(IT/P1-27) Requirements for Fast Particle Measurements on ITER and Candidate Measurements Techniques

F.P. Orsitto1), J-M. Noterdaeme2), A. E. Costley3), A. J. H. Donné4)
1) ENEA C R Frascati, 00044 Frascati, Italy
2) Max Planck IPP Garching(Ge)
3) ITER IT, Naka Joint Work Site(JA)
4) FOM-Rijnhuizen TEC,Nieuwegein(NL)

Abstract.  Recent results on JET and JT-60U [M. Mantsinen, et al., PPCF 47 (2005) 1439]; [K. Shinohara, et al., PPCF 46 (2004) S31-S45] have underlined the need of looking into the parameter measurement requirements of fast particles diagnostics for ITER. Not only alpha particles present in the plasma,but all fast ions (He4,p,D,T,He3): ions used for minority heating, should be diagnosed. The electron diagnostics monitoring the deviations from a Maxwellian distribution function, play a central role in the Electron Cyclotron Heating and Current Drive. In Present measurement requirements only alpha particles and He ions are mentioned: space resolution is δr = a/10 (a is the minor radius), time resolution is δτ = 100 ms, accuracy 10-30%. Proposed measurement requirements for fast particles are: spatial resolution a/20 (10 cm on ITER); time resolution (minimum) 100 t Alfvén (300 microsec for ITER); density of fast ions: the minority ions could be 4-10% of the plasma density. The candidate diagnostic techniques considered for ITER are:gamma-ray spectroscopy; Collective Thomson Scattering (CTS); Charge Exchange Recombination Spectroscopy (CXRS). Gamma-ray spectroscopy detects ions in the energy range 1 < E < 5 MeV, and R&D is needed to demonstrate the feasibility of these measurements in the presence of a neutron background. Techniques using ultraviolet spectroscopy of ions like Krypton are being tested , for the low energy part of spectrum of fast particles. A design study of CTS shows that the requirements are close to be met, the system includes a high power gyrotron operating in a region not yet tested in current applications (i.e. using a gyrotron at a frequency below the first ECE harmonic). For CXRS the spatial resolution and accuracy are not achievable for r/a < 0.3, and R&D is needed to assess the minimum figures in terms of accuracy possible for measurements close to the centre.

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