Evolution of the millimeter-wave collective Thomson scattering system of the high-field tokamak Frascati Tokamak Upgrade

Tartari, U.; Grosso, G.; Granucci, G.; Gandini, F.; Garavaglia, S.; Grossetti, G.; Simonetto, A.; Mellera, V.; Muzzini, V.; Lubyako, L. V.; Shalashov, A. G.; Orsitto, F.; Ciccone, G.; Volpe, F.

doi:10.1063/1.2719197

Cited by 14 publications

(13 citation statements)

References 13 publications

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“…Previous measurements [2][3] were carried out in an updown symmetric scattering geometry accommodated in the narrow vertical ports and providing a scattering angle θ ≅90 o . The experimentation was generally performed with B T ≤7.2T on the vessel axis, with the probing beam that had to cross the EC resonance and the nearby upper-hybrid (UH) cut-off for the X mode at a position inside the beam injection port.…”

Section: Introductionmentioning

confidence: 99%

Collective Thomson Scattering on FTU using a new ECRH launcher

Grossetti

Bruschi

Granucci

et al. 2010

35th International Conference on Infrared, Millimeter, and Terahertz Waves

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Different conditions make the CTS diagnostic experiment presently installed at FTU a unique test bed for a proof-of-principle demonstration for a fast ions diagnostic in ITER. The most relevant one is wave propagation at frequencies below the electron cyclotron (EC) resonance where the extraordinary (X) mode can propagate at higher plasma densities. CTS measurements performed in the past with an up-to-down scattering geometry, showed damages on the launching mirror close to the EC resonance located in the port interior. Therefore a different and more flexible CTS geometry was required to achieve a better insight into this difficult problem (found also in the ITER CTS geometry) and to single out a convenient remedy. This opportunity is now offered by the new ECRH launcher that will be installed at FTU.The system has been designed for both ECRH and CTS. It includes two symmetrical lines with front-steerable mirrors and will provide extended focusing capability, independent toroidal and poloidal scans of the probing and the receiving beams, and the possibility of radially scanning, or even changing, the scattering volume during a single gyrotron pulse.

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Section: Introductionmentioning

confidence: 99%

Collective Thomson Scattering on FTU using a new ECRH launcher

Grossetti

Bruschi

Granucci

et al. 2010

35th International Conference on Infrared, Millimeter, and Terahertz Waves

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“…However, one may expect that by refinement of the experimental setup and future development of the analysis one should be able to determine other plasma parameters such as the ion temperature T i with a higher accuracy than in present CTS-based methods (see, e.g., Ref. [24]). …”

Section: Prl 106 165004 (2011) P H Y S I C a L R E V I E W L E T T Ementioning

confidence: 99%

Measurements of Intrinsic Ion Bernstein Waves in a Tokamak by Collective Thomson Scattering

et al. 2011

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In this Letter we report measurements of collective Thomson scattering (CTS) spectra with clear signatures of ion Bernstein waves and ion cyclotron motion in tokamak plasmas. The measured spectra are in accordance with theoretical predictions and show clear sensitivity to variation in the density ratio of the main ion species in the plasma. Measurements with this novel diagnostic demonstrate that CTS can be used as a fuel ion ratio diagnostic in burning fusion plasma devices. Waves and particle dynamics in the frequency range of ion cyclotron motion (ICM), ! ci ¼ q i B=m i , play important roles for diagnostic of ion composition in magnetized plasmas. Under certain conditions collective Thomson scattering (CTS) spectra are distinctively sensitive to ion Bernstein waves (IBWs) and the ICM. The combined effect of IBWs and ICM gives rise to an ion cyclotron structure (ICS) in CTS spectra which depend on the ion species densities and their ratios. Measurements of the ICS in CTS spectra can thus demonstrate basic plasma and wave physics as well as provide great diagnostic potential for characterizing the composition of magnetized plasmas.We present in this Letter the first measurements of CTS spectra with signatures of intrinsic IBWs and ICM in a multispecies tokamak plasma. In experiments on multispecies plasmas containing, e.g., hydrogen, deuterium, and 3 He, we demonstrate that we resolve changes in the ICS in CTS spectra caused by variations in the isotope ratios. In addition, calculations and experimental results agree. This indicates that the relevant physics of CTS and the interaction with IBWs and ICM are well represented by our kinetic, fully electromagnetic model.While our results are of general interest and have application in plasma physics, there is a particular implication on the field of fusion energy research. The issue of measuring the fuel ion ratio in future burning plasma magnetic confinement devices has recently received increasing attention. The fuel ion ratio in burning plasmas is the ratio of the number densities of the main ion species. On ITER it is not clear if this ratio can be determined in the plasma center (normalized radius < 0:3) with the diagnostic set currently included in the ITER baseline design [1]. As measurements of the fuel ion ratio are of high priority for machine protection and basic control, it is of great interest to develop alternative diagnostic methods capable of measuring the tritium-deuterium ratio. Our results represent a key step for developing a novel CTS-based fuel ion ratio diagnostic which can fulfill the measurement needs for ITER and future devices.IBWs are electrostatic hot plasma waves generally present in magnetized plasmas [2,3]. IBWs are weakly damped for propagation near perpendicular to the magnetic field (k k % 0) while the damping of the waves increases strongly as k k increases. The frequencies of propagating IBWs lie between the harmonics of the cyclotron frequency for each ion species in the plasma, ! ci . The frequencies of IBWs with wave vectors...

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“…The CTS installed on the FTU tokamak which runs at below fundamental have also seen similar phenomenã where they refer it to "anomalous spectra" and concluded that is was caused by backreflections from breakdown plasma or arcs in the transmission line. 18 There are currently three hypothesis: the first is that spurious signals intrinsically come from the gyrotron for specific gyrotron parameter settings ͑beam voltage, coil current, etc.͒ where the conversion efficiency it not optimized and cause parasitic oscillations. The second hypothesis is backreflected radiation from either a surface or from arcs in the transmission line that affects the electron beam in the resonator causing spurious signal.…”

Section: Spurious Signals In the Receivermentioning

confidence: 99%

Commissioning activities and first results from the collective Thomson scattering diagnostic on ASDEX Upgrade (invited)

Méo

Bindslev

Korsholm

et al. 2008

Review of Scientific Instruments

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The collective Thomson scattering ͑CTS͒ diagnostic installed on ASDEX Upgrade uses millimeter waves generated by the newly installed 1 MW dual frequency gyrotron as probing radiation at 105 GHz. It measures backscattered radiation with a heterodyne receiver having 50 channels ͑between 100 and 110 GHz͒ to resolve the one-dimensional velocity distribution of the confined fast ions. The steerable antennas will allow different scattering geometries to fully explore the anisotropic fast ion distributions at different spatial locations. This paper covers the capabilities and operational limits of the diagnostic. It then describes the commissioning activities carried out to date. These activities include gyrotron studies, transmission line alignment, and beam pattern measurements in the vacuum vessel. Overlap experiments in near perpendicular and near parallel have confirmed the successful alignment of the system. First results in near perpendicular of scattered spectra in a neutral beam injection ͑NBI͒ and ion cyclotron resonance heating ͑ICRH͒ plasma ͑minority hydrogen͒ on ASDEX Upgrade have shown evidence of ICRH heating phase of hydrogen.

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Evolution of the millimeter-wave collective Thomson scattering system of the high-field tokamak Frascati Tokamak Upgrade

Cited by 14 publications

References 13 publications

Collective Thomson Scattering on FTU using a new ECRH launcher

Collective Thomson Scattering on FTU using a new ECRH launcher

Measurements of Intrinsic Ion Bernstein Waves in a Tokamak by Collective Thomson Scattering

Commissioning activities and first results from the collective Thomson scattering diagnostic on ASDEX Upgrade (invited)

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