RESUMEN
Faraday cup fast ion loss detectors have attractive properties for fusion applications, as they can measure wide ranges of energy, are intrinsically neutron-hardened, and can be packaged in very small form factors. The latter allows them to be installed as arrays, offering opportunities to decouple fast ion loss location and magnitude in fully three-dimensional magnetic fields. In this work, we characterize the layer thicknesses of detector prototypes using spectral reflectance measurements, confocal laser scanning microscopy, as well as raster electron microscopy with a focused ion beam. We find that the measured layer thicknesses agree well enough with the specification to allow for accurate measurements. The as-manufactured heights are on the high side, increasing reliability. The data presented here further sets the basis for future optimizations in manufacturing.
RESUMEN
This paper characterizes the correlation of simultaneous measurements with different fast-ion H-alpha (FIDA) spectroscopy sightlines on Wendelstein 7-X. Using a collisionless guiding-center code, it is shown that, for two investigated volumes in the bulk of the plasma, some regions of phase space are correlated and the magnetic configuration has little influence on this correlation. For the sightlines of the FIDA system, the correlation between these is explained well by the magnetic configuration. Sightlines with measurement volumes at the same spatial locations have the highest correlation, and sightlines with measurement volumes near the same flux surface but on different sides of the magnetic axis have a high correlation. The correlation between the blueshifted signal in the starting sightline and redshifted signal in the detection sightline is investigated, demonstrating that it is possible to investigate any finite interval of detection wavelengths. Due to the different shapes of the weight functions for the toroidal and oblique sightlines, the blue-redshift correlation is very different from the total-spectrum correlation. The correlation between the toroidal and oblique sightline fans is relatively much larger than the internal correlation in the oblique sightlines, which is however, much larger than the internal correlation in the toroidal sightlines. This is a result of the dependence of the weight functions on the angle between the sightline and magnetic field, illustrating how important it is for the FIDA sightlines to cover different angles with the magnetic field.
RESUMEN
The development and testing of a Faraday cup fast-ion loss detector capable of measuring sub 100 keV particles is documented. Such measurement capabilities play an important role in the assessment of particle confinement of nuclear fusion experiments. The detector is manufactured using thin-film deposition techniques, building upon previous work using discrete foils. This new manufacturing method allows the form factor of the sensor to become that of essentially a microchip. Analysis of the diagnostic response is performed using Monte-Carlo particle simulations. These simulations show peaks in the detector response at 40 and 70 keV. The sensor is then tested in a tunable linear accelerator capable of accelerating protons from 20 to 120 keV. The detector response was found to be well matched to simulations. Improvements to the design to facilitate robustness are discussed.