Electrostatic Electrodes Research Articles

Stress and its Effect on Surface Morphology in Multi-Layer Ti-Cu Films

AbstractWe have characterized the stress and its effects on surface morphology for multi-layer thin films of about 3μm total thickness, consisting of three or seven layers of Ti and Cu. These films constitute the electrostatic suspension electrodes for the gyroscope housings of the Relativity Mission Gravity Probe B. Full understanding of surface morphology is critical for meeting the complex requirements of this application.The residual stresses have been measured using a laser curvature technique, while the surface morphology was studied by scanning electron microscopy (SEM). We find that the surface morphology depends strongly on the stress, which evolves with the Ti-Cu multi-layer period. Average stress and the resulting surface roughness decrease for thinner Cu layers (increased total number of layers). Seven layer Ti-Cu films with low stress and very smooth surface have been successfully used for the electrodes of the gyroscope housings.

Corona and electrostatic electrodes for high-tension separators

A systematic reseach has been performed, aiming at the optimization of the corona and electrostatic electrodes of roll-type high-tension separators for mixed granular solids. The theoretical analysis of corona-charging and charge-neutralization processes has led to a crude evaluation of the electrical parameters (corona current per unit of length, power of the corona discharge) which should characterize the electrodes for a certain application. Computer modelling of the electric field has enabled the formulation of several design principles, which have been fully-verified by the experiments. Laboratory tests have been carried out in order to compare the various technical solutions and to state some criteria for electrode evaluation. The preliminary reports on the industrial application of the suggested electrode designs are extremely encouraging.

Factors which influence the insulation-metal electroseparation

The experimental study of insulation-metal electroseparation as a multifactorial process has been performed by means of a console-type laboratory apparatus, with four high-voltage electrode carriers, interchangeable roll electrodes, and a set of collecting boxes. The paper illustrates how an electroseparator like this can be employed by research-, design- or application-engineers to investigate the role of each parameter or operating variable. It was revealed the influence exerted on the process by: (i) the homogeneity (composition, granulometric distribution) and the superfacial moisture of the feed material; (ii) the positioning of the corona electrodes and the type of their emitting elements. A special study, based on a charge simulation program, was devoted to the shape, size and location of the electrostatic electrode. The interdependence between the electrical and mechanical factors, such as roll speed and roll radius, are distinctively discussed, with reference to an experiment made with a sample of chopped electric wire and cable scrap, containing stranded and massive copper, polyethylene and polyvinyl chloride. Several technical solutions suggested by the authors (corona electrodes with radially-orientated emitting wire segments, non-circular electrostatic electrode) have been adopted by the recycling industry.

Observations of dust trapping phenomena in the TRISTAN accumulation ring and a study of dust removal in a beam chamber

Using a gamma-ray detector and a television camera system for synchrotron light, high-energy bremsstrahlung and horizontal growth of the synchrotron light source were observed when sudden decrease in the electron-beam lifetime occurred due to dust trapping in the electron beam. Two types of beam current losses were found; one was a continuous beam current loss, and the other was a short-term beam current loss. High-energy bremsstrahlung at a location was observed in a short time and after that, the bremsstrahlung was not detected in spite of the occurrence of dust trapping phenomena. The fact suggests motions of the trapped dust particles in the longitudinal directions. Materials collected in the beam chamber are dust particles from ion pumps and dust particles made during the beam chamber processing for welding. Most of the collected dust particles were less than 2 mm in size and surfaces of some dust particles were melted with the electron beam. Simple analysis was carried out for the conditions necessary for a dust particle to be trapped, for motions of the trapped dust particle, and for interactions between the trapped dust particle and the electron beam. The analysis showed that a dust particle less than 3 mm in size, made of Al, can be trapped and that the trapped dust particle can move in the vertical and longitudinal directions. The analysis also suggested that a dust particle in size of about 2 mm can be continuously trapped around the electron beam without being destroyed by the electron beam. Furthermore, the analysis explained the difference between the two types of beam current losses observed in the ring. Experiments which simulate the electron beam using a Cu wire in an evacuated beam chamber show that a dust particle (less than 70 μm) is trapped sufficiently. The experiments also coincide with theory for an attractive force acting to a conducting small particle. The calculated electric field of the electron beam and the calculated electric charge of dust particles given through the photoelectric effect in the TRISTAN accumulation ring are 100 times and 104–106 times higher than those of the simulated experiments, respectively. In the ring, the attractive force caused with the average electric field and with the expected charge is 10–103 times larger than that of the simulated experiments. Therefore, a dust particle (less than 2 mm) can be trapped sufficiently. An electrostatic dust collector using an electron beam and an electrostatic force are effective in removing all of the sample dust particles in the test chamber for the simulated experiments. A method to remove trapped dust particles using electrostatic electrodes is also discussed. It is expected that such electrodes can be useful for trapped dust particles moving in a longitudinal direction.

The Nissin NH-20SP medium-current ion implanter

The NH-20SP medium-current ion implanter has been developed to meet the needs of advanced ULSI fabrication processes. The NH-20SP has the following features: (1) parallel-beam implantation, (2) 8 in. wafer compatible, (3) precise dose-uniformity control, (4) in-situ parallelism and uniformity monitor, (5) large-tilt-angle implantation, (6) step wafer-rotation during implantation. The NH-20SP employs a hybrid scan system. The horizontal parallel-beam sweep is accomplished with two sets of electrostatic electrodes. A wafer is scanned vertically by a swing-arm scan mechanism. A digital beam sweep system controls the dose uniformity across the wafer. Implant dose uniformity is achieved by adjusting the speed of the vertical wafer motion. The swing-arm scan mechanism provides a large-tilt-angle implantation and stepwise rotation of the wafer during implantation. In this paper an overview of these features will be given and performance data will be presented.

Modelling of high-intensity electric fields - a method to improve the design of corona-electrostatic separators

The equations of the corona-electrostatic field in electroseparators, presented in this paper, can not be solved analytical. Therefore, testing different models of either corona or electrostatic electrodes has proven to be the most reliable way to decide the basic structure of new electroseparators. Conductive sheet and electrolytic tank analogues facilitate optimization of electroseparation equipments.

Noninterceptive wideband pickups for measuring the properties of very low intensity beams

Nondestructive wideband rf beam diagnostics, designed for use in the IUCF Cooler storage ring, are being used in the cyclotron beam lines. Wall gap monitors monitor the beam microscopic time structure, macroscopic time structure, and phase with respect to the main synthesizer; electrostatic pickup electrodes monitor the beam position and intensity. The signal processing and rf-inter-ference-elimination techniques which allow these monitors to operate with beam intensities as low as 10 nA are described. The performance limitations for rf pickups in low energy, low intensity accelerators, and possible methods for using the powerful synchronous detection techniques with nonbunched beams are discussed.

Electrostatic electron focusing in the betatron

The possibility of using the field generated by electrostatic quadrupole electrodes to increase the focusing force in the working chamber of a betatron is considered. It is shown that with a number of quadrupoles N ≥3 focusing in the axial direction, for an equal number of quadrupoles focusing in the radial direction at electrode voltage U ≥15 kV during injection and the initial stage of the cycle an increase in focusing force to the limits of rigid focusing is possible. Experimental testing was performed with an operating betatron. A pair of electrodes with azimuthal extent of 26° located above and below the beam being accelerated was used, with the second electrode pair formed by the conductive chamber coating. An increase in radiation intensity of 30% was achieved.

Measurement of ion beam parameters with electrostatic induction electrodes

One source of information concerning ion beam parameters is the electromagnetic field which can be sensed in a non-destructive manner by means of electrostatic induction electrodes. It is shown that the response of an electrode system is a solution of the Laplace equation with boundary conditions specified by the weighting function of the system. Electrode systems as integral devices can provide information on the beam intensity, transverse beam coordinates, and some coefficients associated with the beam profile. A new class of electrode systems based on the Walsh weighting functions is introduced. Methods are studied for computing the response of electrode systems of a circular as well as of a rectangular cross section. A lower bound, known as the Cramer-Rao bound, on the performance of a measuring system using an electrode system is presented. A concept of spatial filtering is discussed and a novel closed-loop scan generator is proposed. Finally, a brief discussion on the applications of electrode systems indicates that the systems meet requirements for non-destructive sensors suitable for automated equipment employing continuous ion beams.

Estimation of time-varying co-ordinates of ion beams

A method is presented to estimate the time-varying co-ordinates of a continuous, low-energy ion beam. The method is noncontacting and exploits noise-like signals induced by the beam on electrostatic induction electrodes. Results of some preliminary experiments are also shown.

Ion beam co-ordinate monitor

It is shown that the co-ordinate of a continuous low-energy ion beam can be determined by measuring the angle of inclination of an elliptical pattern observed on an oscilloscope whose deflecting plates are driven directly by two noise-like signals induced by the beam on two electrostatic induction electrodes.

Characteristics of a high frequency ion source used in a low-energy accelerator

This work presents the characteristics of a high frequency ion source operating on a low energy, 150 keV accelerator. The latter is to be used as a neutron generator and its design is based on a theoretical analysis which shows that if the axial potential in an electrostatic electrode system is made to increase with four thirds the power of axial distance, inward electric forces will compensate space charge forces tending to blow up the beam. This results in a simplified acceleration tube much shorter and of higher gradient than the conventional acceleration columns. The ion source itself is an ordinary type using axial extraction of the beam, and its main properties investigated are the beam current and beam quality (or emittance). Dependence of the two on different parameters is investigated in a series of tests.

Beam Position Measurement During Fast Ejection

A series of electrostatic pick-up electrodes is used to measure the horizontal position of a single bunch during fast ejection in the Serpukhov proton synchrotron. Any one of the 30 circulating bunches can be followed, whether it is being ejected or stays in the accelerator. The electrode signals go directly into long coaxial cables and no active components are present in the radioactive zone. The signals are digitized and go to a minicomputer. The response of the system is linear over the whole width of the electrodes (200 mm).

Sensitivity of probes used to measure the electron current in a betatron

Calibration of the probes (consisting of a magnetic loop, turns on the accelerating chamber, and an electrostatic signal electrode) used to measure the current circulating in the accelerating chamber of the 15 MeV betatron is reported for various phases of the acceleration. The calibration was carried out in the working part of the accelerator with a current of electrons which had undergone a single revolution in the chamber. Results found in a calculation of the sensitivity and other probe characteristics are reported. A method is described for measuring the current involved in the acceleration by means of turns on the chamber and an electrostatic deflection of electrons. Recommendations are given for the use of probes to adjust a betatron.

Negative Oxygen Ions from a Glow Discharge Source

A simple source of O- ions suitable for accelerator applications is described. Negative atomic ion currents of over 2 μA can be directly extracted at 10 keV energy for a low-pressure cold-cathode oxygen discharge source which incorporates an electrostatic constrictor electrode. The input power is only 25 watts and the gas consumption 14 cm3 h-1 of oxygen at atmospheric pressure.

The Paths of Ions and Electrons in Non-Uniform Crossed Electric and Magnetic Fields

The integration of the force equations for a charged particle moving in the presence of particular types of crossed, non-uniform, electric, and magnetic fields is shown to be possible in a very simple manner. The cases which admit of the integration are those such that: the magnetic field is a function of only one coordinate (either Cartesian or the radius vector in a polar system); the electric field is a function of only one coordinate which for any particular case is the same coordinate with which the magnetic field varies; the electric field has a component only in the direction of the variable with which it varies; and the two fields are orthogonal. Since these conditions, in most cases, are only met on a median plane symmetrically situated relative to magnetic pole faces and electrostatic electrodes, the calculations refer to the motion in this plane. The equations are solved and discussions made of the orbits for several different field arrangements and for one a new type of perfect focusing. The method can be used with numerical integration when the analytical difficulties are too great or when the fields are only known empirically.