1 / 29

Density issues & Lithization in RFX-mod A. Alfier , A. Canton, R. Cavazzana,

Density issues & Lithization in RFX-mod A. Alfier , A. Canton, R. Cavazzana, S. Dal Bello, P. Innocente, P. Scarin. Summary. Density issues in RFX-mod Proposed lithization techniques on RFX-mod Lithium pellet injector Capillary Porous System

catherine-blackwell
Download Presentation

Density issues & Lithization in RFX-mod A. Alfier , A. Canton, R. Cavazzana,

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. Density issues & Lithization in RFX-mod A. Alfier, A. Canton, R. Cavazzana, S. Dal Bello, P. Innocente, P. Scarin A. Alfier – RFX-mod PROGRAMME WORKSHOP 2009 – 20/22 Jan 2009

  2. Summary • Density issues in RFX-mod • Proposed lithization techniques on RFX-mod • Lithium pellet injector • Capillary Porous System Status, schedule, application, advantages, disadvantages • Expectations & open issues on Lithium in RFX-mod A. Alfier – RFX-mod PROGRAMME WORKSHOP 2009 – 20/22 Jan 2009

  3. Absorbing wall: wide range of density regimes Not absorbing wall: I/N forced to the value 2x10-14 Am Density issues on RFX-mod • RFX-mod first wall (graphite tiles) is an extended reservoir of particles • -> density at flat top (FT) it does not depend on the fuelled particles • -> it is entirely sustained by particles fluxes from the wall • Wall condition affects density: the capability of the wall to absorb particles influences the value of I/N more than the absolute number of particles stored in the wall Des% (desorption)= outpumped-part. / filled-part (%) A. Alfier – RFX-mod PROGRAMME WORKSHOP 2009 – 20/22 Jan 2009

  4. Density issues on RFX-mod • Plasma itself extracts particles from the wall (PWI):Density depends on Ohmic Power, that regulates particle influxes from the wall. •  Particles stored in the wall are not enterely accessible by plasma (implantation depth, toroidal and poloidal asymmetries). •  In RFX-mod we outgas a minimum part of the particles that we inject  we should always fuel the discharge with the minimum gas to allow breakdown.  Wall pre-loading by means of H2 GDC is under test as a reproducible method to obtain a discharge with desired flat top density. A. Alfier – RFX-mod PROGRAMME WORKSHOP 2009 – 20/22 Jan 2009

  5. Why Lithium? • More pronounced pumping effect than Boron (strong H and H+ retention, LiH) • - High impurity getter (O2, N2, CO, H2O, CO2…) • - Reduction of C chemical and physical sputtering (H. Sugai, JNM 1998) • Ionization potential (1s2 2s1): 5.6 eV (I), 75 eV (II), 122 eV (III) • Highest specific heat capacity of any solid element Total wall inventory > 3 times, no sign of saturation Sanchez and the TJ-II Team, PSI 2008 A. Alfier – RFX-mod PROGRAMME WORKSHOP 2009 – 20/22 Jan 2009

  6. Available lithization techniques on RFX-mod • Non-cryogenic pellet injector • 262.30° • equatorial port 2. Capillary Porous System 262.30° central bottom oblong port Top view of RFX-mod A. Alfier – RFX-mod PROGRAMME WORKSHOP 2009 – 20/22 Jan 2009

  7. On RFX-mod:Non-cryogenic pellet injector • Injector characteristics • Pellet speed: 50÷200 m/s • Pellet size: Ø 0.5÷2 mm x 1÷4 mm • 30 pellets in the charger • Materials: Li, C, B • Aims • Measurement of the pitch of the magnetic field lines • Transport studies • First wall conditioning A. Alfier – RFX-mod PROGRAMME WORKSHOP 2009 – 20/22 Jan 2009

  8. On RFX-mod:Non-cryogenic pellet injector • Pellet size: Ø 1.5 mm x 4 mm = 28 mm3 •  NLi≈ 1021 &SRFX=36.3 m2 •  ≈ 2.6 monolayers if uniformely distributed • Schedule: • Installation at middle/end of february ’09; • Delivery of interface system with vessel (the injector is already here) at end of february ’09; • Tests on RFX-mod available since middle/end of march (related to the RFX-mod 2009 experiments schedule). A. Alfier – RFX-mod PROGRAMME WORKSHOP 2009 – 20/22 Jan 2009

  9. On RFX-mod:Non-cryogenic pellet injector • Strategy: 1. first wall conditioning with He glow discharge; 2. injection in standard and then performing RFP discharges at the end of the current flat-top; hint: the injection on tokamak discharge could be usefull to obtain a more uniform distribution of Lithium, but probably a tokamak discharge will not ablate entirely the pellet and sustain the incraese of density. • Advantages: - control the amount of the injected Lithium; - easy to use (well-established technique) and to compare with similar discharge w/o pellet; - injected lithium of good pureness; - lithium effective during the discharge; - non uniform deposition (only where plasma touches the wall); • Disadvantages: - thin Lithium layer deposited (few monolayers)  short length beneficial effects (few shots); - maybe non uniform deposition also where plasma touches the wall; - Li-pellet injection perturbs plasma before its beneficial effects appear  being at the end of the flat-top, it prepares the first wall for next discharge A. Alfier – RFX-mod PROGRAMME WORKSHOP 2009 – 20/22 Jan 2009

  10. On RFX-mod:Capillary Porous System (CPS) CPS unit operating position 500mm CPS unit storage position Schematic layout of CPS on RFX-mod Hint: The gate valve should be installed below coils  additionl 500÷800mm A. Alfier – RFX-mod PROGRAMME WORKSHOP 2009 – 20/22 Jan 2009

  11. On RFX-mod:Capillary Porous System ~120mm RFX-mod oblong window port with CPS 120mm clearness Ø150mm valve General view of the CPS A. Alfier – RFX-mod PROGRAMME WORKSHOP 2009 – 20/22 Jan 2009

  12. On RFX-mod:Capillary Porous System Modification of the FTU support A. Alfier – RFX-mod PROGRAMME WORKSHOP 2009 – 20/22 Jan 2009

  13. Capillary Porous System on FTU A. Alfier – RFX-mod PROGRAMME WORKSHOP 2009 – 20/22 Jan 2009

  14. On RFX-mod:Capillary Porous System • Strategy: 1. First wall conditioning in H2 GDC + Baking  decrease impurity content; hint: Li reacts with O, C, N (LiOH, Li3N, Li2CO3) 2. He discharge  decrease H content (Li reacts with H); 3 Baking  decrease He content. hint: He can be captured in Li voids, and it could then released during several discharges 4. Define a “suitable” Tokamak dicharge (60-80 kA, n=1-21018 m-3, t=400ms, q=2-4); 5. Condition the first wall with CPS in tokamak discharges. 6. Extract the CPS. 6. RFP plasma @ Ip ~ 0.5-1.5MA, F=-0.03 ÷ -0.08. 7. …. We’ll keep you informed! • Schedule: • Procurements of materials on loan from FTU: end of summer 2009. • Installation and test : autumn 2009. • Tests on RFX-mod available beginning of winter 2009. A. Alfier – RFX-mod PROGRAMME WORKSHOP 2009 – 20/22 Jan 2009

  15. On RFX-mod:Capillary Porous System • Advantages: - on loan from FTU for first attempt on RFX-mod. - easy to handle; - injected lithium of good pureness; - high heat load threshold (10 MW/m2) compatible with reactorial previsions • Disadvantages: - not usefull during RFP discharges (Li would be deposited in +-20 tor. deg. from CPS) - the amount of Li deposited on the first wall not straighforward to control. - requires first wall conditioning with tokmak discharges. - never used before on other RFP experiments. A. Alfier – RFX-mod PROGRAMME WORKSHOP 2009 – 20/22 Jan 2009

  16. Expectations & open issues on Lithium in RFX-mod Expected effects (from experience on other machines): • lower & controlled recycling with absorbing wall • lower Zeff and radiation losses • Te increase • tE improved Open issues: • Lithium deposition on optics if Li+ born in field lines, it does not result in window coating • Effects on internal probes : • Li does not react with Mb, Fe, Ti, Stainless steel • Li reacts with Cu, but no effect reported in literature & no relevant effect on NSTX and TFTR if not with evaporator (priv. com.) • Effect of Li penetration (“intercalation”) in graphite tiles  experience from other experiments • Too low recycling  fuelling issues • 3-8 hours He GDC used to recover wall condition w/o lithium (Vershkov, IAEA ’08 & in Sugai, J. Nucl. Material ’95). A. Alfier – RFX-mod PROGRAMME WORKSHOP 2009 – 20/22 Jan 2009

  17. Further tasks: • Real time or inter-shot measurement of the deposited Lithium (e.g.: quartz crystal oscillator). • Expose samples (of graphite, mirror and windows) to plasma.  three experimental proposal for 2009. A. Alfier – RFX-mod PROGRAMME WORKSHOP 2009 – 20/22 Jan 2009

  18. Thank you A. Alfier – RFX-mod PROGRAMME WORKSHOP 2009 – 20/22 Jan 2009

  19. Available lithization techniques 1. Lithium pellet injection (TFTR) • J.A. Snipes et al. J. of Nucl. Mater. (1992) 686 - 2 mm Ø x 2 mm • 1-2 Monolayers coated on TFTR graphite limiter • Pellet injected in conditioning He discharges and standard discharges 2. Lithium aerosol - DOLLOP (TFTR) • D.K. Mansfield et al. Nucl. Fusion 41 (2001) 1823 • Li contained in a small (17.5 cm3) boron nitride cauldron positioned 15 cm below the shadow of the TFTR RF limiter edge • The highest total energy confinement time was obtained in TFTR with this technique (about 80% improvement, Zeff = 1.2-1.3) A. Alfier – RFX-mod PROGRAMME WORKSHOP 2009 – 20/22 Jan 2009

  20. Available lithization techniques 3. LIThium EvaporatoR - LITER (NSTX) • R. Kaita & H. Kugel, APS 2008 • Li heated inside an “oven” • tE improved, Te profile broadened Lowered recycling 4. Lithium aerosol with powder (NSTX) • Mansfield, APS 2008 • 98.5% Li +1.5% Li2CO3 particles (Ø =50mm) • Similar effect of LITER, with even more reduced impurity accumulation 100 mm A. Alfier – RFX-mod PROGRAMME WORKSHOP 2009 – 20/22 Jan 2009

  21. Available lithization techniques 5. Li Capillary Pore System (CPS) • Tested in T-11M and FTU Tokamaks (S.V. Mirnov et al. Fusion Eng. Des. 65 (2003) 455, M.L. Apicella at al. J. of Nucl. Mater. (2007) 1346. • See previous talk. 6. CDX-U low aspect ratio tokamak (PPPL) • Lithium tray limiter filled with a total of 300 g (0.6 l) of lithium + evaporator • tE improved, lower Zeff, lowered recycling A. Alfier – RFX-mod PROGRAMME WORKSHOP 2009 – 20/22 Jan 2009

  22. Lithium chemistry • Low thermal expansion: 46 µm·m−1·K−1 • Highest specific heat capacity of any solid element: 24.860 J·mol−1·K−1 • Thermal conductivity: (300 K) 84.8 W·m−1·K−1 •  heat transfer applications • Melting point: 180.54 °C • Boiling point: 1342 °C • High electrochemical potential, light weight, and high current density  lithium-ion batteries • 6Li + n → 4He + 3H (blanket of ITER) • high surface tension  effect on physical sputtering A. Alfier – RFX-mod PROGRAMME WORKSHOP 2009 – 20/22 Jan 2009

  23. Lithium chemistry • Ion Li+, which have a smaller diameter, can easily displace K+ and Na+ and even Ca2+, in spite of its greater charge, occupying their sites in several critical neuronal enzymes and neurotransmitter receptors. • Although Li+ cannot displace Mg2+ and Zn2+, because of these ions' small size and greater charge (higher charge density, hence stronger bonding), when Mg2+ or Zn2+ are present in low concentrations, and Li+ is present in high concentrations, the latter can occupy sites normally occupied by Mg2+ or Zn2+ in various enzymes. • Lithium hydroxide (LiOH) is an important compound of lithium obtained from lithium carbonate (Li2CO3). It is a strong base, and when heated with a fat, it produces a lithium soap. Lithium soap has the ability to thicken oils and so is used commercially to manufacture lubricating greases • lithium peroxide (Li2O2) • 2 Li2O2 + 2 CO2 → 2 Li2CO3 + O2. • lithium hydroxide (LiOH and LiOH·H2O), lithium nitride (Li3N) and lithium carbonate (Li2CO3, the result of a secondary reaction between LiOH and CO2). • Lithium carbide, Li2C2: molten lithium + graphite are reacted at high temperature A. Alfier – RFX-mod PROGRAMME WORKSHOP 2009 – 20/22 Jan 2009

  24. Effect on impurity on T-10 High Z imp. Carbon Before Li with Li Vershkov, IAEA ‘08 A. Alfier – RFX-mod PROGRAMME WORKSHOP 2009 – 20/22 Jan 2009

  25. Wall control on T-10 Vershkov, IAEA ‘08 He GDC used to recover wall condition w/o lithium (also in Sugai, J. Nucl. Material ’95). A. Alfier – RFX-mod PROGRAMME WORKSHOP 2009 – 20/22 Jan 2009

  26. Scanning quartz deposition monitor (QDM). A. Alfier – RFX-mod PROGRAMME WORKSHOP 2009 – 20/22 Jan 2009

  27. Expose samples (of graphite, mirror and windows) to plasma. A. Alfier – RFX-mod PROGRAMME WORKSHOP 2009 – 20/22 Jan 2009

  28. Kaita et al. IAEA 2008 A. Alfier – RFX-mod PROGRAMME WORKSHOP 2009 – 20/22 Jan 2009

  29. Kaita et al. IAEA 2008 A. Alfier – RFX-mod PROGRAMME WORKSHOP 2009 – 20/22 Jan 2009

More Related