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Plan of the talk

Presentation On RF Heating By :- Saurabh Kumar Vij University of Delhi, India IPR, Bhat , Near Indira Bridge Gandhinagar , Gujarat. Plan of the talk. RF Heating Why is heating required? Methods of heating the plasma ICRH and Requirements ECRH Results so far Summary. RF Heating.

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Plan of the talk

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  1. Presentation On RF HeatingBy:-Saurabh Kumar VijUniversity of Delhi, IndiaIPR, Bhat, Near Indira BridgeGandhinagar, Gujarat Presentation on RF Heating by - Saurabh Kumar Vij

  2. Plan of the talk • RF Heating • Why is heating required? • Methods of heating the plasma • ICRH and Requirements • ECRH • Results so far • Summary Presentation on RF Heating by - Saurabh Kumar Vij

  3. RF Heating • Radio-Frequency Heating is one of the most efficient way to heat the Tokamak plasma. • RF Range – 3KHz to 300 GHz Presentation on RF Heating by - Saurabh Kumar Vij

  4. Presentation on RF Heating by - Saurabh Kumar Vij

  5. Why do we need to Heat the Plasma? • Lawson Criterion derived by John D. Lawson in 1955. • To achieve the stage of ignition in a Fusion reactor. • Attaining conditions to satisfy the Lawson criterion ensures the plasma exceeds Breakeven – the point where the fusion power out exceeds the power required to heat and sustain the plasma. • Later on, a new much improved version was found. • The “Triple Product” serves as a criterion to reach ignition. • heTtE>= 1021keV s/m3 • Power required is about 20 MW. Presentation on RF Heating by - Saurabh Kumar Vij

  6. Different methods of Heating • Ohmic Heating - Q = I2R • RF Heating ICRH ECRH LHCD • Neutral Beam Injection • Adiabatic Compression Presentation on RF Heating by - Saurabh Kumar Vij

  7. Why Not just Ohmic Heating? • For Fusion Plasma, we need Temperature around 10 KeV . • Ohmic Heating has a limit of 2KeV. • Because R = C. T-3/2 , So as temp. Increases resistance decreases. • Auxiliary Heating like RF heating is required which could provide the remaining 8-9KeV of power. • Additional Power Required: • P = 3V.D(nT)/(2Te ) • D(nT) = Additional rise in density and temperature. Presentation on RF Heating by - Saurabh Kumar Vij

  8. Why RF is a better method? • Ohmic Heating cannot go beyond a limit of 2KeV. • Neutral beam injection is not fully developed and is also quite difficult to achieve. • Difficult to inject NB at high density because of collisions, leading to Plasma Disruption. • With NBI, particles hitting the inner wall is a problem. • Can also puncture the walls if NB particles hit normally. • ICRH and ECRH provides much more localized heating because B varies inversely with R. • Absence of density limit and direct Ion heating in case of ICRF. • Most important, RF heating at ITER can lead to temperatures of 150 Million0 C. Presentation on RF Heating by - Saurabh Kumar Vij

  9. RF Heating • ICRH – Ion Cyclotron Resonance Heating • ECRH – Electron Cyclotron Resonance Heating • LHCD – Low Hybrid Current Drive Presentation on RF Heating by - Saurabh Kumar Vij

  10. ICRH Ion Cyclotron Resonance Heating Mechanism • Plasma ions are confined to rotating around the magnetic field lines in the Tokamak. •  If the waves have the correct frequency and polarization, their energy can be transferred to the charged particles in the plasma • Cyclotron Frequency, Wci = e.B/mi • The EM waves of a frequency matched to the ions are able to resonate – or damp its wave power into the plasma ions. • Which in turn collide with other plasma particles and heat up the Plasma. • Increasing the temperature of the bulk plasma. • Localised heating of Plasma. Presentation on RF Heating by - Saurabh Kumar Vij

  11. Fundamental and Second Harmonics • Fast RF wave is required for ICRH an it is Left hand circularly polarized. • Ions are right hand circularly gyrating around the magnetic field. • So at the fundamental mode W = Wci • There is no heat transferred to the ions by the RF wave. • So at W = 2Wci , there is an energy transfer by RF wave to the ions. • This is referred to as Second Harmonic heating. Presentation on RF Heating by - Saurabh Kumar Vij

  12. Requirements for ICRH Tokamak Region Control System Interface Antenna Faraday Shield A.C D.C Oscillator P.m Phase Shifter Stub Matching Network Hybrid coupler Stub Phase Shifter Interface Antenna Faraday Shield Presentation on RF Heating by - Saurabh Kumar Vij

  13. Requirements for ICRH • Generator sources – Tetrode tubes, Klystrons and Gyrotrons. • Transmission Lines • Interface Window – Interface between Transmission line and Tokamak. • Antenna • Faraday Screens/Shields. Presentation on RF Heating by - Saurabh Kumar Vij

  14. Antenna(JT-60) Presentation on RF Heating by - Saurabh Kumar Vij

  15. Antenna(JET) Presentation on RF Heating by - Saurabh Kumar Vij

  16. Antenna Presentation on RF Heating by - Saurabh Kumar Vij

  17. Faraday shield • The Faraday shield forms the plasma facing component of the antenna. • It blocks all the plasma particles from entering the Antenna. • But allows the passage for EM waves towards Plasma. • They are a series of parallel metal rods. • This reduces the RF resistive losses. • Can also improve the heating efficiency by 2.3 times. Presentation on RF Heating by - Saurabh Kumar Vij

  18. ECRHElectron Cyclotron Resonance heating • It is similar to ICRH, the only difference being that it specifically heats the electrons only. • Electrons being almost 2000 lighter than the ions, have higher cyclotron frequencies. • Wce = eB/Me • Mi >>> Me • Wce > Wci • Thermalization is low as compared to ICRH. Presentation on RF Heating by - Saurabh Kumar Vij

  19. ECRH Advantages over ICRH • ICRH with its frequencies much lesser than ECRH cannot penetrate much in the vacuum vessel. • ECRH waves can propagate in vacuum and can be steered with high precision. • In ECRH beam can be transmitted through air which simplifies the design and allows the source to be far away from the plasma, simplifying maintenance. Presentation on RF Heating by - Saurabh Kumar Vij

  20. Results so Far • At JT-60U, a strongly peaked Te profile was observed and the central electron temperature increased up to ∼ 15KeV under ECRH with power of 9 MW. • Temperature in excess of 10KeV are a routine now in JET with central temperature of 16KeV with ICRH with power of 32 MW. Presentation on RF Heating by - Saurabh Kumar Vij

  21. Summary • To achieve Fusion, we require many Auxiliary heating methods. • Only one of them is not sufficient enough. • So a combined effort of methods like ICRH, ECRH, NBI is the best way to reach the desired goal. • With experiments like Aditya, JET, JT-60, Textor etc. and the most ambitious ITER project, we can definitely create a star like Fusion on Earth. Presentation on RF Heating by - Saurabh Kumar Vij

  22. Thank You Presentation on RF Heating by - Saurabh Kumar Vij

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