Effect Of High Energy Electrons Research Articles

Effects of high energy electrons on electron temperature measurements of asymmetric double Langmuir probes

In this work, electron temperature was measured with both the asymmetric double Langmuir probe (ADLP) and the single Langmuir probe to investigate the reliability of the ADLP on the electron temperature measurement in multi-temperature Maxwellian plasmas. A series of I–V traces of the ADLP were obtained at various plasma conditions with different area ratios and analyzed with different methods including conventional ADLP analysis and two-temperature Maxwellian fitting with results measured by a single planar Langmuir probe analyzed with three-temperature Maxwellian fitting as reference. The measured Te of the ADLP is found to reflect that of the temperature of the degraded primary electrons when the area ratio of the probe tips is close to ∼16 and approaches the real effective electron temperature as the area ratio increases to a value of ∼30% higher than that measured by a single Langmuir probe, which occurs even when the area ratio is higher than the flux ratio of electrons and ions entering their respective sheaths. This effect is consistent with the distortion effect of Langmuir probe I–V traces caused by the presence of hotter electron species, which was computationally reconstructed and agreed well with the experimental observations. This result implies that an area ratio, possibly ∼20 times much larger than what was conventionally assumed, is needed for an ADLP to be reliably treated as a single Langmuir probe in practical settings, where electron energy distribution functions of plasmas are generally expected to be multi-temperature Maxwellian. This effect is also analogous to the current balance between a single Langmuir probe and the device wall, implying that this effect would also affect the application of the single Langmuir probe in plasmas, where the ion loss to the device wall can be reduced, such as plasmas in miniaturized devices, strong magnetic fields, or a highly ion-neutral collisional environment.

Effect of high-energy electrons on the thermal, mechanical and fire safety properties of fire-retarded polypropylene nanocomposites

Fire-retarded nanocomposites (FRNC) based on polypropylene, clay and allylamine polyphosphate (PP-FRNC) was processed firstly. Effect of high-energy electrons on the thermal, mechanical and fire safety performances of PP-FRNC were then investigated systematically. After that the relevant fire safety mechanism of irradiated PP-FRNC was discussed. The thermal and mechanical properties of the irradiated PP-FRNC were increased by (electron beam) EB treatment at suitable dose, whereas these properties reduced by high-energy electrons because of the degradation or chain scission of polymer at higher dose. Moreover, the increase dose of EB treatment could improve the LOI values of PP-FRNC. Furthermore, EB treatment modified PP-FRNC improved better quality char residue, which effectively enhance fire safety of PP-FRNC. Particularly, the results suggest that EB treatment is a sustainable green and efficacious surface modification for heat and smoke suppressions rate of FRNC.

Polarization effect of Schottky-barrier CdTe semiconductor detectors after electron irradiation

Spectrometric properties of cadmium telluride (CdTe) radiation semiconductor detectors with Schottky-barrier contacts were studied after irradiation with a high energy electron beam of 5 MeV-energy. The total cumulative dose of 2.25 kGy was delivered stepwise and the response of detectors to 241Am radioisotope source was acquired using a standard spectrometric chain at reverse bias voltages of 300 V, 400 V and 500 V. To evaluate the radiation damage, the spectral parameters of the 59.5 keV-photopeak were determined, namely the peak position, the full width at half maximum (FWHM), the peak amplitude and the net peak area. The time evolution of these parameters was followed by recording the spectra in 30-seconds (or 2-minutes) intervals after applying the reverse bias voltages. The results demonstrated significant effect of high energy electrons on the spectral characteristics even after applying the lowest dose of 0.5 kGy. The shift of the photopeak to lower energies, the increase of the FWHM and decrease of the peak height and area were confirmed. The time evolution of the observed tendencies disclosed that electron irradiation results in earlier onset of the polarization mechanism. After irradiating with the highest dose of 2.25 kGy, the polarization effect occurs practically immediately after applying the bias voltage.

Product analysis and mechanism of toluene degradation by low temperature plasma with single dielectric barrier discharge

A single dielectric barrier discharge (DBD) low-temperature plasma reactor was set up, and toluene was selected as the representative substance for volatile organic compounds (VOCs), to study the reaction products and degradation mechanism of VOCs degradation by low-temperature plasma. Different parameters effect on the concentration of O3 and NOx during the degradation of toluene were studied. The exhaust in the process of toluene degradation was continuously detected and analyzed, and the degradation mechanism of toluene was explored. The results showed that the concentration of O3 increased with the increase of the power density and discharge voltage of the plasma device. However, as the initial concentration of toluene increased, the concentration of O3 basically keep steady. The concentration of NOx in the by-products increased with the discharge voltage, power density, and initial concentration of toluene in the plasma device, and the concentration of NO2 was much higher than the concentration of NO. The degradation process of toluene was detected and analyzed. The results showed that the degradation mechanism of toluene by plasma includes high energy electron bombardment reaction, active radical reaction and ion molecule reaction. Among them, the effect of high-energy electrons on toluene degradation is the largest, followed by the effect of free radicals, in which oxygen radicals participated in the reaction mainly through the formation of C–O bond, CO bond, (CO)–O– bond and –OH radical, while nitrogen radicals participate in the reaction mainly through the formation of C–NH2, (CNH)- bond, CN bond and C–NO2 bond. The results can provide some data supports for the study of low-temperature plasma degradation of VOCs.

The effect of electron irradiation on the properties of polyimide films of various grades

The physico-mechanical properties of PIAB polyimide film irradiated by high-energy electrons have been studied. Changes in the surfaces and chemical composition of PI under the influence of electron irradiation were studied. The effect of high-energy electrons on polyimides of various grades leads to significant changes in their deformation-strength characteristics and depends significantly on the structure and technology of material synthesis.

Microstructure evolution of polyimide films induced by electron beam irradiation-load coupling treatment

Polyimide films are widely used in space with extreme environments, where high energy beam irradiation and corresponding coupling treatment could occur. The combined effect of high energy electrons (1.2 MeV) and high tensile stress (50 MPa) on the degradation behavior of polyimide films was studied by means of scanning electron microscopy, atomic force microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and mechanical testing. The degradation of polyimide films was evaluated by analyzing the microstructure and mechanical properties. The results indicated that the external tensile stress and irradiation coupling treatment resulted in the breakage of a larger number of chemical bonds and greater deterioration of the surface quality when compared with the irradiated polyimide samples. After irradiation-load coupling treatment, numerous micro-cracks were formed on the polyimide surface, facilitating the diffusion of oxygen into polyimide films and thus increasing the probability of free radical reactions. Moreover, the coupling treatment led to a more significant decrease in tensile strength and elongation of polyimide films by 10% and 35%, respectively. The mechanism of molecular chains' scission and crosslinking as well as correlations between molecular chains and mechanical performances were discussed. The obtained results indicated that the external tensile stress accelerates the degradation process during electron beam irradiation; thus, the tensile stress potentially seriously deteriorates polyimide film properties in irradiated environments.

High energy electron sintering of icy regoliths: Formation of the PacMan thermal anomalies on the icy Saturnian moons

The so-called ‘PacMan’ features on the leading hemispheres of the icy Saturnian moons of Mimas, Tethys and Dione were initially identified as anomalous optical discolorations and subsequently shown to have greater thermal inertia than the surrounding regions. The shape of these regions matches calculated deposition contours of high energy plasma electrons moving opposite to the moon’s orbital direction, thus suggesting that electron interactions with the grains produce the observed anomalies. Here, descriptions of radiation-induced diffusion processes are given, and various sintering models are considered to calculate the rate of increase in the contact volume between grains in an icy regolith. Estimates of the characteristic sintering timescale, i.e. the time necessary for the thermal inertia to increase from that measured outside the anomalous regions to that within, are given for each of the moons. Since interplanetary dust particle (IDP) impact gardening and E-ring grain infall would be expected to mix the regolith and obscure the effects of high energy electrons, sintering rates are compared to rough estimates of the impact-induced resurfacing rates. Estimates of the sintering timescale determined by extrapolating laboratory measurements are below ∼0.03 Myr, while the regolith renewal timescales are larger than ∼0.1 Myr, thus indicating that irradiation by the high energy electrons should be sufficient to form stable thermal anomalies. More detailed models developed for sintering of spherical grains are able to account for the radiation-induced anomalies on Mimas and Tethys only if the regoliths on those bodies are relatively compact and composed of small (≲ 5 µm) grains or grain aggregates, and/or the grains are highly non-spherical with surface defect densities in the inter-grain contact regions that are much higher than expected for crystalline water ice grains at thermal equilibrium. These results are consistent with regolith thermal conductivity models which can only be reconciled with spacecraft observations if the contacts between grains are assumed to have much lower thermal conductance than predicted for idealized grains. The strength of the anomalies on Tethys and Dione appear to be limited by E-ring grain infall, while on Mimas IDP gardening limits the strength of the anomaly. The smaller flux of more deeply penetrating high energy (>1 MeV) electrons on Dione can account for the small thermal inertia differences measured there. Determining regolith sintering rates and the corresponding effect on thermal conductivity can, in principle, provide an independent constraint on the regolith grain geometries and exposure timescales for icy bodies.

Effect of high energy electrons on H⁻ production and destruction in a high current DC negative ion source for cyclotron.

Recently, a filament driven multi-cusp negative ion source has been developed for proton cyclotrons in medical applications. In this study, numerical modeling of the filament arc-discharge source plasma has been done with kinetic modeling of electrons in the ion source plasmas by the multi-cusp arc-discharge code and zero dimensional rate equations for hydrogen molecules and negative ions. In this paper, main focus is placed on the effects of the arc-discharge power on the electron energy distribution function and the resultant H(-) production. The modelling results reasonably explains the dependence of the H(-) extraction current on the arc-discharge power in the experiments.

The role of high-energy electrons during the formation of nonstationary optical emission and transmission spectra of plasma behind the edge of high-velocity ionization waves

The dynamics of the population of excited states of atoms in metastable states and nonstationary optical emission and transmission spectra of nanosecond discharges in plasma waveguides filled with inert gases in a wide range of variation of external conditions are studied experimentally. Estimates of the energy of electrons accelerated at the edge of the high-velocity ionization wave are given, and the effect of high-energy electrons on the dynamics of the development of nanosecond discharge in shielded dielectric tubes is analyzed. The results of the experimental study of the processes of formation of the transverse plasma parameter distribution are presented, and their role during the formation of the transmission spectra of nonuniform plasma of nanosecond discharges near narrow spectral absorption lines is determined. For the first time, the formation of transmission spectra of the dispersion type near spectral absorption lines of neon atoms is discovered and studied in experiments outside the resonator.

Effects of high energy electrons on physical and tensile properties of non-mulberry silk fibers

Tassar silk fiber (Antheraea mylitta) was irradiated with the available maximum dose range upto 100 kGy using 8 MeV electron beam at room temperature. Irradiation effect in these fibers is quantified in terms of the changes in microstructural parameters studied using wide-angle X-ray scattering data (WAXS). The crystal imperfection parameters such as crystallite size (〈N〉), lattice strain (g in %), and surface weighted crystallite size (Ds in A) have been determined by line profile analysis (LPA) using Fourier method of Warren. For this purpose, exponential, lognormal, and Reinhold functions for column length distribution have been used for the determination of these parameters. These parameters were compared with tensile properties of the fibers. The increasing trend of crystallite size values (〈N〉 as well as Ds in A) and tenacity (gf/den) with increasing dosage of radiation clearly indicates the cross linking polymer network in fiber. Comparison of SEM photographs also confirms the X-ray results.

Method for Simultaneously Improving the Thermal Stability and Mechanical Properties of Poly(lactic acid): Effect of High-Energy Electrons on the Morphological, Mechanical, and Thermal Properties of PLA/MMT Nanocomposites

Nanocomposites derived from poly(lactic acid) (PLA) and organically modified montmorillonite (oMMT) have been cross-linked by high-energy electrons in the presence of triallyl cyanurate (TAC). The morphology of untreated and cross-linked PLA/MMT nanocomposites was characterized by wide-angle X-ray scattering (WAXS) and transmission electron microscopy (TEM). This treatment can improve both the thermal stability and the glass-transition temperatures of the PLA nanocomposites (e.g., PLA-MMT-TAC 30kGy, 50kGy, and 70kGy) because of the formation of cross-linking structures in the nanocomposites that will considerably reduce the mobility of polymers. Interestingly, at relatively low irradiation doses (e.g., 30 and 50 kGy) a good balance between tensile strength and elongation at break for the PLA nanocomposites could be achieved. These mechanical properties are superior to those of pure PLA. Therefore, combining nanotechnology and electron beam cross-linking is a promising new method of simultaneously improving the mechanical properties (toughness and tensile strength) and thermal stability of PLA.

Mechanooptical investigations of polyimide films exposed to electrons, mechanical loads, and temperatures

Joint effect of high-energy electrons, mechanical loads, and temperature on polyimide films of thicknesses in the range 30–130 µm is investigated. The films were preliminary irradiated by electrons in air using an ELU-6 linear accelerator with energy of 2 MeV and doses D = 1, 5, 10, 20, 30, 40, and 100 MGy and then subjected to uniaxial mechanical tension at temperatures (T) from 293 to 593 K. It is established that at T = 293–450 K and D = 20–40 MGy, the mechanical load causes almost the same deformations (el max) of nonirradiated and irradiated samples; at T = 450–550 K, deformations of films sharply increase, and the character of their dependence changes. The el max value of the initial sample increases almost linearly with temperature by a factor of 10, whereas the character of changing el max(T) of the irradiated films is more complex, and its value increases approximately by a factor of 4. For T > 500 K, the deformation reaches limiting values. Irradiation increases the intensity of IR-spectra by 2–6 times and essentially increases the widths of absorption bands at 720, 1380, and 1775 cm−1, which is caused by the formation of hydrogen bonds and cycles with nitrogen as well as by the formation of nitrogen oxides. External loading applied to film rupture causes an increase in the EPR signal amplitude from 3·103 to 5·103, which is connected with an increased concentration of radicals =N-H and-NH 2. The electron irradiation of the polyimide films with their subsequent mechanical loading causes the spectrum lines to displace from 3475.0 to 3512.5 cm−1 with simultaneous reduction of the signal amplitude from 6·103 to 4·103.

Electron and γ-irradiation of ion implanted MOS structures with different oxide thickness

Effects of high-energy electrons or gamma irradiation on the interface states of ion implanted MOS structures have been investigated by thermally stimulated charge method. The n-type Si–SiO 2 samples with oxide thickness of 20, 200 and 300 are implanted with 50 keV boron ions to a dose of 1.5 × 10 12 cm −2. Formed MOS structures are irradiated with 11 MeV electrons or 60Co γ-rays. The energy position and the concentration of the radiation-induced interface traps are determined. It is shown that the kinds of radiation-induced interface traps and their concentration depend on the disposition of the maximum of the previously implanted boron ions with respect to the Si–SiO 2 interface.

The effect of high energy electrons during the growth of ZnSe and ZnMgSe by molecular beam epitaxy

Electron irradiation during reflection high-energy electron diffraction is shown to affect the growth of ZnSe and ZnMgSe by molecular beam epitaxy. The high-energy electrons produce an electron stimulated desorption effect during growth of ZnSe which primarily affects adsorbed Se. Se desorption rates under electron irradiation are shown to be significantly larger than thermal desorption rates. Electron irradiation also decreases ZnSe growth rates under Zn-rich conditions. The decrease in growth rate can be suppressed by either growth under Se-rich conditions or by using high-index substrate orientations, in this case (211)B. High-energy electron irradiation does not alter composition during the growth of ZnMgSe.

Radiation degradation of polychlorinated biphenyls

Abstract Gradual dechlorination of the polychlorinated biphenyls (PCBs) in alkaline solutions in 2-propanol under the effect of high energy electrons (4.5 MeV) produced by electron accelerator has been studied using a flow-through apparatus of the volume of about 50 L. The dependence of both relative radiation chemical yield and the dechlorination degree on the initial concentration of OH − ions or PCBs, absorbed dose as well as on dose rate has been investigated.

Experimental perforating injury with high energy electrons to inhibit intraocular proliferation.

Since 1980, the fibroblast model creating experimental proliferative vitreoretinopathy has been used to evaluate the antiproliferative effect of various drugs. In previous studies radiation therapy was found to reduce effectively intraocular proliferation in this model. We therefore investigated the effect of high energy electrons in a standard perforating injury model creating a traumatic proliferative vitreoretinopathy. In 36 eyes we performed a 8 mm pars plana incision and injected 0.4 ml of 80% fibronectin solution intravitreally. Ten rabbits (20 eyes) received radiation therapy with a Betatron accelerator in a total dosage of 3000 cGy to each eye divided into 10 single fractions starting on the first post-operative day. Maximum concentration of the dose was focused to the posterior vitreous. The other 9 rabbits, 18 eyes, served as control. In our perforating injury model we observed a reduction of retinal detachment rate of 72% in the controls to 55% in the treated group. The effect of radiation therapy with high energy electrons and total dosage of 3000 cGy was not statistically significant in experimental traumatic proliferative vitreoretinopathy.

Radiation-Resistant Properties of Inp-Related Materials

AbstractIrradiation effects of high-energy electrons and protons, and 60Co gamma-rays on InP-related materials have been examined in comparison with those of GaAs and Si. Superior radiation-resistance of InP-related materials and their devices compared to GaAs and Si has been found by using deep-level transient spectroscopy (DLTS), photoluminescence (PL) and properties of devices such as solar cells and lightemitting devices. Moreover, minority-carrier injection enhanced annealing phenomena of radiation-induced defects in InP-related materials have also been observed even at low temperature of around 150K.

Electron beam crystallization of Te 1−xSe x films

In situ transmission electron microscopy has been used to study the effect of high energy electrons on the amorphous-to-crystalline phase transformation, the isothermal growth rates, as well as the structure and orientation of the recrystallized Te 0.7Se 0.3 thin films. It is shown that the beam effect is not a pure thermal effect. It is proposed that the electron beam initiates nucleation and promotes growth by the interaction of the high energy electrons with the van der Waals type bonds between the short composite Te-Se chains.

Damage effects of high energy electrons on metals

In this paper, we present results obtained both experimentally, using in-situ electrical resistivity measurements in the high voltage electron microscope, and theoretically, using molecular dynamics computer simulations. These data give a detailed picture of the mechanisms of atomic displacement in Cu and make it possible to quantitatively predict the production rate of point defects given the incident electron beam energy and direction relative to the crystalline axes. Damage effects are found to be important at energies as low as 100–400 keV. We also review the work that has been carried out on other metals and the effect of temperature on the damage production process.

The Effects of High-Energy Electrons on the Charging of Spacecraft Dielectrics

Results are presented of a laboratory investigation of discharges in spacecraft dielectrics using both a low-energy electron and a combined low- and high-energy electron environment. Comparison of the charging and discharge characteristics indicates that the presence of high-energy electrons in space will result in significantly different behavior from that predicted for low-energy electron simulations alone. For Kapton, fiberglass, and second-surface mirrors, the effect of the high-energy electrons is primarily to increase the conductivity, thus often limiting surface potentials to below discharge threshold values. Variation of the relative fluxes of low- and high-energy electrons can lead to discharge; however, the magnitude of the charge blowoff is significantly smaller (~1/20) than that observed upon exposure to low-energy electrons alone. Astroquartz, which for low-energy electron exposures exhibited no measurable charge blowoff, exhibited significant charge blowoff (Ip = 2 amp) upon exposure to a combined high- and low-energy electron environment.