MAST-UThe Mega Amp Spherical Tokamak (MAST) facility at Culham Centre for Fusion Energy is undergoing a major upgrade that will enhance the UK's role in international fusion research.

When completed in 2016/17, MAST-Upgrade will enable scientists to:

  • Make the case for a fusion Component Test Facility (CTF). A CTF would test reactor systems for the DEMO prototype fusion power plant, and a spherical tokamak is seen as an ideal design for the facility;
  • Add to the knowledge base for ITER and help resolve key plasma physics issues to ensure its success;
  • Test reactor systems. MAST-Upgrade will be the first tokamak to trial the innovative Super-X divertor – a high-power exhaust system that reduces power loads from particles leaving the plasma. If successful, Super-X could be used in DEMO and other future fusion devices.


The diagram below shows MAST-Upgrade's relevance in the fusion R&D programme.

Research plan

MAST-Upgrade will be implemented in three stages. Funding has been agreed with the Engineering and Physical Sciences Research Council for the core upgrade (Stage 1a), which will be ready for plasma operations in 2016/17. Two additional phases (Stage 1b and Stage 2) will follow in later years subject to funding.

Main features of the Stage 1a and 1b upgrade include:

  • New centre column, divertor coils, cryopump and power supplies – providing pulse lengths up to ten times that of the existing machine;
  • Improvements to MAST’s neutral beam heating system, including on- and off-axis beams allowing heating in different configurations;
  • Super-X divertor – plasma escaping from the core will be guided along a longer exhaust path, cooling the particles and spreading them over a larger area so that the impact on the wall of the machine is reduced;
  • Improved machine parameters (see table below) enabling study of steady-state plasmas at near-fusion conditions.

Stage 2 will see neutral beam power increased to 12.5 megawatts and new features to improve profile control and study of plasma instabilities.


Before upgrade

Stage 1a upgrade

Stage 1b upgrade

Stage 2 upgrade

Peak power injected

up to 5,000,000 watts

up to 5,000,000 watts

up to 7,500,000 watts

up to 12,500,000 watts

Toroidal magnetic field

0.55 Tesla

0.84 Tesla

0.84 Tesla

0.84 Tesla

Energy deposited in plasma at high current

2.5 megajoules

10-20 megajoules

up to 30 megajoules

up to 30 megajoules

Pulse length at high current/field

up to 0.5 seconds

2-4 seconds

4 seconds

5 seconds

Profile control





Particle control





Plasma current

1,300,000 amps

2,000,000 amps

2,000,000 amps

2,000,000 amps

Opportunities for collaboration

MAST-Upgrade will offer excellent possibilities for scientific collaborators from the UK and overseas. Research partners can advance their own physics and engineering studies by developing systems for the upgrade. Once the new MAST is online, it will be operated as a 'user facility' to allow scientists from other fusion laboratories and from universities to exploit its capabilities. Contact CCFE to discuss the possibilities for MAST-Upgrade collaborations.

MAST Upgrade resources

MAST-Upgrade Research Plan, June 2015 – PDF file (1mb)

News on the MAST-Upgrade project

Brochure: MAST-Upgrade – Advancing compact fusion sources – PDF file (1244kbs)

MAST-Upgrade poster – PDF file (286kbs)

Interactive model of MAST-Upgrade's main features

Videos of MAST-Upgrade

Photos of MAST-Upgrade