b. pourshahab

Tokamaks are recognized as one of the most promising devices for achieving nuclear fusion, operating within complex environments with high radiation levels. Upgrading these devices to enhance plasma efficiency and duration inevitably leads to increased radiation levels, making precise radiation dose estimation and the design of effective shielding systems essential. The Damavand tokamak, with its pure hydrogen plasma, generates both soft and hard X-rays. With sufficient data on these indirect ionizing radiations, the potential adverse effects can be minimized. Planned upgrades to the Damavand tokamak will extend plasma pulse duration from 22 ms to approximately 200 ms, resulting in a significant increase in radiation levels, estimated to be up to ten times higher in work areas, posing safety risks for personnel. In this study, we estimate the radiation dose in different areas of the upgraded Damavand tokamak laboratory based on experimental data, and we calculate specifications for new radiation shields using the MCNPX code to ensure laboratory safety. The required shielding dimensions were calculated for lead and concrete materials, allowing for a cost and feasibility assessment to guide the selection of the optimal implementation material.

Determining the magnetic field profile is very important for studying flux surfaces, elongation, plasma boundaries, and real-time control in tokamaks. In this research, a system for calculating and displaying the shape, position, and boundary of plasma for Damavand Tokamak control room has been developed. This system determines the magnetic field profile and flux surfaces in the time interval between two consecutive shots. This software is implemented based on measurements with the probes' sensors and electromagnetic flux loops. It also solves mathematical equations based on the physics of the problem. In order to calculate the magnetic field profile and the plasma shape, after preparing and collecting the data from the data acquisition system, a developed code is used to pre-process the data, such as noise reduction, removing unnecessary data, etc. Then, using another code, the cross-section parameters such as shape, position, and plasma boundary are calculated and displayed in the tokamak control room. All the codes of this system are written in MATLAB software and as a graphical user interface procedure. This is so the tokamak operator has easy access to the results after every shot. This system is currently installed and operated in the Damavand tokamak control room.

Plasma impurities are one of the loss factors of confined energy in tokamaks, so from this regard their study in order to maintain the stability of tokamak plasma and improve the confinement quality is essential. In this research, in order to study the impurities of Damavand tokamak plasma, a monochromator along with a Line Scan CCD array in the assembly of a visible light spectrometer was used. The modified spectrometer system was calibrated by the characteristic wavelengths of a mercury-vapor lamp and was used in the normal plasma regime of Damavand tokamak to record and analyze the radiation in the wavelength range of 3000-7000A°. The finest instrumental resolution of the spectrometer was about 0.9A° at entrance slit width of 50μm, which was used for intensive hydrogen plasma radiation lines such as Hα and Hβ. To study the radiation from the impurities, due to their low intensity, the entrance slit width of 100 μm and the resolution of 1.8A° were selected. The results showed that the predominant impurities in Damavand tokamak plasma are oxygen, nitrogen and carbon, which are generally originated from air molecules trapped in the wall of the vacuum chamber and the plasma facing components, also iron impurities are produced as a result of hot plasma interaction with the limiter and other components inside the vacuum chamber.