Status of the Multi-Pinch/Proto-Sphera Load Assembly Stamos Papastergiou, Franco Alladio, Alessandro Mancuso, Paolo Micozzi CR-ENEA, CP 65, 00044 Frascati (Roma), Italy Outline of the Talk 1) Introduction to PROTO-SPHERA 2) Engineering Design and Analysis of PROTO-SPHERA 3) Multi-Pinch Experiment 4) Timetable 5) Conclusions The Joint Meeting of 4 th IAEA Technical Meeting on Spherical Tori and 14 th International Workshop on Spherical Torus Frascati, 7 to 10 October 2008
Engineering Design of PROTOSPHERA The Joint Meeting of 4 th IAEA Technical Meeting on Spherical Tori and 14 th International Workshop on Spherical Torus Frascati, 7 to 10 October 2008
Main Breakdown features ØScrew pinch (SP) formed by a hot cathode breakdown ØFilling pressure p. H~10 -3÷ 10 -2 mbar ØCathode filaments heated to 2600 °C ØVe~100 V applied on the anode ØInitial electrode arc current limited to Ie~8. 5 k. A The Joint Meeting of 4 th IAEA Technical Meeting on Spherical Tori and 14 th International Workshop on Spherical Torus Frascati, 7 to 10 October 2008
Design Philosophy - Simplicity, symmetry, conservatism. - Viewing capability and good access to electrodes. - All connections to PF coils from top and bottom flanges, external to Machine. - Bellows in coil feedthroughts for adjustment. - Operation and disruption (but no fault) conditions considered. The Joint Meeting of 4 th IAEA Technical Meeting on Spherical Tori and 14 th International Workshop on Spherical Torus Frascati, 7 to 10 October 2008
Design Aims üOperationability, Reliability, Repairability of Machine. üReliability of electrodes and avoidance of arc anchoring. üMinimise Technological Risks: provide appropriate elecrical insulation, avoid local coil overheating ( >100°C ) due to hot anode and cathode ( 12 MJ, 2750°C ) üminimise electromagnetic stresses. The Joint Meeting of 4 th IAEA Technical Meeting on Spherical Tori and 14 th International Workshop on Spherical Torus Frascati, 7 to 10 October 2008
Operating conditions Temperature Vacuum 20°C < 1 • 10 -7 mbar (predicted outgassing rate: ~3 • 10 -5 mbar • l/s) Baking 80 -90°C Adequate for water removal, coil protection; compatible to Viton O-rings Possibility of N 2 1 mbar contact gas The Joint Meeting of 4 th IAEA Technical Meeting on Spherical Tori and 14 th International Workshop on Spherical Torus Frascati, 7 to 10 October 2008
Machine Parameters Spherical Torus (ST) diameter Longitudinal Screw Pinch current Toroidal ST current Plasma pulse duration Minimum time between two pulses Maximum heat loads on first wall componenets in divertor region Maximum current density on the plasma-electrode interface The Joint Meeting of 4 th IAEA Technical Meeting on Spherical Tori and 14 th International Workshop on Spherical Torus 0. 7 m 60 k. A 120÷ 240 k. A 1 s 5 min. 2 MW/m 2 , for 1 ms 1 MA/m 2 Frascati, 7 to 10 October 2008
Protection Componenets • Thermal and Heat Transfer Behaviour Philosophy: collect the heat ( via radiation ) from the electrodes to black resilient componenet and then conduct or radiate it away in a controlled way. Hot spots are thus avoided. Danger: the hot cathode (less the anode) radiates at 2750°C with ~3. 5 MW/m 2 and even a 10 mm thick coil casing cannot sustain this power density for more than 0. 5 s without exceeding 100°C The Joint Meeting of 4 th IAEA Technical Meeting on Spherical Tori and 14 th International Workshop on Spherical Torus Frascati, 7 to 10 October 2008
Thermal and Heat transfer Behaviour • Solution: 1. Use of Cu componenets to collect or reflect the heat away from coils. Conservative (but symmetrical) design for the anode. Thermal mass of these components results in operational temperature < 100°C. Water cooled! Optimum design; i. e. one circuit/component, D~10 -15 mm, v~2 m/s, duty cycle 5 min. 2. Use of thermocouples in no water cooled componenets to avoid >100°C with frequent pulses; every 5 min. 3. Use of 10 mm divertor AISI 304 LN plates. 2 MW/m 2 for 1 s gives DT~120°C, sth~320 MPa 4. Use of optical diagnostics to view the electrodes which are relatively easily accessible. The Joint Meeting of 4 th IAEA Technical Meeting on Spherical Tori and 14 th International Workshop on Spherical Torus Frascati, 7 to 10 October 2008
Electromagnetic Forces and Stresses B=50 T/s B=500 G t≤ 1 ms Subdivision of Cu and 304 LN plates to achieve ≤ 100 MPa of eddy current stresses. Unaccounted skin effects (t ~1 ms) significant. Conservative prediction of eddy current effects. Electromagnetic forces in the coils (~x 10 weight) require to be sustained. The Joint Meeting of 4 th IAEA Technical Meeting on Spherical Tori and 14 th International Workshop on Spherical Torus Frascati, 7 to 10 October 2008
Predicted and Permitted Stresses ASME III-NB 3221 Stainles Steel Allowable Sm for 304 LN 100°C : 200 MPa [304 L Sm~150 MPa] Predicted e-m stresses : 320 MPa Thermal (divertor) local stresses : 320 MPa (2 MW/m 2 , 1 s) Criterion 1 : 100 <200 x 1. 5 Criterion 2 : 100 320 <200 x 3 Copper Minimum required allowable at 100°C> 70 MPa (100 MPa<70 x 1. 5) Thus sy >115 Mpa and su > 230 MPa at 20°C i. e. Cu hardenned The Joint Meeting of 4 th IAEA Technical Meeting on Spherical Tori and 14 th International Workshop on Spherical Torus Frascati, 7 to 10 October 2008
Multi-Pinch Experiment Provisional single anode Cathode START Vacuum Vessel Aim: verification of the arc formation & stability ~ START Dimension Pinch Current Ie=8. 5 k. A(same of Proto. Sphera) - PF-Coils do not need cooling The Joint Meeting of 4 th IAEA Technical Meeting on Spherical Tori and 14 th International Workshop on Spherical Torus Frascati, 7 to 10 October 2008
START in Frascati Arrival May 2004 Disassembling October 2004 The Joint Meeting of 4 th IAEA Technical Meeting on Spherical Tori and 14 th International Workshop on Spherical Torus Frascati, 7 to 10 October 2008
Multi-Pinch Experiment: Phase I & Phase II The Joint Meeting of 4 th IAEA Technical Meeting on Spherical Tori and 14 th International Workshop on Spherical Torus Frascati, 7 to 10 October 2008
ANODE PHASE - ASSEMBLY ELECTRICAL CONDUCTORS Cu GAS W 80%Cu ≤ 1000°C The Joint Meeting of 4 th IAEA Technical Meeting on Spherical Tori and 14 th International Workshop on Spherical Torus Frascati, 7 to 10 October 2008
ANODE PHASE 2 - ELECTRICAL CONDUCTORS ASSEMBLY Cu WCu GAS WATER The Joint Meeting of 4 th IAEA Technical Meeting on Spherical Tori and 14 th International Workshop on Spherical Torus Frascati, 7 to 10 October 2008
SECTION OF ANODE PHASE 2 ELECTRICAL CONDUCTORS GAS WATER COOLED PROTECTION PLATES WCu The Joint Meeting of 4 th IAEA Technical Meeting on Spherical Tori and 14 th International Workshop on Spherical Torus Frascati, 7 to 10 October 2008
Protection Plate Cu W-Cu The Joint Meeting of 4 th IAEA Technical Meeting on Spherical Tori and 14 th International Workshop on Spherical Torus SECTION OF ANODE PHASE 2 SECTOR Frascati, 7 to 10 October 2008
CATHODE - ASSEMBLY ELECTRICAL CONDUCTORS Water W Cu The Joint Meeting of 4 th IAEA Technical Meeting on Spherical Tori and 14 th International Workshop on Spherical Torus Frascati, 7 to 10 October 2008
CATHODE - CROSS SECTION WATER COOLED PROTECTION PLATES W Cu 15 V Mo The Joint Meeting of 4 th IAEA Technical Meeting on Spherical Tori and 14 th International Workshop on Spherical Torus Frascati, 7 to 10 October 2008
COIL PF 2 The Joint Meeting of 4 th IAEA Technical Meeting on Spherical Tori and 14 th International Workshop on Spherical Torus Frascati, 7 to 10 October 2008
Multi. Pinch Coils Delivery: 04/06/2007 EURATOM, ENEA & ASG Personnell The Joint Meeting of 4 th IAEA Technical Meeting on Spherical Tori and 14 th International Workshop on Spherical Torus Frascati, 7 to 10 October 2008
SECTION OF PF 2 The Joint Meeting of 4 th IAEA Technical Meeting on Spherical Tori and 14 th International Workshop on Spherical Torus Frascati, 7 to 10 October 2008
ASG – Test of PF 2 Coil The Joint Meeting of 4 th IAEA Technical Meeting on Spherical Tori and 14 th International Workshop on Spherical Torus Frascati, 7 to 10 October 2008
Multi. Pinch Timetable • Delivery of Load Assembly • I. a Construction & Delivery Magnetic Diagnostics to ASG • II International Tender Action for Construction • of Power Supplies • II. a Delivery of Power Supplies • III Site Preparation • IV Services (Vacuum, Electricity, Diagnostics) • V Commissioning • VI First Plasma The Joint Meeting of 4 th IAEA Technical Meeting on Spherical Tori and 14 th International Workshop on Spherical Torus * September 2009 * April 2009 * March 2009 * June 2010 * June 2009 * June 2010 * December 2010 Frascati, 7 to 10 October 2008
CONCLUSIONS • There is high degree of confidence that the design, construction and reliable operation of PROTO-SPHERA are feasible • The Multi-Pinch experiment is being constructed to prove the formation and stability of the PROTO-SPHERA initial arc • The PF Coils have been delivered, while the Load Assembly is half way in construction using the START Vacuum Vessel • First Plasma can be obtained in December 2010 • PROTO-SPHERA can be obtained by simply adding components to Multi-Pinch The Joint Meeting of 4 th IAEA Technical Meeting on Spherical Tori and 14 th International Workshop on Spherical Torus Frascati, 7 to 10 October 2008
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