Diagnostics for FIRE and Some Challenges for FIRE and ITER Diagnostics

1. Diagnostics for FIREandSome Challenges for FIRE and ITER Diagnostics K. M. Young (PPPL) FIRE Physics Validation Review March 30, 2004 Gaithersburg, MD

2. OUTLINE • Measurement requirements, taking account of Advanced Tokamak operations and control. • Diagnostics proposed to meet the requirements. • Proposed implementation of diagnostics and integration issues: interfacing with: • Port structure and shielding, remote maintenance, • First wall tiles, copper cladding inside vacuum vessel, • (Divertor structures and pumping, • RWM-stabilizing coils, • Heating systems.) • Physics issues for diagnostic implementation: • Implementing magnetic diagnostics in FIRE, • Active spectroscopy and a Diagnostic Neutral Beam, • Alpha-particle measurements. • Significant developments required/relevance for and comparison with ITER issues. FIRE PVR, Gaithersburg, MD

3. Main Measurement Priorities for FIRE FIRE PVR, Gaithersburg, MD

4. Examples of Measurement Requirements for FIRE Specific measurement requirements to meet Advanced Tokamak goals* * Boivin, Casper and Young (9th Technical Meeting on H-Mode Physics and Transport Barriers (Sept. 2003)). FIRE PVR, Gaithersburg, MD

5. Proposed Edge and Divertor Measurements in FIRE Measurements of divertor plasmas are very constrained, particularly for inner leg FIRE PVR, Gaithersburg, MD

6. A: MSE (2), CXRS (2), Beam Emission Spectroscopy, Lost-a System RWM Coils B: Diagnostic Neutral Beam C: ICRF/LH Launcher RWM Coils D: Pump Duct, Pellet Injector, UV Survey Spectrometer, X-ray Crystal Spectrometer, X-ray PHA, Ion Gauges, RGA (Remote Handling) E: Neutron Camera, Neutron Fluctuation Detectors Bolometer Array Hard X-ray Detector TVTS Dump RWM Coils F: TVTS Detection Plasma TV, IR TV, MM-wave Receiver Metrology System G: ICRF/LH Launcher RWM Coils H: ECE Systems, Reflectometers, MM-wave Collective Scattering Source and Receiver, Magnetics Wiring Fast Edge Probe (Remote Handling) I: TVTS Detection, Plasma TV, IRTV Soft X-ray Array Metrology System RWM Coils J: TVTS Laser, Pellet Charge Exchange, Li-Pellet Injector, Hard X-ray Detector Synchrotron Rad. Detector K:ICRF Launcher RWM Coils L: ICRF Launcher (Remote Handling) M: ICRF Launcher RWM Coils N: ICRF Launcher O: FIR Interferometer/ Polarimeter, Plasma TV, IR TV, Bolometer Array Metrology System RWM Coils P: MSE (1), CXRS (1), Visible Survey Spectrometer, Visible Filterscopes, Visible Bremsstrahlung, a-CHERS (Remote Handling) FIRE Diagnostics: Midplane Port Assignments Blue: Diagnostics Components Orange: Diagnostics-provided Services Red: Auxiliary Systems Green: Services FIRE PVR, Gaithersburg, MD

7. Port-Plug Pre-concepts for Calculation of the Impact of Streaming in Penetrations • Radiation streaming is a critical concern for FIRE. Impacts: • Coil insulation and local diagnostic components in real time, • activation levels in the hall. • Pre-conceptual designs done of penetrations of two ports for first streaming calculations. • First calculations of average fluxes at the back-plate (150 MW pulse, 1.1 m plug): • No penetrations 1.0x107 n/cm2/s, • With 100 mm dia. 1.3x1011 n/cm2/s, straight penetration, • With 100 mm dia. 2.0x109 n/cm2/s, 4-bend penetration. • Activation levels acceptable with 3.4m port neck filled by shielding and additional component shielding. 1.1 m shield • No engineering design of the port configurations or remote handling interface has • been possible. No implementation design made for any optical diagnostic. FIRE PVR, Gaithersburg, MD

8. Radiation Impact and Concerns Radiation-induced Conductivity in Ceramics • Insulators for Diagnostics • Radiation dose at first wall ~ 8 x 103 Gy/sec, significantly higher than for ITER magnetic diagnostics. • Radiation-induced emf (RIEMF) and temperature changes in MI cable may be most severe issue (work in progess in EU & JA). • Optical Properties of Refractive Optics and Fiberoptics • Radiation requires use of reflective optics close to the plasma (issue of coatings). • FIRE (and ITER) still require intensive R&D on radiation effects. Conductivity too high ______________ X FIRE PVR, Gaithersburg, MD

9. Access for Magnetic Diagnostics at Vacuum Vessel, Passive Plates and First Wall • For R=2.14 m device. • Increased spacing provided for magnetic diagnostics between vacuum vessel passive plates and first wall tiles. 4 mm gap Copper Tiles ~ 220 mm side x 38 mm thick Magnetic diagnostic will transition in front of inboard passive plate into slots added in divertor baffle “Pocket” in tiles for mounting magnetic diagnostics FIRE PVR, Gaithersburg, MD

10. Issues for Magnetic Diagnostics in FIRE • Pre-conceptual design carried out for equilibrium coils, Mirnov coils, Rogowski, flux loops and diamagnetic loop. • All mounted inside vessel, behind tiles. • For Equilibrium Coils behind 4 mm gap in copper tiles: • nA ~ 2.5 x 10-2 m2. • 1 mm o.d. MgO-insulated, SS conductor and sheath MI-cable on Al2O3 mandrel. • Using filament model, shielding factor ~ 3 x 10-3 (better modeling required). • Impact of copper plate behind coils on radial field measurement large but not calculated. • Temperature rise from nuclear heating ~ 200°C in 20 sec. • RIC, RIEMF, fabrication and thermal issues for MI cable. • No design for remote handling, etc, for coils (their cooling), connectors, and feedthroughs. FIRE PVR, Gaithersburg, MD

11. The Issue of Active Spectroscopy • Parameters to be measured: • Current density: MSE, polarimetry, Zeeman (edge) • Core helium-ash: CXRS, Fast-Wave Reflectometer (?) • Core impurities: CXRS (low-Z), X-ray Crystal (high-Z) • Ion temperature: CXRS, X-ray Crystal, Neutrons • Poloidal rotation: CXRS, X-ray Crystal • Toroidal rotation: CXRS, X-ray Crystal • Thermalizing Alphas: CXRS • Turbulence: Beam Emission Spectroscopy, Reflectometry • Modulated neutral beam-dependent diagnostics. • MSE can provide much better spatial resolution than possible with polarimetry. • CXRS can provide much better spatial resolution than possible with X-ray or neutrons. FIRE PVR, Gaithersburg, MD

12. The Development Issue for a DNB Source current density for ITER/FIRE ~40 x JT-60U spec. New source scheme needed for IDNB to get low beam divergence. FIRE PVR, Gaithersburg, MD

13. The Challenge of Alpha-particle Diagnostics for BPXs(to meet Snowmass expectations) • Alpha-particle (and high-frequency wave) diagnostics must be available at much higher quality and reliability than for TFTR or JET/DTE1. • Escaping alpha-particle (fast-ion) system: • IR temperature measurement only gives total flux. • Faraday cup and scintillator to go on JET; only possible on mid-plane port-plug in FIRE. • Confined alpha-particle measurement: • Microwave collective scattering operating on thermal ions on TEXTOR1; distribution function data limited. 1Bindslev, Woskov • CO2 scattering not operational on JT-60U; cannot use on FIRE because of access requirements, poor spatial resolution. • Li-pellet with fast NPA: penetration limits spatial range. • Alpha-CHERS: bremmstrahlung noise and fiberoptic fluorescence will be major issues. • Knock-on alphas: development of time-repeating, sharp energy resolution bubble chambers needed (ITER R&D). FIRE PVR, Gaithersburg, MD

14. Urgent Technical Developments needed for FIRE and ITER • Irradiation Tests of Materials (Work mostly in collaboration with ITER but note: FIRE first wall fluxes higher than ITER’s) • Evaluation of radiation-induced conductivity (RIC) in selected ceramics and MI cable to define design materials • Determine cause of radiation-induced emf (RIEMF) with MI cables to prevent signal pollution • Test selected optical fibers for performance in realistic radiation environment at relatively low light-signal levels. • Selection and development of an optimal Diagnostic Neutral Beam. • Advanced -ve ion-based system, • Advanced +ve ion-based system, • Intense pulsed (~1ms) neutral beam. • Evaluate metallic mirror performance and effects on reflectivity of neutral particle bombardment and nearby erosion (ongoing ITER R&D activity). • Develop microwave sources for reflectometry at high field. • Development of electrical connection techniques for vacuum, insulation properties and remote handling. FIRE PVR, Gaithersburg, MD

15. Urgent Physics Developments neededfor FIRE and ITER • Some examples: • Investigate new and improved alpha-particle diagnostics • Extend the operational range of Faraday-cup based and scintillator-based escaping-a diagnostics to FIRE parameters - temperature and radiation qualification. • Seek new techniques for measuring the confined fast-alphas. • Development of New Techniques • High throughput spectroscopic techniques for active spectroscopy, • Bolometric techniques, • Continue development of small rad-hard high-temperature magnetic probes based on integrated-circuit manufacturing techniques. • Prototype Study of “typical” Port Plug • Develop a prototype “port-plug” to incorporate required tolerances, alignments, assurance of ground isolation, actuation of shutters, etc. FIRE PVR, Gaithersburg, MD

16. Concluding Comments • Physics goal of demonstrating successful AT operation in a burning plasma requires a more complete and reliable array of diagnostics than in present-day devices. • Must demonstrate ability to control full range of plasma operation. • FIRE’s diagnostics meet very much the same challenges as ITER’s • Smaller size, higher fields and higher neutron fluxes are more challenging, • Shorter pulse-length, better accessibility are better. • FIRE provides very challenging observation geometries. These will be a major topic of effort in the next design phase. • Sightline availability, • Narrow gaps between first-wall elements, • Usable materials in the environment, • “Vertical” access needed for neutron profile measurements. • An aggressive R&D program in diagnostics is urgently required for BPX plasmas. FIRE PVR, Gaithersburg, MD