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Diagnosing the density profile at the edge of high temperature fusion plasmas by accelerated Lithium beam is a known technique since decades. By knowledge of the relevant atomic physics rate coefficients the plasma electron density profile can be calculated from the relatively calibrated light profile along the beam. Several additional possibilities have already been demonstrated: CXRS for ion temperature/flow, Zeeman polarimetry for edge plasma current; therefore the Li-beam diagnostic offers a wealth of information at the plasma edge. The weaknesses of the method are the relatively faint light signal, background light and technical difficulties of the beam injector which usually seriously limit the applicability. In this talk we present systematic developments in alkali-beam diagnostics (Li, Na) both for the injector, observation system and detectors which resulted in strongly increased capabilities. Advanced systems have been built and microsecond scale density profile, turbulence and zonal flow measurement demonstrated. A novel edge current measurement technique has also been designed and components tested with potentially microsecond-scale time resolution. Additional possibilities of these advanced systems for spectral measurements (CXRS, various Zeeman schemes) are also discussed.

Relativistic runaway electrons are a major concern in tokamaks. Albeit significant theoretical development had been undertaken in the recent decades, we still miss a self-consistent simulator that could simultaneously capture all aspects of this phenomenon. The European framework for Integrated Modelling (EU-IM), facilitates the integration of different plasma simulation tools by providing a standard data structure for communication that enables relatively easy integration of different physics codes. A three-level modelling approach was adopted for runaway electron simulations within the EU-IM. Recently, a number of runaway electron modelling modules have been integrated into this framework. The first level of modelling (Runaway Indicator) is limited to the indication if runaway electron generation is possible or likely. The second level (Runaway Fluid) adopts an approach similar to e.g. the GO code, using analytical formulas to estimate changes in the runaway electron current density. The third level is based on the solution of the electron kinetics. One such code is LUKE that can handle the toroidicity-induced effects by solving the bounce-averaged Fokker-Planck equation. Another approach is used in NORSE, which features a fully nonlinear collision operator that makes it capable of simulating major changes in the electron distribution, for example slide-away. Both codes handle the effect of radiation on the runaway distribution. These runaway-electron modelling codes are in different stages of integration into the EU-IM infrastructure, and into the European Transport Simulator (ETS), which is a fully capable modular 1.5D core transport simulator. ETS with Runaway Fluid was benchmarked to the GO code implementing similar physics. Coherent integration of kinetic solvers requires more effort on the coupling, especially regarding the definition of the boundary between runaway and thermal populations, and on consistent calculation of resistivity. Some of these issues are discussed.

The atomic beam probe diagnostic concept aims at measuring the edge magnetic field and through that edge current distribution in fusion plasmas by observing trajectories of an ion beam stemming from a diagnostic neutral beam. The diagnostic potentially has microsecond scale time resolution and can thus prove to be a powerful option to study fast changes in the edge plasma. A test detector has been installed on the COMPASS tokamak as an extension of the existing lithium beam diagnostic system. It employs a relatively simple concept of an array of conductive detection plates measuring the incident ion current, which is then amplified and converted to a voltage signal. The aim of the test detector is to experimentally examine the idea of the diagnostic and provide background data for design and installation of a final detector. Also, a numerical code based on the CUDA parallel computing platform has been developed for modeling lithium ion trajectories in the given COMPASS plasma discharges. We present the developments of the detector design and test measurements of the diagnostic performed both in a laboratory beam system and on the COMPASS tokamak.

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