kV High Voltage Research Articles

Nitrogen segregation and blister formation of 316LN austenitic steel during electron beam welding tests for ITER gravity supports

316LN has been widely applied in the design of ITER components, such as shield blanket and gravity supports, due to its excellent corrosion resistance and high strength. The behavior of nitrogen in this steel during welding is important for the mechanical properties of the components. In this study, a focused 150 kv high voltage electron beam with 300 mA beam current has been used to weld 316LN steel under vacuum condition. The microstructure and composition of the welding area were observed and analyzed. The influence of welding on the shock resistance and tensile strength at both room temperature and low temperature were examined. It was found that the mechanical properties are strongly related to the defects formed in the welding process.

In situ dynamic HR-TEM and EELS study on phase transitions of Ge 2Sb 2Te 5 chalcogenides

The phase transition phenomena of Ge 2Sb 2Te 5 chalcogenides were investigated by in situ dynamic high-resolution transmission electron microscopy (HR-TEM) and electron energy loss spectroscopy (EELS). A 300 kV field emission TEM and a 1250 kV high voltage TEM were employed for the in situ heating experiments from 20 to 500 °C for undoped and 3 wt% nitrogen-doped Ge 2Sb 2Te 5 thin films deposited by DC sputtering. Crystallization of amorphous Ge 2Sb 2Te 5 to its cubic structure phase started at 130 °C and then rapid crystal growth developed from cubic to hexagonal phase in the range of 130–350 °C; finally, the hexagonal crystals started to melt at 500 °C. For nitrogen-doped Ge 2Sb 2Te 5, its crystallization from amorphous film occurred at higher temperature of ca. 200 °C, and the cubic and hexagonal phases were usually formed simultaneously without significant growth of crystals at further heating to 400 °C. EELS measurements showed that the electronic structures of Ge, Sb and Te stayed almost the same regardless of the amorphous, FCC and hexagonal phases. The nitrogen doped in Ge 2Sb 2Te 5 was confirmed to exist as a nitride. Also, the doped nitrogen distributed homogeneously in both amorphous and crystalline phases. Localization of doped nitrogen was not found in the grain boundary of crystallized phases. The dynamic process of phase transition was enhanced by high-energy electron irradiation. Peeling of atomic layers in nitrogen-doped Ge 2Sb 2Te 5 film was detected during heating assisted with electron beam irradiation.

Ruggedness analysis of 3.3 kV high voltage diodes considering various buffer structures and edge terminations

Buffer structures and edge termination have a decisive influence on the static and dynamic characteristics of free-wheeling diodes. In this paper the influence of buffer structures at the cathode side, the influence of the design of the edge termination and of a resistive zone at the anode side are analysed with respect to the ruggedness of free-wheeling diodes. Therefore, we investigated the device behaviour by means of numerical device simulation concerning the formation of current filamentation and the correlated shape of the electrical field distribution. The considered edge termination of the diodes was planar junction termination extensions and a beveled edge. Various buffer structures, a Gaussian buffer and a buried n-doped layer of increased doping called epitaxy level buffer are compared with a reference diode without any buffer structure.

A large acceptance analysing magnet for HTS-ECR source

A large acceptance analysing magnet has been designed, fabricated and tested. The design aim is to analyse highly charged ions from a high temperature superconducting electron cyclotron resonance ion source, PKDELIS on a 400 kV high voltage platform. The magnet has a unique design incorporating multipole corrections to minimise higher order aberrations using special pole shapes. For double focussing condition, the entrance and exit shim angles have been optimised after inclusion of the gap effect. Since the analysing magnet will be operated on a high voltage platform, the magnet and associated high current power supply are designed to be air-cooled. Special care has been taken in the design of the magnet to have minimum weight, good acceptance and moderate mass resolution.

A high charge state all-permanent magnet ECR ion source for the IMP 320 kV HV platform

A 320 kV high voltage (HV) platform has been constructed at Institute of Modern Physics (IMP) to satisfy the increasing requirements of experimental studies in some heavy ion associated directions. A high charge state all-permanent magnet ECRIS-LAPECR2 has been designed and fabricated to provide intense multiple charge state ion beams (such as 1000 eμA O 6+, 16.7 eμA Ar 14+, 24 eμA Xe 27+, etc.) for the HV platform. LAPECR2 has a dimension of ∅ 650 mm × 560 mm. The powerful 3D magnetic confinement to the ECR plasma and the optimum designed magnetic field for the operation at 14.5 GHz makes it possible to obtain very good performances from this source. After a brief introduction of the ECRIS and accelerator development at IMP, the conceptual design of LAPECR2 source is presented. The first test results of this all-permanent magnet ECRIS are given in this paper.

A Comparison of the Hydrogen Incorporation Mechanisms Observed in Plasma, In-line Implantation and PBII Treatments

Hydrogen was incorporated in silicon by plasma-based ion implantation (PBII) with 20 kV high voltage acceleration. Samples treated by hydrogen plasma and by in-line implantation (H, 30 kV) were performed in order to evidence the specific effects promoted by the PBII. Plasma treatments did not induce any significant change in the silicon. With in-line implantation, only classical defects can be observed in the silicon around the ion projected range. Post-annealing is needed to obtain the formation of platelets. On the contrary, bubbles and platelets can be observed immediately after PBII implantation. With the highest doses, no post-annealing is needed to form blisters and cavities, because of the heating due to the PBII treatment.

Effect of irradiation temperature on void swelling of China Low Activation Martensitic steel (CLAM)

CLAM is one composition of a Reduced Activation Ferritic/Martensitic steel (RAFM), which is being studied in a number of institutes and universities in China. The effect of electron-beam irradiation temperature on irradiation swelling of CLAM was investigated by using a 1250 kV High Voltage Electron Microscope (HVEM). In-situ microstructural observations indicated that voids formed at each experimental temperature − 723 K, 773 K and 823 K. The size and number density of voids increased with increasing irradiation dose at each temperature. The results show that CLAM has good swelling resistance. The maximum void swelling was produced at 723 K; the swelling was about 0.3% when the irradiation damage was 13.8 dpa.

Laboratory Experiments for Electrical Insulation Courses Using a New High-Voltage Cell

The objective of the study is to introduce the use of a computer-aided designed high-voltage cell for teaching electrical insulation. The cell allows students to make real applications in high voltage (HV) topics taught in a single-semester course for senior undergraduate students. The system is constituted of two main parts. The first part is a metal cell which consists of a 220 V/0-100 kV HV transformer, a variable transformer driven by an a.c. motor and a motor driver. The second part is a hand-made electrode system made of tempered glass. The system was controlled manually or automatically using a Programmable Logic Controller (PLC), an operation panel and a computer. In experiments, polyester films are used at various thicknesses as a solid insulation, and transformer oil is also used as a liquid insulation. Each student measures the breakdown voltages under various conditions for solid and liquid insulation using this system. Dielectric strength and ageing of the insulation were determined by computing the mean of the data obtained by each group of students from the experiments. The results and educational benefits are also presented in this paper.

Effect of electron irradiation on microstructural damage in the welded portion of a SUS304 weldment

The matrix and heat affected zone (HAZ) of welded SUS304 steel has been irradiated in an 1250 kV high voltage electron microscope at 673 K to 5.4 dpa (displacements per atom) to study the effect of electron irradiation on microstructure. In situ observation shows the voids formed by electron-beam irradiation coalescence which grew to larger sizes with irradiation dose. Values of void size, void number density and void swelling in HAZ were larger than those of the matrix, and these increased and saturated gradually with irradiation dose. Non-equilibrium segregation phenomenon involving Cr depletion and Ni enrichment at grain boundaries were also observed in both the HAZ and matrix of welded SUS304 steel.

An Assessment of the Methods for Calculating Ampacity of Underground Power Cables

Endurance of an insulation material to high temperatures determines the maximum current-carrying capacity (ampacity) of an underground power cable. Cable ampacity is calculated conventionally using the installation conditions and maximum steady-state operation temperature according to IEC-60287 standard. In this article, finite element method results are compared with IEC-60287. A further verification has also been made with experiments. In this work, ampacity analyzes of 154 kV high voltage XLPE underground power cable are made using ANSYS 5.61 finite element analysis software. An experimental set-up is developed to measure conductor and surface temperature of the cable in underground conditions. The results of experiments and numerical calculations are compared to the IEC-60287 standard. Additionally, the thermal regions of three cables in flat installation are investigated to show the versatility of the finite element method. The effects of insulation thickness and external thermal source on ampacity are also analyzed using the finite element method.

Energy response of a PbWO4 scintillation detector to gamma and neutron radiation

A scintillation detector based on PbWO4 is used to measure gamma rays in a mixed neutron/gamma field from a high intensity pulsed reactor. In order to calibrate gamma sensitivities, a series of monoenergetic radioisotope sources are manufactured in a reactor. Two high-energy gamma sources were obtained from nuclear reactions 12C(p, γ)13N and 19F(p, αγ)16O by means of the 600 kV high voltage accelerator. The energy response of the detector to gamma rays in the energy range 0.15 MeV ⩽ En ⩽ 6.13 MeV was measured and the results are in good agreement with the MCNP simulations. In order to get the absolute sensitivities of the detector to neutrons, one experiment was carried out using 2.5 and 14.1 MeV neutrons from D(d, n)3He and T(d, n)4He reactions and another experiment was carried out using 0.565, 1.2, 1.8, 2.5 MeV neutrons from the T(p, n)3He reaction. The result shows the detector has a high gamma-to-neutron discrimination by comparing the gamma sensitivity at 1.25 MeV with the neutron sensitivity at 1.2 MeV. It is an appropriate gamma detector for pulsed gamma rays in a mixed neutron/gamma field.

Experimental design as a tool when evaluating stationary phases for the capillary electrochromatographic separation of basic peptides

Two different capillary electrochromatography (CEC) stationary phases, Hypersil phenyl and Hypersil C 18, have been characterised with respect to their ability to separate the four basic peptides H-Tyr-(D)Ala-Phe-Phe-NH 2 (TAPP), H-Tyr-(D)Ala-Phe-NH 2 (TAP), H-Phe-Phe-NH 2 (PP) and H-Phe-NH 2 (P). Optimal separation conditions were first established separately for the two phases by applying experimental design in a stepwise procedure. The first step comprised a study to acquire basic knowledge about the variables, their influence on the response and their respective experimental domains for each of the two stationary phases. The second step was screening the significant variables and the third step was an optimisation with response surface modelling (RSM) to locate the optimum separation conditions for each stationary phase. The experimental procedure was identical for both stationary phases, but their respective experimental domains were different. The response functions were peak resolution and peak efficiency. This procedure enables specific optimal experimental conditions to be identified for each of the two stationary phases. The optimal conditions identified for the separation on the phenyl stationary phase were to use 50% ACN, 20% 50 mM Tris(hydroxymethyl)aminomethane (TRIS) pH 7.5, 30% H 2O as BGE, operating at 20 °C and 20 kV high voltage. For the C 18 stationary phase optimal separation was achieved using a BGE with 80% ACN, 20% 30 mM TRIS pH 8.5, again operating at 20 °C and 20 kV high voltage. Results show that the phenyl stationary phase is better suited for the separation of basic, hydrophilic peptides.

Electric field effect in pulsed laser deposition of epitaxial ZnO thin film

We have developed a new system in which thin films can be pulsed laser deposited under an external electric field. Application of 1 kV high voltage to a thin metal wire placed 1 mm above an edge of a 14 mm long substrate distributes electric fields ranging from 4500 V/cm at the left to 50 V/cm at the right side of the substrate. The crystallinity of the ZnO thin film was remarkably improved in the area where the electric field higher than +100 V/cm was applied during the film deposition. Thus, the film growth of ZnO with a strong polarity along the c-axis was verified to depend on an external electric field.

Temperature dependence of dislocation processes during plastic deformation of i-Al–Pd–Mn single quasicrystals

In order to investigate the character of dislocation structures, icosahedral Al–Pd–Mn single quasicrystals were plastically deformed between 821 and 580 °C, where quasi-steady state deformation is possible, and down to 482 °C in a state of strong work-hardening during loading up to stresses up to about 1.6 GPa. The dislocation structures are imaged in a 1000 kV high voltage transmission electron microscope. At high temperatures, the dislocations are arranged in a three-dimensional network of low dislocation density. At low temperatures, the dislocations form narrow bands of a high dislocation density. Part of the dislocations strongly bow out between obstacles, dislocation debris or jogs, but other dislocations consist of segments oriented crystallographically, connected by smoothly bent segments. In other samples, dislocation loops are arranged close to many different planes but parts of them bow out onto inclined faces. These observations are discussed in the light of existing models of the dynamics of dislocation motion and of the evolution of the dislocation density considering dislocation multiplication and recovery. However, many features observed cannot be interpreted on the basis of the present understanding of the dislocation behavior.

Effect of He-Injection on Irradiation Damage in Heat Affected Zone of Welded SUS304 Steel

The heat affected zone (HAZ) of welded SUS304 steel has been irradiated using three irradiation modes of electron single irradiation, electron irradiation after He-injection and electron /He ion dual-beam irradiation by 1250 kV high voltage electron microscope (HVEM) connected with an ion accelerator. Void size in the specimen with pre-injected helium increased considerably and the void size distribution was a bi-modal. Void swelling is the highest in the case of electron irradiation after He-injection. The segregation of solutes of Ni and Cr near grain boundary was suppressed in the cases of electron/He þ -ion dual-beam and electron irradiation after He-injection comparing with electron single irradiation.

Static Characteristics of 6.2kV High Voltage 4H-SiC pin Diode with Low Loss

A 4H-SiC pin diode with improved termination named mesa JTE has been developed and a high blocking voltage of 6.2kV and a low VF of 4.7V at 100A/cm2 have been achieved. A developed diode has an excellent trade-off between the blocking voltage and on-state voltage superior to the trade-off limit of the commercialized Si pin diodes. By evaluation of forward characteristics, a developed diode has 5 to 10 times lower differential resistance than that of a commercialized 4.5kV Si diode.

Dynamic Characteristics of 6.2 kV High Voltage 4H-SiC pn Diode with Low Loss

A 4H-SiC pin diode with improved termination named mesa JTE has been developed and a high blocking voltage of 6.2kV and a low VF of 4.7V at 100A/cm2 have been achieved. A developed diode has a short reverse recovery time of 28.5ns at room temperature. By evaluation of reverse recovery characteristics, a developed diode has a minority carrier lifetime of longer than 1μs at 350°C in spite of a minority carrier lifetime of 64ns at room temperature. Furthermore, a developed diode has 1/29th lower recovery loss than those of a commercialized 4.5kV Si diode.

HVEM irradiation damage in heat affected zone of welded SUS304 steel

The heat affected zone (HAZ) of a welded SUS304 steel has been irradiated in an 1250 kV high voltage electron microscope at 673 K and up to 5.4 dpa (displacements per atom) to study the effect of electron irradiation on microstructure. The dislocation loop density of initial irradiation state increased with electron irradiation dose. Void size, void number density and void swelling increased and then saturated gradually with irradiation dose. The depletion of Cr and the enrichment of Ni at the grain boundary were also recognized by EDS analysis in the HAZ of welded SUS304 steel.

Field-portable capillary electrophoresis instrument with potentiometric and amperometric detection

A portable capillary electrophoresis instrument which incorporates both potentiometric and amperometric detection in a single unit is presented. It includes lead acid batteries as independent power source, a 30 kV high voltage power supply and the detection electronics. With a size of 340 mm×175 mm×175 mm and a weight of 7.5 kg it can easily be carried by one person. Possible applications of the instrument are illustrated with the potentiometric detection of alkali and alkaline earth metal cations with coated-wire ion-selective electrodes and the amperometric detection of electroactive anions with gold electrodes. It is further demonstrated that amino acids may be determined with copper electrodes used in either the potentiometric or the amperometric mode.

Neurological Research and Shared Imaging Resources at the National Institutes in Okazaki, Japan

Abstract The Okazaki National Research Institutes, consisting of three cooperative research Institutes, the Inst. of Molecular Science (NIMS), the Inst. of Basic Biology (NIBB) and the Inst. of Physiological Sciences (NIPS), employs about 700 researchers and 200 full time technical staff. To support cooperative research projects, ONRI has several special shared research facilities in addition to those conventionally used for bioscience laboratories: a 1000 kV high voltage electron microscope designed for three dimensional morphometry and computer tomography of biological structures, a 300 kV ultra cryoelectron microscope equipped with an energy filtering system, which is now being set up, and a two photon excitation laser confocal microscope. In addition, there is an MRI, a rapid MRI, SQUID with 37 + 37 channels, and micro SQUID for non-invasive examination of brain function in human and experimental animals. A UVSOR (UV synchrotron orbital radiation) lab., a laser lab., and an ultra-low temperature lab. are available for neuroscience collaboration with Japanese and international scientists.