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The influence of resonant helical field, RHF, on effective ion charge, Zeff, and impurity radiations on IR-T1 tokamak discharges was studied. The theoretical calculation of Zeff with RHF indicated that the Zeff decreased. To observe the effects of reduced Zeff on impurity radiation, two important parts of plasma were investigated, equilibrium region of plasma and disruptive plasma. The results obtained from previous experiments on equilibrium plasma showed the increased radiation of impurities, in comparison with preceding and next regions, whereas the new results indicate that the impurities radiation decreases remarkably in disruptive part of plasma.

It is widely recognized that plasma material interaction in fusion devices is a critical issue that affects the overall machine performance. The process of material selection with a low degradation effect on the confined plasma and on the nuclear fusion production in tokamaks is of great importance. However, plasma materials' interaction studies in tokamaks have some limitations, so it is suggested that a new method for investigating this phenomenon be developed. The high capabilities of plasma focus devices allow one to simulate the interaction studies of tokamak plasma and first-wall materials. Our experiments were performed on a 90-kJ Filippov-type plasma focus, Dena. Experimental results clearly show the influence of materials on the neutron yield and neutron production mechanisms.

The effective ion charge,Z eff, represents the average charge of ionsZ i of gasses inside the system, which indicates the level of the impurities in the plasma. Several techniques have been applied to estimateZ eff, like mass spectroscopy, anomaly factor and Bremsstrahlung radiation. We estimatedZ eff in the IR-T1 tokamak through anomaly factor. The IR-T1 tokamak is a small air-core transformer tokamak with circular cross section and with out conducting shell and divertor. Its aspect ratio is $$\frac{R}{a} = \frac{{45 cm}}{{12.5 cm}}.$$ For a tokamak discharge of 30 kA plasma current and 1.5 V of loop voltage and by anomaly factor we observed thatZ eff value is about 1.5.