# Presentation: 636110

## Diagnostics for FIREandSome Challenges for FIRE and ITER Diagnostics 

**K. M. Young  ****(PPPL)**
**FIRE Physics Validation Review **
**March 30, 2004**
**Gaithersburg, MD**

## 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.

## Main Measurement Priorities for FIRE

## 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)).

## Proposed Edge and Divertor Measurements in FIRE

- Measurements of divertor plasmas are very constrained, particularly for inner leg

## FIRE Diagnostics: 

- CXRS (2),
- Beam Emission Spectroscopy,
- Lost- 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,
- -CHERS
- (Remote Handling)

- Blue: Diagnostics Components
- Orange: Diagnostics-provided Services
- Red: Auxiliary Systems
- Green: Services

**FIRE Diagnostics**:
- Midplane Port Assignments

## 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.

## Radiation Impact and Concerns

- 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.

- X

- Radiation-induced Conductivity in Ceramics

**______________**

**Conductivity too high**

## Access for Magnetic Diagnostics at Vacuum Vessel, Passive Plates and First Wall

- Magnetic diagnostic will transition in front of inboard passive plate into slots added in divertor baffle

- 4 mm gap

- Copper Tiles ~ 220 mm side
-                        x 38 mm thick

- “Pocket” in tiles for mounting magnetic diagnostics

- • For R=2.14 m device.
- • Increased spacing provided
-   for magnetic diagnostics
-   between vacuum vessel
-   passive plates and first
-   wall tiles.

## 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.

## 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.

## The Development Issue for a DNB

|  | JT-60U
-ve Beam | JET | ITER 100 keV DNB
Spec. | IDNB
Spec. |
| --- | --- | --- | --- | --- |
| Energy (keV/amu) | 180 | 65 (D0) | 100 | 100 |
| Neutral Beam Current (A) | 7 | 30 | 22 | 50,000
for 1.5 s |
| Beam Divergence (mrad) | 3 | 14 | 5 | 4 |
| Beam Dimensions (m2) | 0.45 x 1.1 (source) | 0.30 dia. | 0.1 x 0.1 | 0.2 x 0.2 |
| Neutral Current Density (mA/cm2) | 11 | ~ 7 | 70 | 1 x 106 |
| Rep. Rate (Hz) | cw | cw | >10 | 300 |

- Source current density for ITER/FIRE ~40 x JT-60U spec.
- New source scheme needed for IDNB to get low beam divergence.

## 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.         1 Bindslev, 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).

## 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 (~1s) 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.

## Urgent Physics Developments neededfor FIRE and ITER

- Some examples:
- Investigate new and improved alpha-particle diagnostics
- Extend the operational range of Faraday-cup based and scintillator-based escaping- 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.

## 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.