Deflection Yoke Research Articles

Fast magnetic field analysis of a deflection yoke with a slot core

The cylindrical boundary element method is extended to analyze a three-dimensional configuration such as a deflection yoke with a slot core. The analyzed results are compared with the measurements and the peak field discrepancy is less than 1%. Furthermore the beam convergence characteristics on the screen surface are compared with the measured pattern and it is found that the numerical convergence error is less than 0.2 mm. As for the computation time, the matrix calculation and its solution time is reduced by a factor of 9 in comparison with conventional three-dimensional analysis. The field calculation time is also improved to 0.061 sec/point, which is 6 times faster than by conventional analysis. >

Large biomolecule desorption by massive cluster impact

A new method for desorbing large biomolecules caused by shock wave propagation in a liquid matrix under bombardment with massive, multiply charged clusters provides an extremely soft way of sputtering intact biomolecules with remarkably low fragmentation patterns and a significantly reduced chemical noise background since the low energy per nucleon impacts are insufficient to cause damage both to biomolecules and to the matrix material. Positive or negative cluster beams are formed by electrohydrodynamic spray of conductive solutions of water-methanol, water-glycerol, and pure glycerol by applying different polarity voltage to capillary emitters in vacuum. The beam source is equipped with focusing lens and an electrostatic deflection system for beam positioning. A permanent magnet deflection yoke can be externally mounted for separation of the smaller, larger charge-to-mass ratio, molecular ion component causing target material damage, from the larger clusters in the beam. A theoretical estimation of the cluster charge-to-mass ratio threshold for this damage is viewed as knocking out target atoms from their positions in binary collisions with atoms of the projectile. The model shows that the lowest threshold is caused by heavy atom-heavy atom collisions rather than by collisions involving hydrogen atoms as projectile or target. An experiment performed to verify the theoretical model has displayed a drastic decrease of low molecular noise background when passing the predicted charge-to-mass ratio threshold.

Double‐Quadrupole DAF Gun for Self‐Converging Color CRTs

Abstract— A new dynamic astigmatism and focus (DAF) gun has been developed for high‐resolution color CRTs, resulting in a rounder spot than that produced by existing DAF guns. A quadrupole lens adjacent to the triode of a conventional DAF was added. This lens is driven by the same dynamic waveform as employed in conventional DAFs. The new gun solves the problem of elliptically distorted spot shapes characteristic of conventional DAF guns with a self‐converging deflection yoke.

A Numerical Design Study of Auto-Convergent Electron Gun for Color Cathode Ray Tube

An auto-convergent electron beam gun system for a cathode ray tube (CRT) is proposed, designed and numerically simulated. The system can resolve the beam distortion caused by an aberration of symmetric electrostatic lenses and a higher order field of the deflection yoke, and produce a small beam spot diameter and convergence on the screen. The system consists of two kinds of lenses. One kind consists of three pre-forming lenses for the three beams and the other kind involves the assemblage of two quadrupole lenses, which are common to all beams. After the optimization of the shape of the electrodes and applied voltage on the electrodes, the performance of the lens system is verified by a ray tracing of the electron beams. From the calculation, the spot diameters of 0.3 mm×0.45 mm for the central beam and 0.4 mm×0.45 mm for the outer beam on the screen center are obtained.

Computer simulation of double‐mussel deflection‐coil winding

Abstract— A new program package, DUCAD‐C, has been developed to assist in computer‐aided design of double‐mussel deflection coils. In contrast with the very abstract model of our existing package, DUCAD‐Y, this new package, DUCAD‐C, gives an exact description of a deflection coil based on the simulation of winding this coil in the mandrels. Since the coils calculated by DUCAD‐C agree very well with the corresponding real coil, DUCAD‐C is a very powerful tool for the development of new deflection coils.

Electron beam lithography system with new correction techniques

In our electron exposure system, the focal length of the final projection lens is designed to be very short. To decrease aberrations due to beam deflections, which cannot be corrected by a dynamic focus coil or a stigmator, deflection coil parameters are determined by a simulation, which used the conditions: coma length=0, transverse chromatic aberration coefficient=0, and beam incidence is normal to the sample surface. Patterns of the size under 0.2 μm are well resolved inside the whole deflection field of 1.6×1.6 mm. Current density of the system is more than 40 A/cm2. Refocusing and refocus–flyback are necessary to utilize the high current density for spot size between 0.1 and 3.0 μm. Large spot defocusing is refocused by small refocus coils, and refocused beam position shifts are corrected by a refocus–flyback method. Beam-settling retardation caused by an eddy current occurs after an electromagnetic jump. A differentiated electromagnetic signal is added to electrostatic deflectors to compensate for the transitional beam positions between the jump. The beam-settling time is less than 100 μs for a 1 mm jump, about a tenth of that without the compensation.

A Parallel Detection EELS for an Ultra-HVEM

Some improvements of the ultra-HVEM (HU-2000) for STEM-EELS in Osaka Univ. are summarized. At first, the stability of the accelerating voltage of the ultra-HVEM was improved to realize the parallel detection EELS. Two compensators for the residual instability of the accelerating voltage and the beam trajectory were attached; the beam deflection due to the HF leakage magnetic fluxes was cancelled out by a deflection coil attached above the lens column and the spectrum shift due to the ripple and drift of accelerating voltage was compensated by the deflectors in front of the detector

Low-loss Ni-Zn-Cu ferrite for deflection yoke

A low-loss Ni-Zn-Cu ferrite for the deflection yoke used in display monitors with a high resolution (horizontal scanning frequency: 130 kHz) has been developed. By examining the basic composition, the substituent elements for Fe, the deviation of the Fe composition and the firing temperature, the iron loss is reduced to about a half of that of a conventional ferrite: 2.7 × 10 5 W m -3 ( f = 130 kHz, B m = 0.1 T, t = 100°C). On the basis of an iron loss analysis, the reduction of iron loss is discussed.

VDTs

As the use of video display terminals (VDTs) has expanded, questions have been raised as to whether working at a VDT affects the risk of adverse pregnancy outcome. A particular focus for these questions has been the very low frequency (VLF) magnetic field produced by a VDT's horizontal deflection coil. VDTs also produce VLF electric fields, extremely low frequency (ELF) electric and magnetic fields, and static electric fields, Ten studies of pregnancy outcome in VDT operators have been conducted in six countries, and with one exception, none has concluded that magnetic fields from VDTs may predispose pregnant operators to spontaneous abortion or congenital malformation. The epidemiologic studies conducted thus far do not provide a basis for concluding that VDT work and adverse pregnancy outcome are associated. Studies of fetal resorptions and malformations in rodents exposed to VLF magnetic fields have produced inconsistent findings. Two laboratories in Sweden that studied mice have reported positive results, one laboratory showing field-related malformations (but not resorptions) and the other showing field-related resorptions (but not malformations). Two Canadian laboratories have reported negative results in rats and mice. Studies of avian embryos have also yielded inconsistent results, but lacking a maternal-fetal placental interface, avian embryos are a questionable model for evaluating human reproductive risks. Finally, VLF electric and magnetic fields measured at the operator position are in compliance with field strength standards and guidelines that have been established around the world.

Winding schemes for magnetic deflectors

Many scientific instruments and manufacturing tools that use charged particle beams need uniform or specially-shaped magnetic fields to deflect or analyse the beam. In the absence of magnetic materials, the field shape is of course dependent on the distribution of the deflection coil windings. Two procedures for devising winding distributions for highly uniform magnetic deflection fields are demonstrated. The second of these methods is then generalized to provide a procedure for designing winding patterns to produce fields with predetermined non-uniformities. These procedures use path-following methods to match the Fourier coefficients of the scalar potential produced by a discrete winding pattern to the Fourier coefficients of an ideal two-dimensional scalar potential. Numerical results are given for numerous cases.

Position Control of Electron Energy Loss Spectrum in Case of Accelerating-Voltage Fluctuation

In the parallel detection EELS, the fluctuation effect of the accelerating voltage is compensated both by the open loop and negative feedback controls. The fundamental frequency components of the AC power line and the excitation of Cockcroft-Walton circuit are canceled by applying the inverse-phase signal to the deflection coil, while the effect from the drift and the higher-order ripples is controlled by the negative feedback. The energy resolution is increased from 9.3 eV to 5.7 eV by the open loop control and can be improved up to 3.8 eV by the negative feedback. As the loop gain increases, the resolution increases at first, but then decreases. This decrease results from the shot noise of electron beam and the phase shift of the feedback loop. It is theoretically shown that the optimum condition to the loop gain and the bandwidth exists for the feedback control.

Scanning image detection (SID) system for conventional transmission electron microscope (CTEM) images

A new image detection system has been developed to display transmission electron microscope (TEM) images on a CRT without a video camera system. Deflection coils placed in both the upper space of an objective lens and in the lower space of the first intermediate lens scan a small electron probe simultaneously. The electrical signal acquired through an improved scintillator and a photomultiplier is synchronized with the scanning signal and displayed in a similar fashion to a conventional scanning TEM (STEM) instrument. A preliminary system using a 100 kV conventional TEM (CTEM) equipped with a hairpin-type electron gun, produced an image with a spatial resolution of 1 nm.

Analysis of magnetic plates attached to a deflection yoke with a hybrid method

Deflection yokes require several kinds of magnetic plates to correct the misconvergence of three beams. The effects of magnetic plates attached to a deflection yoke were simulated with a computer program. In this program the magnetic fields were computed with a hybrid method combining the surface-charge and finite-difference methods using Fourier transformation. The misconvergence pattern changed by a silicon steel plate attached to a deflection yoke was calculated by this program. Although the calculated vertical misconvergence changes were larger than those measured, the horizontal misconvergence changes agreed with the measured misconvergence changes within the experimental errors. This result shows that the computer program would be efficient for designing the deflection yokes with optimum magnetic plates.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Thermal-field-emission electron optics for nanolithography

A new column design for the 25-kV vector-scan Gaussian beam lithography system is described. A field-emission gun, consisting of a three-element electrostatic lens and Zr/O/W〈100〉 cathode operated in a thermal-field mode for current stability, is combined in a demagnifying optics with a magnetic objective lens to focus a high-current-density (1000–3000 A/cm2) electron beam at high resolution (100–300 Å) at the wafer plane without a severe reduction in field size. Optimum beam semiangle, focus mode, and column magnification are determined. The modified system retains the original deflection coils and pattern-generation system which allows immediate implementation of existing subfield stitching, chip registration, and proximity correction software.

A wire electronic discharge machine saddle-type deflector for electron beam lithography systems

A new type of magnetic deflector [wire electron discharge machine (EDM) deflector] has been constructed for our gaussian round beam exposure system. To optimize the design of conventional saddle‐type deflection coils used for electron beam lithography systems (EBLS), one of the most important technical problems lies in the achievement of consistency between the computer aided design (CAD) calculated model and the actual structure of the windings. The present paper investigates the relation between the deflection aberration and winding width as well as winding distribution when the parameters of the deflector are optimized. The calculated results show that with 30° central angle of the winding and larger variance of the winding width the influence of third‐order aberration is negligible in micron‐EBLS and submicron‐EBLS. The design and experimental results are discussed for a new type of saddle coil used in EBLS and fabricated by the wire electron discharge machine (wire EDM) technology, this deflector indicates consistency between the CAD model and the actual structure of the winding. In our μm‐order EBLS using the wire EDM deflector, field stitching accuracy of <0.3 μm can be realized. The beam positioning accuracy is ∼0.2 μm.

Optimization of the magnetic deflection system by the method of orthogonal design

By using the expressions of the field parameters and with the aid of the Orthogonal Design Method, we optimized the design of the saddle delection yoke with a ferromagnetic shield. The results obtained agree with the practical model. It is pointed out that the end-ear and the distribution of the fleld parameterB 0 (z) have important effects on the deflection aberrations. An example is given in which the electron optical properties of the deflection coils having cosine- distribution and finite length and that of the deflection coils having distributed winding are compared.

Implementation of differential phase contrast Lorentz microscopy on a conventional transmission electron microscope

Differential phase contrast (DPC) Lorentz microscopy is a powerful technique for investigating magnetization distributions within magnetic thin films. Previously this imaging technique has only been used on microscopes with nonstandard electron optical configurations because of two conflicting requirements: (1) The electron beam must be focused to a very fine probe on the specimen to obtain a high spatial resolution. (2) The specimen cannot be in the magnetic field of the objective lens, as this would destroy the magnetic domain structures of interest. This paper will describe the implementation of the technique on a conventional microscope, a JEOL JEM 2000 FX fitted with an ASID 20 scanning attachment, which satisfies these two requirements. We have modified the controls for the lenses and deflection coils in the microscope to allow an electron probe of less than 40 nm to be formed using the three condenser lenses, with the objective lens off. A position sensitive quadrant detector, required for DPC imaging, is mounted on a sliding O-ring below the projector lens and can be moved in for DPC work or out for standard microscope operation. Attached to the microscope is a digital image acquisition system based on an IBM PC AT. This system is used to acquire signals from the four quadrants of the detector simultaneously. The signals are then mixed digitally to produce the DPC images and an incoherent bright-field image. These images can be further processed to produce vector maps of the in-plane magnetization distributions within the sample. The spatial resolution of 40 nm is less than that of the VG HB501 STEM vacuum generators (VG) HB501 scanning transmission electron microscope (STEM) previously used for DPC imaging. This is due to the larger emitting area of the LaB6 filament compared to the field emission gun of the VG. The LaB6 has a much lower brightness than the FEG and this necessitates long image acquisition times. DPC images and the corresponding vector map from a NiFe film will be shown to demonstrate the technique.

Emission distribution, brightness, and mechanical stability of the LaB6 triode electron gun

Experiments have characterized the operation of a LaB6 triode gun in a standard three-lens column of the type used for Gaussian electron-beam lithography and scanning electron microscopy. A series of images representing cross sections of the three-dimensional spatial distribution of current emitted from the gun is obtained by configuring the electron optics as a scanning confocal microscope. The gun acts as an immersion objective whose image is scanned by deflection coils and focused by the condenser lenses onto a pinhole transmission detector. Characteristics of the emission distribution include an emission image of the cathode surface situated between two distinct beam crossovers whose origin is either the apex (001) and {310} planes or the large {110} planes on the machined 90° cone angle of the cathode surface. Virtual objects are imaged when the back focal plane of the condensers falls inside the high-field region of the gun. The target axial brightness is dependent on gun excitation and angular acceptance angle. The temperature-dependent brightness of the cathode is used to determine its effective emission area, work function, and surface electric field. Beam positional stability of three-carbon-mounted LaB6 directly heated cathodes is measured. However, for measurement times ≤100 h the drift rate is found to be limited by thermal expansion of the movable anode assembly and not the particular cathode mounting technique.

CRT-high resolution and flatness.

There are several problems to be resolved to improve resolution and flatness of the CRT.A larger caliber lens and/or a multiplex lens are introduced in an electron gun to achieve smaller and sharper beam spot size. Corrections by quadrupole and/or DY (Deflection Yoke) with reactors are applied to imporove beam distortion.There are also difficult problems in negatives, materials, and accuracy in etching processes for mask fabrication.Decreasing power loss, improving response in transient, convergence, and raster distortion are other objects associated with DY.This paper describes the current status for above items and some approaches to resolve and overcome them.

16:9 aspect ratio 38V-high resolution trinitron CRT for HDTV

The development and characteristics of a 38-in (vertical) tube for high-definition television (HDTV) are discussed. Design details are given for the glass vacuum tube, the aperture grill and phosphor screen, and the electron gun and deflection yoke. The characteristics of the cathode-ray tube and display monitor are examined.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>