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A quantitative theoretical framework has been created to model neutral beam injection and fast ion losses in the Wendelstein 7-X (W7-X) stellarator, including a novel method to develop synthetic diagnostics for fast ion loss detectors (FILDs) of many types, such as scintillating and Faraday Cup FILDs. This is the first time that this has been done in stellarator geometry with this level of fidelity, providing a way for fast ion losses to be predicted more precisely in future stellarator experiments and in W7-X. Simulations of the signal seen by a Faraday Cup FILD have been completed for multiple W7-X plasmas and show close agreement with the measured signals. This method is now applied to an actively water-cooled, scintillator-based FILD, which is currently in development to measure the fast ion loss distribution in W7-X in greater detail. The design makes use of a double slit to measure energy-and-pitch-angle-resolved losses of both co-going and counter-going fast ions. The diagnostic, which can be inserted to different radial positions, has been designed to withstand steady-state heat fluxes of up to 120 kW/m2 along with additional transient heat loads of 100 kW/m2 lasting for up to 20 s at a time. Simulations of W7-X standard magnetic configuration show up to 8 × 1013 (s−1 cm−2) ion fluxes onto the sensor from each neutral beam source and no signal from the counter-going slit. These simulations will help inform experimental proposals for future W7-X campaigns after installation of this diagnostic. [ABSTRACT FROM AUTHOR]

Upgrades to electronic hardware and detector design have been made to the JET thin-foil Faraday cup fast ion loss detector [Darrow et al., Rev. Sci. Instrum. 75, 3566 (2004)] in anticipation of the upcoming deuterium–tritium (DT) campaign. An improved foil stack design has been implemented, which greatly reduces the number of foil-to-foil shorts, and triaxial cabling has mitigated ambient noise pickup. Initial tests of 200 kHz digitizers, as opposed to the original 5 kHz digitizers, have provided enhanced analysis techniques and direct coherence measurements of fast ion losses with magnetohydrodynamic activity. We present recent loss measurements in JET deuterium plasmas correlated with kink modes, fishbone modes, edge-localized modes, and sawteeth. Sources of systematic noise are discussed with emphasis on capacitive plasma pickup. Overall, the system upgrades have established a diagnostic capable of recording alpha particle losses due to a wide variety of resonant fast ion transport mechanisms to be used in future DT-experiments and modeling efforts. [ABSTRACT FROM AUTHOR]

Electron cyclotron emission (ECE) has proven to be a useful diagnostic in tokamaks for measuring T[sub e] and its radial variation. The application of ECE to mirror devices is discussed here, with emphasis on measurements of the properties of energetic electrons in tandem mirror end cells, which can be viewed both parallel and perpendicular to B. The parallel or whistler view is generally optically thick and can yield a measurement of perpendicular temperature. High harmonic perpendicular emission is optically thin and can yield important information about the hot electron buildup and the energy and spatial distribution. Experimental results from TMX-U and appropriate modeling are presented. [ABSTRACT FROM AUTHOR]

The motional Stark effect (MSE) diagnostic on DIII-D has been expanded to take advantage of a change in the neutral beam geometry, adding 24 new MSE channels viewing a beam injected counter to the plasma current. When data from these channels are used with those from two older MSE arrays viewing a different beam, the overall radial resolution improves near the magnetic axis at least a factor of 2, and the uncertainty in calculations of vertical magnetic field and radial electric field decreases in the edge at least a factor of 4. The new design uses two optical systems mounted on the same vacuum port with a common shutter and shielding. [ABSTRACT FROM AUTHOR]

Good confinement of alpha particles in a large magnetic fusion device is a precondition for building a magnetic fusion reactor. The direct measurement of alpha particle losses is of particular interest. Appropriate diagnostics are now being prepared for the Joint European Torus tokamak: a scintillator probe and a set of Faraday cups. Both systems are capable of measuring charged fusion products and ion cyclotron resonance heating tail ions. The design of the lost alpha particle scintillator probe is in the scope of this article. It will allow the detection of particles with a gyroradius between 20 and 140 mm (15% resolution) and a pitch angle between 30° and 86° (5% resolution). As scintillating material P56 will be used. The light emitted by the scintillator caused by charged particles that pass the collimator and hit the scintillator will be detected via a set of optical lenses and a coherent image fiber bundle with a charge coupled device camera and a photomultiplier array. In the following the present design of the scintillator probe with emphasis on the performance of the system, structural resistance against plasma disruptions, and the requirements on the heat protection against plasma and neutral beam induced thermal loads will be described. [ABSTRACT FROM AUTHOR]

The motional Stark effect (MSE) diagnostic is unique in its ability to measure the current profile and will be essential in the International Thermonuclear Experimental Reactor (ITER) for detailed analysis of Advanced Tokamak and other types of discharges. However, design of a MSE diagnostic for ITER presents many unique challenges. Among these is optical analysis for the convoluted optical path, required for effective neutron shielding, that employs several reflective optics arranged to form a labyrinth. The geometry of the diagnostic has been laid out and the expected Doppler shifts and channel resolution calculated. A model of the optical train has also been developed based on the Mueller matrix formalism. Unfolding the pitch angle for this complicated geometry is not straightforward and possible methods are evaluated. The CORSICA code is used to model a variety of ITER discharges including start-up, Ip-ramp, and reverse shear. The code also incorporates a synthetic MSE diagnostic that can be used to evaluate different viewing locations and optimize channel locations for the above discharges. Simulation of the optical emission spectrum is also under way. [ABSTRACT FROM AUTHOR]

The power flow to the DIII-D divertor targets is routinely measured using infrared (IR) thermography. An IR television camera sensitive to radiation in the 8-12-µm range views the divertor region using a set of germanium optics. Digital signal processing is used to extract the desired surface temperature profiles from the analog data (... 12 Mbytes) stored on videotape. Inversion of these data using a simple matrix formulation of the inverse heat conduction problem then yields the incident heat flux as a function of space and time. Results from a DIII-D discharge are included. [ABSTRACT FROM AUTHOR]

Perpendicular electron-cyclotron emission (PECE) is used on Tandem Mirror ExperimentUpgrade (TMX-U) to diagnose thermal-barrier hot electrons (T[sub H] ∼ 100400 keV, yielding the time history of the temperature of these relativistic electrons. We describe an improved quasioptical viewing system for these measurements that uses high-sensitivity superheterodyne receivers at fixed frequencies of 60, 98, 130, and 196 GHz. The improved viewing and transport system consists of an off-axis ellipsoidal mirror that images the plasma onto a V-band conical collection horn, an overmoded circular waveguide (7/8 in. diam) that transports the radiation outside the vacuum vessel where the polarization is selected, and a high-absorptivity Macor beam dump to prevent internal wall reflections from entering the viewing system. A relativistic code is used to calculate optically thin PECE signals from relativistic electrons for various energy and pitch angle distributions. [ABSTRACT FROM AUTHOR]

Perpendicular electron cyclotron emission (PECE) from the electron cyclotron resonant heating of hot electrons in TMX-U is measured at 30-40 and 50-75 GHz. This emission is optically thin and is measured at the midplane,f[sub ce] ... 14 GHz, in either end cell. In the west end cell, the emission can be measured at different axial positions thus yielding the temporal history of the hot electron axial profile. These profiles are in excellent agreement with the axial diamagnetic signals. In addition, the PECE signal level correlates well with the diamagnetic signal over a wide range of hot electron densities. Preliminary results from theoretical modeling and comparisons with other diagnostics are also presented. [ABSTRACT FROM AUTHOR]

The vertical-viewing electron cyclotron emission diagnostic on DIII-D will be used to assess the nonthermal electron distributions resulting from electron cyclotron heating and electron cyclotron current drive experiments. Electron cyclotron emission along a vertical chord is collected using an ellipsoidal focusing mirror and retroreflector (the latter to minimize wall reflections). The emission is then transported ∼ 20 m using a quasioptical transport system composed of eight lenses and three mirrors, and detected between the 2nd and the 10th harmonics by a fast-scanning (40-Hz) Michelson interferometer. The entire system has been aligned using a Gaussian beam simulator and absolutely calibrated in situ using a cold liquid-nitrogen bath. Details of the design, installation, and calibration will be discussed. [ABSTRACT FROM AUTHOR]

Images of the neutron-emitting region of high-yield inertial confinement fusion targets have been obtained with a penumbral coded-aperture imaging system. The major components of the imaging system are the penumbral aperture, neutron detector, alignment hardware, and image reconstruction software. We describe these components and present an example of the neutron imaging results. [ABSTRACT FROM AUTHOR]

Co- and counter-viewing bolometers aimed along a common tangency chord are being used to study power losses due to charge exchange (CX) of fast ions in neutral beam injection (NBI) heated TFTR plasmas. For unidirectional injection, tangential bolometers oriented to view CX loss of circulating fast ions detect losses from the thermal target plasma (impurity radiation and CX) plus power due to the fast ion CX loss, whereas bolometers oppositely directed measure only the target plasma contribution, The difference between the two signals is a measure of the fast ion CX loss. Additional information is obtained by comparing the tangential bolometer signals with those of perpendicularly viewing bolometer monitors and arrays. The measurements are compared to results of the TRANSP code analysis. [ABSTRACT FROM AUTHOR]

Perpendicular electron-cyclotron emission (PECE) from relativistic (T[sub H] ∼ 100-400 keV) hot electrons within the thermal-barrier region of Tandem Mirror Experiment-Upgrade (TMX-U) is detected at 35, 60, 94, and 98 GHz. For the operating regime of TMX-U, these signals are optically thin (τ « 1) and thus proportional to the radial hot-electron line density. A relativistic code is used to calculate the theoretical temperature dependence of the perpendicular emission coefficient, j[sub ⊥] (ω, T[sub H]), for each of the detected frequencies. This dependence has been verified experimentally by x-ray measurements of the hot electron temperature, T[sub H]. The observed qualitative agreement demonstrates that optically thin PECE signals can be used to determine the temporal evolution of T[sub H]. An inability to absolutely calibrate the present PECE waveguide system has prevented quantitative agreement. [ABSTRACT FROM AUTHOR]

This ECE (electron cyclotron emission) diagnostic utilizes a fast-scanning Michelson interferometer to determine two parameters, the temperature and the loss cone angle, of the distribution function of the hot electrons (T ... 100 keV) generated in the axisymmetric plug plasma of the TARA tandem mirror device. The radiation transport system employs a lens relay and a low-pass grating filter in order to transmit the synchrotron radiation over a spectral range of 2.9-18.6 cm[sup -1]. This enables us to study the emitted radiation spectrum up to the 40th harmonic of the electron-cyclotron frequency in the plug plasma (B = 5 kG). Details of the design principles and the development of the diagnostic at TARA will be presented. [ABSTRACT FROM AUTHOR]