CN

The anomalous currents in the front foils of the JET lost alpha diagnostic KA-2.

The anomalous currents in the front foils of the JET lost alpha diagnostic KA-2.

The Review of scientific instruments (2010-11-09)

F E Cecil, V Kiptily, A Salmi, A Horton, K Fullard, A Murari, D Darrow, K Hill

ABSTRACT

We have examined the observed currents in the front foils of the JET Faraday cup lost alpha particle diagnostic KA-2. In particular, we have sought to understand the currents during Ohmic plasmas for which the ion flux at the detectors was initially assumed to be negligible. We have considered two sources of this current: plasma ions (both deuterium and impurity) in the vicinity of the detector (including charge exchange neutrals) and photoemission from scattered UV radiation. Based upon modeling and empirical observation, the latter source appears most likely and, moreover, seems to be applicable to the currents in the front foil during ELMy H-mode plasmas. A very thin gold or nickel foil attached to the present detector aperture is proposed as a solution to this problem, and realistic calculations of expected fluxes of lost energetic neutral beam ions during TF ripple experiments are presented as justification of this proposed solution.

MATERIALS

Product Number

Brand

Product Description

Nickel, foil, 10mm disks, thickness 0.30mm, as rolled, 99.98%

Nickel, foil, 10mm disks, thickness 0.125mm, as rolled, 100%

Nickel, foil, 8mm disks, thickness 0.03mm, 99.9%

Nickel, foil, light tested, 25x25mm, thickness 0.05mm, as rolled, 99.98%

Nickel, foil, 8mm disks, thickness 0.0075mm, 99.9%

Nickel, foil, light tested, 100x100mm, thickness 0.025mm, 99.9%

Nickel, foil, 100x100mm, thickness 0.125mm, as rolled, 99.999%

Nickel, foil, 8mm disks, thickness 0.125mm, annealed, 99.98%

Nickel, foil, 100x100mm, thickness 1.0mm, as rolled, 99.99+%

Nickel, foil, 25mm disks, thickness 0.25mm, annealed, 99.98%

Nickel, foil, 6mm disks, thickness 0.3mm, annealed, 99%

Nickel, foil, 6mm disks, thickness 0.5mm, as rolled, 99.99+%

Nickel, foil, light tested, 25x25mm, thickness 0.038mm, 99.9%

Nickel, foil, 100x100mm, thickness 0.30mm, as rolled, 99.98%

Nickel, foil, 8mm disks, thickness 0.5mm, as rolled, 100%

Nickel, foil, 8mm disks, thickness 0.038mm, 99.9%

Nickel, foil, light tested, 25x25mm, thickness 0.0125mm, 99.99+%

Nickel, foil, light tested, 150x150mm, thickness 0.01mm, 99.95%

Nickel, foil, 100x100mm, thickness 0.125mm, as rolled, 99.99+%

Nickel, foil, 100x100mm, thickness 0.15mm, annealed, 99%

Nickel, foil, light tested, 100x100mm, thickness 0.025mm, annealed, 99%

Nickel, foil, 25mm disks, thickness 0.25mm, annealed, 99%

Nickel, foil, not light tested, 45x45mm, thickness 0.004mm, hard, 99.98%

Nickel, foil, light tested, 100x100mm, thickness 0.05mm, as rolled, 99.98%

Nickel, foil, light tested, 25x25mm, thickness 0.075mm, annealed, 99%

Nickel, foil, light tested, 150x150mm, thickness 0.025mm, 99.9%

Nickel, foil, 25mm disks, thickness 0.25mm, as rolled, 99.99+%

Nickel, foil, not light tested, 50x50mm, thickness 0.00025mm, temporary acrylic support, 99.95%

Nickel, foil, 6mm disks, thickness 0.075mm, annealed, 99%

Nickel, foil, 2m coil, thickness 0.025mm, coil width 600mm, as rolled, 99%