High Voltage Instrument Research Articles

Pluggable 56 kV Instrumentation Feedthrough Prototypes for ITER Magnets

Pluggable high voltage feedtroughs lead voltage or sensor signals from superconducting magnets that are located in the cryostat vacuum, to the data acquisition system. ITER issued a call for tender for the production of such high voltage feedthrough prototypes with a maximum test voltage of 56 kV. In the frame of an ITER contract, KIT and the company ODU connector systems (Mühldorf, Germany) have designed, constructed and tested prototypes of high voltage instrumentation feedthroughs for the ITER magnets. Four feedthroughs have been successfully tested with maximum voltages of 56 kV dc and 35 kV ac peak. In addition the feedthroughs have been Paschen tested with 35 kV dc. Details about design, construction and successful testing are given.

Structure Design and Test Research on the Electrical Properties of High Voltage Instrumentation Cables for the Fusion Reactor

The HV instrumentation cable is an important route for the signals transmission from the superconducting magnets to the control system, it should be long term operated at around 4.2 K and withstand the high voltage over several dozens of kilo volts during the failure operational contrition, meanwhile the cable should be flexible enough to assemble and arrange to the magnet system. According to the instrumentation cable technical requirement, one new type instrumentation cable was designed, after the electrical properties under high voltage were verified in ASIPP lab, the new type instrumentation cables fully meet the technical requirement.

Condition Assessment of High Voltage Instrument Transformer Using Partial Discharge Analysis

Determining the incipient faults in high voltage apparatus is important because failure without warning can result in damage to adjacent equipment, personnel injures, customer dissatisfaction and disruption to economic activity. The failure of several high voltage instrument transformers during in-service prompted Tenaga Nasional Berhad (TNB) to identify more effective diagnostic tool to predict insulation breakdowns. The viability of partial discharge (PD) measurements in the field on instrument transformers is investigated. This paper presents the results of partial discharge tests that have been carried out under laboratory experiments and field measurement on high voltage instrument transformers.

Key Components of the ITER Magnet Feeders

Now that ITER is entering construction, many of its systems are in the final stages of design and analysis. Among them the 31 feeders, which will be supplied in-kind by the Chinese ITER partner. The feeders supply the electrical power and cryogens through the warm-cold barrier to the ITER superconducting magnet systems. They are complex systems with their independent cryostats and thermal shields, densely packed with many components, such as the current feeds, the cryogenic valves and High-Voltage (HV) instrumentation hardware. Some of the feeder components are particularly critical and have been designed with great care. Among them the High-Temperature Superconductor (HTS) current leads, designed for unprecedented currents, the 30 kV class, Paschen-hard HV insulation and the bus bar support system, designed to react the multi-ton Lorentz-forces from the bus bars at minimal heat load. This paper discusses the design challenges for these (and other) key components of the ITER magnet feeders.

나노복합체를 이용한 고효율 전기소재 설계 기술

Recently, research works for electrical properties on the elastic epoxy have been also progressing to diagnose insulation materials by development of measure technology. The epoxy which specially applied for high voltage instillments have required for the electrical, mechanical and thermal properties. Nanocomposites were made from insulating material epoxy resin using for power transformer as v

Mixed D-Core With a Distributed Air Gap as an Alternative for Medium Voltage Instrument Transformers

This paper propounds a practice of using cut cores with a distributed air gap in the production of magnetic circuits for high quality medium voltage instrument transformers. It discusses utilization, for this purpose, of both grain-oriented and non-oriented electrical steel sheets of different grades, hence of considerably different characteristics and cost. The magnetic properties of the transformers were enhanced, and substantial technical and economical benefits in the manufacture of the end product were realized.

Study on Polyimide/Nano-SiO2 Corona-resistance Composite Film

this paper, Polyimide/nano-SiO2 composite films were prepared by means of ultrasonic mechanism. The corona-resistance of composite films were measured by high-voltage instrument which was assembled according to the international standard. The structure of the composite films were described by Fourier transform infrared analysis. The dispersion of the inorganic particles in the films, the morphology of the composite films before and after corona aging were characterized by atomic force microscopy. The results showed that it was effective for the dispersion of nano-SiO2 particles to use ultrasonic. Nanoparticles distributed uniformly in the polyimide matrix. Comparing with pure polyimide films, corona-resistance time of the composite films involved the particles less than 6wt%, was longer. The longest corona-resistance time of composite films reached four times than pure polyimide films.

Determination of the atomic structure of a Σ13 SrTiO3 grain boundary

New elements of a symmetric [001] 67.4∘ SrTiO3 near Σ 13 tilt grain boundary are identified by a quantitative analysis of lattice images, reconstructed electron exit waves, and HAADF images. The analysis reveals local, geometrical variations of structural grain boundary units that relate to the presence of defects introduced by a tilt deviation of 0.65 + 0.02 degrees from the perfect Σ13 geometry. Sr and TiO columns are discriminated in HAADF images while the reconstructed electron exit wave reveals all oxygen columns in addition. Both methods depict the crystal and boundary structure directly while lattice imaging with a high voltage instrument requires image simulations to link the image intensity to structure. For the first time we observe a Sr column splitting by 90 pm that supports theoretical predictions. An inhomogeneous, preferential etching at the grain boundary is attributed to local charge variations and hampers a quantitative investigation and local stoichiometry. The near Σ13 boundary forms a dense and compact structure with chemically identical columns in close proximity. Therefore, it is different from the relaxed, bulk like configurations described in previous reports.

A new high-voltage electric field instrument for studying sprites

The high-voltage (HV) electric field detector is a new high-voltage, high-impedance, double Langmuir probe instrument designed for stratospheric electric field measurements. In the Sprite Balloon Campaign 2002-2003, this HV instrument was used to measure electric fields between 100 and 200 V/m associated with lightning discharges, which is nearly an order of magnitude higher than previously reported above 30 km in altitude. This increased range is made possible by the availability of new low-leakage HV operational amplifiers. This is a critical instrument, since a large quasi-DC electric field associated with positive cloud-to-ground lightning is a primary component of most sprite generation mechanisms. The difficulty that exists when making electric field measurements in the high-resistance environment of the stratosphere is presented, and how this difficulty is remedied is described. The HV detector is compared to another electric field instrument, the low-voltage detector, used simultaneously on the Sprite Balloon Campaign to verify the accuracy of the HV probes. Finally, a large field perturbation (E/sub z//spl ap/-101 V/m and E/sub x//spl ap/79 V/m) measured by the HV detector during Flight 1, correlated with nearby +15-kA and +53-kA cloud-to-ground strokes, is presented.

Advanced computing for ultra-high-resolution in TEM

1. Introduction Attempts to push the resolution of electron microscopes towards 1 Å follow presently two different strategies. One approach takes advantage of the short electron wavelength provided by high-voltage instruments (E > 1 MeV) resulting in an "interpretable" point resolution close to the information limit. An alternative strategy is based on the idea to extend the information limit of conventional medium-voltage instruments (E ≈ 200 - 300 keV) by taking advantage of the excellent coherence properties of field-emission guns (FEG). In the latter approach, however, the gain of extra information beyond the "interpretable" point resolution is of no direct use for structure interpretation. Generally, the interpretability of single highresolution images suffers from a loss of phase information and from contrast-delocalization effects, the latter being caused by the spherical aberration and the defocussing of the objective lens. These derealization effects become drastically apparent when aiming at the ultra-high resolution regime (d < 1.5 Å) which is routinely accessible with medium-voltage FEG-TEMs.

Design, construction, and test of a passive optical prototype high voltage instrument transformer

This paper describes an optical voltage transformer (OVT) for a 132-130 kV system based on the Pockels effect in a Bi/sub 4/Ge/sub 3/O/sub 12/ crystal. Different from the majority of OVTs reported, this construction does not use any capacitive voltage division. To accomplish this, it was necessary to redesign the optical modulator. A prototype of the OVT has been constructed and tested. >

Limits of electron probe formation

SUMMARYThe performance of many electron optical instruments is fundamentally limited by the dimensions of the focused probe. This is true of the scanning electron microscope and the scanning transmission electron microscope and, by inference, it may affect the transmission electron microscope. There has been very little improvement over the past few years and it seems reasonable to look for the explanation. It is possible to arrive at some simple expressions for the limiting performances of conventional instruments in a way that is independent of the design details and depends upon practical limits of field strength. Experiment and theory also appear to be in agreement with the fact that the limit for high‐voltage instruments has been reached, although there is still room for improvement for low voltages.

Alternative approaches to ultra-high resolution imaging

By extrapolation of past experience, it would seem that the future of ultra-high resolution electron microscopy rests with the advances of electron optical engineering that are improving the instrumental stability of high voltage microscopes to achieve the theoretical resolutions of 1Å or better at 1MeV or higher energies. While these high voltage instruments will undoubtedly produce valuable results on chosen specimens, their general applicability has been questioned on the basis of the excessive radiation damage effects which may significantly modify the detailed structures of crystal defects within even the most radiation resistant materials in a period of a few seconds. Other considerations such as those of cost and convenience of use add to the inducement to consider seriously the possibilities for alternative approaches to the achievement of comparable resolutions.

High resolution electron microscopy of polymers near surfaces

The molecular organization of polymer solids near surfaces is important for understanding properties such as adhesion, friction, mass transport, and fracture initiation. Materials comprised of small molar mass atoms or molecules can exhibit detailed reorganization near free surfaces. It might be expected that the perturbing influence of a free surface on structure would be even more pronounced for materials comprised of large macromolecules. Local information about structure near surfaces of inorganic materials is often obtained by High Resolution Electron Microscopy (HREM). Unfortunately, direct imaging of local structure in solid polymers by HREM is problematic because of the extreme sensitivity of organic molecules to electron beam irradiation. However, the systematic application of low dose techniques and the development of stable high voltage instrumentation has made it possible to apply HREM techniques to certain polymer systems. Here, we describe our recent studies which have concerned the microstructure of polymer solids near surfaces. In these experiments we used a JEOL 2000 EX TEM operating at 200 kV and a JEOL 4000 EX TEM operating at 400 kV.

Fulfilling the needs of physical and biological scientists in intermediate and HVEM

There are three (therefore 4 or 5) reasons that high voltage microscopes have remained viable tools for applications in both biological and materials science. Higher voltage means higher penetration with lessened effect from image degrading mechanisms, higher resolution due to decreased electron wavelength, and more (or less) damage to structure due to irradiation effects (more) or to decreased ionization cross section (less). Of the 47 high voltage instruments (V > 500kV) installed worldwide, many remain operational for at least one of these three reasons.Few existing instruments are capable of delivering all three advantages. Earlier microscopes were primarily focussed on providing increased penetration and more or less damage since the high voltage stability and objective lens designs were not optimized to provide high resolution imaging as well. Though the past requirements for fulfilling the needs of physical and biological scientists have not changed for now nor are they likely to change in the future, many of the requirements fulfilled by high voltage microscopes are now achievable using lower kV intermediate voltage instruments, and in some cases, even more ubiquitous lower kV ones.

Experimental module concept for in situ high-voltage electron microscopy

Historically specimens for TEM have been introduced into TEMs either in a small cup into a top entry stage or as a part of a specimen rod in side entry, the various translations and tilt/rotations of the specimen being controlled by a stage mechanism which is essentially permanently installed in the TEM. Generally this technology, when applied to high voltage instruments, has simply been scaled up with the increased objective pole piece gap associated with such emersion lens instruments. While this has allowed somewhat improved access for incorporation of various in situ capabilities, only a very small part of the available space within the objective lens region of an HVEM has ever actually been utilized, typically 5 percent or even less. The concept of an "experimental module" for HVEM in situ studies combines the specimen holder and stage into a single, significantly larger system which can retain most of the convenience of a side entry holder, yet utilize 80 or 90 percent of the available space rather than 5 percent, This allows development and inclusion of a much more diverse array of experimental components, services and analytical capabilities, along with the possibility of improved vacuum or of other environments. The concept of "experimental module" is well established in the synchrotron community, for example, where a given experiment is assembled into a system, the "module", which is interfaced finally to the photon source at the time of the experiment. In the electron microscopy community, however, commonly specimen holders have been designed to be accommodated by the instrument as supplied by the manufacturer, with little resultant design flexibility. With the emergence of contemporary HVEMs having significantly improved specifications for image resolution and analytical capability, it is now time to rethink this, especially for the case of microscopes to be employed for observations of dynamic phenomena.

Quantitative high resolution transmission electron microscopy: the need for energy filtering and the advantages of energy‐loss imaging

SUMMARYEvidence is presented that inelastically scattered electrons contribute significant detail at the atomic level to high resolution images, particularly in high voltage instruments. The implications for quantitative image interpretation are shown to be serious and a case is made for incorporating facilities for energy‐filtered imaging in future high resolution electron microscopes.

A procedure for making phosphor viewing screens for the transmission electron microscope.

A technique is described for preparing uniform, durable phosphor layers for viewing screens suitable for the transmission electron microscope; a settling procedure is used. The example described here is for a high-voltage instrument, but with adjustment of the coating density, the technique should be equally suitable for screen preparation for transmission electron microscopes that operate at lower acceleration voltages.

Observation of Defects in Crystalline Polymers by HREM

The importance of crystalline defects in determining the macroscopic properties of metals, ceramics, and semiconductors is well known. Crystalline polymers also exhibit defect structures, but analyzing of defects in polymers is more difficult because the topological connectivity of the covalently bonded polymer chains means that solid polymers typically exhibit larger amounts and types of disorder than crystals of low molar mass molecules. Imaging is also more complex because of the inherent electron beam sensitivity of these typically organic materials. Recent developments in synthesis and processing have made it possible to achieve very highly ordered polymer systems. Defects in these materials will undoubtedly play a critical role in determining mechanical properties, optical behavior, and transport properties such as electrical conductivity.Direct imaging techniques are particularly important for studying defects because the typically low volume fraction of defects in the crystalline phase makes diffraction experiments difficult if not impossible. Also, in diffraction information about the relative orientation of individual crystallites is lost. It is not surprising, then, that High Resolution Electron Microscopy (HREM) has become extremely important for studying defects in inorganic materials systems. HREM studies of polymers have been limited by the beam sensitivity of organic compounds. Recently, however, high voltage instruments, low dose techniques, and image processing procedures have made it possible to obtain lattice images in systems with beam sensitivities as low as 0.003 C/cm2 (2 e-/A2).This review discusses the nature of defects in crystalline polymer systems and illustrates how proper application of high resolution imaging techniques promises to answer questions in polymer morphology.

A Many-Beam Technique for Enhanced Resolution of Partial Dislocations

The “weak-beam” and systematic many-beam techniques are the currently available methods for resolution of closely spaced dislocations or other inhomogeneities imaged through strain contrast. The former is a dark field technique and image intensities are usually very weak. The latter is a bright field technique, but generally use of a high voltage instrument is required. In what follows a bright field method for obtaining enhanced resolution of partial dislocations at 100 KV accelerating potential will be described.A brief discussion of an application will first be given. A study of intermediate temperature creep processes in commercial nickel-base alloys strengthened by the Ll2 Ni3 Al γ precipitate has suggested that partial dislocations such as those labelled 1 and 2 in Fig. 1(a) are in reality composed of two closely spaced a/6 <112> Shockley partials. Stacking fault contrast, when present, tends to obscure resolution of the partials; thus, conditions for resolution must be chosen such that the phase shift at the fault is 0 or a multiple of 2π.