Deflection Plates Research Articles

Equipment and method for ion beam control in implantation and science experiments

An experimental method has been developed and electronic equipment has been created both for the experimental research of the small-angle (less than 10 −3 rad) scattering of ions with the energy of MeV range on thin gaseous or single-crystal targets and for industrial applications in doping of materials by ion implantation. A discrete deflection of the slimly collimated ion beam within some angle range is implemented with electrostatic field of a deflector. The electronic equipment generates a stepwise potential difference between the deflector plates with the frequency of a few kHz and forms a numerical code, corresponding to the deflection angle value. Due to the periodic deflection the ion beam scans the surface of the material to be doped and forms the required dope pattern. In the case of experimental research the beam scattered in a target scans a collimated detector. Deflection angle codes are recorded at the moment of ion detection and accumulated as a spectrum of the angular distribution of the scattered ions. Depending on the task the equipment complex makes a number of operating modes available. A digital–analog forming of potentials on the deflector and representation of the deflection angle as a numerical code enables the microprocessor devices and computers to be effectively applied for forming and measuring an ion beam profile.

Tolerancing of electron beam lithography columns

A new software package has been developed for the tolerancing of complete electron and ion beam columns. The software computes the asymmetry aberrations caused by small mechanical imperfections in the construction and alignment of the lenses and deflectors. The imperfections considered include misalignments, tilts and ellipticities of individual polepieces, electrodes, coil windings and deflection plates. The asymmetry fields due to these mechanical errors are computed by perturbation methods, and the resulting parasitic aberrations are evaluated with asymmetry aberration integrals. The effects of aberration correction elements, such as alignment coils and stigmators, are also handled by the software. The overall effects of the aberrations can be displayed graphically. Illustrative results are presented for nanolithography and high-throughput lithography systems.

Observations on patterns of granular fertiliser deposition beside hedges and its likely effects on the botanical composition of field margins

SummaryPatterns of granular fertiliser deposition differed markedly between a pneumatic boom applicator and a spinning disk machine, both of which were tractor‐mounted. The pneumatic applicator gave relatively even distribution across the boom width. A spinning disk gave more variable deposition and significant amounts were spread further than the expected 12 m overlapping pattern. When operating with a deflector plate on the spinning disk, significant amounts of fertiliser were also spread further than the expected 6 m. However, when operating next to a hedge, there was evidence of fertiliser concentration at the base of the hedge and prevention of granules passing through to adjacent habitat. A peak concentration of up to 150 kg ha‐1 of fertiliser was deposited at the hedge/field edge interface.In a tray experiment on seedling competition and establishment, there was no evidence of nitrogen fertiliser effects, at rates found in the field, on early plant establishment or species diversity. However, in a competition experiment with established plants of four grass species grown in pots, the nitrophilous species Bromus sterilis was able to increase growth at increasing nitrogen level, at the expense of slow‐growing Brachypodium sylvaticum and Anthoxanthum odoratum. Whilst hedges may buffer fertiliser contamination of habitats adjacent to agricultural fields, deposition of concentrated nitrogen fertiliser beside the hedge is likely to encourage the growth of nitrophilous plant species. In the short term, this may not affect botanical composition or diversity, but to reduce the likely long‐term adverse effects of fertiliser misplacement, we recommend that farmers are encouraged to use pneumatic fertiliser applicators and to introduce vegetation buffer strips at field edges.

98/00557 Gas concentration profiles and NO x formation in circulating fluidized bed combustion

The problem of ash settling on super-heater tube bank, due to improper velocity distribution, in the cyclone separator used at Circulating Fluidized Bed Combustion (CFBC) has been investigated by means of computational fluid dynamic techniques. With the help of Computational Aided Design (CAD) software packages, the geometries of recycling cyclone, has been constructed. With the suitable domain decomposition for the cyclone geometry, multi-block structured mesh has been generated and exported to commercial Computational Fluid Dynamic (CFD) solver – TASCflow. After assembling these grids in the flow solver, duplicate elements at mating surfaces are eliminated through generalized grid interfaces. Incompressible viscous flow for the specified flow conditions are simulated and numerical results are interpreted through contour plots and streak lines. The velocity distribution pattern obtained from the analysis exhibits strong flow recirculation with large turbulent eddies in the cyclone outlet. The analysis also observed high pressure drop across the cyclone separator. To improve the velocity distribution and to reduce the pressure drop, geometry has been modified with the deflector plates in the outlet duct and repeated the simulation. The results obtained for modified geometry are encouraging and shown the improved velocity distribution pattern in the outlet duct. The calculation of particle trajectories depends upon Stokes number, relative velocity of fluid/particles and concentration of particles. If the Stokes number, defined as the ratio of particle response time to system response time is less than one, particles motion is inline with the fluid motion. If the Stokes number is greater than one, particle motion deviates the fluid streams. Effects of these particle impacts are significant on component surface, especially, when they reacts/rebounds the wall surfaces.

Simultaneous measurement of flight time and energy of large matrix-assisted laser desorption ionization ions with a superconducting tunnel junction detector

We evaluated a cryogenically cooled superconducting Nb-Al2O3-Nb tunnel junction (STJ) for use as a molecular ion detector in a matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometer. The STJ responds to ion energy and theoretically should detect large molecular ions with a velocity-independent efficiency approaching 100%. The STJ detector produces pulses whose heights are approximately proportional to ion energy, thus the height of a pulse generated by the impact of a doubly charged ion is about twice the height of a singly charged ion pulse. Measurements were performed by bombarding the STJ with human serum albumin (HSA) (66,000 Da) and immunoglobulin (150,000 Da) ions. We demonstrate that pulse height analysis of STJ signals provides a way to distinguish with good discrimination HSA+ from 2HSA2+, whose flight times are coincident. The rise time of STJ detector pulses allows ion flight times to be determined with a precision better than 200 ns, which is a value smaller than the flight time variation typically observed for large isobaric MALDI ions detected with conventional microchannel plate (MCP) detectors. Deflection plates in the flight tube of the mass spectrometer provided a way to aim ions alternatively at a MCP ion detector.

Conceptual design of a novel instrument far producing intense pulses of 10 ps X-rays for ultra-fast fluorescence measurements

We report a conceptual design of a novel bench-top device for producing intense, fast pulses of X-rays with 10 ps fwhm (full-width at half-maximum) X-ray pulse width, 120 keV maximum energy, 100 kHz repetition rate, and 1 A peak current onto the X-ray anode. The device includes three sections: (1) an electron gun that generates 5 ns wide pulses of electrons; (2) solenoidal magnetic lenses and rectangular deflection plates that focus the electrons onto an aperture plate and sweep the pulsed beam past the slit aperture, respectively; and (3) a tungsten anode onto which the post-aperture electrons are focused, producing X-ray pulses. Solenoidal magnetic lenses with a current density of 150 A/spl middot/turns/cm/sup 2/ focus the 120 keV electron beam to a spot diameter of 0.32 mm such that a deflection plate dV/dt of 10/sup 13/ V/s (achieved with power triode circuitry) will yield X-ray pulse widths of about 10 ps. We used EGUN, an electron optics and gun design program, to simulate the electron trajectories throughout the instrument.

A study for the installation of the TEXT heavy-ion beam probe on DIII-D

An assessment of the feasibility of installing the TEXT 2 MeV heavy-ion beam probe on the DIII-D tokamak has been completed. Detailed drawings of the machine cross section were imported into the CAD application AutoCAD. A set of programs written in AutoLisp were used to generate trajectories. Displays of the accessible cross section of the plasma, scan lines for the entire range of primary beam energy and injection angle ranges, and sample–volume dimensions can be rapidly generated. Because of the large deflection between the primary input beam and the emergent secondary beam, either the analyzer needs to be tracked over a ±20° angle or secondary poloidal deflector plates need to be installed at the exit port. Toroidal deflector plates will be installed at both the injection and exit ports to compensate for toroidal displacements and deflections. The sample volumes generated by this procedure are within a few centimeters of the locations derived from a full three-dimensional calculation.

5494407 Wind turbine with savonius-type rotor : Benesh Alvin Pierre, SD, 57501, UNITED STATES

Savonius wind turbines are the most suitable devices used in urban areas to produce electrical power. This is due to their simplicity, ease of maintenance, and acceptable power output with a low speed and highly variable wind profile. However, their efficiency is low, and the development of optimization tools is necessary to increase the total power output. This work presents a metamodel-based method to optimize the size and shape of a set of deflector plates to reduce the reverse moment of the turbine, using a genetic algorithm combined with an artificial neural network, reducing the computational cost. A parametrization of the deflectors geometry is proposed, and a Computational Fluid Dynamics model was implemented to train and validate the artificial neural network. The method was applied to design the deflectors of an actual 8-blade, 1[kW], 2.5[m] height turbine. Results showed an efficiency increment of 30%, from 0.215, to 0.279 in the turbine with the optimized deflectors. Furthermore, it is capable of producing power at 4[m/s], while the reference design had null power at that point. This methodology demanded 159 h, a substantial reduction of the computational cost of up to 97% in contrast to the classical simulation-based optimization approach.

Radial velocity distributions of secondary ions ejected from PTFE by MeV atomic ions

In this paper, systematic investigations of the initial radial velocity distributions of CnFm+ secondary ions sputtered by 72.3 MeV 127I+13 ions from polytetrafluoroethylene (PTFE) foils are presented. The initial radial velocity distributions are obtained by monitoring the secondary ion yield as a function of the voltages applied to two sets of deflection plates installed parallel to the ion optical axis of a time-of-flight mass spectrometer. The mean radial velocity, 〈vx〉, of CnFm+ ions (1 < n < 6and0 < m < 13) depends on the number of fluorine atoms, showing a periodic behaviour when plotted as a function of the ion mass. Ions with low fluorine content have 〈vx〉 directed towards the primary ion's line-of-incidence (positive mean velocities). Ions with a large number of fluorine atoms are ejected in an off-normal direction away from the incoming MeV ion trajectory (negative mean velocities). The ion emission can not be explained only by evaporative type processes. Mechanisms involving correlated momentum transfer e.g. pressure pulse or shock wave induced ejection, should also be taken into account. The data obtained for fluorocarbon ions from a purely fluorinated compound generalise a similar effect observed previously for CnHm+ ions, sputtered from different hydrogen containing polymer targets [R.M. Papaléo et al., Nucl. Instr. and Meth. B 91 (1994) 667].

Drop Size Distributions for Irrigation Sprinklers

A set of drop size distribution data is presented covering a wide range of sprinkler types including single nozzle impact sprinklers with straight bore and square nozzles, and sprayheads with various types of deflector plates. Drop sizes were measured by the laser-optical method and comparisons with other types of drop size measurement techniques are presented. Distributions are parameterized with an exponential function, and a method is provided to estimate the parameters given the sprinkler type, nozzle size, and pressure head.

Detection of electric-field-ionized Rydberg atoms originating from laser ablation of Si

Si* Rydberg atoms in plasmas originating from laser ablation of Si were identified, employing deflection plates for electric-field ionization and a quadrupole mass spectrometer. The angle-resolved time-of-flight and yield distributions of these species showed that both the most probable time-of-flight and the yield of the Si* atoms decreased with an increasing detection angle, as in the case of laser ablated neutrals.

Laboratory models of growing flanges, and a comparison with other growth mechanisms of “black smoker” chimneys

The first measurements of the structure of black smoker chimneys suggested that they form initially by the precipitation of anhydrite from seawater, because of the reverse solubility effect due to the heating of its surroundings by the effluent, rather than directly from the less dense hot plume. This initial growth is followed by replacement of the solid anhydrite framework, successively by iron, zinc and copper sulfides. More recent observations of very large chimneys have shown that later precipitation directly from the plume can occur through the growth of flanges, or large horizontal protrusions at the side of the chimneys. Light sulfide-rich fluid, leaking out of holes in the chimney wall, ponds under these flanges, which grow as the hot fluid percolates through the porous top or flows over their nearly horizontal edges and precipitates as it cools. Both of these processes have been demonstrated in laboratory models using the crystallization of solutes such as KNO 3 and Na 2CO 3 which have a strong dependence of solubility on temperature. Crystallization from the surroundings can be produced using an inflowing plume of cold K 2CO 3 into a warm nearly saturated KNO 3 solution, and in this case an axisymmetric chimney grows in length at a nearly constant rate, and at the same time thickens as further crystallization takes place. Further experiments, in which the inflowing K 2CO 3 was constrained to spread horizontally near the source, produced a cluster of chimney structures. The first experiments demonstrating the second mechanism, the process of crystallization directly from the incoming fluid, were reported in the context of replenished magma chambers. When dense saturated KNO 3 is injected slowly into cold surroundings, some of the incoming fluid is quenched while the rest is forced upwards to form columns with a flat top. These grow upwards as the gravitationally constrained fluid flows over the lip, cooling and crystallizing as it does so. In the new laboratory experiments reported here the same physical effects are observed in a more appropriate “flange” geometry if a small deflector plate is provided to produce an initial horizontal flow of the nearly saturated KNO 3 solution. Growing flanges have also been produced on the outer face of an existing crystal column, in a geometry which is directly applicable to black smoker chimneys.

Design and performance of an in-line surface-induced dissociation device in a four-sector mass spectrometer

A new in-line surface-induced dissociation device has been designed and characterized in a high performance four-sector tandem mass spectrometer. The design incorporates a target electrode parallel to the ion beam axis and an angled deflector plate (45° relative to the ion beam) to provide large collision angles. In addition, an extraction electrode (parallel to the target electrode) is employed to efficiently extract product ions from the target surface. Results obtained with this device indicate high internal energy deposition (up to 16. 3 eV) as measured with the thermometer ions W(CO) 6 (+·) and Si(C2H5)4/+·, as evidenced by extensive dissociation of the refractory pyrene molecular ion, and as indicated by the b 3/y 2 ratio in the product ion spectrum of leucine enkephalin. High resolution provided by the four-sector instrument for both precursor ions and product ions allows the observation of previously unobserved dissociation products in the surface-induced dissociation spectra of Si(C2H5)4/+· and novel ion-surface reaction products in spectra of W(CO)6/+· ions after collisions with hydrocarbon-covered surfaces. Both hydrogen atom and hydrocarbon abstraction products are observed. The dissociation efficiencies measured with the in-line device are approximately 1% when hydrocarbon-coated surfaces are used and increase fivefold with a fluorinated surface.

Formation and diagnostics of electron beams for micro-FELs

In single electron beam columns the alignment of the beam is obtained either by mechanical shifting the lenses or by x/y alignment deflectors. We are developing multi electron beam columns for electron microscopy and lithography. The problem in multi-beam systems is that mechanical alignment and simple x/y deflectors can only align the total array of beams in the x/y direction and not correct the position of individual beamlets. We present here a simple design, fabrication, electron-optical analysis and experimental results of a multi-beam x/y deflector array that can deflect each beamlet separately. The array is fabricated with micro-fabrication technology with in-plane deflection plates made of molybdenum. The electron optical properties of this in-plane deflector are simulated and compared to a traditional deflector. The experimental measurements are compared with the simulations and are in agreement.

The computer aided manufacture of ceramics using multilayer jet printing

Techniques are currently being developed to allow complex shapes to be created directly from a computer program by the addition of material to, rather than the abstraction of material from, the component. These are mouldless manufacturing operations, variously known as solid free-form fabrication [1,2], rapid prototyping [3] or, more colloquially, "art to part" technology [4, 5]. Various materials processing operations have been adapted for this purpose. In laminated object manufacture (LOM), laser-cut layers of foil are stacked to produce the shape [5]. In stereolithography, an ultraviolet (UV) laser is used to scan and cure a photosensitive monomer [6]. In selective laser sintering, a more powerful laser is used to scan and sinter a deposit of ceramic, metal or polymer powder [1, 7]. Although the last process is attractive for ceramics manufacture, considerable problems of particle packing before sintering and of residual stresses set up during sintefing remain. So far, the main practical use of these techniques is the rapid creation of a prototype from a computer program, but the longer term possibilities for ceramics include the manufacture of high resolution mulfilayer circuits and devices, the fabrication of solid oxide fuel cells of complex design, the preparation of ordered ceramic composites for structural or piezoelectric applications and the manufacture of highly complex small monolithic ceramics. Previous work at Brunel University has considered manufacturing operations for ceramics in which the powder is dispersed in an organic vehicle [8, 9]. These processes do not depend on agglomerated powders and have the capability to achieve the excellent dispersion necessary for high performance ceramics [10]. Similar requirements are applicable in paint and printing operations. Recent work has shown that the random deposition of droplets of a ceramic paint can be used to produce multilayer ceramic composites [11]. Although many printing operations are used in the traditional ceramics industry, only screen printing is widely used for advanced ceramics. Jet printing [12] is a non-contact printing process in which small ( 5 × 10-13m 3) drops of ink are ejected when required from a thermal or piezoelectric activated nozzle of diameter 25-75/xm (drop on demand ink jet printing). In contrast, continuous ink jet printing uses charged drops from a continuously recycled stream, which are diverted to the substrate when required by a voltage applied to deflector plates. Ink jet technology has been used to deposit a binder solution on to layers of roll-compacted ceramic powder to fix particles in place before conventional sintering [13]. This allows the creation of a porous ceramic by computer aided manufacture (CAM). A ceramic ink was prepared by selecting a thermoplastic resin, dispersant and ceramic powder such that the ceramic occupied 60 vol% in the absence of solvent. This volume fraction was chosen to avoid shrinkage cracks [11]. It also confers thermoplastic properties to the dried ink to allow subsequent plastic forming operations if required. This composition was diluted with solvent for printing. The sources of materials and composition of the ink are given in Table I. The polyvinyl butyral

Degradation of Thermal-Barrier Coatings at Very High Temperatures

Thermal-barrier coatings are finding increasing use in engineering applications, particularly in gas turbines. Such coatings, consisting of ceramic insulating layers bonded to the superalloy substrate by oxidation-resistant alloy coatings, are deposited onto components to reduce heat flow through the cooled substrate and to limit operating temperature. They have been used effectively on static components such as combustor cans, flare heads, hot gas seal segments, fuel evaporators, and deflector plates, giving considerable improvements in component life. They have been used successfully on vane platforms. In recent years, the emphasis has shifted toward the development of coatings for high-risk areas, such as turbine blades.A ceramic thermal-barrier coating needs to be refractory and chemically inert, and to have low thermal conductivity. However, it also needs to possess a high thermal expansion coefficient of ~11 × 10−6 K−1, to match the nickel-base superalloy substrate. The latter specification has focused attention on ZrO2. However, ZrO2 is polymorphic and undergoes two phase changes, cubic to tetragonal at 2350°C and tetragonal to monoclinic at 1170°C. The latter transformation is accompanied by a 5% volume increase which means that ZrO2 has to be alloyed to stabilize one of the high-temperature phases. Early systems in the 1970s consisted of ZrO2 stabilized with MgO, but this has been shown to be a metastable system. Present-day commercial thermal-barrier coatings consist of a plasma-sprayed yttria- or magnesiastabilized zirconia layer on top of an M-Cr-Al-Y bond coat. The latter plays a very important role by helping to key the ceramic to the alloy substrate and to accommodate the mechanical strains arising because of differences in thermal expansion coefficients and elastic moduli between the ceramic and the substrate.

A new collimator design for energetic neutral atom instruments

A new type of collimator design is described for energetic neutral atom instruments for space research applications. The collimator consists of annular entrance and exit slits with charged particle deflection plates between them. This configuration allows one to meet three seemingly contradicting requirements of compact design, efficient rejection of the incoming ions, and a large field of view.

INCA: the ion neutral camera for energetic neutral atom imaging of the Saturnian magnetosphere

Techniques developed for the detection and characterization of energetic (>20 keV) ions in space plasmas have been modified to include imaging so that energetic neutral atoms at Saturn may be used to form images of the Saturnian magnetosphere and its interaction with the atmosphere of the moon Titan. The basic elements of the ion-neutral camera head on the magnetospheric imaging instrument for the Cassini mission are described, with emphasis on developmental detection techniques and components. In particular, pulse-height analysis of the microchannel plate responses to different mass neutrals is used for rough composition determination, and deflection plates in the aperture as well as time-of-flight measurements allow imaging of neutral atoms from within regions of moderate intensity ambient ion and electron fluxes.

Reflectron time-of-flight mass spectrometer for laser photodissociation

We describe a new reflectron time-of-flight mass spectrometer configuration for laser photodissociation of mass-selected ions and the initial performance characteristics observed for this instrument. Ions are produced by laser photoionization within the acceleration region of the instrument or by laser vaporization in an external pulsed-nozzle cluster ion source. Mass selection is accomplished with pulsed deflection plates at the end of an initial drift section. Laser photodissociation of selected ions takes place at the turning point in the ion trajectory in the reflectron. The transit time through a second drift section defines the fragment ion masses. Optimized operating conditions and the role of mass discrimination in this instrument are discussed.

A piezoelectric droplet generator for use in wind tunnels

This article describes a compact piezoelectric droplet generator. A unique feature of this instrument is the small size of its nozzle assembly which includes a cylindrical piezoelectric ceramic transducer, an interchangeable orifice, a charging ring, and deflection plates. The nozzle assembly is housed in an acrylic tube, 19 mm in outside diameter and 150 mm in length, which can be placed inside a wind tunnel without causing a significant blockage. The main mechanical components consist of a pressurized system which discharges liquid through the orifice to create a free liquid jet in the nozzle assembly. The transducer causes this jet to break up into uniform droplets by exciting the instability mechanism of symmetric varicose deformations. Droplets tend to be closely spaced because of this method of generation so increased separation is obtained by selectively charging and deflecting some of the droplets from the main stream to a drain. One droplet out of 1–9999 droplets can be selected to exit from the nozzle assembly. The electronic circuitry consists of a transducer driver, and circuits for charging and deflecting the droplets. Power metal-oxide-semiconductor field-effect transistors are used in an H bridge and a push-pull configuration to provide rapid operation of the transducer-driver and droplet-charging circuitry. A transient analysis is performed to obtain the gain factor between the applied voltage and the corresponding flow modulation of the liquid jet. This analysis provides operating characteristics of the transducer and may be used to calculate the breakup length of the jet for a typical applied voltage. Uniform droplets can be produced reliably with this instrument over a large range of size and speed. For the current research application, involving droplet drag in turbulent flows, droplets with diameters from 150 to 1000 μm are required at speeds from 3 to 20 m/s. For other studies, the range of size can be changed by using different orifices.