Enormous Toroidal Plasma Device

Experimental physics device
The Enormous Toroidal Plasma Device (ETPD) is an experimental physics device housed at the Basic Plasma Science Facility at University of California, Los Angeles (UCLA). It previously operated as the Electric Tokamak (ET) between 1999 and 2006 and was noted for being the world's largest tokamak before being decommissioned due to the lack of support and funding. The machine was renamed to ETPD in 2009. At present, the machine is undergoing upgrades to be re purposed into a general laboratory for experimental plasma physics research.

The Electric Tokamak (ET) was the last of a series of small tokamak machines built in 1998 under the direction of principal investigator and designer, Robert Taylor, a UCLA professor. The machine was designed to be a low field (0.25 T) magnetic confinement fusion device with a large aspect ratio. It is composed of 16 vacuum chambers made of 1 inch thick steel, with a major radius of 5 meters and a minor radius of 1 meter. The ET was the largest tokamak ever built at its time, with a vacuum vessel slightly bigger than that of the Joint European Torus. The first plasma was achieved in January 1999. The ET is capable of producing a plasma current of 45 kiloamperes and can produce a core electron plasma temperature of 300 eV. Four sets of independent coils are necessary for OH (ohmic heating) current drive, vertical equilibrium field, plasma elongation and plasma shaping (D or reverse D). The OH system provides 10 V·s using a 10 kA power supply. Up to 0.1 T of vertical field can be applied for horizontal control and this is more than sufficient for all plasma configurations, including high beta. An additional set of coils provide a small horizontal field to correct for error field and to stabilize the plasma vertically. All the coils are located outside the vessel and are constructed out of aluminium. A Rogowski probe outside the vessel and sets of Hall probes inside the vessel are used to monitor plasma current, position and shaping and are used in the control feedback loop. The poloidal system was designed using an in house equilibrium code as well as a variety of other codes in order to cross check computations and to assess the stability of the resulting plasma. Like most tokamaks, the machine uses a combination of RF heating and neutral beam injection to drive and shape the plasma.