Search

The n = 1 static or quasi-static magnetohydrodynamic (MHD) mode such as locked mode (LM) is measured by using LM coils in KSTAR. The delicate signal processing scheme is established to measure the time-evolution of the amplitude and phase of n = 1 LM even low mode-signal sensitivity than non-mode poloidal field sources of LM coils. The effective area of each LM coils are calibrated by comparing the obtained signal and calculated signal responding to a current in the poloidal field (PF) coils without plasma. To pick up only the plasma response two kinds of analytic solutions - the lumped circuit model and the autoregressive with exogenous terms (ARX) model - are introduced to estimate the induced signals to the LM coils from the non-axisymmetric in-vessel coils (IVCs) including its eddy current effect. The developed mode diagnostic method is applied to KSTAR disrupted plasmas and shows consistency with other diagnostics.

The neutral beam injection (NBI) system was designed to provide plasma heating and current drive for high performance and long pulse operation of the Korean Superconducting Tokamak Advanced Research (KSTAR) device using two co-current beam injection systems. Each neutral beam injection system was designed to inject three beams using three ion sources and each ion source has been designed to deliver more than 2.0 MW of deuterium neutral beam power for the 100-keV beam energy. Consequently, the final goal of the KSTAR NBI system aims to inject more than 12 MW of deuterium beam power with the two NBI for the long pulse operation of the KSTAR. As an initial step toward the long pulse (∼300 s) KSTAR NBI system development, the first neutral beam injection system equipped with one ion source was constructed for the KSTAR 2010 campaign and successfully commissioned. During the KSTAR 2010 campaign, a MW-deuterium neutral beam was successfully injected to the KSTAR plasma with maximum beam energy of 90 keV and the L-H transition was observed with neutral beam heating. In recent 2011 campaign, the beam power of 1.5 MW is injected with the beam energy of 95 keV. With the beam injection, the ion and electron temperatures increased significantly, and increase of the toroidal rotation speed of the plasma was observed as well. This paper describes the design, construction, commissioning results of the first NBI system leading the successful heating experiments carried in the KSTAR 2010 and 2011 campaign and the trial of 300-s long pulse beam extraction.

The Korea Superconducting Tokamak Advanced Research (KSTAR) device is aimed at advanced tokamak (AT) research. Three years have passed since it achieved its first plasma in 2008. Because it is a superconducting machine and is working toward AT research, it has unique features in terms of the machine engineering and operation. The toroidal field (TF) magnet coils are made of Nb3Sn, which provide high TFs up to 3.5 T, and have been fully tested. The poloidal field (PF) magnet coils, consisting of both Nb3Sn and NbTi, which have a maximum current of 25 kA in their design, were tested up to 15 kA. A thermal hydraulic analysis is being conducted for PF magnet coil operation. All plasma-facing components (PFCs) are equipped with water cooled graphite tiles and have the capability of being baked up to 350°C. A startup scenario, which considered both the effect of the ferromagnetic material in the cable in conduit conductor jacket of the magnet coils as well as a nonferromagnetic up-down asymmetry in the cryostat structure, was developed and demonstrated its effectiveness by the last two year's reliable operations. Passive stabilizers and in-vessel control coils (IVCCs) are key components to realize AT operation in KSTAR. The segmented IVCC coils were connected to form circular coils for internal vertical control in 2010, and diverted plasmas with high elongation (κ~1.8, δ>;0.6) were achieved. A neutral beam injection (NBI) system was developed aiming at 2 MW, 300 s per ion source which meets the long-pulse requirement of KSTAR. An NBI ion source with a power of 1.7 MW at 100 kV has been commissioned for 10 s. Finally, ELMy H-modes were successfully produced with 1.3-MW NBI power at a plasma current of 0.6 MA in the 2010 campaign. The first H-mode discharge (#4200) in KSTAR was achieved one year earlier than officially planned and was done at BT = 2 T with Ip = 0.6 MA in a well-balanced double null configuration after boronization on the PFC. Successful operations in the early days of KSTAR including H-mode experiments revealed the capability of advanced and steady-state operation which is essential for the international thermonuclear experimental reactor (ITER) and future fusion reactors.

It is possible to detect the presence of small field errors in a tokamak with an electron beam. This was demonstrated earlier on T-15 and TEXTOR. This paper discusses the concept, past experience on these tokamaks, calculations for the Korea Superconducting Tokamak Advanced Research (KSTAR) device, an electron beam source, measurement devices for these measurements, and some results. It is shown that small toroidally averaged field errors can be detected by this method. A low voltage electron beam (e-beam) gun and fluorescent screen were mounted in a vertical port and inserted into the vacuum vessel at the end of the KSTAR 2nd campaign plasma experiments. A camera with a narrow field of view was mounted in midplane port in a tube tangent to the field lines at R ∼ 1.3 m and photographed the beam striking the screen. The poloidal field (PF) currents were held constant during the camera exposure period. Many shots with various PF coils energized were made and the deflections of the e-beam were measured. The measurements were made with a camera integration time of 300 ms because of the low light intensity. The results show that there are large field errors that diminish as the PF currents are raised. There appears to be no significant up–down asymmetry for static fields. Measurements with a 7 PF coil scenario with a calculated field null located at e-beam radial position show much larger fields than calculated. KSTAR was constructed with Incoloy 908 conduit using cable-in-conduit conductors (CICC) in 10 of the 14 PF coils and all 16 of the toroidal field (TF) coils. Incoloy 908 has a relative magnetic permeability, μ, of about 10. The field errors appear to be largely due to Incoloy 908.

The construction of the Korea Superconducting Tokamak Advanced Research (KSTAR) device has been completed by August 2007. Key achievements in the KSTAR construction are (i) fabrication process establishment in the Nb3Sn superconducting coils including interface components, (ii) development of magnet structures to resist high magnetic force and thermal loads of TF and PF coils, (iii) accurate assembling of all components using special assembly tools, and (iv) development of ancillary systems including a control system, magnet power supplies, diagnostic systems, heating systems, and cryogenic facility. Device commissioning has been started and the milestone for first plasma discharge is by the end of 2008. The KSTAR operation plan is targeted on the high performance plasma confinement research and long pulse operation achievement using the fully superconducting tokamak device. There is a lot of engineering similarity between KSTAR and ITER, such as using Nb3Sn superconductor for TF and CS magnets. The experience of the KSTAR device could be an important technical basis for the design, procurement, and initial operation of the ITER device, as a role of a ITER pilot device.

The Korea superconducting tokamak advanced research (KSTAR), which is under construction at the National Fusion R&D Center, Korea Basic Science Institute, Daejeon, Korea, has the mission to develop a steady-state capable advanced superconducting tokamak to establish the scientific and technological bases for a fusion reactor. After an intensive R&D program, substantial progress of the KSTAR tokamak engineering had been made on major tokamak structures, superconducting magnets, in-vessel components, diagnostic system, heating system, and power supplies with industrial manufacturers by May 2002. The engineering design has been elaborated to the extent necessary to allow a realistic assessment of its feasibility, performance, and cost. Since May 2003, the project has been in the phase of procurement. The fabrication of main tokamak structure such as vacuum vessel, cryostat, and supporting structures is well progressed. The manufacturing work of superconducting coils is also proceeding favorably. The tokamak assembly started in July 2003 after site preparation and assembly jig. The start of commissioning is scheduled for June 2006. This paper describes the key features and engineering progress of the KSTAR tokamak and elaborates the work currently underway.

HANBIT is a magnetic mirror confinement device. Recently, after finishing the first campaign for the basic system development, it started the second campaign for high-temperature plasma confinement physics study in a mirror configuration. Here, we introduce briefly the HANBIT device and report initial physics experiment results on RF-plasma heating and confinement in the simple mirror configuration. It appears that the discharge characteristics of HANBIT are quite different from those in other mirror devices, and an explanation is presented to clarify the difference.

Analyses of a beam under five-point and three-point bending are presented, using orthotropic plane elasticity to investigate the interlaminar shear failure of unidirectional composites. The approach uses Fourier series expansions of the applied concentrated loads, together with the Saint Venant's semi-inverse method in which the stresses are obtained by a non-dimensional stress function. The computations of the stresses and displacements are conducted by a CRAY XM-P/25 supercomputer. The comparison of stress analyses between the fivepoint and three-point bending configuration is presented for a T300/5208 graphite/epoxy unidirectional composite with a span-to-height ratio of four. It has been found that five-point loading provides the advantage of a specimen having both high shear stresses and almost zero bending stresses over a substantial region of the specimen. This provides the possibility of using the five-point test configuration to measure interlaminar shear strength of unidirectional composites. In addition to the shear dominated stress distributions, the five-point bending fixture has several advantages against other test methods, such as simple fabrication of the specimen, economical testing jig, and easy stopping of test for study of phenomenon, and it can be used to take photographs of a failure. An optimal design in terms of the loading configuration, especially the load line distance of the upper loading applicators, is recommended for the most favorable stress states for interlaminar shear failure of a given composite beam.

The construction of ITER is an extremely important project, not only within the fusion society but also for mankind: By solving critical energy and environmental problems, another major step in human history will be taken. Design, construction, and assembly of an ultra large scale machine such as ITER require thoroughly well defined plans, strategies, and predictions of potential problems and solutions. It is believed that preceding devices and projects may provide useful references for the several important considerations noted above. The KSTAR (Korea Superconducting Tokamak Advanced Research), a representative superconducting tokamak, has the most similar characteristics to the design concept of the ITER. Therefore, the lessons learned from KSTAR can be categorized according to the following engineering aspects: 1) policies to prioritize decisions, 2) catch-up plans for delayed schedules, 3) strategies in site assembly, 4) troubleshooting, 5) standard indexes or guides for tests and acceptance of individual systems and of site assemblies, and 6) interfaces that can be easily omitted in view of the system integration. This paper will summarize the lessons we have learned from the KSTAR project, focusing on engineering related points that can be considered to suggest guidelines for the ITER construction.

A method for determining the critical debond size between the facesheet and the core in composite sandwich panels under in-plane compression is described. The approach uses fracture mechanics together with a buckling criterion for a debonded faceskin. The technique yields predictions for the critical in-plane compressive load for debond propagation as a function of core-to-faceskin debond size, faceskin thickness, lay-up, composite material properties, and honeycomb properties and geometries. A computer program, developed in this work, calculates the critical buckling load and facesheet deformed shape by solving an eigenvalue problem. An experimental study was conducted to determine the onset of delamination buckling in composite sandwich panels containing such flaws. Sandwich panel specimens of graphite/epoxy faceskins and aluminum honeycomb core were constructed with embedded delaminations and with varying faceskin thicknesses and core sizes. Four-point bending tests were conducted such that the faceskin containing the debond was under in-plane compression. The predicted critical fracture loads, computed using the proposed theoretical models which were solved using a numerical computational scheme, closely followed the experimental measurements.

A method for determining the critical debond size between the facesheet and the core in composite sandwich panels under in-plane compression is described. The approach uses fracture mechanics together with a buckling criterion for a debonded faceskin. The technique yields predictions for the critical in-plane compressive load for debond propagation as a function of core-to-faceskin debond size, faceskin thickness, lay-up, composite material properties, and honeycomb properties and geometry. A computer program, developed in this work, calculates the critical buckling load and facesheet deformed shape by solving an eigenvalue problem. The output predicts, for several cases, critical initial debond lengths comparable to those that have been observed on tests on sandwich panels.

The development of the plasma shape control system of the Korea Superconducting Tokamak and Advanced Research (KSTAR) continues from the first utilization for plasma current/ major radii to the full-scale utilizations of the poloidal superconducting magnets and the in-vessel stabilization coils for the highly elongated (κ ∼ 2.0) plasmas planned in 2009/2010. In this paper the shape control of KSTAR is analyzed as a complete integrated form, including the operation design and experiences. In the first plasma campaign held in 2008, the plasma shape control system has been prepared as part of the pulse operation controls for the first daily operation. A time-synchronized shot sequence supervisions and actuator integrations has been done by the full-digital centralization scheme via the EPICS communicating layers and the dedicated fast communication layers. In the end a reliable real-time plasma feedback system have been accomplished for making/sustaining plasma current and major radius. The status of the shape control upgrade proposed for upcoming years is shown as well as the actuator control developments and the newly-introduced in-vessel vertical stabilization control scheme.

The KSTAR cryostat is a 8.8 m diameter vacuum vessel that provides the necessary thermal barrier between the ambient temperature test cell and the supercritical helium cooled superconducting magnet providing the base pressure of 1/spl times/10/sup -5/ torr. The cryostat is a single walled vessel consisting of central cylindrical section and two end closures, a flat base structure with external reinforcements and a dome-shaped lid structure. The base structure has 8 equally spaced support legs anchored on the concrete base. The cryostat vessel design was executed to satisfy the performance and operation requirements. The mechanical penetration components with bellows were designed to restrict the displacements of all kinds of ports due to EM loads and thermal loads within the allowable limits. The major loads considered in this paper for the design of cryostat vessel are the vacuum pressure, the dead weight of vacuum vessel, PFC, and magnet which are total about 400 tons, the electromagnetic load driven by plasma disruption, and seismic loads. Based on these loads, structural analyses were performed. It was found that the maximum stress intensity was below the allowable limit, and that the cryostat vessel had buckling safety of over 5. Based on the results, structural robustness of the cryostat vessel has been proved.

Experiments on a 28 GHz, five cavity gyroklystron amplifier are underway. Initial hot tests show that the stable amplified radiation produces a peak power of 50 kW at 27.85 GHz. A strong oscillation in the output cavity with power exceeding 200 kW is measured near the amplifier operating point. A careful magnetic field tuning near 10 kG is currently underway to optimize the amplifier performance. Experimental results and comparison with numerical simulation results are presented.

The KSTAR (Korea Superconducting Tokamak Advanced Research) project is the major effort of the Korean National Fusion Program to design, construct, and operate a steady-state-capable superconducting tokamak. The project is led by Korea Basic Science Institute and shared by national laboratories, universities, and industry along with international collaboration. It is in the conceptual design phase and aims for the first plasma by mid 2002. The key design features of KSTAR are: major radius 1.8 m, minor radius 0.5 m, toroidal field 3.5 T, plasma current 2 MA, and flexible plasma shaping (elongation 2.0; triangularity 0.8; double-null poloidal divertor). Both the toroidal and the poloidal field magnets are superconducting coils. The device is configured to be initially capable of 20 s pulse operation and then to be upgraded for operation up to 300 s with non-inductive current drive. The auxiliary heating and current drive system consists of neutral beam, ICRF, lower hybrid, and ECRF. Deuterium operation is planned with a full radiation shielding.

A high power microwave-assisted plasma heating experiment is underway at KBSI. The plasma heating system consists of a 28 GHz, 200 kW gyroklystron amplifier, TE01 transmission lines with low loss mitre bends, and a quasi-optical mode launcher. The design of the 200 kW gyroklystron amplifier has been completed. An experimental tube for peak power demonstration is fabricated and currently under rf cold-tests.

A high power five-cavity gyroklystron amplifier operating at 28GHz is under development at KBSI. The amplifier consists of a high power magnetron-injection-gun (MIG), a hybrid coaxial input coupler, three idler cavities, an output cavity, and a beam collector. Numerical codes used in the amplifier design include large-signal non-linear codes for amplifier gain and efficiency calculations, a 3-D electromagnetic simulator (HFSS), a thermal analysis code (ANSYS), and an electron trajectory code (EGUN).

An in-situ ellipsometer based on four-detector polarimeter(FDP) is under development at KSTAR. In-situ ellipsometer for tokamak discharges will measure the characteristics of thin films deposited onto a quartz window near the edge region in real time. These characteristics contain local deposition/erosion rates as well as hydrogen to carbon ratio, which have to be measured in-situ, for more clear insight view of plasma-wall interaction in tokamak edge plasmas. This paper reports the status of in-situ ellipsometer development for tokamak discharges at KSTAR, to study plasma-wall interaction and fuel retention. Basic concept, design and construction of the ellipsometer are described.

A fracture control plan for composite structures is proposed. Such a plan provides for a fail-safe approach to the design of composite primary structures. It integrates inspection techniques with proof testing to define the minimum flaw that can exist in a structure without failure. While crack propagation of a general flaw in composites is a complex problem, a specific flaw such as delamination is a common failure mode in typical engineering laminates. Using linear fracture mechanics, it is relatively straightforward to calculate the tendency for a delamination flaw to propagate. This approach, coupled with appropriate inspection techniques, constitutes the basis of the proposed plan. Currently, no fracture control plans exist for composite structures. The proposed plan is envisaged as a first step toward assuring the design of damage-tolerant composite structures.

Identifying which business ideas have real commercial potential is fraught with uncertainty, and even the most admired companies have stumbled. It's not as if they don't know what the challenges of innovation are. A new product has to offer customers exceptional utility at an attractive price, and the company must be able to deliver it at a tidy profit. But the uncertainties surrounding innovation are so great that even the most insightful managers have a hard time evaluating the commercial readiness of new business ideas. In this article, W. Chan Kim and Renee Mauborgne introduce three tools that managers can use to help strip away some of that uncertainty. The first tool, "the buyer utility map," indicates how likely it is that customers will be attracted to a new business idea. The second, "the price corridor of the mass," identifies what price will unlock the greatest number of customers. And the third tool, "the business model guide," offers a framework for figuring out whether and how a company can profitably deliver the new idea at the targeted price. Applying the tools, though, is not the end of the story. Many innovations have to overcome adoption hurdles--strong resistance from stakeholders inside and outside the company. Often overlooked in the planning process, adoption hurdles can make or break the commercial viability of even the most powerful new ideas. The authors conclude by discussing how managers can head off negative reactions from stakeholders.