The importance of this study lies in the use of a mercury-thallium for different levels of concentration and applied voltage mixture in arc plasma to enhance the efficiency of high-pressure lighting systems, reduce costs, and mitigate electrode corrosion. Mercury is the main element used in arc lamps. The addition of thallium has contributed to improving the emitted light characteristics and stability, reducing energy loss, and extending operating life. The NCPL model was used to interpret and analyze the physical changes in the region near the cathode surface. This model simulates the thermal and electrical interactions that control the transfer of current and energy density, providing accurate data that helps in optimizing high-pressure lighting systems, and measure the ratio of the ionization length to the mean free path, while the THERMCAT model was used to measure the total energy released from the cathode surface of a mixture of mercury and thallium at different concentration and applied voltage. At a concentration of (0.5 mol) of thallium in the mixture, it contributed to improving the physical and chemical properties due to the abundance of a large number of ionisable atoms. The energy flux increases with increasing cathode surface temperature, where the increase is linear at (Tw<3500 K) and non-linear at (Tw>3500 K). When the applied voltage is increased to (50 V), the energy flux (q) increases due to the acceleration of the charged particles in the electric field. This increases their energy, leading to an increase in collisions between the charged particles. Whilst THERMCAT model The energy emitted from the cathode surface increases with the increase of the diffusion or spot current, where the relationship is linear between the energy emitted from the cathode surface and the spot current due to the accumulation of charges and the rise in temperatures in the spot area.