8 th IAEA Technical Meeting on Energetic Particles in Magnetic Confinement Systems

1. 8th IAEA Technical Meeting on Energetic Particles in Magnetic Confinement Systems Summary of Experimental Papers 8th IAEA Technical Meeting on Energetic Particles San Diego, CA, October 6 – 8, 2003

2. Alpha Particles Source of instabilities. Energy source of self-sustainable burning plasma Supra-thermal, run away electrons Source of dangers on disruption Source of dangers Should be understood and controlled Energy source Should be utilized most effectively 8th IAEA Technical Meeting on Energetic Particles San Diego, CA, October 6 – 8, 2003

3. -- 28 “Experimental” Papers -- 11 Tokamak papers 8 Helical 1 Linear 7 Diagnostics 1 energetic electrons 8th IAEA Technical Meeting on Energetic Particles San Diego, CA, October 6 – 8, 2003

4. use a energy understand understand 8th IAEA Technical Meeting on Energetic Particles San Diego, CA, October 6 – 8, 2003

5. Understad Instabilities---Tokamak • Testa JET/ITER Active excitation/passive excitation • Damping Rate Study extended • PNBI Threshold for Excitation of n=5-8 TAEs Increases with Edge Magnetic Shear • Mode Splitting and Lower Damping Rate for n=1 TAEs at PNBI>3MW , in Low magnetic shear. • nonlinear coupling of EPMs with MeV ions in advanced scenarios . • Error Field Affects Radial Profile of fFAST(E,r) • error field locks to q=2 surface distorting the magnetic topology: • q=2 TAEs disappear completely • q=3 EAEs only marginally affected • fast ions scattering: possible method to control peaking of bFAST(r)? 8th IAEA Technical Meeting on Energetic Particles San Diego, CA, October 6 – 8, 2003

6. Damping Rate of n=0/1/2 AEs Increases with Edge Elongation and Triangularity conventional tokamak scenario: monotonic q-profile agreement with theory: role of edge magnetic shear Nucl. Fusion 41 (2001), 809 8th IAEA Technical Meeting on Energetic Particles San Diego, CA, October 6 – 8, 2003

7. Understad Instabilities---Tokamak • Testa JET/ITER Active excitation/passive excitation • PNBI Threshold for Excitation of n=5-8 TAEs Increases with Edge Magnetic Shear • Mode Splitting and Lower Damping Rate for n=1 TAEs at PNBI>3MW , in Low magnetic shear. • nonlinear coupling of EPMs with MeV ions in advanced scenarios . • Error Field Affects Radial Profile of fFAST(E,r) • error field locks to q=2 surface distorting the magnetic topology: • q=2 TAEs disappear completely • q=3 EAEs only marginally affected • fast ions scattering: possible method to control peaking of bFAST(r)? 8th IAEA Technical Meeting on Energetic Particles San Diego, CA, October 6 – 8, 2003

8. A.Fasoli A new antenna system has been designed and is being constructed to excite MHD modes in the Alfvénrange of frequencies, in the range n~5-15, which can be driven unstable by fusion generated alphas or other fast particles in large machines. 8th IAEA Technical Meeting on Energetic Particles San Diego, CA, October 6 – 8, 2003

9. Alfvén Eigen Modes Stability---Tokamak Sharapov JET Alfvén Cascades modes associated with qmin excited by fast ions. Used successfully for monitoring the qmin(t) evolution The temporal correlation between Alfvén grand-Cascades, ITB triggering events and integer values of qmin has been established for a wide range of plasma conditions and pre-heating scenarios on JET 8th IAEA Technical Meeting on Energetic Particles San Diego, CA, October 6 – 8, 2003

10. 8th IAEA Technical Meeting on Energetic Particles San Diego, CA, October 6 – 8, 2003

11. Alfvén Eigen Modes Stability---Tokamak Sharapov JET A technique for obtaining ITBs in shear reversed plasmas by applying the main heating shortly before the AC time has been established on JET A new way of detecting Alfvén Cascades with interferometry has been found. These measurements give a high-accuracy monitoring of qmi (t) and may lead to a systematic diagnosis of the transport properties of the layer surrounding qmi 8th IAEA Technical Meeting on Energetic Particles San Diego, CA, October 6 – 8, 2003

12. Alfvén Eigen Modes Stability---Tokamak • Snipes C-Mod • Active and Passive Study has been carried out with a pair of active MHD antennas. Stable TAE resonances at q=1.5 are actively excited with a single high n antenna in both limited and diverted discharges in the range of toroidal fields and densities expected in ITER . • Software synchronous detection provides good fits to the stable TAE resonances on multiple pick-up coil signals with 0.5% < γ/ω< 4% • Diverted discharges require an outer gap < 1 cm to see the resonance • Alfvén Cascades are observed in the current rise at low density with strong ICRF heating indicating slightly reversed shear with qmin= 3 Results agree well with MISHKA modeling of the Alfvén Cascades • ･Modes are also observed in the EAE frequency range ~ 1 MHz in relatively low density EDA H-modes rotating in the electron direction 8th IAEA Technical Meeting on Energetic Particles San Diego, CA, October 6 – 8, 2003

13. Alfvén Cascades in the Current Rise • Rapidly chirping Alfvén Cascades in the current rise with strong ICRF heating at low density indicate a reversed shear q profile and determine the minimum q value at the minimum mode frequency 8th IAEA Technical Meeting on Energetic Particles San Diego, CA, October 6 – 8, 2003

14. Time 1.5 E40744 1 Magnetic Fluctuation [10-5 T] E40743 E40739 0.5 0 3 2.8 2.6 2.4 2.2 2 q min Bt=3.7T, Ip=1.3MA for all shots Alfvén Eigen Modes Stability---Tokamak Shinohara JT-60U/JFT2M • Reversed-Shear-induced Alfvén Eigenmode (RSAE) • To investigate dependence of mode amplitude on q-profile, NNB was injected into RS plasmas with various qmin • n=1 mode amplitude has its maximum around qmin = 2.4 - 2.7 8th IAEA Technical Meeting on Energetic Particles San Diego, CA, October 6 – 8, 2003

15. Time 1.5 E40744 1 Magnetic Fluctuation [10-5 T] E40743 E40739 0.5 0 3 2.8 2.6 2.4 2.2 2 q min Bt=3.7T, Ip=1.3MA for all shots • A gap is formed due to the reversed shear q-profile at the zero magnetic shear location and is not induced by toroidal coupling • AE was found around the upper and the lower boundary of the gap using the calculation of TASK/WK code • RSAE and its transition to TAE is consistent with the observed upward and downward frequency sweeping and subsequent frequency saturation. 8th IAEA Technical Meeting on Energetic Particles San Diego, CA, October 6 – 8, 2003

16. E39672 ALE (a) (b) n 1.3 ] -1 s 15 1.2 [10 (c) S ch.1 r/a=0.21 1.1 6 ch.2 r/a=0.34 ch.3 r/a=0.48 5 ] neutron emission rate ch.4 r/a=0.58 4 -2 m -1 ch.5 r/a=0.75 s 3 13 2 ] ch.6 r/a=0.86 [10 -4 2 B/B [10 Time [s] 1 1 ~ 0 0 4.35 4.4 4.45 4.5 4.55 Alfvén Eigen Modes Stability---Tokamak Shinohara JT-60U/JFT2M • Escaping ion measurement in JFT-2M • Heat flux in Complex magnetic field produced by ferritic inserts 8th IAEA Technical Meeting on Energetic Particles San Diego, CA, October 6 – 8, 2003

17. Alfvén Eigen Modes -- SphericalTokamaks Fredrickson NSTX Neutral beam injection into the National Spherical Torus Experiment (NSTX) results in a broad spectrum of instabilities . The lowest frequency energetic ion driven modes have a bursting character with strong frequency chirpingas "fishbones". Mode activity in the frequency range of 80 to 150 kHz are classified as Toroidal Alfvén Eigenmodes (TAE). When the TAE exhibit bursting, they can cause substantial fast ion losses. In the frequency range from 0.5 MHz to over 3 MHz for CAE and in ST geometry Belova NSTX Numerical Study on Compressional Alfvén Eigenmodes (CAEs) and Global Alfvén Eigenmodes (GAEs), which are driven unstable through the Doppler shifted cyclotron resonance with the beam ions [2]. The strong anisotropy in the fast-ion pitch-angle distribution provides the energy source for the instabilities. 8th IAEA Technical Meeting on Energetic Particles San Diego, CA, October 6 – 8, 2003

18. TAE bursts responsible for most of fast ion loss here • Neutron drops ≈ 10-15 %. • Period is again ≈ 10 ms. • In steady-state, predicted reduction in fast ion beta of 40 %. • TAE have strong bursting character with multiple modes present. 8th IAEA Technical Meeting on Energetic Particles San Diego, CA, October 6 – 8, 2003

19. Alfvén Eigen Modes -- SphericalTokamaks Fredrickson NSTX In the frequency range from 0.5 MHz to over 3 MHz for CAE and in ST geometry Belova NSTX Numerical Study on Compressional Alfvén Eigenmodes (CAEs) and Global Alfvén Eigenmodes (GAEs), which are driven unstable through the Doppler shifted cyclotron resonance with the beam ions [2]. The strong anisotropy in the fast-ion pitch-angle distribution provides the energy source for the instabilities. 8th IAEA Technical Meeting on Energetic Particles San Diego, CA, October 6 – 8, 2003

20. Alfvén Eigen Modes -- SphericalTokamaks Darrow NSTX loss of 80 keV D beam ions . Comparison of the measurements and modeling. A detailed model is being developed which compute the loss to a specified detector location, incorporating the measured plasma magnetic equilibrium, inferred beam deposition profile, and the range of orbits which enter the detector. Medley NSTX Horizontally scanning Neutral Particle Analyzer(NPA) whose sightline views across the three co-injected neutral beams. For example, onset of an n = 2 mode leads to relatively slow decay of the energetic ion population (E ~ 5 - 100 keV) and consequently the neutron yield. The effect of reconnection events, sawteeth and bounce fishbones differs from that observed for MHD modes. 8th IAEA Technical Meeting on Energetic Particles San Diego, CA, October 6 – 8, 2003

21. Illustration of MHD-induced Ion Loss during H-mode BT = 4.8 kG, IP = 0.8 MA, Source A & B @ 90 keV, Low MCP Bias • Following H-Mode onset at 230 ms, the NPA spectra show significant loss of energetic ions only for E>Eb/2. 8th IAEA Technical Meeting on Energetic Particles San Diego, CA, October 6 – 8, 2003

22. Alfvén Eigen Modes Stability---Tokamak Gryaznevich MAST / START Experimental study of Alfvénic instabilities in STs provides an opportunity to test theoretical models, which could then be applied to alpha-particle physics predictions in ITER and beyond. Several types of high frequency MHD activity that may be associated with toroidal Alfvén eigenmodes and energetic particle modes have been observed on START, MAST and NSTX in neutral beam heated discharges. Chirping down modes in STs were first observed on START. In contrast to START, chirping modes on MAST often exhibit a symmetric chirp up and down in frequency simultaneously. This behaviour can be described by the hole-clump model. MAST exhibits post-sawtooth humpbacked fishbones as well as conventional ones. EPD modes on MAST can trigger long-lasting tearing modes with NTM features. Results of the modelling (MISHKA and HAGIS codes) of the mode structure and frequency sweeping show good agreement with the experimental data and with theoretical predictions. 8th IAEA Technical Meeting on Energetic Particles San Diego, CA, October 6 – 8, 2003

23. Impact of EPD MHD on START and MAST plasmas 8th IAEA Technical Meeting on Energetic Particles San Diego, CA, October 6 – 8, 2003

24. Heidbrink NSTX/DIII-D The major radius dependence of Alfvén Eigen Modes stability is studeid by creating plasmas with similar minor radius, shape , magnetic field, density, Te, and beam population ( near tangential 80 keV deuterium injection) on both NSTX and DIIID. The major radius of NSTX is half of that of DIID. The stability threshed for the TAW is similar in the devices. The most unstable toroidal mode number n is larger in DIIID. 8th IAEA Technical Meeting on Energetic Particles San Diego, CA, October 6 – 8, 2003

25. K. ToiEnergetic-Ion Driven Alfvén Eigenmodes in Large Helical Device Plasmas with Three-Dimensional Structure and Their Impact on Energetic Ion Transport • 3D-configuration: Non uniformity of the field strength on the magnetic surface in both poloidal & toroidal diections. • q-profile: Negative shear configuration in the edge, and change to positive shear in the core with the increase in the toroidal beta. 8th IAEA Technical Meeting on Energetic Particles San Diego, CA, October 6 – 8, 2003

26. When the minimum i(0) goes through 0.4, m~2,3/n=1 TAE is converted to m=3/n=1 GAE and m=2/n=1 mode. m=2/n=1 mode will suffer from strong continuum damping, and it is consistent with exp. Results. This phenomenon is similar to RS-TAEs in a RS-plasma of JT-60U. Eigenmode transition from TAE to GAE during time evolution of i-profile 8th IAEA Technical Meeting on Energetic Particles San Diego, CA, October 6 – 8, 2003

27. At low Bt<0.7T, coherent magnetic fluctuations less than 500 kHz in LHD are observed. Its frequency is about 8 times higher than TAE gap frequency. They will be Helicity induced Alfven Eigenmode (HAE) whose frequency is by about Nq-times higher than TAE-frequency. Observation of new AEs in 3D-configuration(Helicity-Induced Alfven Eigenmodes) 8th IAEA Technical Meeting on Energetic Particles San Diego, CA, October 6 – 8, 2003 S. Yamaoto et al., to be publshed in PRL (2003)

28. MHD induced loss of energetic particles are also observed in Helical Systems Osakabe LHD Increase and/or decrease of fast neutral flux being associated with the MHD-bursts were observed for low magnetic field (Bt=0.5~1.2[T]) LHD standard configuration (Rax=3.6[m] and 3.75[m]), for co.-going particles, with dominant components of the MHD burst being assigned as TAE of n=2/m=3~4. Isobe CHS Escaping fast ion probe is installed and observation shows that MHD activity induces beam ion loss toward small R side. 8th IAEA Technical Meeting on Energetic Particles San Diego, CA, October 6 – 8, 2003

29. Evidence for the influence of fast ions on plasma rotation(L.-G. Eriksson) • The absorption by fast resonating ions of toroidal momentum carried by directed ICRF waves, and its subsequent transfer to the bulk thermal plasma, is found to influence the toroidal plasma rotation • Discharges with co (+90O antenna phasing) and counter (-90O) current propagating waves have been compared. • A reference discharge with about 30% of +90o ICRF power exchanged for LH power was also performed, giving a lower stored energy and ion pressure. 8th IAEA Technical Meeting on Energetic Particles San Diego, CA, October 6 – 8, 2003

30. Carbon rotation profiles measured with the charge exchange recombination spectroscopy using NBI blips (method described in Noterdaeme et al.1) • The +90o discharge rotates more strongly in the centre than –90o, consistent with fast ion absorption of wave momentum. t=51 s (co-current wave momentum) With LH • LH discharge shows the difference is not due to modified WDIAor ion pressure. 1J.M. Noterdaeme et al, Nuclear Fusion 2003 8th IAEA Technical Meeting on Energetic Particles San Diego, CA, October 6 – 8, 2003

31. Orbit Topology/alpha channeling/Momentum injection/Diffusion Wong DIII-D Alpha channelling is demonstrated by experimental data from the DIII-D tokamak. 1. It is shown that spontaneous redistribution of energetic ions by the excited Alfven eigenmodes can reduce the central magnetic shear and produce velocity shear at the same time - the two ingredients needed for ITB. 2. Quasi-steady-state ITB can be sustained in DIII-D when Alfven modes are excited. This experimental result demonstrates that the process envisioned in (1) can indeed occur. 3. This mechanism offers the possibility of having an ITB as a natural steady state of a burning plasma. 4. There may not be enough energetic alpha particles in the present ITER design to form an ITB, but it may be possible in a different design. 5. Partial effects, i.e., stabilization of part of the ITG turbulence, may be possible in ITER, and it can still be beneficial to plasma confinement. 8th IAEA Technical Meeting on Energetic Particles San Diego, CA, October 6 – 8, 2003

32. Orbit Topology/Ripples/Diffusion in Helical Systems The ripple trapped energetic particle is one of important issues in the development of a reactor based on the helical system. toroidal angle B~cnst. transition Toroidalprojection(Boozer co.) helically trapped 8th IAEA Technical Meeting on Energetic Particles San Diego, CA, October 6 – 8, 2003

33. Murakami LHD Radial transport of energetic particles due to the ripple trapped particle. Complex behavior and radial transport of energetic ions during NBI and ICRF heating using a global transport simulation code (GNET) Ozaki LHD Charge Exchange Neutral Particle Flux during Fueling Pellet Injection. The decay times depend on the particle energy.The radial information of the diffusion coefficient obtained Saida LHD Effect of helical magnetic field ripples on energetic particle confinement was investigate. Matching of drift surfaces for trapped particles and Magnetic flux surfaces is important. Matsushita CHS DNB is scanned to see the confinement of energetic partilces. Notake LHD Electric Field effect on partilce orbit is studied. Resonant Loss-cone, cancellation of ExB drift and grad-B drift 8th IAEA Technical Meeting on Energetic Particles San Diego, CA, October 6 – 8, 2003

34. Zhao LAPD Liner basic plasma physics machine, 500 eV ions source. Plan for study of wave-particle resonance between a helium beam and Alfven waves. 8th IAEA Technical Meeting on Energetic Particles San Diego, CA, October 6 – 8, 2003

35. Diagnostics M. Sasao Overview of Fusion Products Measurements of ITER 10 sub-systems are now on the planned for fusion product measurement on ITER. Neutron emission rate (time response) measurement for burn control and MHD study will have the 1 MHz capability. Neutron /Alpha birth profile can be obtained by 20 viewing chords and 7 viewing chords from the divertor. Deviation from the uniformity can be detected Measurement of confined alpha particle distributions is a challenge. Several proposals are now under examination. Escaping Alpha Diagnostics is a challenge. Several proposals are now under examination. 8th IAEA Technical Meeting on Energetic Particles San Diego, CA, October 6 – 8, 2003

36. Darrow JET/ITER Design of two lost alpha particle diagnostics for JET They consist of a poloidal array of five sets of thin foil Faraday collectors, with good time resolution (1 kHz) A scintillator based probe located slightly below the midplane, the energy and pitch angle distribution resolution The two candidate scintillator materials, Y3Al5O12:Tb (P53) and Y2O3:Eu (P56), both are luminous to at least 400 C, Experience in operating both diagnostics in a high temperature and high radiation environment will be valuable in preparation for the design of similar diagnostics for ITER. • Gyromotion of fast ions • Particle selection by slits • Light emission by scintillator 8th IAEA Technical Meeting on Energetic Particles San Diego, CA, October 6 – 8, 2003

37. Thin (2.5 m) m a Ni foils Plasma Current flow to amplifiers Thin foil Faraday cups allow some energy resolution • Detector composed of multiple thin metal foils • Ion energy determines deposition depth • Ion current measured for each foil individually • Current vs depth gives energy distribution (DE~30–50%) 8th IAEA Technical Meeting on Energetic Particles San Diego, CA, October 6 – 8, 2003

38. Cecil JET/ NSTX / DIII-D A new lost ion diagnostic on DIII-D and a redesigned probe on NSTX. The Faraday foil collectors New Results are shown. RoquemoreNSTX The neutron emission is seen to be very sensitive to fast-ion related phenomena such as MHD and internal reconnection events. A study presented being performed to evaluate the feasibility of installing a neutron profile monitor on NSTX to spatially resolve the fluctuations in the neutronsignal as well as provide information on fast ion transport and confinement. It is important to minimizeBackscattering Lu DIII-D Measurement of re-neutralized beam ions for beam ion profile. Gontcharov LHD The multidirectional passive neutral particle analyzer has been applied to investigate the behavior of anisotropic distributions of suprathermal protons Local measurements of the plasma ion distribution function by detecting charge exchange neutrals from an impurity pellet ablation cloud. Osakabe LHD BLIP experiment was performed with NPA to see the confinement of energetic partilces. New technics based on the Maximum Entropy and Maximum Likelihood Method(MEMLM). 8th IAEA Technical Meeting on Energetic Particles San Diego, CA, October 6 – 8, 2003

39. V.V. Plyusnin Super-thermal and runaway electrons at reconnection events during JET disruptions. Study on major disruptions in JET spontaneous and intentional has been carried out to further understanding of the trends of disruption induced runaway process. Runaway electron parameters have been measured using the hard X-ray and neutron diagnostics. Soft X-ray inverse reconstruction and ECE measurements of the electron temperature profile have been used in order to investigate the effect of the magnetic field re-arrangement at disruptions on the runaway process. Soft X-ray inverse reconstruction of the magnetic field evolution at a reconnection event has shown that an axis-symmetric confining configuration has been created again in a very short time-scale (~200 microseconds) after reconnection providing confinement of the super-thermal or low energy runaway electrons generated at this event. 8th IAEA Technical Meeting on Energetic Particles San Diego, CA, October 6 – 8, 2003

40. Interaction between energetic ions and MHD perturbations are studied in major tokamaks, spherical tokamaks and LHD. Progress in understanding and development of tools for understanding (codes, diagnostic) will be made by collaboration between different configurations. 8th IAEA Technical Meeting on Energetic Particles San Diego, CA, October 6 – 8, 2003