) and the energy response were investigated. The 0.3% KI:Tl showed the highest LY of 7,300 photons/MeV among the prepared samples and ∼11% energy resolution under 137Cs γ-ray (662 keV) irradiation. The energy response of the 0.3% KI:Tl illustrated a good linearity against γ-ray energies from 22 to 1,408 keV.

Experimental investigation into impacts of neutron irradiation on pMOS dosimeter behaviors

The p-channel metal–oxide–semiconductor (pMOS) transistor is a frequently used dosimeter for ionizing radiation, such as γ-rays, since its threshold voltage changes (ΔVth) in proportion to the ionization dose. When a pMOS is subjected to γ-ray and neutron radiation fields, the neutrons can influence the ΔVth response to γ-rays. Individual cobalt-60 γ-ray irradiation and sequential irradiation by fission neutrons and subsequent cobalt-60 γ-rays are used to explore the neutron-induced impacts. Experiments show that preceding neutron irradiation can reduce γ-ray sensitivity of ΔVth while accelerating the recovery of ΔVth during the post-γ-irradiation annealing. Additionally, the component of ΔVth induced by oxide charges (ΔVox) is separated from that induced by interface traps as determined by mid-gap tests. This proves that the neutron sensitivity of ΔVox accounts for that of ΔVth. According to nuclear collision theory, this work suggests that the electronic loss of neutrons rather than the nuclear loss dominates the neutron-induced influences on ΔVth.

Enhancement of optical absorption and dispersion characteristics of nanocrystalline In2Se3 films: impact of γ-ray irradiation

Thermal evaporation was used to deposit In2Se3 thin films with a thickness of 276 nm on different glass and quartz substrates under vacuum. The 60Co rays were used to irradiate thin films at dosages of 10, 20, 30, 40, and 50) kGy. X-ray Diffraction (XRD) and scanning electron microscopy (SEM) were used to investigate the crystalline and morphological structure of In2Se3 thin films, respectively. The results revealed that powder has a polycrystalline structure, whereas pristine and irradiated thin films are amorphous. The computed absorption coefficient indicates that direct transition is allowed for the as-deposited and γ-irradiated thin films, and the value of the measured energy gaps increases when the dose is increased from 10 to 50 kGy. Using single-oscillator models to obtain the dispersion parameters, the spectral dependency of the refractive index in the higher wavelength area was studied. The effect of irradiation on dielectric constants and dispersion characteristics suggests that the examined films are highly sensitive to appropriate irradiation dose. The nonlinear optical susceptibility has improved, making it appropriate for a variety of device applications.

Fabrication and scintillation properties of a flexible optical-guiding crystal scintillator

Scintillation properties of a flexible optical-guiding crystal scintillator with a thallium-doped CsI (Tl:CsI) crystal and borosilicate glass as the core and cladding, respectively, are reported. The as-fabricated optical-guiding crystal scintillator exhibits a light yield of 31,000 photons MeV−1 under 662 keV γ-ray irradiation. The recrystallized sample is transparent and provides a higher light yield of 54,000 photons MeV–1, which is comparable to that of single-crystal Tl:CsI. The decay times are 400 ns (28%) and 1,350 ns (72%). This material can serve as a scintillator fiber with high sensitivity to γ- and X-rays, high light yield, and energy discrimination.

Study of bias-induced total ionizing dose radiation damage mechanism in SiC MOSFETs

γ-ray irradiation experiments are conducted at different biases to investigate the differences in total ionizing dose damage of SiC MOSFET by the I-V and Split C-V curves. Combined with TCAD simulation, it is found that the total ionizing dose effect at different biases can generate positive charges at different locations in the oxide. For gate and motor-drive bias, the charges are uniformly located in the SiO2 layer, causing a negative shift of the C-V and I-V curves. For drain bias, charges are mainly in the JFET oxide due to the inhomogeneous distribution of the electric field in the oxide, resulting in a change in the shape of the C-V curve. The results further deepen our understanding of the radiation damage mechanism of SiC power MOSFETs.