UCRL-PRES-210109 Magnet Design Considerations & Efficiency Advantages of Magnetic Diversion Concept W. Meier & N. Martovetsky LLNL HAPL Program Meeting NRL March 3-4, 2005 Work performed under the auspices of the U.S. Department of Energy by the University of California, Lawrence Livermore National Laboratory under contract No. W-7405-ENG-48.

Many system trades need to be considered for magnetic diversion concept Costs + Chamber (smaller chamber  lower cost first wall and blanket) Magnets, cryo refrigeration system, magnet structural support and shielding Ion dump (ion dump “first wall”, cooling, shielding) Performance + Lower first wall heat flux  more options for FW coolant + Possible higher operating temp  higher thermal conversion efficiency, but - requires advanced materials  higher costs, longer development time? + Possible direct conversion of ion energy  possible higher conversion eff., but - requires added equipment, cost and complexity Nuclear Considerations Small chamber  shorter FW life for given fusion power Neutron leakage thru ion port  reduced TBR, shielding issues Need to shield cryo magnets + Ion dump wall out of direct line of sight of neutrons  less n damage Meier HAPL March 05

ITER Central Solenoid (CS) Cable in Conduit Conductor (CICC) Conductor consists of: Nb3Sn superconducting strands Pure copper strands Multi-stage cable including wraps and central spiral Jacket Extruded segments 4-8m long Butt welded/inspected Cable inserted and compacted Strand Nb3Sn (0.83 mm diameter) Conductor in winding pack: 1 mm per side insulation 1 mm axial shim 0.5 mm radial shim Shims are used to compensate winding errors and keep winding pack tolerances CICC (49 mm x 49mm) Meier HAPL March 05

CS CICC Construction Strand Subcable wrap (to reduce AC losses) Conduit Cable wrap (protects cable against damage during pull through) Subcables Helium flow Meier HAPL March 05

ITER PF Conductor (NbTi+Cu) Strand (courtesy of EMI, 0.81 mm diameter, Ni plated) CICC in 316 LN steel jacket, 1152 strands Meier HAPL March 05

PF magnets for ITER are similar in size and complexity – possible prototype PF2 is about same radius as our middle magnets PF3 is about same radius as our deflector magnet 12.5 m Meier HAPL March 05

Conceptual design of the magnet system Meier HAPL March 05

Peak field is 5. 4 T at inner edge of smaller radius (3 Peak field is 5.4 T at inner edge of smaller radius (3.25 m) coils – allows NbTi CICC Field, T Field, T Meier HAPL March 05

Forces and stored energy are significant, comparable to ITER PF coils Forces, 106 N Mag Hoop Axial 1 3 4 5 Stored energy in system = 2.9 GJ – very significant, requires good quench detection and protection system (dump resistors, fast circuit breakers). 2 Arrows indicate direction of forces. (Not to scale) Meier HAPL March 05

From L. Bromberg and J. Shultz, “ARIES CS Magnets” ARIES is developing magnet costs and scaling for Compact Stellerator study From L. Bromberg and J. Shultz, “ARIES CS Magnets” PPPL Meeting, 12/4/04 Meier HAPL March 05

Near-term, real world cost info is available from ITER (2005$) for six PF coils PF5: I = 9.8 MA-turns, R = 8.4 m Cost ~ $19.6M (14.4M IUA) IFE5: I = 9 MA-turns, R = 7.85 m If Cost ~ Vol, then Cost ~ $17M 1 IUA = $1000 (1989$) ~ $1360 (2005$)* * escalated using US producer prize index for manufacturing Meier HAPL March 05

Power flow diagram with direct conversion Neutrons & x-rays (~70%) HGH Blanket (x M) Steam or Brayton cycle (ht) Chamber: Target gain (G) Charged particles & plasma (~30%) HGH Direct Converter (hi) Pte = thermal-electric Laser power on target Pde = direct-electric Pe = gross electric Laser (hd) Pd = laser power HGH = High Grade Heat Pne = net electric power Meier HAPL March 05 Adapted from A.E. Robson

Efficiency improvement using DC is easily implemented in systems code Meier HAPL March 05

Net plant efficiency can be significantly higher with DC of ion energy Assumes: Gain = 140 Laser eff. = 7% Thermal eff. = 40% Ion dump heat also converted at 40% Net efficiency 50% DC = 38.9% No DC = 30.5% Ion-to-electric efficiency Meier HAPL March 05

COE could be significantly lower depending on added costs of magnets and direct conversion 10% higher capital cost Assumes: Same as previous COE ~ (Capital cost)/Pne Normalized COE No added capital cost Ion-to-electric efficiency Meier HAPL March 05

Next Steps? Next steps depends largely on level of detail desired for evaluation of magnetic diversion concept Need more info on Choice of FW and blanket for chamber Design of ion dumps and cooling method Direct conversion systems and costs Good start on basis for magnet design, costs and scaling Potential plant efficiency improvements are significant, but will be offset to some degree by added costs for magnets, ion dumps and conversion equipment. Meier HAPL March 05