Index Introduction The Research at Rijnhuizen Results in 2008 Education, Training, Outreach and Public Information Output Appendix website Rijnhuizen 2.2 | Instrumentation Development Division: Fusion Physics Group leader: R.J.E. Jaspers Senior scientists: M.G. von Hellermann, M. Kantor (Ioffe) Post-Doc: I.G.J. Classen (MPI)  Graduate students: J.E. Boom, E. Delabie, G.W. Spakman, T. Versloot Undergraduate students: S. Mann (UU), M. Jakobs (TU/e), C. van Essen (Lei) Research engineers: M.J. van de Pol, J. Koning Guests: F. Bonomo (ENEA-RFX), S. Banerjee (IPR-India), N. Conway, M. Wisse, M.F. de Bock (UKAEA), C.W. Domier, B. Tobias (UC-Davis), J. Howard, A. Diallo (ANU - Canberra), J. Chung (NFRI - Korea). K. Razumova, S.Krasnyanskiy, D. Shelukhin (Kurchatov - Moscow), E. Gusakov, D. Kouprienko, A. Gurchenko (Ioffe - St. Petersburg), A. Whiteford (Strathclyde), P. Bohm (IPP.CR - Prague), Q. Zang (ASIPP - China) Collaborators: W.Biel, O. Neubauer (FZJ), X. Duan (SWIP), N.C. Hawkes (UKAEA), P.C. de Vries, C. Giroud (JET), N.C. Luhmann Jr. (UC-Davis), H.K. Park (U. Pohang - Korea), S. Tugarinov (Troitsk), N. Naumenka (Minsk), F. Klinkhamer, B. Snijders (TNO), A. Hogenbirk (NRG) Funding*: FP-74, EURATOM, TU/e, US-DOE, INTAS, NWO, EFDA, FES Research goal The Instrumentation Development Group develops high resolution multi-channel diagnostics with the aim to diagnose small scale structures in hot magnetised plasmas. The goal is to advance novel concepts in optical and microwave diagnostics, as well as expanding and using the available expertise on optical diagnostics for application on ITER and support of the fusion physics programme. Research programme The instrumentation development group focuses on three pillars, each resulting in internationally recognised highlights: • The Thomson scattering system, a high resolution system used to study the electron temperature and density profiles in hot plasmas. This system has been further developed and exploited on the TEXTOR tokamak. Unlike in common Thomson Scattering systems, for the TEXTOR system a novel concept was adopted in which the plasma is part of the laser cavity. Up to 50 pulses, at a frequency of 5 kHz, could be injected into TEXTOR. With the latest addition of a multi-pass capacity, each laser pulse can effectively provide 60 J of probing energy. This system reaches unprecedented spatial resolution. In addition, fast dynamics in the plasma can be diagnosed with it, a feature mostly lacking in other Thomson systems. • The 2D-electron cyclotron emission imaging system (2D-ECEI). This system has been developed in collaboration with the groups from UC-Davis and Princeton, US. This system explores for the first time the 2D nature of temperature structures and fluctuations in the plasma core. This diagnostic is an extension of more common 1D ECE systems that measure a radial profile of the microwave radiation from the plasma, a quantity related to the electron temperature. By using innovations in microwave array technology and an optical setup to couple the emission from the plasma to the array, a radial/vertical area is now imaged, with a resolution of about a 1 cm in all directions. The growth and suppression of a ‘magnetic island’-instability in the plasma can be dynamically followed with this system, allowing for a direct comparison of these measurements with related theories. The system proved its strength even more in the most longstanding problem in fusion research, the sawtooth crash. For the first time the poloidal extent of the crash could be visualized. As a result some existing theories could be falsified. • Active Beam Spectroscopy. Normally, the fully ionised ions in the hot core of a fusion reactor do not emit line radiation. However, by injecting a high energy beam of neutral ions, charge exchange processes between the neutrals and the plasma ions will result in line emission. For ITER, this charge exchange recombination spectroscopy (CXRS) is foreseen to be the prime diagnostic for providing information on ion temperature, plasma rotation and ion concentrations. The efforts of the instrumentation group in this field have resulted in a leading role in the development of such a CXRS system for ITER. A pilot experiment has been installed on TEXTOR, in which the ITER geometry is mimicked; an ITER candidate spectrometer is being tested and some new physics features are being investigated. One of the exciting new features is the possibility to make an absolute calibration of the ion density with independent Beam Emission Spectroscopy (BES) measurements. Secondly, the CXRS system on TEXTOR has been used to diagnose fast ions. These results provide decisive input for the final ITER-CXRS design. Figure 2.2: Novel method of measuring the polarisation of the Beam emission in TEXTOR, from which the magnetic field direction and current distribution profile can be derived in principle. The method employs the coherent imaging technique, developed by the group from the Australian National University. Shown here are 2D views into the tokamak vessel. A) picture taken without plasma present. Only the vessel wall is visible as background. B) plasma present, but no beam injected. The recorded emission is bremsstrahlung from the plasma. C) Neutral beam injected. The interferogram from this emission is a direct proof of the polarisation of the emission. From these raw data the magnetic field direction and current distribution profile can be derived in principle. * supported by the European Fusion Programme (EFP)