MAST Upgrade Capabilities in 2026 Andrew Thornton on behalf of the MAST-U team UK Atomic Energy Authority Machine Parameters Parameter | Design value | 2026 - R / a (m): 0.7 / 0.5 | 0.7 / 0.5 - Bϕ (at 0.8 m): 0.8 T | 0.72 T - Max Ip (MA): 2.0 | 1.0 - Max κ: 2.5 | 2.5 - Maximum δ: 0.6 | 0.6 - Divertor pumping: Closed, cryopumped | Closed, lower cryopump - Max NBI heating power (MW): 8.8 MW for 5s | ~3.8 MW for 1s - Ohmic heating (MW): 0.2 – 1.0 | 0.2 – 1.0 - NBI geometry: 1x on-axis, 2x off-axis, 1x intermediate | 1x on-axis, 1x off-axis WPTE General Programme Meeting for 2026 Experimental Campaigns – MAST Upgrade | 4/11/25 Achieved Plasma Parameters Parameter | Achieved to date - Core Te: Up to 2.0 keV - Core Ti: Up to 4.0 keV - Pedestal top Te: Up to 0.45 keV - Core ne: Up to Greenwald limit - H98y,2: Up to ~1.5 transiently - Max βN: 4.8 - Max βe: Up to 10% - Core toroidal velocity: Up to 200 km/s WPTE General Programme Meeting for 2026 Experimental Campaigns – MAST Upgrade | 4/11/25 Machine Capabilities Gas • D2 as the main fuel gas only • Seeding possible with He, Ne, CD4 (no clean-up pulses required) and N2 (clean-up pulses required) Ip / Bϕ • Operation in standard mode only (Ip anti-clockwise, Bϕ clockwise, viewing from above) RMP & EFCCs • In-vessel (RMP) and ex-vessel (EFCC) coils available to produce non-axisymmetric fields for ELM control and/or error field correction. Requests for specific coil configurations need to be made at least 1 week in advance. • RMP coils – 8 in lower row (up to n=4), 4 in upper row (up to n=2) • EFCC coils – 2 pairs of ex-vessel coils WPTE General Programme Meeting for 2026 Experimental Campaigns – MAST Upgrade | 4/11/25 Machine Capabilities • The lower divertor cryopump will be active as standard • Max pumping speed 25 m³/s per divertor, ~10x increase over existing pumps and comparable to estimated wall pumping early in MAST-U pulses WPTE General Programme Meeting for 2026 Experimental Campaigns – MAST Upgrade | 4/11/25 Plasma Scenarios Standard Plasma Scenarios • L-mode and H-mode scenarios with Ip = 450 kA, 600 kA, 750 kA and conventional or Super-X divertor configurations will be available • H-mode 1 MA scenario conventional divertor scenario available Non-standard scenarios being developed in internal campaign • Negative triangularity • High elongation (κ~2.5) high-performance H-mode (Ip = 750kA) • Open divertor configuration • X-point target divertor • Snowflake divertor configuration (Ip = 600, 750kA) From A.O. Nelson et al 2024 Nucl. Fusion 64 124004 WPTE General Programme Meeting for 2026 Experimental Campaigns – MAST Upgrade | 4/11/25 Diagnostics Information on the available diagnostics can be found here: • WPTE wiki page (https://wiki.euro-fusion.org/wiki/WPTE_MAST-U) • MAST-U diagnostics handbook (https://intranet.ccfe.ac.uk/mastu-handbook, needs VPN connection to UKAEA network) New systems • Upper X-point fast imaging from LLNL • Ultra-fast (800kHz) spectroscopy of lower divertor • GEM soft x-ray imaging camera from University of Milano-Bicocca • Fast imaging of lower divertor under commissioning • Filtered imaging of lower x-point, upper divertor system under development WPTE General Programme Meeting for 2026 Experimental Campaigns – MAST Upgrade | 4/11/25 Plasma Control Shape control: • Rin, Rout, Zx, ROSP in Ip flat-top phase • Calculated using linearised controllers based on a “standard” reference equilibrium; more exotic scenarios may need dedicated controllers • Secondary null formation for X-divertor and X-point target divertor configurations Density control: • Available for routine use, may need tailoring to some scenarios Detachment control: • Based on Fulcher band emission front measured with lower divertor chamber Multi-Wavelength Imaging, requests for use need to be made well in advance • Fuelling from divertors or main chamber are the main actuator WPTE General Programme Meeting for 2026 Experimental Campaigns – MAST Upgrade | 4/11/25 Divertor Configurations - Conventional - Super-X - X-point Target - Snowflake - X-Divertor - DN Extended Leg - SN Extended Leg WPTE General Programme Meeting for 2026 Experimental Campaigns – MAST Upgrade | 4/11/25 Session Leaders Experiments are executed by shift session leader • A reference session leader will be allocated to work with RTCs to guide the development of shot plans. RTCs are strongly encouraged to contact their reference session leader to start preparing shot plans. • Shot plans should be communicated to the shift session leader at least 1 week in advance of the experiment • Plans can be submitted via the Research Topic pages on the WPTE wiki or the MAST-U Users pages (links to WPTE wiki) WPTE General Programme Meeting for 2026 Experimental Campaigns – MAST Upgrade | 4/11/25 Operation schedule The standard operating schedule has operations on Tue, Wed, Thu each week with Fri as contingency • 2 sessions per operating day, normally 8 shots / session (16 total shots per day) • Typically 10 shots per day on Fridays Future programme is presented to the Friday MAST-U Science Meeting, plus reporting results from the previous week WPTE General Programme Meeting for 2026 Experimental Campaigns – MAST Upgrade | 4/11/25 Operation schedule Experiments in 2026 will start in mid-January until the end of April Aiming to execute 704 total pulses plus up to 130 contingency • 176 pulses allocated for the Tokamak Exploitation programme Schedule overview (January–April 2026) indicating Operations, No operations (area open/closed), Maintenance, Bank holidays, Boronization, Contingency, and Commissioning periods. WPTE General Programme Meeting for 2026 Experimental Campaigns – MAST Upgrade | 4/11/25 General Information Useful links for information about MAST Upgrade: • WPTE device information page: https://wiki.euro-fusion.org/wiki/WPTE_MAST-U • MAST-U Users: https://users.mastu.ukaea.uk/ (requires UKAEA IT account) • MAST-U visualiser: https://users.mastu.ukaea.uk/internal/mastu-visualiser (requires UKAEA IT account) • MAST-U diagnostics handbook: https://intranet.ccfe.ac.uk/mastu-handbook (requires UKAEA IT account and VPN connection) To access MAST-U data, please request a data access form (available on WPTE device information page for MAST-U) and return signed copy to me or James Harrison For any further information, please feel free to contact: [email protected] WPTE General Programme Meeting for 2026 Experimental Campaigns – MAST Upgrade | 4/11/25