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The final hardware modifications for tritium operation have been completed for the Tokamak Fusion Test Reactor (TFTR) [Fusion Technol. 21, 1324 (1992)]. These activities include preparation of the tritium gas handling system, installation of additional neutron shielding, conversion of the toroidal field coil cooling system from water to a FluorinertTM system, modification of the vacuum system to handle tritium, preparation, and testing of the neutral beam system for tritium operation and a final deuterium–deuterium (D–D) run to simulate expected deuterium–tritium (D–T) operation. Testing of the tritium system with low concentration tritium has successfully begun. Simulation of trace and high power D–T experiments using D–D have been performed. The physics objectives of D–T operation are production of ≊10 MW of fusion power, evaluation of confinement, and heating in deuterium–tritium plasmas, evaluation of α‐particle heating of electrons, and collective effects driven by alpha particles and testing of diag...

During lower hybrid current drive on tokamaks, suprathermal electrons are generated that emit hard x‐ray bremsstrahlung. A pinhole camera has been installed on the PBX‐M tokamak that records 128×128 pixel images of the hard x‐ray plasma bremsstrahlung emitted in the 30–200 keV photon energy range. The camera has a temporal resolution of 3 ms and a spatial resolution of 3–4 cm in the plasma. The detector is a 230‐mm‐diam hard x‐ray image intensifier. This instrument has identified hollow radiation profiles on PBX‐M, indicating off‐axis current drive. A detailed account of the construction of the hard x‐ray camera, its operation, and its performance is given.

In advanced tokamak research involving complex magnetic geometries, midplane visible plasma TV images can indicate the need for tokamak control corrections not evident from other diagnostics. Suitable midplane viewports are often unavailable. The PBX‐M plasma TV system uses four tangential midplane vacuum viewports. One tangential vacuum viewport is on a standard re‐entrant midplane port flange. The other three vacuum viewports are tangentially aligned along the inside vessel wall and connected to port flanges 40 cm from the midplane via 60‐cm‐long re‐entrant bellows. Fiber optic bundles transmit images from the re‐entrant viewports through the off‐midplane ports and out to TV cameras positioned beyond the TF coils. The VCR recorded images from each discharge were used to obtain information not available from other diagnostics.

The modification and control of the plasma current profile by lower hybrid current drive is considered one of the most promising avenues to control MHD instabilities and improve the high beta performance of tokamaks. The Hard X‐ray Camera on PBX‐M records images of the bremsstrahlung emitted by suprathermal electrons that carry part of the plasma current during lower hybrid current drive. The Hard X‐ray Camera is a pinhole camera that uses a 9 in. diam x‐ray intensifier as detector. It provides a tangential view of the tokamak plasma and delivers 64 images with 128×128 pixels per plasma shot. The spatial resolution in the plasma is approximately 2 cm, and the time resolution 3 ms. The camera is sensitive to x rays between 30 and 200 keV. The photon energy (and the energy of the suprathermal electrons) is measured with an absorber foil method. Modeling of the x‐ray emission has reproduced the experimental images with a better than 10% accuracy. In addition, two inversion techniques have been developed: one...