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Present Status of the Nd:YAG Thomson Scattering System Development for Time Evolution Measurement of plasma profile on

Present Status of the Nd:YAG Thomson Scattering System Development for Time Evolution Measurement of plasma profile on Heliotron J. 2011.11.3 APFA2011. Takashi Minami , Shohei Arai, Naoki Kenmochi, Hiroaki Yashiro,

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Present Status of the Nd:YAG Thomson Scattering System Development for Time Evolution Measurement of plasma profile on

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  1. Present Status of the Nd:YAG Thomson Scattering System Development for Time Evolution Measurement of plasma profile on Heliotron J 2011.11.3 APFA2011 • Takashi Minami, Shohei Arai, Naoki Kenmochi, Hiroaki Yashiro, • Chihiro Takahashi, Shinji Kobayashi, Tohru Mizuuchi, Shinsuke Ohshima, Satoshi Yamamoto, Hiroyuki Okada, Kazunobu Nagasaki, Yuji Nakamura, Kiyoshi Hanatani, Shigeru Konoshima , Fumimichi Sano • Institute of Advanced Energy, Kyoto University, Gokasho, Uji 611-0011, Japan

  2. Outline • Introduction of Heliotron J • Recent results • SMBI Experiments • Plasma startup without ECH • Nd:YAG Thomson scattering • Introduction • Design overview for collective optics • polychromator • present status of development • Summary

  3. Heliotron J Project Aims To Develop Attractive Compact Fusion Reactor • A steady-state, compact, • high-β helical reactor • No disruptions • (currentless operation) • No close conducting wall or active feedback control of instabilities • (no serious MHD instabilities) • High Qeng (= net Pele. / Poper. ) • (at minimum recirculating powers) • High power density • (3~4 MW/m2 under the development of advanced wall materials) FFHR HSR SPPS Compact Reactor ITER

  4. Inner Vertical Coil Outer Vertical Coil Toroidal Coil A Vacuum Chamber Toroidal Coil B Plasma Helical Coil Heliotron J Device • Major Radius: R=1.2 m • Plasma Minor Radius: a=0.1-0.2 m • Magnetic Field: B≦1.5 T • Vacuum iota: 0.3-0.8 with low magnetic shearHeating System: • ECH 0.4MW • NBI 0.8MW • ICRF 0.4MW • Magnetic coil system : • one l/m=1/4 continuous helical coil • two sets of toroidal coils • three pairs of vertical field coils • Typical plasma parameters; • ne=0.2-4 x 1019 m-3 • Te=0.3-1 keV • Ti=150-200 eV

  5. SMBI Has Extended Operational Regime • The stored energy reached Wp~4.5 kJ for ECH(~0.35 MW)+NBI(~0.6 MW), about 50% higher than that of conventional gas-puff fueling. • The optimization study of SMBI-relevant operation scenario is in progress. Mizuuchi, Contribution to Plasma Physics 50 (2010) 639

  6. NBI Plasmas Have Been Successfully Started Up By Assist of 2.45GHz 5kW Microwaves • Plasmas of ne=1x1019 m-3 have been successfully produced 20msec after NBI turn-on with assistance of 2.45GHz 5kW microwaves • No high-power ECH is applied • Plasma startup without ECH widely will extend the operation region • High β experiment • B dependence of confinement • B dependence of high-energy particles • Extension of configuration • Off-axis 70GHz ECH Kobayashi, Nucl. Fusion 51 (2011) 062002

  7. No density build-up Production of Low-Density Plasma and High-Energy Electrons by 2.45GHz Microwaves is Important • There is no EC resonance for 2.45GHz microwaves • Plasma is successfully started up when ECE intensity exceeds a critical value

  8. Objective for Construction new Nd:YAGThomson • Previous experiments show the improved confinements phenomena accompany with the transient phenomena. The plasma profile is rapidly changed by the transition. • Therefore, the time evolution of the plasma profile should be measured to understand the physics of the improved confinement. • For this purpose, we are developing new Nd:YAG Thomson scattering system for Heliotron J device.

  9. Design of Heliotron J Nd:YAG Thomson system • Goal: Performance • Spatial resolution ~1cm • Spatial channels : 25 • Time intervals of measurement ~10ms (Period of discharge ~200ms,confinement time~1-10ms) • Range of Te10eV-10keV • Range of ne>0.5x1019m-3 • Nd:YAG Laser spec • 100Hz (50Hz two lasers), 550mJ 10ns pulse by Continuum.inc. • We have a future plan to improve time interval to ~5ms (2 lasers->4 lasers)

  10. Schematic of YAG Thomson Scattering system

  11. 20度 Design of Scattered Light Collective System Large concave mirror is used for large solid angle Higher F number for low aberration Dimeter: 800mmF/2.25 Scatter volume image (mm) concave mirror Scattered angle:20deg. (mm) • 25 spatial points • ->resolution ~10mm • Image length:14cm • Scattered angle: 20degree • Laser Length inside plasma: 25-30cm • Magnification: 0.3-0.5

  12. Solid angle and aberration • Large solid angle: 0.08-0.1str.=>Considerable scattered light can be collected • Back scattered light is small due to small backward region.=>Good S/N ratio • Aberration (<3mm) is small due to larger F number (Fiber width ~3mm) • It is easy to choose optical fiber, because required fiber NA(numerical aperture) is >0.25. • Uniform optical characteristic for all spatial points >80mstr <3mm ~0.25

  13. Polychromator 6 channel Interference Polychromator • Wavelength channel 5ch. • Rayleigh channel1ch. APD • Interference filter • Relay lens • Detector • Avalanche photo diode -Hamamatsu photonics: S8890-30,[area: 3Φ] • Bias: High voltage regulator with temperature control • Preamplifier is made by JFET input OP amplifier. HV regulator

  14. Output signal of preamplifier Gate width 60ns-80ns APD signal Time Amplifier performanceSignal response by SPICE Circuit Simulator ADA4817

  15. Design for Filter Combination of Polychromator >80% • Filter Combination • Ch1(FIlter1) : 700-845nm • Ch2(FIlter2) : 845-960nm • Ch3(FIlter3) : 960-1025nm • Ch4(FIlter4) : 1025-1050nm • Ch5(FIlter5) : 1050-1060nm • Te : 10-10keV ne: 3x1019m-3 • Error from bremsstrahlungis below 2% for Te and 3% for ne • Filter set optimization using modeling code. • Te : 10-10keV ne: 3x1019m-3 • Error is below 2% for Te and 3% for ne • 制動輻射だけを考慮 • Filter Combination • Ch1(FIlter1) : 700-845nm • Ch2(FIlter2) : 845-960nm • Ch3(FIlter3) : 960-1025nm • Ch4(FIlter4) : 1025-1050nm • Ch5(FIlter5) : 1050-1060nm • Te : 10-10keV ne: 3x1019m-3 • Error is below 2% for Te and 3% for ne • 制動輻射だけを考慮

  16. V792 CINOS Development of Data Acquisition System for Fast SIgnal CAEN V792 32 Channel Multi-event QDC（Charge-to-Digital Conversion) VME bus system based on CHS CINOS system Polychromators 25x6ch. =150ch. V792 QDC 32ch.x5 CINOS Controller Memory VME CAMAC Heliotron J Fedora Linux Data base

  17. Movie:Manufacturing new port on Heliotron J Outer Port Inner Port

  18. New Heliotron J port for Nd:YAG Thomson Heliotron J Window for scattered light(30cm) Laser injection port

  19. New Nd:YAG Thomson Scattering Stage

  20. Summary • To investigate the relation between the plasma profile and the improved confinement on Heliotron J. We develop the new Nd:YAG Thomson scattering system. • Spatial resolution ~1cm • Spatial channels : 25 • Time interval of measurement ~10ms • Range of Te10eV-10keV • Range of ne>0.5x1019m-3 • Laser optics, Collection optics for scattered light (Concave mirror, optical fiber bundles), Polychromator (filter combination, relay lens, preamplifier), Data acquisition system are developed.

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