1 / 19

Progress in Development of Time-of-Flight Refractometer for ITER

ITPA-10. Progress in Development of Time-of-Flight Refractometer for ITER. Alexei Petrov, Vladimir Petrov, Massimo De Benedetti, Onofrio Tudisco (FTU). SRC RF TRINITI, Troitsk Moscow region, Russia E-mail: vpetrov@triniti.ru. 2006. OUTLINE SPECIFIC FEATURES PROBLEMS, TASKS PROGRESS

irma
Download Presentation

Progress in Development of Time-of-Flight Refractometer for ITER

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. ITPA-10 Progress in Development of Time-of-Flight Refractometer for ITER Alexei Petrov, Vladimir Petrov, MassimoDe Benedetti, Onofrio Tudisco (FTU) SRC RF TRINITI, Troitsk Moscow region, RussiaE-mail: vpetrov@triniti.ru 2006

  2. OUTLINE SPECIFIC FEATURES PROBLEMS, TASKS PROGRESS RECENT EXPERIMENTS, STATUS CONCLUSION, PLANS, TASKS

  3. SPECIFIC FEATURES A robust measurement of line integrated electron density (without fringe jumps) needed for many application, in particular for real time control. Measure time delay • Unambiguous line int. density for feedback control • Microwave pulse - just above Xl cutoff freq. from LFS: single or double pass • ITER– using transparency window on X-mode in low frequency band (60 – 100 GHz): to avoid “first mirror” problem • Less sensitive to the reflection surface quality

  4. PROBLEMS, TASKS -1 • SNR – long distances, long waveguides, accuracy of measurements ~ • Refraction – attenuation, change of wave trajectory- need ray-tracing/(Full wave-analysis) to take into account • Additionally, for high Te (45keV) regimes: absorption, relativistic effects). Transparency window – 60-80-100 GHz - ? • Choose of probing geometry: double- or single pass • Multi-freq. probing to avoid profile dependence • Experiments on tokamaks • Integration with ITER-chamber, LFS-X reflectometer (76-220 GHz; F.02 system, Eq#11)

  5. PROBLEMS, TASKS - 2 SNR – accuracy of measurements: • Optimization of probe geometry, optimization of antenna-waveguide system, use scheme with low-noise microwave amplifier, measure time delay by phase measurements • Probe geometry: • 1. Double-pass (DB). • Pro - use only LFS antennas. • Contra –absorption higher. Influence of refraction larger? • 2. Single pass (SP), using HFS antenna and LFS antenna. • Pro – absorption less. • Contra – complicate HFS antenna system. Compare two systems: k = P1/P2 ~ A1·L22/A2·L12, A1~ 9*9 cm2, A2~9*1 cm2;L1~2·(2a+l), L2~(2a+l). k~10 dB (DB - better), w/o absorption and refraction

  6. PROBLEMS, TASKS - 3 - 50dB (single pass) - 10dB - 0.4dB G. Vayakis, J. Sánchez, ITPA-6 Absorption, choice frequencies Reference Te profiles Integrated absorption for equatorial trajectories at different frequencies (60-100 GHz) and Te values (25-45 keV), ne(0) = 1.03·1020 m-3 ~4.7 dB Total single pass transmission: At least 3 freq. in a range 60-78? GHz to secure immunity to density profile, 95-96 GHz – up to 25 keV

  7. PROGRESS - 1 SNR • 1. Development of the prototype of a receiver for a refractometer with a pulse microwave amplifier (PMA) based on a IMPATT-diode (SNR): • Frequency 60.0±0.5 GHz • Gain >20 dB • Noise <5 dB • Net effect – 15 dB • 2. Improved prototype of a time delay measurements unit with a fast peak detector (PD) - enhanced accuracy of time delay measurements (for low SNR), net effect - 2-3 times better accuracy • 3. Method of a double-frequency differential refractometry (DFR) for time delay measurements is offered and tested in T-11M (higher SNR, sensitivity) [1,2] (CW, net effect +10 dB and more) • Measurements of phase shift between 2 waves with close frequencies (fringe jump-free) :12,Df12 < 2p [1]. V. Petrov et al.Plasma Physics Reports, 2006, Vol. 32, No. 4, p. 317. [2]. V. Petrov et al.Instr. and Exper. Techn., 2006, Vol. 49, No. 2, p. 238.

  8. T-11M FTU ITER BT [T] 1.2 5.0– 8.0 5.3 R [м] 0.70 0.935 6.2 a [м] 0.2 0.305 2.0 R/a 3.5 3.07 3.1 Ne [м-3] 0.5*1020 >1*1020 RECENT EXPERIMENTS - 1 • Experiments in tokamaks – T-11M, FTU Tokamak Parameter • Testing 60 GHz prototype of refractometer (X-mode) in ITER-like conditions on the FTU tokamak (Frascati, Italy) >1*1020 0.5 10-12 15 Te [keV]

  9. RECENT EXPERIMENTS - 2 • Experiments in tokamaks – FTU Transparence window on FTU: Df =50-120 GHz N0 Df flc B0 Df flc fuc N= N0(1-r2)a B0 > 3.5 T needed The behavior of cut-off and ECE frequencies on FTU for typical plasma parameters

  10. RECENT EXPERIMENTS - 3 • Experiments in tokamaks – T-11M, FTU • MO – microwave oscillator, I-isolator, DC-directional coupler, PCS- pulse current source, A1, A2 – amplifiers, D1, D2 – detectors, PD – adaptive threshold pulse discriminator, TVC – time-to-voltage converter P ~ 200 mW, tpulse = 5 ns, tfr< 2 ns, f (PRR) ~ 500 kHz

  11. RECENT EXPERIMENTS - 4 • Experiments in tokamaks – FTU, geometry and picture Signal detector with pulse amplifier CO2/CO interferometer Refractometer Electronic unit for signal handling (PD) Pulse microwave oscillator Antenna system of ECE and reflectometer for the firstexperiments in FTU, antennae directed along minor radius – refraction minimal

  12. Ip = 500 kA Bt = 6 T <N> = 0.8 RECENT EXPERIMENTS - 5 • FTU experiments Time delays ~1.5 ns Now accuracy ~10 ps (~1 ms time resolution) Sensitivity of density measurements ~ 1.5 ns/1020 m-3. Lower density limit: 0.7% of max density. N= (N(0)-N(a))·(1-r2)a+N(a) J= J0(1-r2)g g= q(a)-1 Time delay, ns The behavior of the calculated time delays for X-mode versus density for typical plasma parameters

  13. RECENT EXPERIMENTS - 6 FTU experiments ADC, code 0.8 ns 0.8 0.4 Time, ms Time, s Raw data of TFR: Time delay (code ADC) versus shot time for the typical shot # 27992 (Bt = 6 T, Ip = 500 kA, Ohmic heating Mean density, 1020 m-3: Refractometer (blue) and Interferometer(red) for the shot #27982

  14. Cut-off at the density 1-1.1•1020 m-3; Adequate density measurements up to cut-off RECENT EXPERIMENTS - 7 FTU - Reflectometry regime Mean density 1020 m-3 Td, ns 1 1 -3 Time, s Time, s Mean density: Refractometer (blue line) and Interferometer (red) for the shot #27983

  15. Blue – refractometer Red –IR-interferometer (22.5 cm) RECENT EXPERIMENTS - 8 Mean density, a.u. Time, ms

  16. STATUS -1 Eq#11 Integration in ITER: • TFR probing geometry is part of HFS/LFS antennae-wave guide system (A. Malaquias)

  17. STATUS - 2 C.I.Walker, et.al, ITPA-6 Eq#11

  18. CONCLUSION, PLANS, TASKS -1 1. Development of the prototype of a receiver with a pulse microwave amplifier (PMA) based on a IMPATT-diode (SNR): + 15 dB. 2. Improved prototype of a time delay measurements unit with a fast peak detector (PD) - enhanced accuracy of time delay measurements (for low SNR), net effect - 2-3 times better accuracy 3. Method of a double-frequency differential refractometry (DFR) for time delay measurements is offered and tested in T-11M. +10 dB and more. 4. Testing of TFR in ITER-like configuration (X-mode, double-pass horizontal probing, the same frequency) has been performed successfully in FTU. The first measurements of plasma density with TFR on X-mode have been performed, up to the cut-off density, influence of refraction is low for reflectometry type antenna system (looking along density gradient). Good signal-to-noise ratio is obtained with time resolution of ~50 ms

  19. CONCLUSION, PLANS, TASKS - 2 Density measured by TFR corresponds to the one measured by interferometer (along vertical chord) within 10%. Double-pass scheme of TFR is preferential. Plans: to proceed testing of TFR in different regimes of FTU (ITER-relevant regimes), to develop algorithms of data elaboration (refraction, relativistic effects), hardware modernization (ADC, signal handling electronic); test measurements in JET (D-shape large plasma); testing in T-11M of prototypes of TFR; development of multifrequency prototype; Tasks. Integration in ITER. Study influence of refraction – experimentally and numerically.

More Related