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The λ ≈ 1 mm (f = 288 GHz) interferometer for the Lithium Tokamak Experiment-β (LTX-β) will use a chirped-frequency source and a centerstack-mounted retro-reflector mirror to provide electron line density measurements along a single radial chord at the midplane. The interferometer is unique in the use of a single source (narrow-band chirped-frequency interferometry) and a single beam splitter for separating and recombining the probe and reference beams. The current work provides a documentation of the interferometry hardware and evaluates the capabilities of the system as a far-forward collective scattering diagnostic. As such, the current optical setup is estimated to have a detection range of 0.4 ≲ k⊥ ≲ 1.7 cm-1, while an improved layout will extend the upper k⊥ limit to ∼3 cm-1. Measurements with the diagnostic on LTX are presented, showing interferometry results and scattered signal data. These diagnostics are expected to provide routine measurements on LTX-β for high frequency coherent density oscillations (e.g., Alfvenic modes during neutral beam injection) as well as for broadband turbulence.

Magnetic perturbation measurements will be invaluable for characterizing Lithium Tokamak Experiment Beta (LTX-β) plasmas due to the time-evolving 3D nature of the magnetic fields generated by eddy currents in the vessel and copper shell segments, as well as enhanced MHD instability drive due to newly introduced neutral beam heating. The LTX-β upgrade includes two new arrays of Mirnov coils: a shell eddy sensor array of two-axis coils distributed over the back surface of one shell segment and a toroidal array of poloidal field coils at the low-field side midplane gap. Evaporative lithium wall-coating and the high temperatures required for liquid lithium wall operation both complicate the implementation of in-vessel diagnostics. While the shell array is protected from lithium exposure, the shell segment to which it is mounted will at times exceed 300 °C. The toroidal array, however, will experience direct line-of-sight exposure to the lithium evaporator as well as close proximity to the hot shell and may also be subject to poorly confined beam-driven fast ions. We describe how the two new Mirnov coil arrays meet these environmental challenges and enhance the LTX-β diagnostic suite.

An important issue for future tokamaks is real‐time plasma control for the avoidance of magnetohydrodynamic instabilities and other applications that require detailed plasma profile and fluctuation data. Although measurements from diagnostics providing this information require significantly more processing than magnetic flux data, recent advancements could make them practical for adjusting operational settings for plasma heating and current drive systems as well as field coil currents. On the Princeton Beta Experiment‐Modification (PBX‐M), the lower hybrid current drive phasing can be varied during a plasma shot using digitally programmable ferrite phase shifters, and neural beam functions can be fully computer controlled. PBX‐M diagnostics that may be used for control purposes include motional Stark‐effect polarimetry for magnetic field pitch angle profiles, soft x‐ray arrays for plasma position control and the separation of βp from li, hard x‐ray detectors for energetic electron distributions, a multich...

A new set of radiated-power-density diagnostics for the National Spherical Torus Experiment Upgrade (NSTX-U) tokamak have been designed to measure the two-dimensional poloidal structure of the total photon emissivity profile in order to perform power balance, impurity transport, and magnetohydrodynamic studies. Multiple AXUV-diode based pinhole cameras will be installed in the same toroidal angle at various poloidal locations. The local emissivity will be obtained from several types of tomographic reconstructions. The layout and response expected for the new radially viewing poloidal arrays will be shown for different impurity concentrations to characterize the diagnostic sensitivity. The radiated power profile inverted from the array data will also be used for estimates of power losses during transitions from various divertor configurations in NSTX-U. The effect of in-out and top/bottom asymmetries in the core radiation from high-Z impurities will be addressed.

Although the region of the Tokamak Fusion Test Reactor (TFTR) vacuum vessel wall which is susceptible to damage by neutral beam strike is armored with a mosaic of TiC‐clad POCO graphite tiles, at power deposition levels above 2.5 kW/cm2 the armor surface temperature exceeds 1200 °C within 250 ms, and itself becomes susceptible to damage. In order to protect the wall armor, a neutral beam interlock system based on infrared pyrometry measurement of the armor surface temperature was installed on TFTR. For each beamline, a three‐fiber‐optic telescope views three areas of ∼30 cm diameter centered on the armor hot spots for the three ion sources. Each signal is fiber‐optic coupled to a remote 900‐nm pyrometer which feeds analog signals to the neutral beam interrupt circuits. The pyrometer interlock system is designed to interrupt each of the 12 ion sources independently within 10 ms of the temperature exceeding a threshold which can be set in the range of 500–2300 °C. A description of the pyrometer interlock sy...

Five diagnostic systems were used for initial species measurements during tokamak fusion test reactor (TFTR) neutral beam test stand operations involving four ion sources, as well as several different configurations and operating conditions. Initial results were obtained for total neutral species fractions at the beamline input and the beamline output, differential radial profiles of species fractions, angular divergences of species components, species radial power density profiles, and beam impurity components for various conditions.

A neutral beam has been designed and fabricated to aid in the measurement of ion temperatures of hot, dense tokamak fusion test reactor (TFTR) plasmas. The injected fast neutral atoms offer a twofold benefit: (1) Penetration to the plasma center considerably increases charge exchange neutralization of thermal plasma ions, leading to a localized enhancement of the thermal neutrals efflux into charge exchange neutral analyzers; and (2) charge exchange recombination of fully stripped intrinsic impurity ions, C or O, with fast neutrals allows Doppler broadening and shift measurements of the emitted light to determine both the impurity ion temperature and toroidal rotation with unbalanced beam heating. The design and construction of the beam and those features of the beam unique to its function as a diagnostic tool for TFTR will be presented.