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Status of the ASDEX Upgrade Tokamak Programme

This document provides an update on the status of the ASDEX Upgrade Tokamak Programme, including the repair of the EZ4 generator, compatibility with ITER relevant plasmas, joint experiments, and future campaign plans.

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Status of the ASDEX Upgrade Tokamak Programme

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  1. Status of the ASDEX Upgrade Tokamak Programme R. Dux, J. Schweinzer, A. Sips, AUG team MPI für Plasmaphysik, EURATOM Association • Status of flywheel generators EZ4 & EZ3 • Compatibility of W wall with ITER relevant plasmas • Status of ITPA joint experiments • Planning for 2008/2009 campaign(s) • Midterm hardware extensions Joint Executive Committee session of IEA-IAs on Pol. Div. Tokamaks and Large Tokamaks, GA, San Diego, June 3rd, 2008

  2. Status of Generator EZ4 • ASDEX Upgrade powered by 3 flywheel generators: • EZ2 (1450 MJ / 167 MVA) for toroidal field coils • EZ3 ( 500 MJ / 144 MVA) +EZ4 (650 MJ / 220 MVA) for poloidal field coils and auxiliary heating • Accident in April 2006 led to severe damage on EZ4 • failure of control system – generator continued to run until out of oil • rotor touched stator – damage to stator windings, rotor shaft Repair by Siemens almost finished, but higher level of operational saftey requires additional systems (e.g. brake, new control) which still have to be built. rotor - can be repaired stator - must be rebuilt • Delivery of all main parts + Re-assembly - Oct. 08 • Implementation of all additional saftey systems + commissioning - Feb. 09

  3. limit limit 800kA/ 7.5MW NBI in 2007 (#21838) 800kA/ 7.5MW NBI in 2006 (#21164) Higher EZ3 generator power in 2008 campaign 2007 limit 2008 limit even higher by 30% IEZ3 IEZ3+IEZ4 • Successful optimisation in 2007: • lower voltages for PF coils  softer controllers reduce inductive load • higher plasma currents, longer pulses and higher heating powers possible Next step in 2008: • Higher EZ 3 generator current of 10.514 kA in 2008 campaign  power increases from 144 to 175 MVA  higher Ip and more Pheat

  4. April 2007 Tungsten Wall Project - PWI related part later

  5. Wet cleaning of tiles before campaign starts (07 & 08) to remove older C and B layers No boronisation before/during 2007/8 campaign (until April 2008)no B spectroscopically detectable in 2008 The all tungsten ASDEX Upgrade (AUG) • W coating of all PFCs completed before2007 camapign (no change for 2008): • 3-4 m,PVD on most tiles • 200 m, VPS on outer strike point area • Bulk W for divertor Langmuir probes • Maschine conditioning: • Long baking (10 days @ 150 oC) • Several overnight DGs in He • Intershot DGs in He • W stores and releases He -> later DGs in D

  6. Control of W concentration in the confined plasma

  7. ICRF heating increases W limiter source and central W concentration (cW)

  8. At too low ELM frequency control over central W content lost

  9. Improved H-mode performance & low W concentration is possible

  10.  =0.27  =0.33 Improved H-modes before and after boronisation Best performance for an un-boronised machine - Repeat directly after boronisation -Repeat with no gas fuelling 1MA / 2.55T (q95 ~ 4.7, =0.27 - 0.33) The stored energy is somewhat lower compared in direct repeats of discharges after a boronisation. Only when the gas puff is completely removed(possible as long as the boron layer covers the outer limiters), the stored energy exceeds the best discharges before boronisation, by ~5-10%.

  11. Status of ITPA joint experiments

  12. Contributions to ITPA joint experiments • Done so far in 2008: • ITER breakdown and ramp-up simulations SSO-5 • Improved H-mode scenarios in a full W device SSO-2.1 • ELM Resolved Divertor Characterisation and Tungsten DSOL-19 Sputtering • Dependence of Impurity peaking on ECRH location CDB-9 • Response of pedestal structure to power (beta) scans in SSO-PEP-1 AUG and comparison with DIII-D • Mitigation of disruptions with massive gas puff MDC-1 • SOL and Divertor Characterization for Benchmarking and DSOL-14 Development of Plasma Edge Codes • Vertical stability studies MDC-13 Further contributions are planned and will follow, e.g.: • 2 weeks of He, H operation planned for July 2008 CDB-12 • L/H threshold, confinement ...

  13. ITER relevant breakdown and current rise at AUG

  14. Reduction of loop voltage pre-ionisation using 0.5-1MW ECRH, 2nd harmonic X-mode at 140 GHz (2.3T), Rdep ~1.55m Ip A E V/m PECRH MW D

  15. O-mode ECRH at 3.2T Ip MA ne 1019 m-3 MW PECRH D

  16. Planning for 2008/2009 campaigns

  17. ASDEX Upgrade - Operation Schedule in 2008/9 • 2007 shutdown (19 Oct 07 - 15 Jan. 08): • additional EZ3 brake + new generator control system • removal of PWI probes, smaller repairs & maintenance, wet tile cleaning • Restart Feb 08 again without boronisation • Operation mid Feb - end July 24 weeks / 60 expr. days / 1100# • 22 April 2008 first boronisation, up to 5 until summer break • Summer break Aug 2008 no vessel opening • OperationSept. - Oct. 08 8 weeks / 20 oper. days / 370# • Shutdown Nov. - Dec. 08 required by restart and commissioning of EZ4 generator • Restart January 09 again without EZ4, full operation • expected from Feb. 2009 onwards

  18. Midterm Hardware Extensions

  19. Recent diagnostic improvements • Improved density profile reconstruction using an Integrated Data Analysis (IDA) method - which employs probabilistic models of an integrated set of diagnostics - applied to edge lithium beam emission spectroscopy and core DCN interferometry data t=50s spatial resolution edge: 5mm, core: 10cm • Edge CXRS, high photon throughput, t=1.9ms for Ti, cimp, vtor • Edge radial electric field based on passive spectroscopy of HeII line (468 nm) using the lithium beam observation system. • Fast bolometer diagnostic (104 foil bolometers mounted in several poloidal distributed cameras, t=1ms • Various upgrades of data acquisition to RT systems

  20. Midterm Hardware Extensions ECRH Extension: Gyrotron 2 out of 4:multi-frequency gyrotron (GYCOM): 105 / 115 / 127 /140 GHz, 1 MW, 10 s Gyrotrons 3 and 4 are foreseen to be delivered in autumn 2008 / early 2009, resp.With fast steerable launcher start of feedback controlled deposition (poloidal angle variation of 10° in 100 ms) Pellet injector for small pellets (2009): ELM control without parasitic plasma fuelling

  21. Conducting Wall & Active Coils for MHD control in AUG 3 x 8 active in-vessel saddle coils & five segments of vacuum vessel • ELM suppresion • NTM rotation control(locked mode avoidance) • RWM stabilisation similar to the ITER design • EU preferential support granted • Installation of first 8 “B” coils in autumn 2009

  22. Internal Coils and Conducting Shell 3 poloidal sets (midplane outside) 4 toroidal sets • Proposal is staged to allow several physics applications • 24 coils to generate up to n=4 error fields with different poloidal strucuture • with 1 power supply, n=1,2 and 4 is possible (fast track to ELM suppression) • with 12 power supplies, n=3 and rotating helical field studies can be done • together with conducting shell, n=1 RWM stabilisation experiments possible • further upgrade to 24 power supplies would enable multi-mode control

  23. Optimisation of energy confinement in H-mode discharges

  24. Improved H-modes before and after boronisation - II • Best performance discharges for an un-boronised machine • Repeat of the discharge directly after boronisation • Repeat with no gas fuelling • Total radiated power and core tungsten concentration (CW) drop:Prad/Pheatdeclines from 55%-60% to 35% increasing to 40%-45% when the gas is turned off • CW goes down from 2.0x10-5 -3.0x10-5 to 1.0x10-5for boronised conditions. • The plasma density typically drops by 10% indicating additional wall pumping • The stored energy is somewhat lower compared in direct repeats of discharges after a boronisation. Only when the gas puff is completely removed (possible as long as the boron layer covers the outer limiters), the stored energy exceeds the best discharges before boronisation, by ~5-10%. • The H98 confinement factors show a more marked difference as the confinement scaling predict poorer confinement at lower density.(In calculating H98, the radiation in the core of the plasma has not yet been taken into account.)

  25. Two weeks of He, H operation, July 2008 CDB-12

  26. Overview of the AUG tungsten programme 1: See Table 1, R. Neu, Fus. Eng. Des 65 (2003) 367 2: See Table 1, R. Neu, Journal of Nuclear Materials, 367-370 (2007) 1497

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