Optical and electrical measurements of edge turbulence in TPE-RX
Abstract
Electrostatic turbulence in the edge region of RFPs has shown coherent structures emerging from the background. A new diagnostic system has been developed, aimed at identifying these structures by non-intrusive methods, at high plasma currents and thermal loads. The system consists of a gas-puffing nozzle, 32 optical chords measuring the Dalpha radiation emitted from the puffed gas and a removable array of Langmuir probes. The signals can be sampled at 10 MHz with 2 MHz band-width. The first extensive measurement campaign has been carried out in the TPE-RX RFP device in the AIST, in low and high current discharges, exploring different plasma conditions. High quality signals with large signal-to-noise ratio and effective band-width up to 400 kHz are obtained. Preliminary analyses show a distinct difference in the power spectrum of the optical signals between those from the puffed gas and those from the background radiation. The frequency spectrum obtained with gas puffing is consistent with the expected features of the turbulence in RFP edge region. Moreover the presence of coherent structures, propagating with a velocity of the order of 10 km/s, has been identified.
- Publication:
-
APS Division of Plasma Physics Meeting Abstracts
- Pub Date:
- November 2004
- Bibcode:
- 2004APS..DPPCP1062S