Experimental Results from Large-scale MTF Compression Experiments on the LM26 Device

LM26 is a new large-scale magnetized target fusion (MTF) experiment with a goal of demonstrating the compressional heating of a spherical tokamak plasma to achieve fusion conditions. The device began experimental operation in February of 2025 and we will present results so far from a sequence of deuterium plasma compression tests. Incremental milestone goals include reaching 1 keV, 10 keV, and then ultimately approaching D-D Lawson equilivalent with a series of upgrades to the machine. LM26 uses fast coaxial helicity injection to form a magnetized plasma inside an electrically insulating high vacuum composite vessel with inner radius of 1 meter in which the compression takes place. The compression is powered by a 13 MJ capacitor bank which drives a 36-turn theta-pinch coil which surrounds the vessel and can either launch a lithium cylindrical liner radially inward with high velocity and high symmetry, or directly compress the plasma with the vacuum poloidal field from the theta-pinch coils. Current on a center shaft can be ramped to track the compression to maintain plasma stability. Lithium liner operation can achieve a radial compression factor of 2 to 10 in a time of 7 to 3 ms. Direct magnetic compression can achieve a radial factor of 2-3 in 300 us to 1 ms compression time. In this current campaign of plasma compression experiments we are working to demonstrate that plasma temperature measurements match theoretical heating predictions.