CASTOR

Figure 1:Tokamak at CASTOR in Prague (Czech Republic)

Introduction to CASTOR
CASTOR Parameters
CASTOR Diagnostics
CASTOR Research Topics
CASTOR Ongoing Projects

Introduction to CASTOR

The CASTOR (Czech Academy of Sciences TORus) device is the tokamak with a circular cross section. The last closed magnetic surface is defined by a poloidal limiter made of molybdenum. Hydrogen is used as a working gas. As a source of energy for the toroidal magnetic field, 1 MJ condensor bank is used. A delay LC line with the energy of several tens of kJ generates and heats the plasma. The plasma position is stabilized by a feedback system.

CASTOR Parameters

Plasma major radius	0.4 m
Plasma minor radius	0.4 m
Toroidal magnetic field	Bt < 1.5 t
Plasma current	I < 25 kA
Pulse length	t < 50 ms
Plasma density	ne = 0.2-3.0 x 1019 m-3
Electron temperature	Te(0) < 200 eV
Ion temperature	Ti(0) < 100 eV

CASTOR Diagnostics

The basic diagnostic equipment on the CASTOR tokamak in the following:

• VUV spectrometer Seya-Namioka with high spatial resolution
• XUV spectrometer with multi-layer mirrors as disperse elements
• Bolometer array for radiation losses measurements
• Energy spectrum analyzer of fast neutrals
• Radiometer of electromagnetic radiation at 17-27 GHz and 27-40 GHz
• Microwave reflectometer at 29, 33, and 35 GHz
• Langmuir probe arrays for edge plasma monitoring both in radial and poloidal directions
• Advanced probes for measurements of ion and electron temperatures, plasma potential, and flows in the edge plasma
• Array of coils for magnetic turbulence measurements

CASTOR Research Topics

The research topics of the Tokamak Dept. in the IPP are oriented towards contributing to the physics basis of ITER and future fusion facilities. The work is performed on the home device, CASTOR tokamak, as well as on large and medium sized devices in Europe (JET, Tore Supra, TCV, Mast, and Textor tokamaks and on TJ-II stellarator). The main areas covered by the intitute activities both in theoretical and experimental ways are as follows:

Edge Plasma and Magnetic Confinement Physics

• electrostatic and magnetic turbulence studies
• studies of sheared flows in the edge plasmas
• external control of the density and temperature profiles in the SOL plasma
• active control of SOL fluctuations by a properly biased poloidal ring of electrodes
• transport of non-intrinsic impurities through sheared electric fields
• modeling of the ion diffusion in a system of magnetic islands and turbulent structures
• edge plasma modelling
• analysis of VUV and XUV radiation from plasma-sprayed specimens

Diagnostic Development

• design and development of advanced electrostatic and magnetic probes
• design and construction of spectroscopic diagnotstic tools
• numerical simulations of probes behaviour in plasma
• irradiation tests of magnetic sensors

Wave Interactions in Plasmas

• theoretical and experimental studies of electron Bernstein waves conversion to X-mode at the upper hybrid resonance
• studium of fast electron generation in front of LH grills, induced plasma flows and density variations
• modelling of random field effects on enhancement of the fast particle production

CASTOR Ongoing Projects

• Electrostatic and magnetic turbulence of the edge plasma
• Teoretical and Experimental Studies of Microwave Emission and Absorption at Electron-Cyclotron Frequencies
• Quasineutral simulations of tokamak edge plasma near lower hybrid grills Code development. Response of resonant electrons to grill electric field and interaction with ions via induced space charge.
• Anomal diffusion
• Spectroscopy of intrinsic and seeded impurities in the tokamak plasma spatial and temporal resolved measurements of light impurities emission in VUV and XUV spectral range
• Bolometry observation of radiation profile - spatially resolved temporal evolution of the plasma emission
• Helium discharges on CASTOR
• Hydrogen retention using metalic membranes