1. 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

2. MAST Upgrade: Status and plans
Andrew Kirk
On behalf of
CCFE is the fusion research arm of the United Kingdom Atomic Energy Authority 2

3. Contents Motivation for MAST-U MAST-U capabilities MAST-U progress
1st physics campaign
Future Upgrades
Summary 3

4. Contents Motivation for MAST-U MAST-U capabilities MAST-U progress
1st physics campaign
Future Upgrades
Summary 4

5. 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

6. 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

7. 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

8. 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

9. 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

10. MAST-U: divertor configurations
Flexible poloidal field coil set allows for a wide variety of magnetic geometries
Conventional Super-X Snowflake 10

11. 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

12. 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

13. 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

14. 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

15. 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

16. 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

17. Current drive studies
Off-axis NBI will provide ability to study current drive physics
TRANSP 17

18. Contents Motivation for MAST-U MAST-U capabilities MAST-U progress
1st physics campaign
Future Upgrades
Summary 18

19. 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

20. MAST Upgrade Divertor Closed divertor with very flexible PF coil set
Divertor nose D6 D7 DP D1
Gas baffle D2 D5 D3
Cryopump

21. MAST-U: divertor configurations
Flexible poloidal field coil set allows for a wide variety of magnetic geometries
Conventional Super-X Snowflake 21

22. 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

23. 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

24. 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

25. 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

26. 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

27. Contents Motivation for MAST-U MAST-U capabilities MAST-U progress
1st physics campaign
Future Upgrades
Summary 27

28. 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

29. = + 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

30. Build Progress: lower cassette
Lower cassette complete 30

31. 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

32. Build Progress: outer cylinder
Outer cylinder – complete
PF coil and embedded diagnostics -
Fitted over lower cassette 32

33. Build Progress: OC+LC
Outer cylinder complete and lower cassette installed 33

34. 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

35. Build Progress: lower end plate
Trial fitting of tiles…
and tile heaters
Allowing tiles to be baked to 250 ⁰C 35

36. 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

37. Build Progress: Centre column
Solenoid - complete
New TF centre rod impregnated with Cyanate ester
Passed full electrical tests
Trial assemblies are ongoing 37

38. Build Progress: NBI Being upgraded for 5 second operation
NBI ion dumps
NBI bend magnets 38

39. Build Progress: Centre column
New Toroidal field power supply installed and commissioned into dummy load
Poloidal field and divertor power supplies installed 39

40. Build Progress: Control room
New Control and server room built 40

41. Contents Motivation for MAST-U MAST-U capabilities MAST-U progress
1st physics campaign
Future Upgrades
Summary 41

42. 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

43. 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

44. 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

45. Contents Motivation for MAST-U MAST-U capabilities MAST-U progress
1st physics campaign
Future Upgrades
Summary 45

46. 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

47. 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

48. Double beam box layout

49. Indicative campaign timeline
Assuming external funding can be secured

50. Contents Motivation for MAST-U MAST-U capabilities MAST-U progress
1st physics campaign
Future Upgrades
Summary 50

51. 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