29th Symposium on Fusion Technology (SOFT 2016)

P3.043 Real-time elaboration system for two-color medium-infrared scanning interferometer for electron density measurements on FTU

7 Sep 2016, 11:00

1h 20m

Foyer 2A (2nd floor), 3A (3rd floor) (Prague Congress Centre)

Board: 43

Poster C. Plasma Engineering and Control P3 Poster session

Speaker

Luca Boncagni (FSN)

Description

In this work we present a new real-time acquisition and elaboration system for the two-color scanning beam interferometer installed on FTU. The real-time system provides the density informations that can be used to approximate the plasma and runaway beam radial position. Furthermore, the central chord plasma line density will be used to substitute the actual feedback signal for the fueling controller,  that runs on the main real-time feedback control system. The system architecture is based on MARTe framework, running under a Linux operation system installed on a  industrial controller, tuned for this application. For the acquisition of interferometric data (10 channels at 1.5 $MHz$), we adopt three high speed acquisition boards and one Reflective Memory (RFM) module to share data between nodes of our real-time network. The three boards are externally synchronized by mean of 30 MHz clock and gate signals. The first two DAQ boards have been devoted to the acquisition of  4 channels: sen(theta), cos(theta)  (where theta is the phase) from each CO2 and CO lasers beam. The third board is dedicated to the data acquisition of the scanning system (CRS: counter rotating system) that moves backwards and forwards each probe beam  with a 8kHz frequency. Each  millisecond the system collects 1500 samples from each channel and reads the plasma current using the RFM. After the acquisition step, the software corrects the sen(theta), cos(theta) and CRS signals removing the offset from the two probing beam laser and scanning system. Then  the phase of the CO2 and CO  probing laser beams are evaluated and the total line density is computed with an average over 1 ms. Finally, using CRS information, the new system splits the total line density into 32 vertical chords  with different major radii,   and distributes them over the shared memory network.