PBX-M

Princeton Beta Experiment Modified (PBX-M) was an upgrade of PBX. It was an advanced concept tokamak built with the objective to show the practicality of controlling the plasma current and pressure distributions to achieve stable and advanced operating regimes and to avoid plasma disruptions. As part of the modifications, the plasma major radius was increased from 1.45 m to 1.65 m, which made it possible to include a divertor and new coils inside the vacuum vessel. Other upgrades were the improvement of the plasma shaping control system, the installation of an Ion Bernstein wave antenna and the installation of new diagnostics. With this modifications, the volume-averaged toroidal β values and ion temperatures reached higher values than in PBX, reaching a β of 6.8% by 1988.

PBX-M final operation occurred in November 1993, but it remained unused at PPPL until 2003, when it was finally disassembled.