Effect Of Energy Deposition Research Articles

Mass and energy deposition effects of implanted ions on solid sodium formate

Solid sodium formate was implanted by low energy N +, H +, and Ar + ions. Measured with electron paramagnetic resonance (EPR) and Fourier-transform infrared (FT-IR), it was observed that new CH 2, CH 3 groups and COO − radical ion were produced in the implanted sodium formate. Analyzing with the highly sensitive ninhydrin reaction, it was found that a new NH 2 functional group was formed upon N + ion implantation, and its yield increased along with implantation dose but decreased with the ion’s energy.

Modeling laser treatment of port wine stains with a computer‐reconstructed biopsy

Background and Objective The efficacy of laser treatment of port wine stains (PWS) has been shown to be highly dependent on patient-specific vasculature. The effect of tissue structure on optical and thermal mechanisms was investigated for different pulse durations by using a novel theoretical model that incorporates tissue morphology reconstructed tomographically from a PWS biopsy. Study Design/Materials and Methods An optical-thermal numerical model capable of simulating arbitrarily complex, three-dimensional tissue geometries was developed. The model is comprised of (1) a voxel-based Monte Carlo optical model, (2) a finite difference thermal model, and (3) an Arrhenius rate process calculation to predict the distribution of thermal damage. Simulations based on previous computer-based reconstruction of a series of 6 μm sections from a PWS biopsy were performed for laser pulse durations (τp) of 0.5, 5.0, and 10.0 ms at a wavelength of 585 nm. Results Energy deposition rate in the blood vessels was primarily a function of vessel depth in skin, although shading effects were evident. Thermal confinement and selectivity of damage were seen to be inversely proportional to pulse duration. The model predicted blood-specific damage for τp = 0.5 ms, vascular and perivascular damage for τp = 5 ms, and widespread damage in superficial regions for τp = 10 ms. The effect of energy deposition in the epidermis was most pronounced for longer pulse durations, resulting in increased temperature and extent of damage. Conclusion Pulse durations between 0.5 and 5 ms are likely optimal for the PWS analyzed. The incorporation of a tomographically reconstructed PWS biopsy into an optical-thermal model represents a significant advance in numerical modeling of laser-tissue interaction. Lasers Surg. Med. 24:151–166, 1999. © 1999 Wiley-Liss, Inc.

Effects of energy deposition by nuclear scattering in silicon p-i-n diode detectors

The changes in thick (∼300 μm) and thin (15 μm) Si p-i-n diode detectors that take place as a result of alpha particle and 63Cu 5+ ion irradiation have been studied by Deep Level Transient Spectroscopy (DLTS) and by monitoring the reverse-bias leakage currents. A linear increase in reverse-bias current with α-particle dose was observed that could be attributed to the formation of vacancy-associated defects (divacancy, A- and E-centres). Damage within the active layer of the device, characterised by the increase in leakage current per unit active volume, together with literature pion, proton and heavy ion data, exhibited a linear dependence on the energy deposited in nuclear processes over many orders of magnitude. Annealing at temperatures of 150°C for 4 h (vacuum bakeout) resulted in a reduction in leakage current and the size of the DLTS peaks became smaller. This temperature is much lower than expected for removal of divacancies, suggesting that recovery of the reverse bias current is mediated by other defect centres.

Characterization of oxide layers induced by oxygen ion implantation into Ti, V, Cr, Zr, Nb, Mo, Hf, Ta and W

Abstract The mechanism of oxide formation induced by ion implantation with and without mass-analyzed oxygen ions into nine refractory metals of groups IVa, Va, and VIa in the periodic table was investigated by X-ray diffractometry (XRD), X-ray photoelectron spectroscopy (XPS) and Rutherford backscattering spectrometry (RBS). O2+ ions were implanted at an energy of 75 keV per atom with dose ranging from 1 × 1017 to 2 × 1018 ions cm-2 at room temperature using the RIKEN low current ion implanter. The SIT-100 direct ion implanter was used for oxygen ion implantation without mass separation at an acceleration voltage of 80 kV at room temperature. Profiles of implanted oxygen were measured by XPS and RBS and the oxides induced by implantation were identified by XRD. XRD patterns showed almost the same process of oxide formation for both mass-analyzed and non-mass-analyzed implantation. In the case of titanium, however, an effect of energy deposition during the formation of oxides was found by comparing oxides induced by ion implantation with and without mass separation. The formation process was approximately classified into three groups in relation to the groups and periods of the periodic table of elements. The stoichiometric ratio of oxides induced by implantation with high doses is discussed based on data obtained by XRD, XPS and RBS. Finally, the aging behavior of oxides kept in an evacuated desiccator for about 1 year is discussed.

X-ray photoelectron spectroscopy characterization of high dose carbon-implanted refractory metals

Abstract A study has been made of the depth dependence of atomic fraction and chemical bonding states of carbon-implanted group IVa to VIa transition metals, by means of X-ray photoelectron spectroscopy combined with an Ar + sputtering. Implatation of 12 C + was performed with 10 18 ions cm -2 at 100 keV, and at room temperature. A gaussian-like carbon distribution, predicted by the range theory, was observed even following such a very high dose. The implanted carbon combined with both matrix metal and carbon itself to form metallic carbides and graphitic solid state carbon. The carbon-enriched carbides were also found by the deconvolution of C 1s spectra. The depth profile of C-metal bonded carbon was trapezoidal, whereas C-C bonded carbon exhibited a gaussian profile corresponding to the net carbon distribution. The binding energy of core electrons of metals shifted nearly linearly with carbon content at the region deeper than the average projected range and at the shallower region it was large and approximately constant, which indicate the formation of carbides with carbon vacancies and stoichiometric carbides respectively. These results will be discussed with respect to the energy deposition effects accompanied by ion implantation.

Chemical and energy deposition effects of keV ions on the adhesion of Cu films onto polymers

The adhesion of copper films evaporated onto polyethersulfone, polyetherimide and polyimide was studied after ion beam mixing using a wide range of ions between 4 and 40 amu (He to Ar) as a function of the ion mass and energy, 60 and 120 keV ions were deposited in the Cu/polymer interface, and the bulk of the polymer, respectively. The adhesion of the modified polymers was measured using a peel test, and related to the energy deposition mechanisms characteristic for the different ions and energies. A comparison between the chemical, electronic and ballistic (nuclear) contributions of the projectiles to the adhesion changes shows a correlation between the electronic term of energy deposition and the adhesion for lower ion masses (up to 20 amu). When the collisional transfer mechanism becomes predominant, a substantial decrease of adhesion strength is observed. In addition to energy transfer effects, deposition of chemically active ions in the Cu/polymer interface may cause an additional increase of adhesion. The consequences of these findings for practical applications are discussed.

Possible Äccelerated Striatal Aging" Induced by 56 Fe Heavy-Particle Irradiation: Implications for Manned Space Flights

The present experiments were carried out to determine the effects of energy deposition from energetic iron (56Fe particles, an important component of cosmic rays) on motor behavioral performance and to determine if the observed deficits were caused by alterations in the neostriatum (an important motor control area). Neostriatal function was assessed with two correlated parameters, i.e., motor behavioral performance (wire suspension task), and oxotremorine-enhanced K(+)-evoked release of dopamine from perifused striatal slices. Rats were exposed to one of several doses of 56Fe-particle irradiation (0.10-1.0 Gy) and tested on a wire suspension task at 3-180 days postirradiation. Results indicated that profound decrements occurred in both of these indices. The effects on K(+)-evoked release of dopamine were evident for as long as 180 days after irradiation, and a subsequent experiment indicated that these effects appeared as early as 12 h postirradiation. Since similar findings have been observed in aged rats, the results are discussed in terms of these particles producing a possible accelerated striatal aging effect.

Energy deposition effects of additional ion bombardment on titanium oxides formed by oxygen implantation

A study of the formation mechanism of titanium oxides induced by O + implantation has been made by means of XRD analysis. Three kinds of ion implantations were employed to investigate the rutile formation process: (1) 75 keV O + implantation into Ti at −60°C, (2) 150 keV O + bombardment at room temperature (RT) into 75 keV O + implanted Ti at −60°C and (3) oxygen ion implantation without mass-separation (O + + O + 2) into Ti at an acceleration voltage of 80 kV. The induced oxides formed by three kinds of implantations were characterized in terms of R(211/110), the ratio of the rutile(211) intensity to the rutile(110) intensity of XRD patterns. For the process (1), rutile formation was not observed and only TiO was identified from measured XRD patterns. Additional implantation into the TiO layers, that is the process (2), results in the formation of rutile with the ratio R(211/110) of 0.32–0.33. The process (3) also produces rutile with the ratio R(211/110) of 0.37–0.83. Both values are much different from that formed by O + implantation into Ti at RT, 1.73–1.80. This phenomenon is attributed to the effect of energy deposition.

The common envelope phase in classical novae - One-dimensional models

The effects of energy deposition due to the motion of the secondary in an expanding nova envelope are explored for 1 solar mass white dwarfs. Results of one-dimensional hydrodynamic calculations show that a common envelope phase can significantly accelerate mass loss from the system, thereby altering the outburst character. Such a rapid mass loss is necessary in order to explain the early appearance of a nebular spectrum and of X-ray emission, in a number of observed systems. 43 refs.

Heating matter by intense heavy ion beams at SIS energies

The hydrodynamic flow in cylindrical aluminum targets irradiated by intense Xenon beams is discussed for three different beam-target combinations. Solid targets, targets with enclosed cavities, and hollow beams are considered to study the effects of energy deposition and compression waves in matter. Emphasis is put on the occurrence of converging shock waves. The assumed beam intensity of 40TW/cm2 is in the scope of the GSI-SIS/ESR facility that will start operating in 1990/91.A two-dimensional hydrodynamic code, including the energy deposition of heavy ions, a realistic equation of state, and realistic transport coefficients, is used in numerical simulations to obtain information on the temperature and density distributions and the relevant time scales that have to be expected in these experiments.

Inactivation of Synchronized Mammalian Cells with Low-Energy X Rays: Results and Significance

Results for inactivation of hydroxyurea-synchronized V-79 cells by ultrasoft aluminum characteristic X rays of energy 1.5 keV are presented. Limiting RBEs at low doses, relative to 137Cs gamma rays, of 1.8 and 6.4 are, respectively, found for cells at the G1/S and late S stages of the cell cycle. The late-S data are analyzed in the light of previous experiments carried out under similar conditions, also designed to probe the effects of energy deposition in nanometer-sized sites, in which cells were irradiated with correlated pairs of ions. Within the framework of the theory of dual radiation action, the results for ultrasoft X rays and gamma rays can be deduced solely from track simulations and the results of the high-LET molecular ion experiment.

The influence of plasma-induced energy deposition effects, the equation of state, thermal ionization, pulse shaping, and radiation on ion-beam-driven expansions of plane metal targets

In a previous paper by Long and Tahir [Phys. Fluids 29, 275 (1986)], the motion of plane targets irradiated by ion beams whose energy deposition was assumed to be independent of the ion energy, and the temperature and density of the plasma, was analyzed. In this paper, the analytic solution is extended in order to include the effects of a temperature-and density-dependent energy deposition as a result of electron excitation, an improved equation of state, thermal ionization, a pulse shape, and radiation losses. The change in the energy deposition with temperature and density leads to range shortening and an increased power deposition in the target. It is shown how the analytic theory can be used to analyze experiments to measure the enhanced energy deposition. In order to further analyze experiments, numerical simulations are presented which include the plasma-induced effects on the energy deposition. It is shown that since the change in the range is due to both decrease in density and the increase in temperature, it is not possible to separate these two effects in present experiments. Therefore, the experiments which measure the time-dependent energy of the ions emerging from the back side of a plane target do not as yet measure the energy loss as a function of the density and temperature of the plasma or of the energy of the ion, but only an averaged loss over certain ranges of these physical quantities.

Energy deposition effects on amorphous selenium, by low temperature neutron irradiation

Abstract We have observed recently that neutron irradiation at low temperature can induce very strong changes in configurational disorder of glasses. This conclusion has been drawn from enthalpy change diagrams performed near Tg, by differential scanning calorimetry, on amorphous selenium. A progressive change was observed from a stabilized relaxation state to a highly quenched state as a function of the neutron dose. We explain these effects by a local heating process. The irradiation was done at low temperature (30 K) and fission and capture effects were shielded by enclosing samples in NB cells.

An evaluation of microwave diathermy applicators using free space electric field mapping

An electric field mapping study is described which was designed and executed to study the performance characteristics of various prototype and currently used microwave diathermy applicators operating at 2450 MHz. A miniature diode detector/dipole probe, developed by the Bureau of Radiological Health, was used to map the 'near' electric fields in the aperture plane of each applicator. From the field mapping results, parameters for use in the evaluation of the radiation safety of various applicators are developed. A thermographic camera was used to determine heating characteristics of the applicators in simulated biological material. The thermal effectiveness of these applicators was also investigated by determining their Specific Absorption Rate, a recently developed parameter. The superiority of a specially designed prototype applicator (in terms of uniformity and effectiveness of energy deposition, and minimal leakage radiation) compared with currently used applicators is demonstrated.

Explosive carbon-burning nucleosynthesis

Results are presented which show the final abundances of the major nuclei produced in explosive, but partial, carbon-burning taking place in a rapidly expanding medium. the effects of energy deposition due to burning and expansive cooling are taken into account explicity. The results are compatible with those obtained by other authors but show the sensitivity of the final abundances to the assumed initial conditions. A conjecture is made as to the physical site of the burning.