Status of Europe’s contribution to the ITER EC system
At a Glance
Section titled “At a Glance”| Metadata | Details |
|---|---|
| Publication Date | 2015-01-01 |
| Journal | EPJ Web of Conferences |
| Authors | F. Albajar, G. Aiello, S. Alberti, F. Arnold, Konstantinos A. Avramidis |
| Institutions | Thales (France), Fusion for Energy |
| Citations | 8 |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: ITER EC System Diamond Windows
Section titled “Technical Documentation & Analysis: ITER EC System Diamond Windows”This document analyzes the requirements for high-power, low-loss diamond windows in the ITER Electron Cyclotron (EC) system, as detailed in the attached research, and maps these needs directly to the advanced MPCVD diamond capabilities offered by 6CCVD.
Executive Summary
Section titled “Executive Summary”The European contribution to the ITER EC system relies on ultra-high-performance components, particularly the diamond windows, which serve as critical barriers for both high-power RF transmission and primary vacuum confinement.
- Critical Component: High-power, low-loss diamond windows are designated as Safety Important Components (SIC) due to their role in primary confinement and mm-wave transmission at 170 GHz.
- Extreme Operating Conditions: Windows must sustain 20 MW RF power during 3600s pulses, handle high thermal loads (peak ohmic loading up to 2.2 kWcm2), and maintain integrity under seismic and disruption events.
- Material Challenge: The lack of applicable industrial codes for nuclear-grade diamond windows necessitates extensive prototyping and qualification programs, demanding materials with guaranteed purity and consistency.
- 6CCVD Solution: 6CCVD provides Optical Grade Single Crystal Diamond (SCD) and large-area Polycrystalline Diamond (PCD) wafers, specifically engineered for low-loss, high-power microwave applications.
- Customization: We offer custom dimensions (up to 125mm PCD), ultra-low roughness polishing (Ra < 1nm), and integrated metalization (e.g., Ti/Pt/Au) required for robust window assembly and vacuum sealing.
Technical Specifications
Section titled “Technical Specifications”The following hard data points define the operational environment and performance requirements for the EC system components, particularly impacting the diamond window design.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| EC System RF Power | 20 | MW | Total power into plasma (initial configuration) |
| Gyrotron Operating Frequency | 170 | GHz | High-power mm-wave transmission |
| Pulse Duration (CW) | 3600 | s | Required continuous operation time |
| Duty Cycle | Up to 25 | % | Maximum operational duty cycle |
| Peak Cavity Ohmic Loading | 2.2 | kWcm2 | Risk factor for heat load on inner walls (mitigation required) |
| HVPS Voltage Regulation | Within ±1 | % | Instantaneous output beam voltage stability |
| HVPS Arc Shutdown Time | < 10 | µs | Required fast protection response |
| Power Modulation Frequency | Up to 5 | kHz | Required for MHD control (NTM stabilization) |
| UL Port Plug Deflection Limit | < 10 | mm | Over 8 m length (seismic/EM loads) |
Key Methodologies
Section titled “Key Methodologies”The successful implementation of the ITER EC system relies on stringent material qualification and advanced engineering processes, particularly concerning the high-power transmission components.
- High-Power Gyrotron Development: Manufacturing 1 MW, 170 GHz, 3600s TE32,9-mode gyrotrons. Focus areas include improving electron beam quality, suppressing parasitic effects, and reducing peak heat load at the collector.
- Advanced Power Supply Design: Utilizing Pulse Step Modulator (PSM) topology for High Voltage Power Supplies (HVPS) to achieve high efficiency and enable fast power modulation (up to 5 kHz) necessary for MHD control.
- Fast Power Modulation Strategy: Implementing a strategy to switch ON/OFF both the cathode (MHVPS) and body voltage (BPS) in less than 50 µs to achieve the required power modulation depth for NTM stabilization.
- Diamond Window Qualification Program: Establishing an extensive prototype and qualification program for the high-power, low-loss diamond windows. This is critical because standard industrial codes for nuclear safety (e.g., ASME III) are not available for this specific component, which functions as a primary confinement boundary (SIC).
- Launcher Optimization: Iterative design optimization of the Upper Launchers (ULs) and Equatorial Launchers (ELs) to maximize EC power deposition accessibility across the plasma cross-section, including the adoption of poloidal steering for the EL.
6CCVD Solutions & Capabilities
Section titled “6CCVD Solutions & Capabilities”6CCVD is uniquely positioned to supply the high-purity MPCVD diamond required for the ITER EC system’s critical vacuum and RF transmission components. Our capabilities directly address the challenges of high thermal load, stringent vacuum integrity, and large-area requirements identified in the research.
Applicable Materials for High-Power EC Windows
Section titled “Applicable Materials for High-Power EC Windows”The requirement for high-power, low-loss transmission at 170 GHz, coupled with the SIC designation, demands the highest quality diamond materials available.
| 6CCVD Material | Application Suitability | Key Benefit |
|---|---|---|
| Optical Grade Single Crystal Diamond (SCD) | Ideal for high-frequency, ultra-low-loss windows where maximum thermal conductivity and purity are paramount. | Lowest absorption coefficient, highest thermal conductivity, guaranteed material consistency. |
| Optical Grade Polycrystalline Diamond (PCD) | Suitable for large-area windows (up to 125mm) or components requiring robust mechanical properties and cost efficiency. | Scalable dimensions up to 125mm diameter, excellent thermal properties, and high mechanical strength. |
| Boron-Doped Diamond (BDD) | Potential use in integrated diagnostics or grounding components within the EC system (e.g., grounding network assessment). | Tunable conductivity for specialized electrical components or electrodes. |
Customization Potential for ITER Requirements
Section titled “Customization Potential for ITER Requirements”The complexity of the EC system interfaces (ex-vessel waveguides, port plugs) necessitates highly customized diamond components and assembly preparation.
- Custom Dimensions & Thickness: 6CCVD offers PCD plates up to 125mm in diameter, meeting the large-area requirements for high-power windows. We provide precise thickness control for both SCD and PCD from 0.1 µm up to 500 µm, crucial for optimizing RF transmission at 170 GHz.
- Ultra-Low Roughness Polishing: To minimize RF losses and thermal absorption, 6CCVD guarantees Ra < 1 nm for SCD and Ra < 5 nm for inch-size PCD. This superior surface finish is essential for high-power optical components.
- Integrated Metalization Services: High-power diamond windows require robust, vacuum-tight metal seals (brazing interfaces). 6CCVD provides internal metalization capabilities using materials critical for UHV and high-temperature bonding, including Ti, W, Pt, Au, Pd, and Cu. This ensures reliable integration into the ex-vessel waveguide system.
- Laser Cutting and Shaping: We offer precision laser cutting services to achieve the complex geometries and tight tolerances required for the port plug and launcher assemblies.
Engineering Support
Section titled “Engineering Support”The paper explicitly notes the challenge of qualifying diamond windows as SIC components due to the absence of established nuclear industrial codes.
6CCVD’s in-house PhD team specializes in the thermal, mechanical, and RF properties of MPCVD diamond. We offer expert consultation to assist engineers and scientists with:
- Material Selection: Optimizing the diamond grade (SCD vs. PCD) based on the specific balance required between RF loss, thermal load handling, and required window size for high-power 170 GHz EC window projects.
- Thermal Modeling: Providing data and support for simulating the 2.2 kWcm2 peak ohmic loading and 3600s pulse duration to ensure window survival and reliability.
- Interface Design: Assisting with metalization layer selection and preparation for brazing, ensuring compliance with stringent vacuum and safety requirements.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
\nThe electron cyclotron (EC) system of ITER for the initial configuration is designed to provide 20MW of RF power into the plasma during 3600s and a duty cycle of up to 25% for heating and (co and counter) non-inductive current drive, also used to control the MHD plasma instabilities. The EC system is being procured by 5 domestic agencies plus the ITER Organization (IO). F4E has the largest fraction of the EC procurements, which includes 8 high voltage power supplies (HVPS), 6 gyrotrons, the ex-vessel waveguides (includes isolation valves and diamond windows) for all launchers, 4 upper launchers and the main control system. F4E is working with IO to improve the overall design of the EC system by integrating consolidated technological advances, simplifying the interfaces, and doing global engineering analysis and assessments of EC heating and current drive physics and technology capabilities. Examples are the optimization of the HVPS and gyrotron requirements and performance relative to power modulation for MHD control, common qualification programs for diamond window procurements, assessment of the EC grounding system, and the optimization of the launcher steering angles for improved EC access. Here we provide an update on the status of Europe’s contribution to the ITER EC system, and a summary of the global activities underway by F4E in collaboration with IO for the optimization of the subsystems.\n