Design status of the ITER ECRH upper launcher mm-wave system

The purpose of the ITER electron cyclotron resonance heating (ECRH) upper launcher (UL), or antennae will be to provide localised current drive by accurately directing mm-wave beams up to 2MW, out of the four allocated upper port plugs, at chosen rational magnetic flux surfaces in order to stabilise neoclassical tearing modes (NTMs). This paper will present an overview of the UL, with emphasis on the mm-wave components. The mm-wave layout includes corrugated waveguide sections and a quasi-optical path with both focusing mirrors and plane steering mirrors. One of the essential components of the UL is the Steering Mechanism Assembly (SMA), providing variable poloidal injection angles fulfilling high deposition accuracy requirements at the plasma location. The Actuator principle and rotor bearings are frictionless and backlash free, avoiding tribological difficulties such as stickslip and seizure. The underlying working principle is the use of mechanically compliant structures. Validation and proof testing of the steering principle is achieved with an uncooled first prototype demonstrator. A second prototype is currently being manufactured, comprising the functionalities needed for the ITER compatible system such as water cooling and high power mm-wave compatibility. In order to perform the fatigue tests of the actuator bellows, a test facility has been built, under ITER-like vacuum and temperature working conditions. Results of the cyclic fatigue tests are compared to the various manufacturer standards and codes, combining stress and strain controlled material fatigue properties.     

Recent Progress in Plasma Control Studies on the Improvement of Plasma Performance in Heliotron J

Recent progress in plasma control studies on the improvement of plasma performance in Heliotron J is reviewed. The supersonic molecular beam injection (SMBI) fueling is successfully applied to Heliotron J plasma. A supersonic H2-beam is effectively injected to increase fueling efficiency and generate a peaked density profile. Local fueling with a short-pulsed SMBI can increase the core plasma density and avoid the degradation arising from edge cooling. Second harmonic electron cyclotron current drive (ECCD) experiments were conducted by launching a focused Gaussian beam with -0.05 ? N|| ? 0.6. Results show that the EC driven current is determined not only by N|| but also by local magnetic field structure where the EC power is deposited. Detailed analysis of the observed N|| and B dependences is in progress with a ray-tracing simulation using the TRAVIS code. Fast ion velocity distribution was investigated using fast protons generated by ion cyclotron resonant frequency (ICRF) minority heating. For the standard configuration in Heliotron J, charge exchange neutral particle analysis (CX-NPA) measurements show higher effective temperature of fast minority protons in the on-axis resonance case compared to that in the HFS (high field side) off-axis resonance case. However, the increase in bulk ion temperature in the HFS resonance case is larger than that in the on-axis resonance.     

High power millimeter-wave TE03 to TM11 mode converters

Transmission of power from 42 ± 0.2 GHz gyrotron (TE₀₃ mode) to tokamak or dummy load requires a set of transmission line components. It includes a set of mode converters that converts circularly unpolarised TE₀₃ mode to polarised HE₁₁ mode. The mode conversion sequence is methodised in two steps; first from TE₀₃ to TE₀₁ mode and then from TE₀₁ to TM₁₁ mode. The proposed mode converters performance depends on the parameters such as waveguide radius, beat wavelength, number of ripples, its perturbation amplitude (η) and bending angle. These parameters are numerically optimised and verified in CST microwave studio. TE₀₃ to TE₀₁ mode conversion is realised by the generation of intermediate mode TE₀₂. The mode conversion length for TE₀₃ to TE₀₂ mode converter is6λ₀, (where λ_b is the beat wavelength of corresponding mode conversion) which converts 99.15% of an incident circular TE₀₃ mode power into TE₀₂ mode power. Next, mode converter converts TE₀₂ mode into TE₀₁ mode with 99.06% efficiency along the optimal length of6λ_b. For TE₀₁ to TM₁₁ mode conversion, two conversion methodologies have been proposed: first using axis arc bend (34.94°) technique to convert TE₀₁ into its analogous degenerate mode with 99.01% conversion efficiency and second using parabolic curve with 90° bend, which gives a conversion efficiency of 97.5%.     

Development of a 140 GHz Steerable Launcher for the HL-2A ECRH System

A new electron cyclotron resonance launcher system has been designed and installed on heating and current drive （ECRH/ECCD） the HL-2A tokamak to inject four beams and enable continuous millimeter-wave beam scanning independently in the toroidal and poloidal direc- tions for ECRH/ECCD experiments. The launcher is connected to four mm-wave lines capable of transmitting high power up to 3 MW with two 1 MW/140 GHz/3 s and two 0.5 MW/68 GHz/1 s beams. Based on ray tracing simulation using the TORAY-GA code, tile scanning range of wave beams is -15~~15~ in the toroidal direction and 0~~10~ in the poloidal one for 140 GHz beams, which could cover half of the cross section of plasmas and can satisfy the requirements of advanced physical experiments. The beam radii in the plasma is 17.1 mm and 20 mm for the two 140 GHz beams and 29.5 nnn for the two 68 GHz beams, respectively, allowing a very high localization of the absorbed power. The performance of the steering system was proven to be reliable and the linearity is perfect between the displacement of drive shaft and rotate angle of mirror. Addition- ally the injection performance of the wave beams was optinfized by simultaneously setting the injection angle and the polarization to realize desirable pure O- or X-mode injection.     

Design of interaction cavity of a 170-GHz, 1-MW gyrotron for ECRH application

The design of the interaction cavity of a 170 GHz gyrotron operating in the TE_34,10 mode is presented in this article. An in-house developed code GCOMS and Particle-in-Cell (PIC) code MAGIC are used for the mode selection and beam-wave interaction simulations, respectively. The cold cavity analysis and beam-wave interaction computation are carried out to analyze the eigenmode and output power, respectively. A thorough parametric analysis of the interaction cavity geometry and electron beam parameters is also carried out with respect to the output power and frequency. The results show the capability of the interaction cavity, designed for the TE_34,10 mode, to produce more than 1 MW of RF power of a gyrotron at the operating frequency of 170.03 GHz.     

Prototyping of the Blanket Shield Module for the ITER EC H&CD Upper launcher

The design of the ITER Electron Cyclotron Heating and Current Drive (ECH&CD) Upper launcher is recently in the first of two final design phases. The first phase deals with the finalization of all FCS (First Confinement System) components as well as with specific design progress for the remaining In-vessel components.The most outstanding structural In-vessel component of an ECH&CD Upper launcher is the Blanket Shield Module (BSM) with the First Wall Panel (FWP). Both of them form the plasma facing part of the launcher, which has to meet strong demands on dissipation of nuclear heat loads and mechanical rigidity. Nuclear heat loads from 3 MW/m³ at the First Wall Panel’ surface, decaying down to a tenth in a distance of 0.5 m behind of it will affect the BSM and the FWP. Additional heating of maximum 0.5 MW/m² due to plasma radiation must be dissipated from the FWP.To guarantee save and homogenous removal of such extensive heat loads, the BSM is designed as a welded steel-case with specific cooling channels inside its wall structure. Attached to its face side is the FWP with a high-power cooling structure.Based on computational analysis the optimum cooling channel geometry has been investigated. Specific pre-prototype tests have been made and associated assembly parameters have been determined in order to identify optimum manufacturing processes and joining techniques, which guarantee a robust design with maximum geometrical accuracy.This paper describes the design, manufacturing and testing of a full-size mock-up of the BSM. The study was carried out in an industrial cooperation with MAN Diesel and Turbo SE.     

国际热核聚变装置用回旋管的现状及技术分析

回旋管是一种具有重要发展前景的高功率毫米波和太赫兹源.本文简要介绍了回旋振荡管的结构和基本原理,并且评述了国际热核聚变装置中所用110,140和170 GHz回旋振荡管的发展现况和趋势.同时指出了回旋振荡管发展中存在的关键问题并给出了可能解决的技术途径.