Mode Of Energy Deposition Research Articles

The effect of direct laser beam energy deposition modes on single rollers and walls shaping from the HN50VMTUB heat resisting alloy

The effect of direct laser beam energy deposition modes on single rollers and walls shaping from the HN50VMTUB heat resisting alloy

EFFECT OF ENERGY DEPOSITION MODELLING IN COUPLED STEADY STATE MONTE CARLO NEUTRONICS/THERMAL HYDRAULICS CALCULATIONS

In coupled calculations with Monte Carlo neutronics and thermal hydraulics the Monte Carlo code is used to produce a power distribution which in practice means tallying the energy deposition. Usually the energy deposition is estimated by making a simple approximation that energy is deposited only in fission reactions. The goal of this work is to study how the accuracy of energy deposition modelling affects the results of steady state coupled calculations. For this task an internal coupling between Monte Carlo transport code Serpent 2 and subchannel code SUBCHANFLOW is used along with a recently implemented energy deposition treatment of Serpent 2. The new treatment offers four energy deposition modes each of which offers a different combination of accuracy and required computational time. As a test case, a 3D PWR fuel assembly is modelled with different energy deposition modes. The resulting effective multiplication factors are within 30 pcm. Differences of up to 100K are observed in the fuel temperatures.

Retraction Note: Analysis of the dynamics of laser induced plume propagation from liquid matrix using fast photography

Glycerol, a liquid matrix material for matrix-assisted laser desorption ionization mass spectrometry, was irradiated by a tunable pulsed infrared laser at wavelengths of 2.80 μ.m, 2.94 μ.m, 3.10 μ.m and 3.50 μ.m, covering the OH and CH stretch vibrations. A fast photography system was introduced to analyze the dynamic process of plume propagation induced by laser ablation up to 1000 μ.s of the delay time. Propagation distance of the plume front was measured and the corresponding velocities were calculated; they varied with the wavelength and decreased with the delay time. At the tunable wavelength of the peak of the OH absorption (3.0 μ.m), theoretical calculations indicate that energy deposition from the pulsed laser is in the regime of stress confinement. The mode of energy deposition depends on the wavelength of the OH vibration and its distance from the absorption maxima. However, stages after a 10 μ.s delay at various wavelengths show a certain similarity in the distance of plume propagation, which can be well fitted by a drag model.

New energy deposition treatment in the Serpent 2 Monte Carlo transport code

In this work a new energy deposition treatment for the Serpent 2 Monte Carlo transport code is introduced. The treatment is implemented as a set of energy deposition modes, each of which offers a different combination of accuracy and required computational time. The most accurate mode uses the coupled neutron-photon transport available in Serpent 2. In addition to the new modes, a few other improvements such as a new energy deposition detector response was developed. The energy deposition treatment is demonstrated with simple LWR and LFR assembly level test cases. In the LWR cases the results are compared with MCNP6 on a high-level and a good agreement is achieved. In the LFR case differences in the energy deposition estimates of the different modes are highlighted. Based on the test cases, problems in the energy deposition data with ENDF/B-VII.1 and ENDF/B-VIII.0 are presented. Finally, future work concerning energy deposition capabilities of Serpent 2 are briefly discussed.

Microwave plasma enhancement of multiphase flames: On-demand control of solid propellant burning rate

This effort explores the microwave-supported plasma enhancement of an aluminized, ammonium perchlorate composite solid propellant flame. The technique is enabled through novel alkali metal doping, which provides increased levels of ionization and allows efficient microwave energy deposition to the flame structure and subsequent perturbation of the steady-state propellant burning rate. Three potential modes of energy deposition are identified in composite propellants: (1) plasma-enhancement promoted by the presence of sodium, (2) strong absorption by high temperature metallic oxide products, and (3) direct absorption of energy by the propellant burning surface condensed phase. Equilibrium calculations are used to identify propellant compositions with high free-electron populations, and solution of the Boltzmann equation using the BOLSIG + code is used to show the significant effects of sodium doping on microwave absorption of the flame. Experimental emission spectroscopy and imaging of the microwave-enhanced propellant flame structure show evidence of these mechanisms. Propellant burning rates can be increased by up to 60% through the application of 1 kW, continuous 2.46 GHz microwave radiation. Propellant doping with 3.5% by weight of sodium nitrate shows significant improvement in the effectiveness of microwave application in modifying the propellant burning rate. This technique provides high levels of dynamic propellant combustion control from a solid-state system. The on-demand control of energetic material burning rates through low level doping and microwave irradiation is a promising technique which could lead to the development of a new class of ‘smart’ dynamically controllable energetic materials.

Analysis of the dynamics of laser induced plume propagation from liquid matrix using fast photography

AbstractGlycerol, a liquid matrix material for matrix-assisted laser desorption ionization mass spectrometry, was irradiated by a tunable pulsed infrared laser at wavelengths of 2.80 μm, 2.94 μm, 3.10 μm and 3.50 μm, covering the OH and CH stretch vibrations. A fast photography system was introduced to analyze the dynamic process of plume propagation induced by laser ablation up to 1000 μs of the delay time. Propagation distance of the plume front was measured and the corresponding velocities were calculated; they varied with the wavelength and decreased with the delay time. At the tunable wavelength of the peak of the OH absorption (3.0 μm), theoretical calculations indicate that energy deposition from the pulsed laser is in the regime of stress confinement. The mode of energy deposition depends on the wavelength of the OH vibration and its distance from the absorption maxima. However, stages after a 10 μs delay at various wavelengths show a certain similarity in the distance of plume propagation, which can be well fitted by a drag model.

Can We Describe phase Transition in Insulators within the Landau PT theory Framework?

AbstractBased on studies of simple oxides, this paper demonstrates that the specific energy deposition modes under irradiation induce modifications of materials over different length scales. On the other hand, we show the Landau phase transition theory, widely used to explain the structural stability of materials out of irradiation, can give a general framework to describe the behavior of these oxides under irradiation. The use of X-ray diffraction techniques coupled with the Raman spectroscopy allows defining in a quantitative way the phenomenological parameters leading to predictive results. This paper clearly shows that in two model systems, pure zirconia and spinels, no unexpected new phases are produced in these oxides irradiated at room temperature and with different fluxes. Such a phenomenological approach may be useful to study the radiation tolerance of many crystalline ceramics (e.g. the zirconium based americium ceramics).

Effect of the energy deposition modes on the structural stability of pure zirconia

One of the most important goals in materials science is to be able to design materials with specific properties. Irradiation seems to be a powerful tool for the design of advanced materials because of its ability to modify over different scales the microstructure of solids. Nowadays, it is clearly proved that irradiation induces order–disorder phase transitions in metallic alloys and in some ceramics. Recent investigations on pure monoclinic zirconia have clearly shown that a displacive phase transition can be induced by irradiation. In this work, the impact of the energy deposition modes on the structural stability of pure monoclinic ZrO2 is discussed in detail. Based on experimental evidences, a microscopic model is proposed to explain the displacive phase transition observed in this material after irradiation by low and high energy ions within the Landau theory framework. Even if defects generated by low and high energy ions are quite different, these defects are able to quench the same tetragonal phase in pure zirconia.

Evidence of extended defects in pure zirconia irradiated by swift heavy ions

X-ray diffraction, transmission electron microscopy, and optical spectroscopy were used to investigate the microstructure of polycrystalline samples of pure monoclinic zirconia irradiated by high energy ions. These techniques point out the existence of extended defects and they allow to monitor the tetragonal to monoclinic phase transition as a function of the temperature during isochronal annealings. The Landau theory approach explains the phase transition mechanism via the presence of an important strain field induced by dislocations. Though high and low energy ions can effectively stabilize the same tetragonal phase in the irradiated layer, only point defects are produced at low energy whereas extended defects are also observed at high energy, showing the strong influence of the energy deposition modes on the observed microstructures.

The hyper-radiosensitivity effect of human hepatoma SMMC-7721 cells exposed to low dose γ-rays and 12C ions

Hypersensitive response of mammalian cells in cell killing to X- and γ-rays has been reported at doses below 1Gy. The purpose of this study was to examine the low dose sensitivity of human hepatoma SMMC-7721 cells irradiated with 60Co γ-rays and 50MeV/u 12C ions. Experiments using γ-rays and charged particle irradiation were performed, particularly in the low dose range from 0 to 2Gy. The survival effect of SMMC-7721 cells was measured by means of standard clonogenic assay in conjunction with a cell sorter. The result indicates SMMC-7721 cells showed hyper-radiosensitive response at low doses and increased radio-resistance at larger single doses for the carbon ions (LET=45.2keV/μm) and the γ-rays. However, the HRS/IRR effect caused by high-LET irradiation is different from that by low-LET radiation. This might possibly be due to the difference in the mode of energy deposition by particle beam and low-LET irradiation.

High-energy emission from pulsars: the polar cap scenario

The study of pulsars in the three and a half decades since their discovery has highlighted a handful of issues critical to their understanding. To date there is no consensus on the physical mechanism for their radio emission, despite a rapid increase in the observed population due to the Parkes multi-beam survey and prospects for similar growth in the radio population database in the near future. The small subset of pulsars that emit at X-ray to γ-ray wavelengths is critical to refining the pulsar paradigm, since this energy band (i) is where the vast majority of radiative luminosity is observed and (ii) is intimately connected to the pair winds that form the dominant mode of energy deposition in the circum-pulsar environment. The most crucial point of contention pertaining to the high energy astrophysics of pulsars is the location of the acceleration region in their magnetospheres: is an outer gap model or a polar cap scenario (or both) the most appropriate picture. Radiative signatures provide the clues to this current enigma. This review focuses on salient characteristics of the polar cap scenario; these form the basis for discriminating observational diagnostics that should drive pulsars studies in the GLAST era just three years away.

Comparison of Energy Deposition Modes in Polyethylene Films by Megaelectronvolt Range Neutrons, Electrons, Protons, and α Particles as Monitored by Covalent Attachment of Doped Pyrene Molecules

The selectivity and efficiency of the covalent attachment of pyrene molecules to chains of polyethylene (PE) films by various forms of ionizing radiation (neutrons, electrons, protons, and α partic...

Some aspects of radiation-induced free-radical chemistry of biologically important molecules

Biologically relevant material is usually associated with considerable amounts of water; e.g. the living cell contains about 70% water. When ionizing radiation interacts with such material one must consider two modes of energy deposition: the direct effect (ionizing radiation is absorbed by the biomolecules) and the indirect effect (ionizing radiation is absorbed by the surrounding water). In the direct effect, radical cations plus electrons, and excited states of the biomolecules are formed. In the indirect effect the water is decomposed resulting in the formation of the water radicals .OH, H . and e - aq. These reactive intermediates then interact with the biomolecules. When such systems are irradiated oxygen is often present. As a result of this, the radicals formed in the biomolecules by the various routes are converted into the corresponding peroxyl radicals. In certain cases, e.g. with the nucleobases of DNA, radical cations can be produced in dilute aqueous solutions by radiation-generated SO· − 4 radicals, and the fate of these nucleobase radical cations studied by pulse radiolysis and product analysis. Attention will be drawn to the fact that frequently some of the reaction products of the radical cations with water are identical to those formed by OH radical attack, but that there are also marked differences. Similarly, protonation of radical anions (formed by the reaction of solvated electrons with the biomolecules) and the reaction of H-atoms with these molecules can lead to radical intermediates with considerably differing characteristics. Our present knowledge of the variety of reactions of the peroxyl radicals occuring in aqueous solutions will be briefly discussed, emphasizing the large variety of HO . 2/O· - 2 elimination reactions and pointing to the reversibility of the oxygen addition (RO . 2→R . + O 2) in some systems recently studied.

The physics of compensating calorimetry and the new Calor89 code system

The CALOR system has been revised to reflect a better comprehension of high-energy nuclear collisions (HETC88) by incorporating a modified high-energy fragmentation model from FLUKA87. This revision will allow the accurate analysis of calorimeters at energies of 100s of GeV. The authors discuss the fundamental physics of compensating calorimetry, the new CALOR system (CALOR89), the revisions to HETC, and recently generated calorimeter-related data on modes of energy deposition and secondary neutron production (E<50 MeV) in infinite iron and uranium blocks.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Continuous wave (CW) and pulsed laser effects on vascular tissues and occlusive disease in vitro

Human arterial segments with occlusive defects and acute dog hearts were exposed, in vitro, to high-energy pulsed and continuous wave (CW) laser beams at argon (514 nm) and Nd-YAG (1,064 nm) wavelengths, using various pulse powers, durations and pulse repetition rates. The laser effects included vaporization of plaques in the arterial segments and penetration of the pericardial sac, evaporation of pericardial fluid, and discoloration of tissue with crater-like lesions in the impact zone, all as a result of vaporization of heart muscle tissues. The areas affected and depth of penetration depended on the wavelength, power, pulse duration, and mode of energy deposition. Focused nanosecond Nd-YAG laser pulses at repetition rates of 40-50 Hz caused ablation or vaporization of hard plaques and kidney stones in air and saline. Picosecond (mode-locked) argon laser pulses at repetition rates of 3.8 MHz--average power 6.5 W, peak power of 230 W--caused effective vaporization of hard plaques and kidney stones in air and saline. Picosecond argon laser pulses--average power 1 W, peak power 250 W--were not effective in vaporization. Transmission characteristics of the various types of laser pulses through fiber optic waveguides were determined. The energy and power density required to vaporize fatty and hard plaques and kidney stones were tabulated as a function of laser wavelength, pulse energy, duration, and repetition rates.

Comparison of Conductivity Produced in Polymers and Carbon Films by Pyrolysis and High Energy Ion Irradiation

ABSTRACTThe electrical properties of pyrolyzed polymers have been studied recently.1,2 It has been shown that organic, polymeric3 and non-polymeric4 films can be made conductive (ρ ~ 10−3Ωcm) by ion beam irradiation. Common to all of the films was the presence of carbon as a constituent element and both pyrolysis and ion beam irradiation3 was shown to increase the relative carbon content of the films. The ion beam irradiated organic films 3,4 exhibited a temperature dependence of their resistivity of the form ρ(T) = ρ∞e−(TЛ)*, where ρ is the ion-induced resistivity, ρ∞ and T0 are constants and T is the temperature. At very high doses of irradiation (1017cm−2Ar+@ 2MeV) the film resistivity was temperature independent. Very similar transport properties were observed in the pyrolyzed polymers1 as well, though the lowest resistivities achieved were higher than the resistivity values observed in the ion irradiated3 polymer films. In both the pyrolysis and ion-irradiation experiments the temperature dependence has been explained by a model due to Sheng and Abeles,5 which involves charge transport by hopping between conducting islands embedded in an insulating matrix. Such striking similarities between two distinctly different modes of energy deposition in the films, prompted us to compare the effects of pyrolysis and ion irradiation in different carbon containing films. We compared both a polymer (HPR-204°) and a film of electron beam evaporated carbon film. While in the former case one would observe chemical degradation as well as structural modification, by studying pure carbon films the physical nature of the processes could be clarified. We report metallic carrier densities in both films and evidence for significant structural rearrangement. We conclude that pyrolysis and ion beam irradiation have similar effects on both polymer and carbon films.

Free radical initiation in proteins and amino acids by ionizing and ultraviolet radiations and lipid oxidation--part III: free radical transfer from oxidizing lipids.

Parallels and similarities in chemical and functional damage to proteins by ionizing and uv radiations and oxidizing lipids have been recognized for some time. However, only recently have oxidizing lipids been shown directly by electron spin resonance to be radiomimetic also in their capacity for protein free radical production. Free radicals play a key role in the transformation of energy to molecular and cellular damage. It is thus of critical importance to elucidate the general mechanisms of free radical formation and reactions in proteins in order to understand protein involvement in various pathological conditions and in food deterioration. Accordingly, this review is a detailed comparison of gamma-radiation, UV radiation, and lipid oxidation for what is presently known concerning (1) the specific modes of energy deposition and free radical formation, (2) the free radicals formed in proteins and amino acids, and (3) the typical damage correlating with these radicals.

Free radical initiation in proteins and amino acids by ionizing and ultraviolet radiations and lipid oxidation--Part 22: ultraviolet radiation and photolysis.

Parallels and similarities in chemical and functional damage to proteins by ionizing and UV radiations and oxidizing lipids have been recognized for some time. However, only recently have oxidizing lipids been shown directly by electron spin resonance to be radiomimetic also in their capacity for protein free radical production. Free radicals play a key role in the transformation of energy to molecular and cellular damage. It is thus of critical importance to elucidate the general mechanisms of free radical formation and reactions in proteins in order to understand protein involvement in various pathological conditions and in food deterioration. Accordingly, this review is a detailed comparison of gamma radiation, UV radiation, and lipid oxidation for what is presently known concerning (1) the specific modes of energy deposition and free radical formation, (2) the free radicals formed in proteins and amino acids, and (3) the typical damage correlating with these radicals.

Free radical initiation in proteins and amino acids by ionizing and ultraviolet radiations and lipid oxidation--Part I: ionizing radiation.

Parallels and similarities in chemical and functional damage to proteins by ionizing and UV radiations and oxidizing lipids have been recognized for some time. However, only recently have oxidizing lipids been shown directly by electron spin resonance to be radiomimetic also in their capacity for protein free radical production. Free radicals play a key role in the transformation of energy to molecular and cellular damage. It is thus of critical importance to elucidate the general mechanisms of free radical formation and reactions in proteins in order to understand protein involvement in various pathological conditions and in food deterioration. Accordingly, this review is a detailed comparison of gamma radiation, UV radiation, and lipid oxidation for what is presently known concerning (1) the specific modes of energy deposition and free radical formation, (2) the free radicals formed in proteins and amino acids, and (3) the typical damage correlating with these radicals.

Theoretical Analysis of the LET Dependence of Transient Yields Observed in Pulse Radiolysis with Ion Beams

A theoretical analysis of the LET dependence of transient yields 10/sup -5/ sec after energy deposition by /sup 2/H/sup +/ and /sup 4/He/sup 2 +/ is presented. The model used takes into account the separation of the track core and the delta-ray tracks. Diffusion-kinetics methods are used to calculate the time dependences of transient concentrations in the track core and in the delta-ray tracks. Since the model also specifies the relative energetic importances of the different energy-deposition modes, composite G values can be calculated for comparison with experiment, and the agreement is found to be satisfactory.