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Overview of Neutron and Escaping Alpha Diagnostics Planned for ITER

Overview of Neutron and Escaping Alpha Diagnostics Planned for ITER.

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Overview of Neutron and Escaping Alpha Diagnostics Planned for ITER

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  1. Overview of Neutron and Escaping Alpha Diagnostics Planned for ITER M. Sasao1, A. V. Krasilnikov2, T. Nishitani3, P. Batistoni4, V. Zaveriaev5, Yu.A.Kaschuck2, S. Popovichev6, T. Iguchi7, O.N. Jarvis5, J. Kallne8, C.L. Fiore9, Ray Fisher, L. Roquemore10, W.W. Heidbrink11, A.J.H. Donné12, A.E. Costley13, C. Walker14 1 Tohoku Univ.; 2 TRINITI;3 JAERI; 4 FERC; 5 Kurchatov Inst.; 6 JET-EFDA/CSU; 7 Nagoya Univ.; 8 Uppsala Univ.; 9 MIT.; 10 PPPL; 11 UC Irvine; 12 FOM-Inst.; 13 ITER IT, Naka;14 ITER IT, Garching 2003 TCM-EP-M.Sasao

  2. Out lines Background Neutron emission rate (time response) measurement for burn control and MHD study Neutron /Alpha birth profiles Confined Alpha particle distributions Escaping Alpha Diagnostics Summary 2003 TCM-EP-M.Sasao

  3. Background (1) Alpha Particle Related Physics heating particle diffusivity  Alfven Instability particle stabilization of sawtooth oscillation, etc. Localization of Escaping Alpha’s ash density controle Scenarios: Standard ELMy H-mode (300 sec) bn =1.5 - 2 Hybrid (1000 sec) :bn > 2 Steady-state operation bn > 2 An ITB may be created in a region of low (or reversed) magnetic shear in the vicinity of the rational q surface in scenario B) & C) Alpha particle physics in standard H-mode and in high bn mode with ITB should be experimentally studied. 2003 TCM-EP-M.Sasao

  4. Overview of Neutron Diagnostics Absolute neutron yield and fusion output measurement • In-Vessel and Ex-Vessel  flux monitors • Neutron Camera • Neutron Activation Systems (foil and water) Fast Neutron emission rate measurement for Burn control and MHD study • In-Vessel and Ex-Vessel  flux monitors Ti(r,t) measurement • Compact Neutron Spectrometers in Radial Neutron Camera • A big Neutron Spectrometer Neutron /Alpha birth profiles • Neutron Camera Confined Alpha particle distributions • Knock-on Tail Neutron Spectrometers • Gamma-Ray spectrometers Lost Alpha particles • Lost-a Detectors 2003 TCM-EP-M.Sasao

  5. Fast time-resolved measurement of neutron emission rate • In-Vessel m-fission chambers • Ex-Vessel  flux monitors -fission chambers are pencil size gas counters with fissile material, and have been developed to be installed in the vacuum vessel of ITER. At present, a combination of 235U and a ”blank” detector are proposed to be installed behind blankets # 11 and # 16. Number of detectors and locations for other monitors are still under discussion. 2003 TCM-EP-M.Sasao

  6. In-Vessel  flux monitors Ex-Vessel  flux monitors ITER requirement is 107 dynamic range with 1 ms temporal resolution with 10 % accuracy. 235U -Counters (1/v Property) 238U -Counters (Threshold Property) Counting-mode Current-mode Campbelling mode x 2003 TCM-EP-M.Sasao

  7. In-Vessel m-fission chambers Current/campbelling mode 238U-chamber counting mode Current/campbelling mode 235U-chamber counting mode Counting rate (s-1) Neutron Flux behind blanket (s-1) Neutron Source (s-1) DD calibration DT Fusion output (W) 2003 TCM-EP-M.Sasao

  8. In-Vessel m-fission chambers During the full DT operation, counting rates are in the range of 100 MHz for 235U, and 100 kHz for 238U. The thermalization time is a big concern for 235U. Thermalization is affected by surrounding materials and structures, and those between neutron source and detectors. The typcical time is to be order of 1 msec. More detail assessment is needed with neutron transport code. The frequency range of high frequency macro instabilities (Fishbones and TAEs) is expected in 30 kHz - 300 kHz. In-vessel m-fission chambers have capability to cover this range. 2003 TCM-EP-M.Sasao

  9. Neutron /Alpha birth profiles Radial Neutron Camera has been designed in detail. A set of 12 viewing chords covers |Z-Z0| < 0.5b. Only line-integrated neutron emission is measured by each chord. Alpha particle birth profiles can be obtained by assuming a simple analytical form as a function of MFS. Limited plasma coverage. The fraction of neutrons not seen by camera can be larger than10- 20 % Each chord will be equipped with total flux detectors and compact spectrometers. Combination of different detectors are needed to cover the wide range in the expected level of the flux. 2003 TCM-EP-M.Sasao

  10. Can the change of alpha birth profiles due to ITB be observed by the Radial Neutron Camera of 12 viewing chords? Errors might be dominantly from change of back scattered neutrons and gamma’s, and change of detector efficiency. The 2% of maximum flux is assumed for every channels. Profile parameter and a strong ITB profile can be detected, but a moderate ITB cannot be recognized, with 12 viewing chords. 2003 TCM-EP-M.Sasao

  11. Additional viewing chords to Radial Neutron Camera 8 viewing chords Covers |Z-Z0| > 0.5b Addition of 8 chords substantially improves accuracy of the profile parameter and determination of the ITB structure. However, the analysis is on the assumption of uniform neutron emission on a magnetic flux surface. 2003 TCM-EP-M.Sasao

  12. Is the neutron emission uniform on a magnetic flux surface ? Non-uniformity on the MFS, caused by trapped particles, has been observed at JET[1]. Interesting Physics Selective production of trapped particles by ICRF, Selective loss of energetic ions in a -r space induced by MHD, Redistribution of ions during sawtooth oscillation Can those interesting phenomena be observed ? JET KN3 profile monitor uses 2D-tomography. This analysis employs a hybrid pixel/analytic algorithm [8], which involves a poloidal Fourier analysis and a radial Abel inversion, starting from outside and working inward. 2003 TCM-EP-M.Sasao

  13. Non uniform neutron emission on a magnetic flux surface ? Non-uniformity on the MFS, caused by trapped particles, approximated by This cannot be distinguished by 20 chords of radial camera. Mean while, Channels of #-1 ~ #-10 are viewing lower half of the cross section. Up-down asymmetry, and vertical movement can be clearly detected by comparison of those with Channels of #1 ~ #10. 2003 TCM-EP-M.Sasao

  14. Additional Viewings (DNC) are proposed by NWG [Krasilnikov et al.] Non-uniformity on the MFS, caused by trapped particles can be distinguished by 7 additional chords of divertor camera. 2003 TCM-EP-M.Sasao

  15. Poloidal resolution of the alpha birth profile by 27 chords,12 present radial chords, 8 additional, plus 7 additional Divertor chords. Local high emissivity of 40% enhancement in poloidal direction is assumed and tested against 27 viewing chords. It can be resolved with 45o of poloidal angle resolution if the enhancement is higher than 40 %. 2003 TCM-EP-M.Sasao

  16. Confined Alpha particle distributions -1 Measurement of confined alphas is a big challenge on ITER. Several methods are proposed and feasibilities are studied. • Collective Thomson scattering, several approaches. CO2 high power laser (50 J, 10 Hz) with the scattering angle of 0.5 degree (Kondoh) injected from the divertor port. Launching of 50-65GHz radiation from tuneable gyrotron and receiving from the top and bottom of a single equatorial port (H. Bindslev ) Launching 1-2 MW at 170 GHz in the O- mode from an equatorial port and collecting the scattered radiation from the upper port (U. Tartari) Stray beam / operational window changes /ECE background • Charge Exchange Recombination Spectroscopy on the heating beam A signal-to-background-ratio on the DNB Beam attenuation with gas-jet Plasma perturbation Major concern in red 2003 TCM-EP-M.Sasao

  17. Confined Alpha particle distributions -2 • Charge Exchange Neutralization with high energy neutral beams use a tangential 3He beam with energy 0.8-1.5 MeV from port 6(Sasao). accessibility and beam development • Gamma-ray spectroscopy 10B(a, pg) 13C reaction (V. Kiptily ) radial distribution of Be should be known Major concern in red 2003 TCM-EP-M.Sasao

  18. Confined Alpha particle distributions -3 • Alpha knock-on measurements d t a + n + high energy deuteron or triton d a d + a + n t d a + + Neutron high-energy tail 2003 TCM-EP-M.Sasao

  19. Alpha knock-on measurements on NPA Knock-on tritons are neutralized by the 1 MeV D0 beams (R. Fisher et al.) or by electron capture from intrinsic impurities(Petrov), and analyzed by NPA. Stripping foils can be used to separate energetic D+ from He 2+. Calculations for ITER show NPA count rates up to 104/sec for deuterons of E > 1 MeV. 2003 TCM-EP-M.Sasao

  20. Alpha knock-on measurements on the neutron high-energy tail Alpha knock-on neutrons are measured at JET by MPR. J. Källne, L. Ballabio, J. Frenje, S. Conroy, G. Ericsson, M. Tardocchi, and E. Traneus PHYSICAL REVIEW LETTERS,85,1246(2000) Knock-on Tail Neutron Spectrometers Neutron high-energy tail potentially be measured by Magnetic Proton Recoil (MPR) spectrometer or bubble detectors. One potential way to install MPR on ITER is along the side the neutron camera. Separation of other energetic ions, signal to noise ratios Major concern in red 2003 TCM-EP-M.Sasao

  21. Lost alpha detection Localization (Subtask report by S.V. Konovalov, 2000) Heat Load (kW/m2) • Poloidal distribution of the heat load. • Red histogram corresponds to banana particle loss and blue one shows locally trapped  loss FW region marked by the thick red line undergoes alpha particle bombardment. Analysis of TF Ripple Loss of Energetic Particles 2003 TCM-EP-M.Sasao

  22. Lost alpha detection Candidates of Measurement Tools Point measurement (r- resolved) : Faraday-cup scintillator probes Loss imaging: IR camera imaging camera imaging of scintillators on the FW gamma-ray measurement from B-FW, by 10B(a, pg) 13C reaction (V. Kiptily ) Camera Viewing line Probe/FC 2003 TCM-EP-M.Sasao

  23. Summary of lost alpha detection Neutron induced noise is 1- 4% of the signal level, for the FC and Scintillator probe, when loss is 1% of the maximum level. IR camera imaging => robust, but no discrimination, slow • Camera imaging of scintillators on the FW • robust, discrimination of from other plasma particles should be tested, PM+filter should be tested Faraday-cup detectors, => cables should be tested for nA range measurement Scintillator probes, => Cooling system should be designed 2003 TCM-EP-M.Sasao

  24. Summary 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 100 MHz capability, but the effective time-resolution should be assessed with neutron transport code. Neutron /Alpha birth profile can be obtained on the assumption of uniformity on MFS by the addition of 8 viewing chords. Deviation from the uniformity can be detected with 45o of the poloidal angle resolution by the addition of 7 viewing chords from the divertor. Measurement of confined alpha particle distributions is still a challenge. Several proposals are now under examination. Escaping Alpha Diagnostics is still a challenge. Several proposals are now under examination. 2003 TCM-EP-M.Sasao

  25. Prospect of performance of neutron subsystems :Oct. 2003 Accuracy is in red 2003 TCM-EP-M.Sasao

  26. Background (1) - ITER ITER The technical requirements of ITER are • To achieve extended burning in inductively driven plasmas at the capital Q larger than 10 • To aim at demonstrating steady -state operation by non-inductive current drive at Q > 5 • To retain the possibility of exploring controlled ignition 2003 TCM-EP-M.Sasao

  27. Environment and Restriction for FC Neutron Noise on the FC => less than 2%, for 0.01*max. loss but not negligible Dummy probes are necessary. RIC, RIEMF might be problems for current measurement of nA range. ( recent study on RIEMF indicates the effect of nuclear transmutation) Twisted cables should be tested. Discrimination from fast ions might be a problem. 2003 TCM-EP-M.Sasao

  28. Alpha knock-on measurements on NPA Knock-on tritons are neutralized by the 1 MeV D0 beams (R. Fisher et al.) or by electron capture from intrinsic impurities(Petrov), and analyzed by NPA. Stripping foils can be used to separate energetic D+ from He 2+. Calculations for ITER show NPA count rates up to 104/sec for deuterons of E > 1 MeV. 2003 TCM-EP-M.Sasao

  29. 2003 TCM-EP-M.Sasao

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