Strong Radiation Environment Research Articles

Enhanced surface ozone during the heat wave of 2013 in Yangtze River Delta region, China

Under the background of global warming, occurrence of heat waves has increased in most part of Europe, Asia and Australia along with enhanced ozone level. In this paper, observational air temperature and surface ozone in the Yangtze River Delta (YRD) region of China during summer of 2013, and the regional chemistry-climate model (RegCM-CHEM4) were applied to explore the relationship between heat wave and elevated ground-level ozone. Observations indicated that YRD experienced severe heat waves with maximum temperature up to 41.1°C, 6.1°C higher than the definition of heat wave in China, and can last for as long as 27days. Maximum ozone reached 160.5ppb, exceeding the national air quality standard (secondary level) as 74.7ppb. Moreover, ozone was found to increase at a rate of 4–5ppbK−1 within the temperature range of 28–38°C, but decrease by a rate of −1.3~−1.7ppbK−1 under extremely high temperature. A typical heat wave case (HW: 24/7–31/7) and non-heat wave case (NHW: 5/6–12/6) were selected to investigate the mechanism between heavy ozone and heat waves. It was found that chemical reactions play the most important role in ozone formation during HW days, which result in 12ppb ozone enhancement compared to NHW days. Chemical formation of ozone can be influenced by several factors. During heat waves, a more stagnant condition, controlled by anti-cyclone with sink airflow, led to less water vapor in YRD from south and contributed to less cloud cover, which favored a strong solar radiation environment and ozone significantly increasing. High temperature also slightly promote the effect of vertical turbulence and horizontal advection, which beneficial to ozone remove, but the magnitude is much smaller than chemical effect. Our study suggests that the chemical reaction will potentially lead to substantial elevated ozone in a warmer climate, which should be taken into account in future ozone related issues.

Synthesis and Th(IV) sorption characteristics of functionalised graphene oxide

A functionalised graphene oxide (FGO) adsorbent was prepared via the γ-radiation-induced grafting of epichlorohydrin (ECH) onto graphene oxide (GO). X-ray photoelectron spectroscopy revealed that ECH was successfully introduced to the GO surface. The grafting yield of ECH increased with an increase of the irradiation dose and with a decrease of the irradiation dose rate. The sorption kinetics of Th(IV) on GO and FGO followed the pseudo-second-order model and the sorption isotherms can be described by the Langmuir model. The maximum sorption capacities of GO and FGO for Th(IV) are approximately 5.80 × 10−4 and 2.88 × 10−5 mol/L, respectively. GOs is considered as a kind of materials with high radiation resistance and large sorption capacities, ranking it has high potential industrial applications even under strong radiation environment. In addition, the amount of the oxygen-containing functional groups C=O and O=C–O in FGO decrease with the increase of the irradiation dose, which suggests that C=O and O=C–O contribute more than C–O to the sorption of Th(IV) onto GO and FGO.

Irradiation Induced Changes in Semiconducting Thin Films

High-energy electron, proton, neutron, photon and ion irradiation of semiconductor diodes and solar cells has long been a topic of considerable interest in the field of semiconductor device fabrication. The inevitable damage production during the process of irradiation is used to study and engineer the defects in semiconductors. In a strong radiation environment in space, the electrical performance of solar cells is degraded due to direct exposure to energetically charged particles. A considerable amount of work has been reported on the study of radiation damage in various solar cell materials and devices in the recent past. In most cases, high-energy heavy ions damage the material by producing a large amount of extended defects, but high-energy light ions are suitable for producing and modifying the intrinsic point defects. The defects can play a variety of electronically active roles that affect the electrical, structural and optical properties of a semiconductor. This review article aims to present an overview of the advancement of research in the modification of glassy semiconducting thin films using different types of radiations (light, proton and swift heavy ions). The work which has been done in our laboratory related to irradiation induced effects in semiconducting thin films will also be compared with the existing literature.

Performance improvement approach for dependable computing system with optical voting circuit

AbstractThis paper proposes a new voting method using light that makes possible the realization of a high‐performance computing system equipped with both flexibility and dependability. Soft errors inside computers due to terrestrial radiation have become a problem in recent years. We have proposed a highly dependable triple voting‐type computing system that can be used even in the strong radiation environment of space. While this system uses reconfigurable SRAM‐based FPGA to achieve high flexibility, the system operation speed was limited by synchronization problems in voting circuits located on parallel buses, and by the bottleneck of a limited upper speed for the radiation‐tolerant device used in the voting logic circuit. As a result, we study the use of a serial bus, and propose a voting circuit using light that is suitable for a high‐speed serial bus. This optical voting circuit is highly compatible with the high‐speed serial interfaces provided on recent FPGAs, and is easily configurable using existing optical communications devices. In operations tests using an optical communications module, we obtained voting performance at a 1 Gbit/s communication speed, and estimated that the upper speed limit for the test system is 2.14 Gbit/s. Use of a higher speed optical communication module and circuit optimization should make it possible to achieve even higher speeds. © 2007 Wiley Periodicals, Inc. Electron Comm Jpn Pt 2, 90(12): 35–46, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjb.20422

ISA accelerometer onboard the Mercury Planetary Orbiter: error budget

We have estimated a preliminary error budget for the Italian Spring Accelerometer (ISA) that will be allocated onboard the Mercury Planetary Orbiter (MPO) of the European Space Agency (ESA) space mission to Mercury named BepiColombo. The role of the accelerometer is to remove from the list of unknowns the non-gravitational accelerations that perturb the gravitational trajectory followed by the MPO in the strong radiation environment that characterises the orbit of Mercury around the Sun. Such a role is of fundamental importance in the context of the very ambitious goals of the Radio Science Experiments (RSE) of the BepiColombo mission. We have subdivided the errors on the accelerometer measurements into two main families: (i) the pseudo-sinusoidal errors and (ii) the random errors. The former are characterised by a periodic behaviour with the frequency of the satellite mean anomaly and its higher order harmonic components, i.e., they are deterministic errors. The latter are characterised by an unknown frequency distribution and we assumed for them a noise-like spectrum, i.e., they are stochastic errors. Among the pseudo-sinusoidal errors, the main contribution is due to the effects of the gravity gradients and the inertial forces, while among the random-like errors the main disturbing effect is due to the MPO centre-of-mass displacements produced by the onboard High Gain Antenna (HGA) movements and by the fuel consumption and sloshing. Very subtle to be considered are also the random errors produced by the MPO attitude corrections necessary to guarantee the nadir pointing of the spacecraft. We have therefore formulated the ISA error budget and the requirements for the satellite in order to guarantee an orbit reconstruction for the MPO spacecraft with an along-track accuracy of about 1 m over the orbital period of the satellite around Mercury in such a way to satisfy the RSE requirements.

Mid‐ to Far‐Infrared Spectral Energy Distribution of the Diffuse Galactic Radiation

Mid-infrared (MIR; 12-60 μm) diffuse emission in the Galactic plane and the Carina Nebula is investigated relative to the far-infrared (FIR; ≥100 μm) emission. Observations show that the ratio of the 12 μm emission to the total FIR intensity is more or less constant in the Galactic plane but exhibits a slight decrease followed by an increase as the FIR color becomes bluer in the Carina Nebula. The constancy is compatible with predictions from models of stochastic heating of very small grains or infrared fluorescence of polycyclic aromatic hydrocarbons. The decrease can be attributed to a weakening of the unidentified infrared band emission in strong radiation fields. Contrarily, the ratio of the 25 and 60 μm emission to FIR intensity increases linearly with field strength, which is incompatible with the model predictions. The Carina Nebula data show a much bluer FIR color than the Galactic plane, whereas the ratio of MIR to FIR emission is in a range similar to that of the plane. We interpret these characteristics in terms of a superposition of emission from dust grains in various radiation field strengths. The linear increase can be accounted for by an increasing contribution from emission by dust grains in strong radiation environments, whereas the shift in FIR color between the Galactic plane and the Carina Nebula can be attributed to different contributions from grains in weak radiation fields. Other possibilities, such as the effect of multiphoton processes, variations in the incident radiation spectrum, and possible contributions from iron grains, have also been examined, but none can account for the observations consistently. Applications of the present model to external galaxies are also discussed.

The Non-Gravitational Perturbations impact on the BepiColombo Radio Science Experiment and the key rôle of the ISA accelerometer: direct solar radiation and albedo effects

The paper is focused on the estimate of the impact of the non-gravitational perturbations on the orbit of the Mercury Planetary Orbiter (MPO), one of the two spacecrafts that will be placed in orbit around the innermost planet of the solar system by the BepiColombo space mission. The key role of the Italian Spring Accelerometer (ISA), that has been selected by the European Space Agency (ESA) to fly on-board the MPO, is outlined. In the first part of the paper, through a numerical simulation and analysis we have estimated, over a time span of several years, the long-period behaviours of the disturbing accelerations produced by the incoming direct solar radiation pressure, and the indirect effects produced by Mercury’s albedo. The variations in the orbital parameters of the spacecraft, together with their spectral contents, have been estimated over the analysed period. The direct solar radiation pressure represents the strongest non-gravitational perturbation on the MPO in the very complex radiation environment of Mercury. The order-of-magnitude of this acceleration is quite high, about 10−6 m/s2, because of the proximity to the Sun and the large area-to-mass ratio of the spacecraft. In the second part of the paper, we concentrated upon the short-period effects of direct solar radiation pressure and Mercury’s albedo. In particular, the disturbing accelerations have been compared with the ISA measurement error and the advantages of an on-board accelerometer are highlighted with respect to the best modelling of the non-gravitational perturbations in the strong radiation environment of Mercury. The readings from ISA, with an intrinsic noise level of about \(10^{-9}\,m/s^{2}/\sqrt{Hz}\) in the frequency band of 3·10−5–10−1 Hz, guarantees a very significant reduction of the non-gravitational accelerations impact on the space mission accuracy, especially of the dominant direct solar radiation pressure.

Operation of a multiple cell array detector in plasma experiments with a heavy ion beam diagnostic

A multiple cell array detector (MCAD) has been developed to investigate the spatial structure of plasma turbulence in fusion plasmas. This system is expected to provide simultaneous measurements of edge and core density fluctuations with both temporal and spatial resolution, extending the range and number of the sample volumes simultaneously recorded by a heavy ion beam diagnostic (HIBD). Since the detector (usually located close to the vessel wall of a plasma device) operates in a strong plasma radiation environment, the effective shielding of the detector presents a special problem. This article describes and compares the MCAD operation conditions on ISTTOK tokamak and TJ-II stellarator. Experimental results of the detector performance are presented together with the first measurements of neσeff in the TJ-II plasmas.

Atomic processes in near-equilibrium plasmas

A rigorous general theory based on non-equilibrium thermodynamics is developed to treat atoms in a steady-state non-equilibrium plasma with strong radiation environment. The atomic radiative properties are described by a linear response matrix, which relates the emission/absorption coefficients to the surrounding radiation environment. The response matrix is calculated by solution of the usual rate equations with special boundary conditions. There is evidence that the range of linear response is large. According to the general theory of non-equilibrium thermodynamics the response matrix must be symmetric and this symmetry gives a powerful test for NLTE codes. In this paper we prove that excited-state populations in a steady-state near-LTE plasma are characterized by the principle of minimum entropy production and derive the exact formula for the response matrix.

On the Thermal Instability in a Contracting Cloud and Formation of a Bound Cluster

We perform linear analysis of thermal instability in a contracting large cloud filled with warm H I gas and investigate the effect of metallicity and radiation flux. When the cloud reaches critical density nf, the cloud fragments into cool, dense condensations because of thermal instability. For a lower metallicity gas cloud, the value of nf is high. Collision between condensations will produce self-gravitating clumps and stars thereafter. From the result of the calculations, we suggest that high star formation efficiency and bound cluster formation are realized in low-metallicity and/or strong-radiation environments.

Integrity of III-V heterojunction interfaces under gamma irradiation

Reliability of modern III-V semiconductor heterostructure devices meant for strong radiation environment depends upon the integrity of the hetero-interfaces under radiation. In this paper, we present some results of our investigation of a variety of heterojunction structures subjected to gamma irradiation up to 40 Mrads (Si) probed by Hall, C-V and photoluminescence measurements.