A fast moving diagnostic system on the RFX experiment

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The four parameter data fit for Langmuir probes is here generalized within the classical single Langmuir probe theory. The data fit accounts for the variation of the Debye sheath thickness of the probe with the applied voltage which results in a nonsaturation of the ion current. The new fitting formula has been applied to the RFX experimental data. With respect to the use of the simple exponential fit, in general a correction of the order of 20% on electron temperature and ion saturation current has been obtained. © 1998 American Institute of Physics

Section: Application On Rfxsupporting

confidence: 80%

“…8 The R parameter obtained from the data fitting is in good agreement with the values obtained from these models. 8 …”

Section: Application On Rfxsupporting

confidence: 80%

Four parameter data fit for Langmuir probes with nonsaturation of ion current

Desideri¹,

Serianni²

1998

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Magnetically driven filament probe

Schmid

Herrmann

Rohde

et al. 2007

A radially movable probe has been developed for studies of filamentary transport in ASDEX Upgrade during edge localized modes (ELMs) by means of Langmuir tips and magnetic pickup coils. The probe is permanently installed at the low field side in the ASDEX Upgrade vacuum vessel and is not subject to limitations in probe size, as, for example, probes on a shared manipulator are. The probe is moved by a magnetic drive, which allows for easy installation in the vessel, and has moderate machine requirements, as it will only require an electric feedthrough and an external power supply. The drive gives a linear motion with a radial range of 5 cm within 50 ms, where range and velocity can be largely scaled according to experimental requirements. The probe has been installed in the outer midplane of the ASDEX Upgrade vessel, where ELM filaments are expected to have their maximum amplitude. Filaments are coherent substructures within an ELM, carrying a fraction of the ELM released energy towards the wall. The new probe allows to measure the structure of these filaments, in particular, parameters such as filament rotation (by time delay measurements) and size (by peak width analysis). Activating the drive moves the probe from a safe position behind the limiter to a position in front of the limiters, i.e., exposes the Langmuir pins to the scrape-off layer plasma.

A magnetically driven reciprocating probe for tokamak scrape-off layer measurements

Gunn

Pascal

2011

A new in situ reciprocating probe system has been developed to provide scrape-off layer measurements in the Tore Supra tokamak. The probe motion is provided by the rotation of an energized coil in the tokamak magnetic field. Simple analytic approximations to the exact numerical model were used to identify the important parameters that govern the dynamics of the system, and optimize the coil geometry, the electrical circuit, and the stiffness of the retaining spring. The linear speed of the probe is directly proportional to the current induced by the coil's rotation; its integral gives the coil position, providing a means to implement real-time feedback control of the probe motion. Two probes were recently mounted on a movable outboard antenna protection limiter in Tore Supra and provided automatic measurements during the 2011 experimental campaign.