Selection Of Target Material Research Articles

A model incorporating damage evolution to predict the penetration behavior of a ceramic target subjected to the long projectile impact

Predicting the ballistic performance of a ceramic armor composite system requires the accurate constitutive formulation of the ceramic target material. In this study, the analytical spherical cavity expansion model was modified to simulate the penetration process of a ceramic target impacted by a long projectile, and then validated by the data in the literature. Specifically a damage evolution parameter that characterizes the modulus degradation in the ceramic was proposed and incorporated into the model. It was found that the prediction is more accurate when the model includes damage evolution. Parametric modeling further reveals that the properties of the projectile and target materials have a significant effect on the penetration response. The target resistance is sensitive to the damage evolution, especially in the ceramic of higher dynamic compressive strength and lower tensile strength. The modified model enables the selection of target materials for penetration resistance in terms of not just strength but also toughness.

Target Material Selection for Sputter Coating of SEM Samples

Abstract

Remote Viewing of Concealed Target Pictures Under Light and Dark Conditions

The belief that performing a nonlocal task in darkness plays a facilitating role in remote viewing and other psi-related phenomena is well established in esoteric and traditional beliefs (Grim,1983; Hallowell,1942; Lyon,2012). However, the role of darkness in RV success is unclear beyond these esoteric explanations. This study explored the differential effect of darkness/light on remote viewing ability alongside the effect of time and their potential interaction. From an initial sample of twenty, seven remote viewers contributed a total of nineteen sessions each (nine light/ten dark) which utilised randomized target selection, free-response descriptions, and ratings by both participants and an independent judge. The usable data gave the edge to dark condition performance; the difference was not statistically significant. A statistically significant difference between remote viewer and independent judge raw scores attributed to the target image was identified (t (132) = 4.56, p <.001 (two-tailed) Mdiff = 14.21 [8.05, 20.4]) with a medium effect size (d = 0.40 [0.21, 0.57]). Exploratory post-hoc analyses concerning the numinosity of target images were conducted, to determine if this characteristic was associated with success. For numinosity ratings of target images, a mean difference of 11.24, 95% CI [0.12, 22.3] was shown as significant, with the target images of participant 'hit' sessions containing higher numinosity ratings than unsuccessful 'miss' sessions (t (11.47) = 2.22, p (two-tailed) = .048) with a large effect size (d = 1.02, [0.01, 1.99]). The findings may have implications for the use of participant judgments in future remote viewing research. Furthermore, because there are several advantages to what parapsychologists refer to as "free response" targets as opposed to "forced choice" targets (Honorton,1975), the findings for target numinosity may have implications for the future selection of target material.

User Guide for Luminescence Sampling in Archaeological and Geological Contexts

AbstractLuminescence dating provides a direct age estimate of the time of last exposure of quartz or feldspar minerals to light or heat and has been successfully applied to deposits, rock surfaces, and fired materials in a number of archaeological and geological settings. Sampling strategies are diverse and can be customized depending on local circumstances, although all sediment samples need to include a light-safe sample and material for dose-rate determination. The accuracy and precision of luminescence dating results are directly related to the type and quality of the material sampled and sample collection methods in the field. Selection of target material for dating should include considerations of adequacy of resetting of the luminescence signal (optical and thermal bleaching), the ability to characterize the radioactive environment surrounding the sample (dose rate), and the lack of evidence for post-depositional mixing (bioturbation in soils and sediment). Sample strategies for collection of samples from sedimentary settings and fired materials are discussed. This paper should be used as a guide for luminescence sampling and is meant to provide essential background information on how to properly collect samples and on the types of materials suitable for luminescence dating.

Fusion technologies for Laser Inertial Fusion Energy (LIFE)

The Laser Inertial Fusion-based Energy (LIFE) engine design builds upon on going progress at the National Ignition Facility (NIF) and offers a near-term pathway to commercial fusion. Fusion technologies that are critical to success are reflected in the design of the first wall, blanket and tritium separation subsystems. The present work describes the LIFE engine-related components and technologies. LIFE utilizes a thermally robust indirect-drive target and a chamber fill gas. Coolant selection and a large chamber solid-angle coverage provide ample tritium breeding margin and high blanket gain. Target material selection eliminates the need for aggressive chamber clearing, while enabling recycling. Demonstrated tritium separation and storage technologies limit the site tritium inventory to attractive levels. These key technologies, along with the maintenance and advanced materials qualification program have been integrated into the LIFE delivery plan. This describes the development of components and subsystems, through prototyping and integration into a First Of A Kind power plant.

AMS measurements of fission products at CIAE

Fission products are present in special nuclear materials as contaminants remaining from isotope separation or reprocessing, or through ingrowth due to spontaneous and neutron induced fission. The long half-lived fission products (LLFPs) are among the most dangerous radionuclides to the environment. Ultra-high-sensitivity measurement of LLFPs in rocks or soil samples from the fission environment would provide very important information for nuclear safety inspection. The Beijing HI-13-AMS facility with a high terminal voltage of 13MV is suitable for measuring LLFPs, especially for heavy fission products such as 79Se, 93Zr, 99Tc, 107Pd, 121mSn, 126Sn, 129I and 151Sm. In this paper some new methods developed for AMS measurement of 79Se, 93Zr, 99Tc, 121mSn, 126Sn, 129I and 151Sm are presented. Major features of these methods will be introduced, including the preparation of samples, the selection of target material and the molecular ions extracted from the material in the ion source, as well as the identification and detection of the nuclides to be determined.

Characterization and optimization of pyroelectric X-ray sources using Monte Carlo spectral models

Pyroelectric X-ray sources produce emission through bulk heating of a ferroelectric crystal. In this study, a least-square based systematic curve fitting of X-ray emission to predicted models is used to generate an equivalent monoenergetic incident electron energy to simplify further X-ray source optimization. The measured X-ray spectrum of a 1cm3 lithium tantalite crystal cycled over 140K are shown to be approximated by those of an 85keV monoenergetic electron beam. Using monoenergetic electron sources, common configurations for transmission and directional X-ray sources are simulated using electron targets comprised of gold, silver, copper, molybdenum and tungsten. X-ray production efficiency depends on target material selection, incident electron energy, and target thickness for both transmission and reflection geometries. At 20keV, silver produced 69.7% more flux was in comparison to copper, the least efficient target material at this energy. Conversely, at 85keV copper outperformed silver, the least efficient target material at this energy, by 21.6%. Pyroelectric X-ray sources can be improved for flux and energy tuning through the use of modeling and target design. Continued development of pyroelectric X-ray sources can lead to wide scale implementation for industrial X-ray fluorescence and medical therapeutic applications.

Scaled Up Pulsed Deposition Technology: Carburization Resistant Ablation Coatings for Ethylene Pyrolysis Coils

ABSTRACTProducts derived from ethylene have and will continue to replace metallic materials traditionally used for transportation, building materials, and products we use in our everyday lives. As the demand continues to increase, a more suitable material for the outlet coils of ethylene pyrolysis heaters will have to be identified. In this study, we discuss utilization of scaled up pulsed deposition technology to deposit adherent carburization resistant coatings on the inner diameter of ethylene pyrolysis tubing with the intent of extending tube life. Ablation target material selection was based primarily on elevated temperature properties and the ability of the coating to prevent transformation of the inherent protective chromium oxide surface film to metal carbides while in service. The near optimal settings of the processing parameters for pulsed laser deposition of ceramic SiC on heat resistant tubing traditionally used for ethylene service were investigated using a semi quantitative controlled random search methodology. Minimization of the objective function which was based on width, thickness and coverage of the thin film resulted in an optimal deposition time of 4.3 minutes and surface finish of 272 nm.

Small cluster ions from source of negative ions by cesium sputtering

We investigated the delivery of small cluster ions using a source of negative ions by cesium sputtering (SNICS). The negative cluster ions of B n , C n , Si n , Co n , Cu n , Ge n , Au n , GeB n and SiB n have been extracted by SNICS. Adequate beam current of some small clusters was obtained by changing several parameters for cluster ion yield. After a comprehensive study of the operation parameters, such as target material selection, target geometry, sputtering voltage and current, the small cluster ion current can be increased by several orders of magnitude, with little change on the monomer ion yield.

Forty-year design life: the next target Material selection and operating conditions in thermal desalination plants

The operational experience on the first generation of large MSF desalination plant has demonstrated that the original expected life of these units has been largely exceeded. Several contracts for the rehabilitation and upgrading of desalination units installed 20 years ago have been recently awarded, aiming at extending the life of these units by a further 15 years. Developments in materials technology have resulted in the adoption of nobler materials, and it is expected that the second generation of large MSF desalination plants installed in the last 10 years will last for more than 30 years with minimum maintenance and minor overhauling. On this basis, it is assumed that a 40- to 50-year design life is a reasonable target which can be obtained if the material selection is optimized in respect of the operating conditions. The gradual emergence of the MED process in the market portion previously belonging to MSF technology suggests that an evaluation of the operating conditions and material selection for MED plants can also grant an expected life of 50 years. The sharp influence of material selection on plant cost has previously been demonstrated; therefore, the choice of “where” and “how” to invest in upgrading materials and the evaluation of the financial revenue, in term of extension of plant life and reduction of maintenance, are key technical aspects for the future of desalination. By comparing the various operating conditions occurring in the desalination units and the impact on corrosion/erosion of the materials used, this paper aims at giving guidelines that will allow material selection to be optimized with respect to the plant costs.

Criteria for selection of target materials and design of high-efficiency-release targets for radioactive ion beam generation

In this report, we define criteria for choosing target materials and for designing, mechanically stable, short-diffusion-length, highly permeable targets for generation of high-intensity radioactive ion beams (RIBs) for use at nuclear physics and astrophysics research facilities based on the ISOL principle. In addition, lists of refractory target materials are provided and examples are given of a number of successful targets, based on these criteria, that have been fabricated and tested for use at the Holifield Radioactive Ion Beam Facility (HRIBF).

Lithium compounds as targets for (p,n) reactions

It is known that metallic lithium has the highest thick-target neutron yield in (p,n) reactions compared with various lithium compounds. However, lithium metal is highly reactive and possesses a low melting point, which creates difficulty in target design, manufacturing and operation. As a result, lithium compounds should be considered as candidates for the target. As the stopping powers differ among lithium compounds, different compounds lead to different total neutron yields and different epithermal fluxes. This paper presents a quantitative analysis of the relative neutron yields for a series of thick targets made of lithium compounds and the corresponding achievable epithermal neutron fluxes by moderation suitable for BNCT applications. It is shown that the useful epithermal neutron flux in the 4 eV–40 keV range reaches the peak value at about 3 MeV proton energy and decreases when proton energy increases over 3 MeV. For Li 3N and Li 2O targets, a proton current of 5–6 mA may be sufficient for producing a beam of 10 9 n/cm 2/s epithermal flux under ideal conditions. When other factors are considered, a proton current around 10 mA may be needed for producing a feasible BNCT beam. The results may be useful in target material selection and design and accelerator design for epithermal neutron production for BNCT.

Beam heating and cooling of thick targets for on-line production of exotic nuclei

Calculations have been made of energy deposition distributions for “thick” targets (∼1 mole/cm 2) employed in on-line production of exotic nuclei using the Monte Carlo based LAHET code system for high-energy charged particle transport. A variety of target materials and incident proton beam energies have been examined. For 600 MeV protons, the results are compared to those from a similar study reported in the literature. The agreement between the two studies for total energy deposition is reasonably good for monatomic targets, but the results differ in some details of the energy deposition distributions. Target cooling, both radiative and conductive, is examined to assess the suitability of existing target concepts exposed to bombardment by intense (up to 100 μA), energetic (500 MeV to 1.2 GeV) proton beams to produce exotic nuclei. Implications of cooling requirements to target material selection and design are discussed.

Temperature profiles of targets bombarded by electron beams

A calculation technique is presented which relates electron-beam power and the physical properties of a target to the size and temperature of the irradiated spot. The technique permits the selection of target materials which are suitable for use in electron-beam-addressed mass-storage systems. The electron-beam-induced heating within the target is determined by assuming that the beam energy is uniformly deposited within a hemispherical volume of radius rE. This effective radius is determined from Monte Carlo simulation of the beam-target interaction. The thermal calculations can be used to identify the required properties of suitable targets. The steady-state temperature must exceed the boiling temperature of the target material. This requirement places an upper limit on the thermal conductivity of the material. A relationship among thermal conductivity, heat capacity, and mass density is similarly obtained by requiring that the heating is to be done in an acceptably short time. A set of normalized curves is presented which shows the spatial and temporal behavior of the temperature in the target. The denormalization parameters for several materials and beam powers are presented for use with the curves.

Abstract: Electron gun for data storage micromachining

This paper describes an electron gun and associated electron optics developed to provide the capability for electron-beam machining of high-density patterns in metal surfaces for information storage. It is presented with two companion papers by A.B. El-Kareh1 from the University of Houston and Lynwood Swanson2 from the Oregon Graduate Center. We omit certain aspects of the memory system such as analysis of the recording process and the readout considerations. Very briefly, to machine evaporatively at densities of 1010 bits/cm2 and at rates of 107 bits/sec requires a power density greater than 107 W/cm2 at voltages of 5000 V or less with careful selection of target material. Low voltage reduces the scattering range of electrons and high power density produces the high temperatures required for machining in the face of high rates of heat flow encountered with very small heated volumes. The electron gun employs a heated field-emission cathode capable of good angular confinement of emission and low energy spread. An operating temperature of 1800 K allows operation of the cathode in ambient pressures within the range of 10−7–10−8 Torr (10−5–10−6 Pa). The cathode is capable of long life though occasional premature and poorly understood failures do occur. Life tests have shown lifetimes of several thousand hours without failure. The electron gun contains a hairpin filament supporting a (100) -aligned needle cathode. The thermionic emission from the hairpin and needle shank is suppressed by a grid disk surrounding the needle shank. It has little effect on the electric field at the tip of the cathode. The anode with its aperture is positioned 0.020 in. (0.5 mm) from the tip. The anode is followed by a defining aperture at the anode potential. The gun geometry provides very little electrostatic-lens effect to minimize spherical aberration. Imaging is accomplished with two magnetic lenses using collimation of the beam between the lenses to further reduce the spherical aberration. The design of the dual-lens sytem allows a large clearance between the second lens and the target in order to improve deflection capability and reduce the magnetic field in the vicinity of the target. The action of the first lens was improved by decreasing its focal length such that the electric field of the gun and the magnetic field of the lens became overlapping. The computer analysis of the optics for combined fields was done by A.B. El-Kareh at the University of Houston. Two types of cathodes have been used. A great deal of experience has been obtained with a zirconiated tungsten cathode using the usual zirconium-on- tungsten cathode suitably supplied with an oxygen interface. A dispensing Zr source on the shank of the needle delivers Zr to the tip by surface diffusion. A lesser amount (but encouraging experience) has been accumulated with a built-up (100) -tungsten cathode using a build-up procedure developed by L. Swanson of the Oregon Graduate Center. Both cathodes can be operated at temperatures of about 1800 K and a beam current of 0.5 μA in a focused spot of less than 1000 Å diameter has been obtained from both types. If the built-up cathode is used, the spot size will be about 350 Å, while that of the zirconiated one with 0.6-μm radius will be about 950 Å, even though the same electron optics are used. This results from the much smaller source size for the built-up case. Analysis to be published by El-Kareh and Moravan shows that both cathodes have much larger emission-energy spread when operated with an electric field between 2×107 and 4×107 V/cm. This is not a problem, however, at the usual operating field of 1×107 V/cm for the zirconiated cathode and about 6×107 V/cm for the built-up cathode.