Calculations for the optical system for the first ITER plasma

Fusion Science and Technology, 2012

Contributions to Plasma Physics, 1998

Fusion Engineering and Design, 2020

The In-Vessel Viewing System (IVVS) is a metrology instrument designed for deployment inside the ITER Vacuum Vessel (VV) to assess any damage, erosion or displacements of the Plasma-Facing Components (PFCs) through the lifetime of the ITER experiment. The latest developments of the IVVS have identified the Incidence-Angle-Dependent Reflectivity (IADR) of the PFCs to be critical to the assessment of the coverage of the IVVS within the VV. Some ITER PFC prototypes have now been manufactured and a specific instrument has been developed to measure their IADR on site, in an IVVS-like geometry with 100 dB dynamic range. This work presents the first measurements of manufactured ITER PFCs' IADR together with an assessment of the impact of the IADR on the effective coverage of the viewing channel of the IVVS operating through amplitude-modulated lidar.

2008

The highly advanced plan of the RIKEN AVF cyclotron (Japan) is under way. The intensity of the 14 N 5+ ion beam more than 10 p A is required to obtain a sufficient yield of secondary particles. The computer model of the AVF electromagnetic field has been prepared and successfully checked against the measurements. The focus of the present study is on the 2 nd RF harmonic regime. The intermediate goal of the upgrade is improvement of the transmission efficiency and the beam quality of the regime. Measured Hyper ECR output emittances were 64 and 135 mm mrad, from which the emittance of 100 mm mrad was assumed for both transverse oscillations in the simulation. The detailed account of the transmission efficiency and incremental losses are given. The optimization of the starting beam parameters for the existing electrode structure was considered first. The goal is to obtain a sufficiently small axial angle at the exit from the inflector to decrease axial losses in the initial turns. To t...

Fusion Engineering and Design, 2009

The feasibility of using Balmer-␣ emission for a high-speed pressure diagnostic and beam interlock for the ITER neutral beam heating system is investigated. An interlock is needed to prevent excessive re-ionisation of the neutral beam when rapid excursions of pressure occur in either the electrostatic residual ion dump (ERID), or the neutral beam duct (NBD). The re-ionised fraction of the beam, will be deflected by stray tokamak fields, potentially causing excessive thermal loads on beam line components. Experience from JET indicates that a response time of order 100 s is required in order to prevent fast pressure excursions. Fast penning gauges have a time response of around 30-50 ms, however, a faster response (around 1 s) is possible by monitoring the H ˛(656.3 nm)/D ˛(656.1 nm) emission from collisional excitation of the background gas and neutral beam. Published total cross-sections are used to calculate a signal of 3.5 × 10 13 -3.0 × 10 17 photons s -1 m -2 sr -1 for normal conditions. This signal must be distinguished from the background light of the tokamak plasma (line emission and bremsstrahlung). The beam emission is Doppler shifted by up to 21 nm (D operation) and up to 27 nm (H operation) depending on angle of observation and this can be used to help distinguish against background line emission. The distribution of background light along the beam line is calculated with a two-dimensional radiosity code, solving the equilibrium energy balance within the beam line enclosure. The Balmer-␣ signal and background signal due to bremsstrahlung are compared for a 500-MW reference plasma.

2006

Our OFES-sponsored research on IFE technology originally focused on studies of grazingincidence metal mirrors (GIMM's). After the addition of GIMM research to the High Average Power Laser (HAPL) program, our OFES-sponsored research evolved to include laser propagation studies, surface material evolution in IFE wetted-wall chambers, and magnetic intervention. In 2003, the OFES IFE Technology program was terminated. We continued to expend resources on a no-cost extension in order to complete student research projects in an orderly way and to help us explore new research directions. Those explorations led to funding in the field of extreme ultraviolet lithography, which shares many issues in common with inertial fusion chambers, and the field of radiative properties of laser-produced plasma. Our research from 1999 through 2006 led to numerous journal articles and conference publications. Our progress can be best described through these publications, which are listed below. Consistent with the phases of research listed above, the publications are broken into the following categories: A. IFE final optics B. Laser propagation physics in IFE chambers C. Aerosol generation and transport in IFE chambers D. Charged particle transport and magnetic diversion E. Radiative properties of laser-produced plasma F. EUV lithography G. General publications on IFE A. IFE final optics

2001

Fusion Engineering and Design, 2018

The ITER ECRH system consists of 24 gyrotrons with up to 24 MW millimeter wave heating power at 170GHz, power supplies, control system, transmission lines, one Equatorial and the four Upper Launchers. With its high frequency and small beam focus the ECRH has the unique capability of driving locally current. While the Equatorial Launcher mainly acts for central heating and current profile shaping, the Upper Launchers aim on suppressing MHD instabilities, especially neoclassical tearing modes triggering plasma disruptions. The Upper Launchers inject millimeter waves through a quasi-optical section consisting of three fixed and the front steering mirror set. The eight overlapping beams have focal points optimized for suppression of the q=3/2 and q=2/1 NTMs. Several project change requests required the redesign of the Upper Launchers and the connected ex-vessel system. This redesign includes a new boundary geometry of the launchers as well as a newly designed cooling system for the Blanket Shield Module (BSM), a modified flange of the BSM to the structural main frame and a refined optical design. Additionally shield blocks with integrated in-vessel waveguides were added and the closure plate with waveguide and supply line feedthroughs was adapted. Further changes, not all caused by PCRs, include newly designed ex-vessel waveguide components with a reduced aperture and redesigned ultra low-loss CVD diamond windows. Finally several components originally foreseen as off-the-shelf components have become part of the design scope. The new launcher design status is presented with selected results on numerical design validation.

Nuclear Fusion, 2008

The ITER electron cyclotron (EC) upper port antenna (or launcher) is nearing completion of the detailed design stage and will soon be starting the final build to print design. The main objective of this launcher is to drive current locally to stabilise the NTMs (depositing ECCD inside of the island that forms on either the q=3/2 or 2 rational magnetic flux surfaces) and control the sawtooth instability (deposit ECCD near the q=1 surface). The launcher should be capable of steering the focused beam deposition location to the resonant flux surface over the range in which the q=1, 3/2 and 2 surfaces are expected to be found, for the various plasma equilibria susceptible to the onset of NTMs and sawteeth. The aim of this paper is to provide the design status of the principle components that make up the launcher: port plug, mm-wave system and shield block components. The port plug represents the chamber that provides a rigid support structure that houses the mm-wave and shield blocks. The mm-wave system is comprised of the components used to guide the RF beams through the port plug structure and refocus the beams far into the plasma. The shield block components are used to attenuate the nuclear radiation from the burning plasma, protecting the fragile in-port components and reducing the neutron streaming through the port assembly. The design of these three subsystems is described, in addition, the relevant thermo-mechanical and electromagnetic analysis are reviewed for the critical design issues.

Fusion Engineering and Design, 2013

The design of the ITER electron cyclotron launchers recently reached the preliminary design level-the last major milestone before design finalization. The ITER ECH system contains 24 installed gyrotrons providing a maximum ECH injected power of 20 MW through transmission lines towards the tokamak. There are two EC launcher types both using a front steering mirror; one equatorial launcher (EL) for plasma heating and four upper launchers (UL) for plasma mode stabilization (neoclassical tearing modes and the sawtooth instability). A wide steering angle range of the ULs allows focusing of the beam on magnetic islands which are expected on the rational magnetic flux surfaces q = 1 (sawtooth instability), q = 3/2 and q = 2 (NTMs). In this paper the preliminary design of the ITER ECH UL is presented, including the optical system and the structural components. Highlights of the design include the torus CVDdiamond windows, the frictionless, front steering mechanism and the plasma facing blanket shield module (BSM). Numerical simulations as well as prototype tests are used to verify the design