EXTRAP T2R

Intelligence Summary: EXTRAP T2R Reversed-Field Pinch Device

Node Identity: EXTRAP T2R is a medium-sized reversed-field pinch (RFP) magnetic confinement fusion device located at the Alfvén Laboratory at KTH Royal Institute of Technology in Stockholm. The RFP is an axisymmetric toroidal configuration related to the tokamak but with a fundamentally different spatial dependence of toroidal and poloidal magnetic fields — the toroidal field reverses sign at the edge. EXTRAP T2R received EURATOM priority status in 1990, achieved first plasma operation in 1994, and was rebuilt in 2000 with a new resistive shell enabling studies of resistive wall mode (RWM) stability and active feedback control.

Strategic Relevance: EXTRAP T2R's strategic relevance to the FRC/plasma weapons landscape is indirect but technically significant. The RFP configuration is distinct from both tokamaks and stellarators, providing a flexible test bed for plasma control physics that is directly transferable to advanced tokamak scenarios for ITER/DEMO. The device's state-of-the-art digital feedback control system using arrays of active magnetic field coils represents advanced plasma equilibrium control technology — a capability with inherent dual-use potential for any application requiring precise magnetic field manipulation of high-energy plasmas. The RWM control studies contribute directly to the broader tokamak program, as resistive wall mode control is critical for advanced tokamak scenarios with conducting walls. The device also supports non-fusion applications including plasma waste treatment, plasma generators for surface treatment, and material studies.

Technical Focus / Capabilities: EXTRAP T2R's primary research focus is resistive wall mode (RWM) stability and active feedback control using digital systems with arrays of active magnetic field coils. The device is equipped with state-of-the-art digital feedback control hardware. The experimental program is led by Professor Per Brunsell. Additional research includes RF heating and current drive (using the FEMIC finite element wave solver for ion cyclotron resonance heating, applied to JET and ITER), plasma-wall interaction studies, and space/laboratory plasma physics. The device supports applied plasma research including plasma waste treatment and surface treatment via access ports for sample insertion into the plasma edge.

Network Linkage: EXTRAP T2R maintains 1 documented connection: KTH operates EXTRAP T2R. The device collaborates with Consorzio RFX (Padua, Italy) on RFP physics and with the theory group at Chalmers Department of Electromagnetics on RWM stability and active feedback systems for tokamak configurations. EXTRAP T2R is funded through EUROfusion Sweden and participates in the broader European fusion program. The RF heating group's FEMIC code is applied to JET and ITER scenarios.