Fast ion collective Thomson scattering diagnostic for ITER S.B. Korsholm 1,2, H. Bindslev 1, F. Leipold 1, F. Meo 1, P.K. Michelsen 1, S. Michelsen 1, A.H. Nielsen 1, E. Tsakadze 1, and P.P. Woskov 2 1 Association EURATOM-Risø National Laboratory, Technical University of Denmark 2 MIT Plasma Science & Fusion Center This work was supported by the European Communities under the contract of Association between EURATOM/Risø and carried out within the framework of the European Fusion Development Agreement [under EFDA Contract and EFDA Task TW6-TPDS- DIADEV.D2]. The views and opinions expressed herein do not necessarily reflect those of the European Commission.

ITPA Diagnostics Meeting, Princeton, March , 2007 Outline of the talk ITER measurement requirements for confined fast ions Overview of the 60 GHz CTS diagnostic for ITER Measuring potential in alternative scenarios Modeling and measurements of the required HFS blanket cut-out Current state of design – a four mirror HFS receiver Robustness to misalignment Measurements of fuel ion ratio and bulk ion drift velocity by CTS Future work

ITPA Diagnostics Meeting, Princeton, March , 2007 Tools developed and used in the studies Scattering calculations ITER requirements for  ’s CEM Finite difference code Vertical beam properties Gauss3D Horizontal beam properties Design of mirrors Mock-up Measured beam properties Design of gap Current memory limitations

ITPA Diagnostics Meeting, Princeton, March , 2007 ITER measuring requirements for fast ions m -3

ITPA Diagnostics Meeting, Princeton, March , 2007 Schematic of the scattering geometry – LFS-BS The LFS-BS system resolves the perpendicular ion velocity component.

ITPA Diagnostics Meeting, Princeton, March , 2007 Schematic of the scattering geometry – HFS-FS Receiver Probe B ksks kiki kk  Receiver beam Probe beam The HFS-FS system resolves the parallel ion velocity component.

ITPA Diagnostics Meeting, Princeton, March , 2007 Capabilities of the 60 GHz CTS system Using current or near term technology, it meets ITER measurement requirements for fusion alphas Robust mechanically – no moveable components Simultaneous measurements of 10 positions for each system For the ELMy H-mode scenario within the engineering constraints, a previous study demonstrated: Requirements met at different plasma parameters Sufficient beam overlap in the spectral range (dispersion effects). Robustness of the overlap against variations of density such as sawteeth Robustness of the localization of the measurement against variations of density such as sawteeth Operation in alternative scenarios?

ITPA Diagnostics Meeting, Princeton, March , 2007 Measuring potential in reversed shear scenario ParameterStandard H-ModeReversed shear Bo (T) Ne(0) (m -3 )   Te(0) (keV) R mag (m) Z mag (m) Ip (MA)159 NN pp ITER operating scenario database Normalized flux coordinate Electron density (10 19 m -3 ) 25 Elmy H-mode Reversed shear Normalized flux coordinate Electron temperature (keV) e/ITER_Eq_Restricted/equilibria _index.htmhttp://efdasql.ipp.mpg.de/saiben e/ITER_Eq_Restricted/equilibria _index.htm (password protected), Yuri Gribov, website maintained by Gabriella Saibene

ITPA Diagnostics Meeting, Princeton, March , 2007 Measuring potential of HFS receiver – ELMy H-mode L is the resolving power, i.e. the system figure of merit. L/4 ≥ 1 ⇒ 16 velocity bins P in = 1 MW Integration time: 20 ms ECE noise 200 eV

ITPA Diagnostics Meeting, Princeton, March , 2007 Measuring potential of HFS receiver – reversed shear P in = 1 MW Integration time: 20 ms ECE noise 200 eV

ITPA Diagnostics Meeting, Princeton, March , 2007 Comparing effects of scenarios on HFS receiver - scaled n e

ITPA Diagnostics Meeting, Princeton, March , 2007 Modification of the LFS port plug Taking into account more detailed engineering constraints Minor changes in mirror locations ⇒ no significant changes in scattering calculations Small cut of the welding edge of the port plug front plate frame HFS-FS probe 1 st mirror Plug front plate (edge region) Plug front plate anchor point LFS-BS Probe 1 st mirror LFS-BS Probe 2 nd mirror HFS-FS Probe 2 nd mirror LFS-BS Horn array LFS-BS receiver mirror Fuel Ion Ratio Horn array

ITPA Diagnostics Meeting, Princeton, March , 2007 Challenges of the HFS-FS receiver Receiver quasi-optics located behind HFS blanket modules Integration issues Spatial constraints Very astigmatic beams Detected signal transmitted in in-vessel waveguides (via upper port) Similar challenges to the HFS reflectometer Opening angle of the beam determined by height of slit/blanket cut-out. Direct implication to the CTS signal Feasibility study: To satisfy measuring criteria  ≤ 7° ⇒ h = 30 mm

ITPA Diagnostics Meeting, Princeton, March , 2007 Mock-up Mark I of the ITER HFS CTS receiver at Risø Quasi-optical emitter horn Measuring rig Detector emitter horn mirror Emitter horn Blanket modules Non-astigmatic mirrors problem is split up in horizontal and vertical ⇒ two sets of mirrors Goals: verify vertical opening angle calculations study effect of horizontal cut-out

ITPA Diagnostics Meeting, Princeton, March , 2007 Opening angle of HFS receiver beam – measurements h = 30 mm ⇒   = 7.5 ° (7 °) h = 20 mm ⇒   = 9.4 ° (10.5 °) W y = 38 mm W y =45 mm W y =90 mm W y = 111 mm Distance from blanket 1,1 m 1,8 m

ITPA Diagnostics Meeting, Princeton, March , 2007 Blanket cut-out for the HFS receiver – top view Width front = 580 mm Width back = 410 mm

ITPA Diagnostics Meeting, Princeton, March , 2007 Blanket cut-out for the HFS receiver – front view

ITPA Diagnostics Meeting, Princeton, March , 2007 ITER CTS HFS receiver mock-up Mark II - Astigmatic mirrors Upgrade of codes to calculate 3D astigmatic mirrors 2-mirror mock-up with astigmatic mirrors to study astigmatic beams and compare to code to study propagation of off-axis beams Side view Zoom on cut-out Front view

ITPA Diagnostics Meeting, Princeton, March , 2007 Results of ITER CTS mock-up Mark II – beam propagation Distance from blanket: 180 cm Distance from blanket: 64 cm Note that numbers in graphs are dimensions in 110 GHz frame (which is the frequency of source) 60 GHz frame Fit Theory

ITPA Diagnostics Meeting, Princeton, March , 2007 Shortcomings of 2-mirror receiver Studies showed that 2-mirror systems have very astigmatic beams ⇒ distortion of off-axis beams large degree of focusing ⇒ very sensitive to misalignment

ITPA Diagnostics Meeting, Princeton, March , 2007 ITER CTS HFS mock-up Mark III – 4-mirror receiver 4-mirrors ⇒ less focusing less sensitive to misalignment Realistic geometry / Actual antenna mock-up Currently being produced in 1:1 scale, i.e. for 60 GHz source Goals are to: demonstrate an engineering solution to the HFS CTS antenna study misalignment investigate different horn configurations etc. measure the throughput

ITPA Diagnostics Meeting, Princeton, March , mirror HFS CTS receiver integrated into the ITER blanket Location of the mirrors Top view of blanket cut-out

ITPA Diagnostics Meeting, Princeton, March , 2007 Effects of misalignment – CEM modeling and scattering calc ITER CTS R (m) L/4 || || || |||| || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || rec  : 6 rec  : 4 rec  : 2 rec  : 0 rec  : -2 rec  : -4 rec  : -6 Plasma center ++ Vertical receiver misalignment: DS = 1.0 Slit height = 6λ = 30 mm Aligned beam 4° tilt of beam Scattering calculations predict: Vertical misalignment of receiver is less sensitive than for the probe

ITPA Diagnostics Meeting, Princeton, March , 2007 Additional measurements – fuel ion ratio Similar but separate LFS receiver (same aperture) Same probe or separate low power probe – 10 kW Temporal resolution of 100 ms Limited influence of impurity content Could be tested on TEXTOR or ASDEX Upgrade Z eff σ Ri LFS probe transmission line LFS receiver transmission line Horn array Waveguides Mitre bends Quasi-optical mirrors

ITPA Diagnostics Meeting, Princeton, March , 2007 Additional measurements – bulk ion drift velocities Toroidal bulk ion drift velocity readily obtained from the HFS-FS fast ion CTS system uncertainty approximately 20 km/s Poloidal bulk ion drift velocity needs a separate probe and receiver - vertically off-set low power probe – 10 kW uncertainty approximately 4.5 km/s little dependence of impurities

ITPA Diagnostics Meeting, Princeton, March , 2007 Future work EFDA task TW6-TPDS-DIADEV: Effects of RF- and NBI-generated fast ions on the measurement capability of diagnostics Modeling of increased neutron flux EFDA task TW6-TPDS-DIASUP: ITER CTS 2007 Propose a comprehensive outline plan for the full development of the CTS diagnostic for ITER engineering designs for both the HFS receiver system and the port-mounted components critical issues: limited space nuclear heating neutron streaming thermal mechanical studies (misalignment) waveguides and feed-throughs (collaborate with reflectometry team)

ITPA Diagnostics Meeting, Princeton, March , 2007 Summary A number of design and test tools have been developed a series of mock-ups finite difference codes 3D astigmatic Gaussian beam codes for mirror shapes Key design criteria confirmed Blanket cut-out for HFS receiver Potential further development of the diagnostic to measure fuel ion ratio toroidal and poloidal bulk ion drift velocity

ITPA Diagnostics Meeting, Princeton, March , 2007

The resolving power L The resolvong power L, is a measure of the information of the fast ion velocity distribution, independent on number of nodes Unitless by normalizing with the target accuracy  L 2 is approximately the number of nodes resolved with the target accuracy (provided uncertainties at all nodes are independent) 16 nodes ⇒ L > 4 ⇒ 60 GHz HFS-FS: 60 GHz LFS-FS:

ITPA Diagnostics Meeting, Princeton, March , 2007 Opening angle of HFS receiver beam – calculation Near field Gaussian half width – far field Feasibility study: 2D full wave calculations of the beam pattern through a slit. Asymptotic opening angle: To satisfy measuring criteria:  ≤ 7° ⇒ h = 30 mm

ITPA Diagnostics Meeting, Princeton, March , 2007 Vertical distance between blankets = 14 mm Probe f (GHz): 60 Rec f (GHz): 60 L/4 Tnoise (eV): 200 Probe Y: Probe  : 195 Probe  : Probe diam: 0.200, rec diam: 0.350, Probe f (GHz): 60 Rec f (GHz): 60 L/4 Tnoise (eV): 200 Probe Y: Probe  : 195 Probe  : Probe diam: 0.200, rec diam: 0.350, Probe f (GHz): 60 Rec f (GHz): 60 L/4 Tnoise (eV): 200 Probe Y: Probe  : 195 Probe  : Probe diam: 0.200, rec diam: 0.350, ITER CTS R (m) L/4 Probe f (GHz): 60 Rec f (GHz): 60 L/4 Tnoise (eV): 200 Probe Y: Probe  : 195 Probe  : Probe diam: 0.200, rec diam: 0.350, DS: 0.4 DS: 0.7 DS: 1.0 DS: 1.2 Vertical distance between blankets = 14 mm

ITPA Diagnostics Meeting, Princeton, March , 2007 Vertical distance between blankets = 20 mm Probe f (GHz): 60 Rec f (GHz): 60 L/4 Tnoise (eV): 200 Probe Y: Probe  : 195 Probe  : Probe diam: 0.200, rec diam: 0.350, Probe f (GHz): 60 Rec f (GHz): 60 L/4 Tnoise (eV): 200 Probe Y: Probe  : 195 Probe  : Probe diam: 0.200, rec diam: 0.350, Probe f (GHz): 60 Rec f (GHz): 60 L/4 Tnoise (eV): 200 Probe Y: Probe  : 195 Probe  : Probe diam: 0.200, rec diam: 0.350, ITER CTS R (m) L/4 Probe f (GHz): 60 Rec f (GHz): 60 L/4 Tnoise (eV): 200 Probe Y: Probe  : 195 Probe  : Probe diam: 0.200, rec diam: 0.350, DS: 0.4 DS: 0.7 DS: 1.0 DS: 1.2 Vertical distance between blankets = 20 mm

ITPA Diagnostics Meeting, Princeton, March , 2007 Vertical distance between blankets = 30 mm Probe f (GHz): 60 Rec f (GHz): 60 L/4 Tnoise (eV): 200 Probe Y: Probe  : 195 Probe  : Probe diam: 0.200, rec diam: 0.350, Probe f (GHz): 60 Rec f (GHz): 60 L/4 Tnoise (eV): 200 Probe Y: Probe  : 195 Probe  : Probe diam: 0.200, rec diam: 0.350, Probe f (GHz): 60 Rec f (GHz): 60 L/4 Tnoise (eV): 200 Probe Y: Probe  : 195 Probe  : Probe diam: 0.200, rec diam: 0.350, ITER CTS R (m) L/4 Probe f (GHz): 60 Rec f (GHz): 60 L/4 Tnoise (eV): 200 Probe Y: Probe  : 195 Probe  : Probe diam: 0.200, rec diam: 0.350, DS: 0.4 DS: 0.7 DS: 1.0 DS: 1.2 Vertical distance between blankets = 30 mm