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MAST Upgrade: Status and plans
Andrew Kirk ST workshop 2015, Princeton, USA CCFE is the fusion research arm of the United Kingdom Atomic Energy Authority
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MAST Upgrade: Status and plans
Andrew Kirk On behalf of CCFE is the fusion research arm of the United Kingdom Atomic Energy Authority 2
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Contents Motivation for MAST-U MAST-U capabilities MAST-U progress
1st physics campaign Future Upgrades Summary 3
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Contents Motivation for MAST-U MAST-U capabilities MAST-U progress
1st physics campaign Future Upgrades Summary 4
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MAST Upgrade: Introduction
MAST Upgrade has 3 primary objectives, namely to contribute to: Developing novel exhaust concepts Knowledge base for ITER (e.g. understanding and controlling ELMs with 3D fields) Exploring the route to fusion power with an ST 5
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MAST Upgrade MAST-Upgrade after initial construction (“core scope”)
Increased TF Improved confinement New Solenoid Greater Ip, pulse duration 19 New PF Coils Improved shaping Super-X Divertor Improved power handling Off-Axis NBI Improved profile control 6
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Long pulse (steady state)
MAST-U contributions to current issues JET < ITER < DEMO Ph/R ~ 7 20 80-100 Divertor Challenge High heat flux needs to be mitigated → radiation, novel divertor concepts Fast-ion physics Fast particle driven instabilities may change confinement, current drive, fast-ion redistribution Long pulse (steady state) Need means to sustain the plasma current → current drive schemes (NBI, RF), optimise bootstrap fraction VTi << VA < Va << VTe For ITER 9x105 m/s 8x106 m/s 12x106 m/s 6x107 m/s JET < ITER < DEMO tpulse< 20s 500s Hours 7
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Divertor Challenge MAST-U contributions to current issues
JET < ITER < DEMO Ph/R ~ 7 20 80-100 Divertor Challenge High heat flux needs to be mitigated → radiation, novel divertor concepts 8 8
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Plasma exhaust in DEMO To have viable heat flux on divertor plates must either: Radiate many 100’s MW inside separatrix But is this compatible with good core plasma performance? Use alternative divertor to increase divertor radiated power MAST-U aims to compare and contrast the alternatives X-divertor Snowflake Super-X X-point Target 9
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MAST-U: divertor configurations
Flexible poloidal field coil set allows for a wide variety of magnetic geometries Conventional Super-X Snowflake 10
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Divertor Challenge Fast-ion physics
MAST-U contributions to current issues JET < ITER < DEMO Ph/R ~ 7 20 80-100 Divertor Challenge High heat flux needs to be mitigated → radiation, novel divertor concepts Fast-ion physics Fast particle driven instabilities may change confinement, current drive, fast-ion redistribution VTi << VA < Va << VTe For ITER 9x105 m/s 8x106 m/s 12x106 m/s 6x107 m/s 11
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Fast particle physics Perhaps the biggest change in ITER will be a dominant source of fusion-born alpha particles Why do we care? Loss of bulk heating Unacceptable for efficient power plant Possible ignition problems Damage to first wall Can only tolerate a few % losses 12
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Provide enhanced profile control
MAST-U will be able to tailor the fast ion distribution Provide enhanced profile control Core heating and current drive with on-axis NBI 13
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Tailoring the fast ion distribution
Provide enhanced profile control Core heating and current drive with on-axis NBI Hollow deposition with off-axis NBI 14
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Tailoring the fast ion distribution
Provide enhanced profile control Core heating and current drive with on-axis NBI Hollow deposition with off-axis NBI Broad profiles with both systems 15
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Long pulse (steady state)
MAST-U contributions to current issues JET < ITER < DEMO Ph/R ~ 7 20 80-100 Divertor Challenge High heat flux needs to be mitigated → radiation, novel divertor concepts Fast-ion physics Fast particle driven instabilities may change confinement, current drive, fast-ion redistribution Long pulse (steady state) Need means to sustain the plasma current → current drive schemes (NBI, RF), optimise bootstrap fraction VTi << VA < Va << VTe For ITER 9x105 m/s 8x106 m/s 12x106 m/s 6x107 m/s JET < ITER < DEMO tpulse< 20s 500s Hours 16
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Current drive studies Off-axis NBI will provide ability to study current drive physics TRANSP 17
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Contents Motivation for MAST-U MAST-U capabilities MAST-U progress
1st physics campaign Future Upgrades Summary 18
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MAST Upgrade: parameters
MAST Upgrade Overview: Parameter / System Upgrade Toroidal Field Increased from 0.5 to 0.8T (at R = 0.8m) Plasma Current Increased from 1MA to 2MA Pulse Length Increased from 0.5 to 5s In-vessel Coils Increased from 10 to 20 Ex-vessel PF Coils Increased from 1 to 4 NBI injection 2 on-axis beams reconfigured to 1 on-axis, 1 off-axis RMP coils Two rows of in-vessel coils Divertor Fully reconfigured for advanced divertor configurations => Result, 90% of the Load Assembly is new (only vacuum vessel and a few coils re-used) 19 19
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MAST Upgrade Divertor Closed divertor with very flexible PF coil set
Divertor nose D6 D7 DP D1 Gas baffle D2 D5 D3 Cryopump
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MAST-U: divertor configurations
Flexible poloidal field coil set allows for a wide variety of magnetic geometries Conventional Super-X Snowflake 21
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Possible to study the effect of extended inner leg
MAST-U: Super-X configurations Different poloidal flux expansions possible Possible to study the effect of extended inner leg
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MAST Upgrade: operational space
MAST-Upgrade will have expanded operational space Maximum plasma current increased up to 2.0MA Lower main chamber neutral pressure Lower ne, higher Te edge pedestal Higher elongation, triangularity Very flexible magnetic geometry “Conventional”, Super-X and snowflake divertor configurations possible MAST-U MAST 23
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Diagnostics At day 1 plan to have similar set of diagnostics as on MAST MAST-U will retain diagnostic capabilities 130 point, ~1cm resolution Thomson scattering Extensive beam spectroscopy Charge-exchange recombination spectroscopy Motional Stark Effect Fast Ion Dα Wide-angle high speed imaging Divertor diagnostics will be extended and enhanced 24
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New Divertor Diagnostics
Extensive Langmuir probe coverage Strike points will be monitored in a wide range of magnetic configurations Thomson scattering will be used to measure ne, Te in the divertor chamber Measurements at 16 locations along laser path Monitor parallel pressure balance → detachment physics Benchmarking Langmuir probes and spectroscopy Radiated power in main chamber and divertor will be monitored using gold foil bolometer arrays 32 channels in main chamber 32 channels in divertor 25
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New Divertor Diagnostics
Divertor Thomson scattering Spectroscopy radiation from SOLPS core system Infra red views of PFCs Others, especially Coherence imaging (flows) Divertor science facility Bolometer arrays for divertor Langmuir probes 26
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Contents Motivation for MAST-U MAST-U capabilities MAST-U progress
1st physics campaign Future Upgrades Summary 27
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Timeline Conceptual Design Scheme Design Detailed Design Construction
2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 Dec 2016, Based on revised budget latest Pump down projection, Start of Integrated commissioning Jan 2008, MAST-U + Super-X Divertor, Scoping studies and Conceptual Design started Oct 2013, MAST Operations finish, Strip out starts Aug 2017, First MAST-U Plasma April 2010, MAST-U Construction Approved March 2014, MAST-U rebuild underway 28 28 28 28
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= + Progress Summary MAST-U Load Assembly - Modular Construction
Upper End Plate Upper Cassette Outer Cylinder = + Centre Tube Centre Column Lower Cassette Lower End Plate 29
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Build Progress: lower cassette
Lower cassette complete 30
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Build Progress: lower cassette
Lower Cassette complete – including diagnostics • All lower cassette magnetic diagnostics fully installed • magnetics wiring complete from coils to conduits and out to port locations ready for termination 31
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Build Progress: outer cylinder
Outer cylinder – complete PF coil and embedded diagnostics - Fitted over lower cassette 32
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Build Progress: OC+LC Outer cylinder complete and lower cassette installed 33
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Build Progress: lower end plate
Lower End Plate and cryopump Throttle plates in position, Particle shield positioning ongoing Particle shield Cryopump with Throttle plate 34
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Build Progress: lower end plate
Trial fitting of tiles… and tile heaters Allowing tiles to be baked to 250 ⁰C 35
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Build Progress: Centre tube
Centre tube – nearing completion • Final Mirnovs being wound to go on to the centre tube • LP wiring being installed on centre tube • Thermocouples ready to install • Finishing tasks before tube can go into its vertical positon 36
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Build Progress: Centre column
Solenoid - complete New TF centre rod impregnated with Cyanate ester Passed full electrical tests Trial assemblies are ongoing 37
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Build Progress: NBI Being upgraded for 5 second operation
NBI ion dumps NBI bend magnets 38
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Build Progress: Centre column
New Toroidal field power supply installed and commissioned into dummy load Poloidal field and divertor power supplies installed 39
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Build Progress: Control room
New Control and server room built 40
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Contents Motivation for MAST-U MAST-U capabilities MAST-U progress
1st physics campaign Future Upgrades Summary 41
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Scientific Goals of Core Scope
Improving the understanding of exhaust physics Closure and connection length Flux expansion at the divertor targets Volumetric losses and detachment Fast ion physics and current drive Tailoring super-Alfvenic fast ion distribution High elongation plasmas with reduced fast ion redistribution Other high-priority ITER, DEMO and CTF needs RMP ELM control Pedestal & core turbulence at low collisionality 42
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Priorities for first physics campaign
Experimental proposals in the following two areas will be given priority for the first physics campaign in 2017 Scenario development: MAST-U is effectively a new machine and so we will need to establish new scenarios that can be used by other areas. Need to understand 1) intrinsic error fields in MAST-U 2) H-mode access in conventional and Super-X divertor configuration 3) on vs off-axis neutral beam heating and current drive Exhaust: Experiments that exploit the new features in MAST-U namely a closed conventional divertor allowing detachment studies and experiments comparing a super-X and conventional divertor configuration. In addition to involvement in these areas, in future campaigns there are a wide range of other topics that we would welcome collaborators to lead 43
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CCFE Programme Topic Areas
CCFE concentrating on 5 major areas: Integrated scenarios and SOL and divertor transport and Divertor performance optimisation and Pedestal physics and Fast particles & Other areas to be led by collaborators to express and interest please contact or 44
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Contents Motivation for MAST-U MAST-U capabilities MAST-U progress
1st physics campaign Future Upgrades Summary 45
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MAST Upgrade MAST-Upgrade after Stage 1 Increased TF New Solenoid
Improved confinement New Solenoid Greater Ip, pulse duration 19 New PF Coils Improved shaping Super-X Divertor Improved power handling Off-Axis NBI Improved profile control Cryoplant Divertor particle control Double NBI Box 7.5MW auxiliary heating 46
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MAST Upgrade MAST-Upgrade after Stage 2a Increased TF New Solenoid
19 New PF Coils Super-X Divertor Off-Axis NBI Cryoplant Double NBI Box 10MW auxiliary heating 47
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Double beam box layout
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Indicative campaign timeline
Assuming external funding can be secured
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Contents Motivation for MAST-U MAST-U capabilities MAST-U progress
1st physics campaign Future Upgrades Summary 50
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Summary MAST Upgrade is an exciting new facility
- build now well underway with 1st plasma due mid 2017 The machine will offer many interesting divertor configurations - super-X, conventional, snowflake Many similarities with NSTX-U, which we think should be exploited We welcome collaborators to lead research activities MAST Upgrade Research Plan found here: 51
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