Radiation-induced Electrical Conductivity Research Articles

Dual electrical and optical detection of ionizing radiation: Radiation-induced currents and radioluminescence in NaMgF3:Sm

Simultaneous optical and electrical detection of ionizing radiation was achieved using near tissue-equivalent NaMgF3:Sm. The electrical characteristics of the system were capacitive and ohmic and the resistivity of the compound was on the order of 1013 Ω cm. During exposure to X-rays, the compound exhibited both radiation-induced electrical conductivity and radioluminescence from Sm2+ and Sm3+. Initially, strong dose history dependences were observed for both detection methods. The radiation-induced current stabilized after a priming dose and increased with dose rate according to a power law with an exponent Δ = 0.73, and the radioluminescence intensities increased linearly with dose rate. The mobility-lifetime product of the dominant charge carriers was high and estimated to be 1.6 × 10−4 cm2/V. Our results show that dual detection of ionizing radiation is possible using NaMgF3:Sm where the minimum detectable dose rates were 46 μGys−1 and 1.5 mGys−1 for the electrical and optical detection techniques, respectively.

Particle size effect of silica gel on the ɤ-radiation induced electrical conductivity of urea aqueous solutions

Different concentrations (0.1, 3, 6 M) of urea aqueous Solutions (UAS) have been irradiated with 60Co- ɤ-rays in the presence of silica gel (SG) with different particle size (0.1-0.5mm) at room temperature. The radiation induced electrical conductivity (RIC) of the irradiated solutions was measured. The RIC values of the 0.1 M solutions increase as the particle size of SG decreases i.e., the particle surface area increases. This observation points to a radiation induced chemical reactions, which are catalyzed by SG. These reactions, probably, yield products, which increase the RIC such as urea peroxide (UP). On the other hand, different behavior was observed in the case of 3, 6 M solutions, where, the RIC increases as particle size increase. So, the mechanism of production of the species which increase the RIC of 0.1 M samples is different than that in the case of 3, 6 M. In all irradiated samples the pH values tend to increase slightly as particle size increases. A mechanism was proposed to explain the obtained data.

Effect of Silica Gel on the Electrical Conductivity of ɤ- Irradiated Pure Water: A Radiation Chemical Study

EFFECTS of silica gel (SG) and its particle size on the radiation-induced electrical conductivity (RIC) and pH of pure water were studied. RIC of pure water in the absence of SG increases as absorbed dose increases. In the presence of SG the values of the RIC are higher than the corresponding values in the absence of SG up to 12.28kGy, which reflects the induced catalytic effect of irradiated SG. Moreover, the particle size of SG seems to affect the RIC of water. Therefore, as the particle size decreases, the RIC increases (below18.99kGy). Also, it was observed that the pH values decrease as the RIC increases and vice versa. The RIC and variation of pH in the studied samples are related to the radiation induced formation of H2O2 and H3O2+. The induced catalytic effect of SG is related to the radiation-induced formation of electron/ +ve hole (e/ h+) pair during ɤ-radiolysis of SG. Therefore, the RIC increases (pH values decrease) as particle size of SG decreases (surface area increases).

Plasma Radiation-Induced Electrical Conductivity of Water

Plasma Radiation-Induced Electrical Conductivity of Water

Radiation-Induced Electrical Conductivity of Nanocomposite Materials

The radiation-induced conductivity of a nanocomposite with the inclusion of spherical nanoparticles as a function of intensity and time of action of gamma-radiation and the concentration and size of inclusions has been studied using the Rose–Fowler–Weisberg model. The energy spectrum of localized states associated with the nanoparticle inclusion has been determined. The numerical experiments have been made for polymethyl methacrylate (PMMA) nanocomposites with inclusion of CdS and α-Al2O3 nanoparticles as well as SrO nanoparticles.

Japanese activities of the R&D on silicon carbide composites in the broader approach period and beyond

The R&D on SiC/SiC composites under the broader approach (BA) activities between Japan and the EU for fusion DEMO developed a fundamental database of mechanical (Task-1) and physical/chemical (Task-2) properties, with a primary target of the application of SiC/SiC composites as functional structure to be used in the dual coolant breeding blanket concept. This paper aims to summarize previous 10-years activities of the R&D of Japan and to provide the key deliverables toward the DEMO design. In Task-1, good creep and fatigue durability were first demonstrated. Besides, in-plane and inter-laminar strength anisotropy maps at elevated temperatures were comprehensively identified. In parallel, the irradiation effects of SiC materials were specifically determined as input parameters of the analytical model to provide for the irradiation-induced residual stresses. In Task-2, the apparent dose-dependence of the radiation-induced electrical conductivity and the indicative radiation-induced electrical degradation was identified by various irradiation sources. In addition, good gas confinement was identified. Furthermore, no accelerated corrosion for duration of 3000 h at below 1173 K was first demonstrated. With these achievements, it is suggested that the in-vessel component technology, e.g., material corrosion database development, activated corrosion product evaluation code development, compact module tests for validation of the key functions of the components, technology integration assessment for fusion nuclear tests, etc., should be further developed toward DEMO in near-term.

Using Rouse-Fowler model to describe radiation-induced electrical conductivity of nanocomposite materials

Using the Rouse-Fowler (RF) model this work studies the radiation-induced electrical conductivity of a polymer nanocomposite material with spherical nanoparticles against the intensity and exposure time of gamma-ray, concentration and size of nanoparticles. The research has found the energy distribution of localized statesinduced by nanoparticles. The studies were conducted on polymethylmethacrylate (PMMA) with CdS nanoparticles.

Pulsed radiation-induced conductivity of polymers in strong electric fields

A theoretical analysis of the nonlinear field dependence of the pulsed radiation-induced conductivity of polystyrene in strong electric fields is performed. An explanation of the previously uncomprehended phenomenon of the sharp increase in the radiation-induced electrical conductivity in the presence of an electric field with a strength of above 5 × 107 V/m is proposed. This behavior cannot be explained within the framework of Onsager’s theory of the field-assisted thermal production of free charges from generated geminate pairs.

Electrical effects in propellant compositions radiated by electrons

Radiation-induced electrical conductivity of composite and ballistite solid propellants under pulsed (2.5 · 10−6 sec) and continuous (1–100 sec) radiation by a flux of fast electrons is studied. Conditions for the development of an electrical breakdown during electron radiation are determined, and the relation between this phenomenon and the composition of the composite propellant is considered. For the ballistite propellant, radiation-induced conductivity is studied both in the highly elastic and in the vitreous state. Based on experimental results, the parameters of a semi-empirical model of radiation-induced conductivity are determined for both types of propellants.

Effect of pressure on the radiation induced electrical conductivity of NBI insulator gases

A study of the effect of pressure on the radiation induced electrical conductivity (RIC) of candidate international thermonuclear experimental reactor (ITER) neutral beam injectors (NBI) insulation gases has been carried out. Large volume, pressure and voltage values similar to those for the ITER system are not readily achievable experimentally. To overcome this problem different experiments have been performed in a Van de Graaff electron accelerator at lower values and the results compared with a theoretical model. Excellent agreement is found between theoretical and experimental results allowing extrapolation to the higher voltage, gas volume and particularly higher gas pressure required in the ITER design. The results show that the use of high gas pressure to increase the voltage breakdown threshold and reduce size may also result in enhanced leakage current losses.

Kinetics of radiation-induced electrical conductivity of CsI crystals in strong electric fields

The kinetics of radiation-induced electrical conductivity (RIEC) of CsI crystals upon x-ray excitation is investigated as a function of the electric field strength and the temperature. It is demonstrated that the increase in electrical conductivity in a strong electric field is caused by the translation of electrons from trapping levels to the conduction band of the dielectric by a collision ionization mechanism.

Procedure for Measuring the Electrophysical Characteristics and Kinetics of Electronegative Gas

The experimental procedure and basic processes affecting the dynamics of radiation-induced electrical conductivity in electronegative (SF6) gas are analyzed. It is demonstrated that in the range of SF6 gas pressure from 10 to 100 torr the measurement error of this procedure does not exceed 10%.

Investigation of the Electrophysical Characteristics of SF6Gas: Obtained Results

The radiation-induced electrical conductivity of SF6gas is experimentally investigated at different pressures. The dependences of the coefficient of attachment of electrons to SF6molecules on the E / Nratio are determined. The obtained results are compared with the results of numerical calculation by the Monte Carlo method and with the data of other authors.

Spectroscopic Investigation of Onset and Enhancement of Electrical Conductivity in PVC/PANI Composites and Blends by γ-ray or UV Irradiation

Electrical conductivity of blends and composites of poly(vinyl chloride) (PVC) with nonconducting polyaniline (PANI) increases when they are subjected to γ-rays or UV radiation. This is attributed to a radiation-induced dehydrochlorination (loss of HCl) of PVC, which in turn oxidizes (dopes) PANI within the PVC matrix causing the increase in electrical conductivity of these films. XPS, UV−vis−NIR and FTIR spectroscopic methods are used to characterize and verify this novel process. After the films are subjected to γ-rays (or UV radiation) the intensities in the XPS spectra of both −N+− and Cl- peaks increase, confirming the increase in charged species within the PVC matrix. Similar observations attributable to radiation-induced electrical conductivity are also observed in both the UV−vis−NIR and FTIR spectra. This radiation-induced conductivity can also be reversed to some extent by further exposing the films to NH3 vapors, where the oxidized centers are partially reduced (undoped). Several UV/NH3/UV cycles can be performed without much loss in conductivity- and/or conductivity-related spectroscopic features. The onset of the photoinduced conductivity both in PVC-only and PVC/PANI composite films is determined to be 300 nm (4.1 eV), which coincides with the first UV absorption band of PVC.

Radiation-induced electrical conductivity in aluminium nitride ceramic

The electrical conductivity of aluminium nitride ceramics, doped with 8 wt% Y 3O 3 and obtained from fine raw powders synthesized in plasma, was measured with and without gamma-neutron irradiation (the maximum fast neutron flux was 3×10 15 n/m 2 s and in the gamma-dose rate range of 10 3–10 6 Gy/h) in the temperature range of 40–400°C. The electrical conductivity at room temperature was 10 −12 S/m and temperature-induced increase of conductivity has an activation energy of 1.06 eV at a temperature range of above 160°C. Radiation-induced conductivity obeys the usual power law dependence on gamma-ray dose rate. The electrical conductivity at high dose rate is less than 10 −6 S/m and is little dependent on temperature.

The effect of ionizing and displacive radiation on the thermal conductivity of alumina at low temperature

The effects of radiation-produced vacancies and of radiation-induced electrical conductivity (RIC) on the thermal conductivity of alumina at low temperatures have been calculated. The phonon scattering relaxation times for these mechanisms have been used in the evaluation of the thermal conductivity integral in order to determine the effect each mechanism has on the lattice thermal conductivity of alumina. It is found that vacancy scattering can significantly reduce the thermal conductivity; for example, a vacancy concentration of 0.01 per atom leads to a fractional change in thermal conductivity of about 90%. It is also concluded that the scattering of phonons by electrons in the conduction band due to RIC does not lead to a large reduction in the thermal conductivity.

Mobility of charge carriers in disordered dielectrics

We compare experimental data on the mobility of holes (the majority charge carriers) in polyepoxy-propylcarbazole, measured using the time-of-flight technique (drift mobility) and the nonsteady-state radiation-induced electrical conductivity method (effective mobility). We show that these two quantities are quite different in the dispersive transport regime; and while the second quantity is a characteristic of the material, the first quantity depends in a complicated fashion on the ratio of the electric field strength to the sample thickness. The “untreated” data on drift mobility measurements using the time-of-flight technique do not have direct physical meaning and cannot be compared with the conclusions of modern microscopic theories of the mobility of charge carriers in disordered matrices.

Effect of gamma-ray irradiation on in-situ electrical conductivity of ZrO 2-10 mol% Gd 2O 3 single crystal at elevated temperatures

Change of electrical conductivity with irradiation of 60Co gamma rays was investigated on ZrO 2-10 mol% Gd 2O 3 single crystal at 623, 723, and 823 K in vacuum. Conductivity increased gradually with irradiation time, while activation energy remained invariant. The increment of in-situ conductivity was attributed to the creation of oxygen vacancies introduced by the formation of Frenkel defects that were produced by the bombardments of Compton electrons. These increased oxygen vacancies were responsible for the radiation induced electrical conductivity (RIC) of the material and their contribution to RIC continued until they recombine with oxygen interstitials.

Radiation-induced electrical conductivity in MgAl 2O 4 spinel

The dc electrical conductivity of high purity, polycrystalline MgAl 2O 4 spinel of 99.5% theoretical density has been measured during irradiation by 18 MeV protons at reactor relevant ionization dose rates. The radiation-induced conductivity (RIC) at 200°C varied in a slightly sub-linear manner with dose rate. At temperatures between 250–350°C the RIC varied in a complex manner with the dose rate dependence being itself dose rate dependent. At higher temperatures the RIC reverted to an essentially linear variation with dose rate. The complex dose rate dependence is ascribed to the magnesium vacancy concentration introduced by the small Al 2O 3 excess ( MgO: Al 2 O 3 = 1:1.05) and the presence of anti-structure defects producing large concentrations of intrinsic electron and hole traps. There was no evidence that the accumulation of radiation damage influenced the details of radiation-induced conductivity and MgAl 2O 4 retained reasonable insulating properties at the highest dose rate and temperature.

Dose rate dependence of the radiation-induced electrical conductivity in MgO

The radiation-induced electrical conductivity (RIC), has been measured for single crystal MgO at dose rates between 10 2 and 10 7 Gy h −1 and temperatures from 14 to 450°C. A correlation is observed between the RIC dose rate dependence, and the thermal stability of well defined electron and hole traps, in agreement with the model of Klaffky et al. The dose rate dependence factor is observed not to be constant, but to depend on dose rate. The possible effects of displacement damage and radiation induced impurity diffusion are noted.