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Carbon-free energy sources are essential to avoid global warming, and nuclear fusion is expected to play a major role in achieving clean and sustainable energy. In the development of magnetic fusion, there exist a lot of issues related with plasma equilibrium to be studied extensively, typical representative of which is a problem of equilibrium reconstruction of plasma. In this paper we propose a new method of equilibrium reconstruction for fusion plasma based on the data assimilation. Aiming at dealing not only with axisymmetric toroidal plasmas but also with more general toroidal plasmas, we formulate the problems of equilibrium reconstruction in generalized forms and derive methods to solve them. We also propose a method for applying the equilibrium reconstruction method to the reversed field pinch (RFP), and it is applied to a real RFP experimental apparatus for its evaluation. It is shown through numerical experiments that the proposed equilibrium reconstruction method works well with reasonable accuracy. And it is also shown through real experiments applying the RFP apparatus that the equilibrium of RFP plasma is appropriately reconstructed.

In the following work, we present the detailed design of a polarization sensitive, NbN based Kinetic Inductance Detector to be employed in a low cost, small footprint polarimeter for fusion plasma diagnostics.

The development of 140GHz and 170GHz MW gyrotron research in BVERI are given in this paper. There are three versions of the 140GHz MW gyrotrons which have been designed and fabricated in BVERI. All of the 140GHz gyrotron have been tested and the experimental results have been enhanced to output power of 500KW with Gaussian beam. Using the techniques achieved in the study on the 140GHz gyrotorns, the 170GHz gyrotron has been designed with the sing-depressed collector and quasi-optical mode converter.

This paper reviews some results from the theory of two-time scale dynamical systems (also called fast-slow systems) and presents the detailed analysis of some systems of interest in electrical engineering and fusion plasma physics. The aim of this work is to introduce engineers to singular perturbation methods as a tool for providing additional insights in modeling and understanding systems whose components evolve on different time scales.

In the following work, we present the study and plans for the realization of a THz QCL based Polarimeter for fusion plasma diagnostics. The device is being developed taking into consideration a reduced footprint, reliability and ease of operation and maintenance.

A dual-frequency gyrotron allowing operation at either 104 GHz or 140 GHz has been developed for use in plasma heating experiments at the W7-X stellarator at IPP Greifswald. The gyrotron has been fabricated, tested, and shipped to the installation site, where long-pulse conditioning is currently in progress (as of January, 2017).

346GHz backward wave oscillations (BWOs) have been considered as a key device for fusion plasma diagnostics, whose development is a joint project under collaboration among Beijing Vacuum Electronics Research Institute (BVERI), University of California Davis (UC Davis) and Lancaster University. In this paper, we report on some progress being made in the development of a 346GHz BWO.

Fusion plasmas in tokamak devices are prone to several unexpected perturbations (ELMs, minor disruptions, L-to-H transitions etc.). These events may terminate prematurely the experiment and hence must be suitably counteracted. To this purpose, suitable modelling is needed. This paper addresses this issue, with particular reference to the JT-60SA tokamak device currently under construction in Japan.

346GHz backward wave oscillations (BWOs) have been considered as a key device for fusion plasma diagnostics, whose development is a joint project under collaboration among Beijing Vacuum Electronics Research Institute (BVERI), University of California Davis (UC Davis) and Lancaster University. In this paper, we report on some progress being made in the development of a 346GHz BWO.

CPI's existing 140 GHz, 900 kW, long-pulse gyrotron design has been adapted to enable operation in an alternative mode at 104 GHz, in addition to the primary 140 GHz mode. The dual-frequency version of this gyrotron has been developed for use in plasma heating experiments at the W7-X stellarator at IPP Greifswald. The gyrotron has been fabricated, and factory testing is currently in progress (as of February, 2016).

CPI has been developing megawatt-class gyrotrons for fusion plasma heating and current drive for a range of frequencies in the mm-wave regime. Gyrotrons at 110 GHz, 117.5 GHz, 140 GHz, and 170 GHz have been designed and fabricated, and have undergone initial factory testing. Some systems have been delivered for commissioning at fusion research facilities, while several await modification following initial test results. Design features and available test data for each design will be presented.

Both capacitive and inductive frequency selective surface (FSS) filters have been applied in millimeter wave imaging plasma diagnostic systems to protect the imaging arrays from stray ECRH power as well as ensure working bandwidth control. Several FSS filters with improved performance have been designed and tested.

The Indian Test Facility (INTF) for Neutral Beams is designed with the objective to not only test the performance of an ion source but also to characterize the transmission of the Neutral Beam to a length of 20.66 m and thereby generate adequate database on the quality of the beam that is required for the CXRS diagnostics for measurement of Helium ash content in the fusion plasma.

Two backward wave oscillator (BWO) designs are proposed for a 346 GHz source for fusion plasma diagnostics applicable for the MAST and NSTX-U devices. Both designs feature a double grating machined from bulk copper, using nano-machining technology.

CPI is developing gyrotrons for fusion plasma heating and current drive at several frequencies. Several of these gyrotrons have undergone initial testing, and are being rebuilt to improve performance. Others are nearing completion of fabrication, with initial testing to begin soon.

Communications and Power Industries (CPI) is currently developing megawatt-class gyrotrons for fusion plasma heating and current drive across a range of frequencies, for use at several different fusion research facilities. These gyrotrons are currently at different stages of development, fabrication, and test. Design features will be compared, available test data will be presented, and future plans will be described.

Korean activities on fusion safety have been going through three phases. The first phase started with the licensing of the Korean Superconductor Tokamak Advanced Research (KSTAR) classified to a radiation generating device on the basis of the existing nuclear regulations. To accommodate the specific characteristics of a tokamak device that was designed to use deuterium to study the fusion plasma physics, a set of instructions to examine the safety of KSTAR and to approve an operating permit were developed and issued by the regulatory body, Korean Institute of Nuclear Safety. The second phase is being done for the ITER. To verify the design of the test blanket module that will be installed and tested in the ITER, safety studies were carried out using the experimental results and computational codes. To minimize occupational irradiation damages, a study on the tritium behaviors is being carried out as Korea will provide a part of the tritium systems of ITER. The last phase has initiated to secure the safety and license for a fusion DEMO plant. Relevant studies have been being carried out in collaboration with the academies funded by the National Fusion Research Institute of Korea. These front-end studies includes the conceptual analysis on the safety and radiological consequences, preliminary studies on the layout research on the future regulatory requirements of the fusion DEMO plant. This paper summarizes these activities on fusion safety with the findings of the front-end studies. It also proposes a pathway for the licensing process of a fusion DEMO plant with the tokamak concept.

Next generation fusion facilities will require many megawatts of RF power from dozens of gyrotrons. Each gyrotron requires a power system that must deliver the high-voltage power, modulate cathode voltage, and protect these expensive gyrotrons from arcing damage. It must be highly efficient, to minimize both the power and cooling costs associated with operation and to ensure high facility availability.

CPI is currently developing megawatt-class gyrotrons for fusion plasma heating and current drive across a range of frequencies in the mm-wave regime. These gyrotrons are currently at different stages of development, fabrication, and test. Design features will be compared, available test data will be presented, and future plans will be described.

This paper reviews the development of millimeter-wave cameras in the 50∼250 GHz region for use in plasma diagnostics on fusion plasma devices.

ECH & CD is widely used in fusion plasmas. Gyrotrons are applied as power sources as they offer continuous wave operation at MW power level. This contribution reports on the status and plans of major projects of KIT towards high power gyrotrons, i.e. results from series production of the W7-X gyrotron, the development of the EU pre-prototype coaxial-cavity gyrotron, the 2 MW, 170 GHz CW coaxial cavity gyrotron for ITER and a frequency step-tunable gyrotron.

A highly parallelized 3D code, based on the Particle-In-Cell approach is used for self-consistent simulations of highly energetic microwave sources (gyrotron resonator and launcher) for fusion plasma heating. We present results for some isolated components of TE 0, 3 and the TE 22, 6 gyrotron.

Final design and assembly are in progress for a 2 MW CW RF load for gyrotrons. Such loads are required for testing high power gyrotrons for electron cyclotron heating of fusion plasmas. The research is building on experience with a 1 MW load to increase the power capability, reduce backscattered RF power, and improve the mechanical design.

The tokamak concept for magnetic confinement of fusion plasmas is now quite mature scientifically. This maturity is evidenced by the ongoing worldwide effort to design and construct an internationally supported multi-billion dollar experimental tokamak called ITER, whose purpose is to demonstrate the scientific and technical feasibility of fusion energy as a power source. To achieve its scientific objectives, the ITER device will need to implement solutions to several challenging control problems. Some solutions to these control problems are already mature, e.g. control of the plasma boundary shape and stabilization of the vertical stability, but many other solutions are currently in development or do not yet have viable solution approaches. In almost all cases, control solutions developed on existing tokamaks are made more challenging on ITER by safety issues arising from its nuclear mission and control actuation margins that are reduced due to cost considerations. However, many of these problems must have robust solutions in place before ITER comes online in approximately 2016. In this paper, we summarize a set of the most urgently needed control solutions and describe the progress made toward solving a few of these problems.

It seems timely to review the performance of large far infrared plasma diagnostics, from design and concept to operation and maintenance. Experience from several recent fusion experiments suggests that a fully integrated approach is required. The teams involved in elaborating the proof of concept, developing engineering, solutions, supervising assembly and installation, as well as operating and maintaining the diagnostic should have a strong collaborative relationship. Selecting the right design and components from the beginning will have major implications on the operation of the device over its operating life. In some cases higher development costs initially can be justified by lower operating and maintenance costs over a long period. These ideas are developed from experience gained by operating some of the largest far infrared plasma diagnostics in the world. Secondly, some criteria for new far infrared devices being designed to work in completely new conditions will be presented. For the next generation of plasma experiments, diagnostics will need to cope with a quite different operating environment including very long period of operation, high radiation and neutron fluxes, very strong magnetic fields and low or zero access to certain parts of diagnostics. This is a major challenge for manufacturers and teams involved in developing new far infrared diagnostics and devices.

The long term strategy of the EU in the field of gyrotrons in fusion plasma applications is based on two approaches: an R&D in laboratories to develop advanced concepts and industrial development of state of the art tubes for use in present experiments like TCV, Tore Supra (118 GHz, 0.5 MW-CW) and W7-X (140 GHz, 1 MW, CW). The results from these two approaches are then applied to the development of a coaxial cavity gyrotron operating at 170 GHz and delivering 2 MW-CW for the electron cyclotron wave system of ITER. The paper recalls the main achievements of this program and outlines the present status of the 170 GHz gyrotron development.

This plenary paper discusses the present state-of-tha-art of high power millimeter wave gyrotron development in EU for electron cyclotron heating and current drive in present and future thermonuclear fusion experiments.

Frequency step-tunable megawatt gyrotrons are of great interest for controlling instabilities in magnetically confined fusion plasmas. The important key for realization of such long-pulse gyrotrons is to minimize the stray radiation inside the gyrotron. Therefore the efficiency of the gyrotron's dimpled-wall antenna has to be optimized for the set of operating modes.

Summary form only given. We have in earlier work reported on intriguing parallels between density fluctuation power versus wavenumber on small (mm) and large (Mpc) scales. In this contribution we expand upon our previous studies of measurements made in fusion plasmas and using cosmological data, respectively. Based on predictions from classical fluid turbulence theory, we argue that our observations are consistent with 2D turbulence. The similar dependencies of density fluctuations on these disparate scales might indicate a common origin

The development of high power gyrotrons in continuous wave operation for heating of plasmas used in nuclear fusion research has been in progress for several years in a collaboration between different European research institutes and industrial partners. The 140 GHz gyrotron is designed for an output power of 1 MW in continuous wave operation and is operated in the TE28,8 mode. The first prototype type had been built with several modification with respect to the "Maquette".

Summary form only given, as follows. A long lifetime neutral beam injector (NBI) system is necessary for heating future fusion plasmas. Therefore negative ion sources for NBI system should be constructed by using high frequency discharge plasmas. A radiofrequency discharge plasma is one of the most promising candidate for long lifetime ion sources. We studied production and control of ECR and RF (i e capacitively coupled plasma.) plasmas by using the magnetic filter method.

Corrugated mirrors are required to change the polarisation state in mm-wave heating of fusion plasmas. Care must be taken to avoid Wood's anomaly which reduces the reflected power in the 0/sup th/ order by transferring energy into an unwanted surface wave propagating along the mirror surface. Measurements and numerical calculations of broadband polarisers are reported.

Gyrotrons at high frequency with high output power are mainly developed for microwave heating and current drive in plasmas for thermonuclear fusion. For the stellarator Wendelstein 7-X now under construction a 10 MW ECRH system is foreseen. A European collaboration has been established to develop and build the 10 gyrotrons each with an output power of I MW for continuous wave operation (30 min). The design parameters of the gyrotron are summarized.

Q, break-even and the n/spl tau//sub E/ diagram are well defined and understood for steady-state fusion plasma conditions. Since many fusion experiments are transient, it is necessary to clarify the definitions for instantaneous Q values and break-even so that the n/spl tau//sub E/ diagram can be interpreted for transient plasma conditions. This discussion shows that there are two mathematically correct methods to describe the n/spl tau//sub E/ diagram for a transient plasma. The Lawson/TFTR method which is consistent with previous analyses of the Lawson cycle, and prior definitions for Q and break-even describes a transient fusion plasma in terms of Q P/sub fusion//P/sub aux/ with the plasma energy confinement time for the n/spl tau/ diagram given by /spl tau//sub E/*=W/sub p//P/sub heat/ where W/sub p/ is the total plasma kinetic energy and P/sub heat/=P/sub aux/+P/sub alpha/-P/sub brem/ is the net power heating the plasma. In the Lawson/TFTR definition break-even (P/sub fusion/=P/sub aux/) occurs at Q=1, ignition occurs at Q=infinity and the n/spl tau//sub E/* values required to achieve a given Q are the same in transient and steady-state plasmas. The JET/JT-60 method uses the definitions of Q*=P/sub fusion//(P/sub aux/-dWp/dt) and /spl tau//sub E/=Wp/(P/sub heat/-dWp/dt). This method produces the confusing result that break-even requires Q*=P/sub aux//(P/sub aux/-dWp/dt) which is >1 for many cases of interest. In addition, the n/spl tau//sub E/ value required to achieve break-even depends on dWp/dt and therefore experimental data points with different dWp/dt must be compared to different Q* curves on the Lawson diagram. For a pulsed plasma, this issue can be avoided by using the definition of fusion gain first introduced by Lawson, namely Q=fusion energy per pulse divided by auxiliary plasma heating energy supplied per pulse.

Fusion plasma research programs and education of Japanese universities are introduced. Finance, numbers of research staff and students, international collaborations, and academic society meetings are also described.

Summary form only given. CAT-SCIENCE Bt, has been working since summer 1998 as a scientific consultancy company in the field of experimental fusion plasma physics. The strategic idea of the company is to use the special knowledge of researchers in governmental institutions by involving them in limited time projects as external experts. We think that in this way we enhance knowledge transfer from the academic to the industrial sector. A special problem of R&D companies in Eastern Europe is the lack of capital on the other hand the advantage is the relatively low staff costs. Taking these into account the company aims at providing services in special fields in R&D.

Summary form only given. The state of development work at KfK Kernforschungszentrum Karlsruhe on 140-GHz high-power gyrotrons for EC wave applications is presented. In particular, the design and experimental results for a 0.5-MW TE/sub 10,4/ gyrotron with axial RF output coupling are discussed. An RF output power up to 0.69 MW at pulse lengths up to 5 ms has been obtained with an electronic efficiency of 31%. Experiments have shown that it is possible to use the aximuthal neighbors of the TE/sub 10,4/ mode TE/sub 9,4/ at 132.6 GHz and TE/sub 11,4/ at 147.3 GHz, as working modes, by decreasing and increasing the magnetic field, respectively (step frequency tuning). The achieved output power in TE/sub 9,4/ and TE/sub 11,4/ modes, 420 kW and 300 kW, respectively, is in good agreement with calculations assuming realistic beam properties and power reflections at the single disc (d = 5/2 /spl lambda/ = 2.76 mm) quartz output window which is optimized for 140.0 GHz.

The development of a high power (⋍1 MW) narrow bandwidth (≤ 50 MHz), pulsed FIR laser for diagnostic research of fusion plasmas has been an area of great activity over the last few years [1,2]. Until recently [3], all of the schemes investigated have consisted of either stable or unstable linear cavities [4,5].

Far infrared (FIR) and millimeter-wave source and receiver development has grown significantly in recent years. The existence of atmospheric windows around the millimeter wavelength has stimulated interest in areas such as communications and radar design. The advantages to be gained by the use of the FIR in fusion plasma diagnostics is already being realized and should prove increasingly important in the future.

The use of microwave energy for ceramic sintering offers exciting new possibilities for materials processing. Based on experience gathered in microwave processing associated with the heating of fusion plasmas, we have developed hardware and methods for uniformly heating ceramic parts of large volume and irregular shape to temperatures in excess of 1600°C, in vacuum or pressurized atmosphere. Microwave processing at 28 GHz yields enhanced densification rates with a corresponding reduction in sintering temperatures.