Thomson Scattering Diagnostics Research Articles

Mdsplus data acquisition in RFX and its integration in legacy systems

The current reconstruction of the RFX power supplies requires a re-engineering of the data acquisition system. The use of mdsplus has been retained, based however on a different architectural organisation. This has been possible as mdsplus is available under many software platforms, including windows and several flavours of unix. The RFX data acquisition architecture defines now a set of compactPCI (cPCI) crates, each hosting a CPU running embedded linux. Each CPU supervises local data acquisition, possibly performing data pre-processing to reduce the amount of data to be stored. Communication among distributed components is achieved using mdsip, the TCP/IP-based data communication layer of mdsplus. This distributed approach allows also the integration of legacy CAMAC-based data acquisition systems and new diagnostic systems using windows PCs for data acquisition. The same approach has been taken for integrating mdsplus subsystems in other experiments, such as spectroscopic and Thomson Scattering diagnostics currently used at FTU and TCV, respectively.

YAG Laser Perfomance Improved by Stimulated Brillouin Scattering Phase Conjugation Mirror in Thomson Scattering Diagnostics at JT-60

An improvement of the output energy of a multistage YAG laser system by using a stimulated Brillouin scattering (SBS) phase conjugation mirror (PCM) was achieved. The phase conjugation of the optically nonlinear SBS process in a liquid material effectively compensated thermal degradation at an average/peak power amplifier, resulting in an average power increase from 1.5 J at 30 Hz repetition rate to 2.6 J at 50 Hz drive. The beam quality was also recovered without wave front deformation and depolarization resulting in a transfer-limited divergence with a good flat-top pattern in a near field.

Interfaces for Thomson Scattering Diagnostics in the Divertor and Sol Near the X-Point Plasmas of Iter-Feat

ITER design has highlighted the fundamental need to monitor and deepen understanding of divertor operations. The designed Thomson scattering (TS) for the divertor leg and SOL near the X-point, has gained a lot from present State-of-the-Art in the diagnostics. However, hostile environment, very restricted access, and required spatial resolution, all impose severe constraints on the diagnostic design for ITER. Signal transmission from diagnostics introduces the further considerations of relative movements of the machine components. Despite the constraints it is feasible using of crossed probe and viewing beams to make measurements of the electron temperature and density profiles in outer divertor leg at the extent from the strike-point to X-point vicinity, and the LIDAR TS technique to make the electron temperature and density scan along the major radial line-of-sight at ∼0.5 m above the X-point. The interfaces for each of the subsystems are presented and discussed in the sections below.

SST and ADITYA tokamak research in India

Steady state operation of tokamaks plays an important role in high temperature magnetically confined plasma research. Steady state Superconducting Tokamak (SST) programme in India deals with the development of various technologies in this direction. SST-1 [1] machine has been engineered and is being fabricated at the Institute for Plasma Research. The objectives of the machine are to study physics of plasma processes under steady state condition and develop the technologies related to steadystate operation. Various sub-systems are being prototyped and developed. SST-1 is a large aspect ratio machine with a major radius of 1.1 m and a plasma minor radius of 0.2 m with elongation of 1.7 to 1.9 and triangularity of 0.5 to 0.7. It has been designed for 1000 sec operation at 3 T toroidal magnetic eld. Neutral beam Injection and Radio frequency heating systems are being developed to heat the plasma. Lower hybrid Current Drive system would sustain 200 kA of plasma current during 1000 sec operation. ADITYA tokamak [2] has been upgraded with new diagnostics and RF heating systems. Thomson Scattering and ECE diagnostics have been operated. 200 kW Ion Cyclotron Resonance Heating (ICRH) and 200 kW Electron Cyclotron Resonance Heating (ECRH) systems have been successfully commissioned. RF assisted initial breakdown experiments have been initiated with these systems.

Experimental Study of Conventional and Multipass Thomson Scattering Diagnostic Systems

A low-cost, simple and effective multipass structure was built and tested for the first time in a theta-pinch device, the compact torus TC-1. A detailed analysis of the gain in the scattered signal produced by the multipass system is presented. The use of a multipass geometry for Thomson scattering experiments in theta-pinch devices or in more dense plasmas as well as in plasmas with higher Z eff is recommended for increasing the relationship between scattered and bremsstrahlung signals.