[en] The ion source is the heart of the cyclotron accelerator machine. It feeds the electrons to start the plasma generation, and consequently the formation of the ions to be accelerated in the cyclotron's chamber. In addition, it controls the ion beam current and intensity. The performance of the ion source is one of the important factors, which determines the durability, and the production efficiency of the cyclotron. The ion source should have a long stable working life in order to provide particles for isotope production.The regular isotope production program in Egypt's cyclotron facility has been interrupted several times by the sudden break down of the traditional tantalum filament cathode of the ion source. This has been the cause of equipment downtime, for filament replacement. A study for the improvement of the ion source lifetime of the MGC-20 cyclotron accelerator has been carried out by selecting three suitable materials for the ion source filament and compare between them. The cathode material plays a very important role for the production of intense ion beams; hence investigation on other low work-function materials is needed to further enhance the source performance. Two materials were selected for the filament, namely tungsten and molybdenum, in addition to the original tantalum filament. The selected materials for the filament have a high melting point and give low wearing rate during the plasma production, since the filament lifetime of the Livingston source, which is the type used in Egypt's Cyclotron, is usually limited due to the high plasma densities near the filament. In the present work, the effect of the normal operation parameters of the MGC-20 cyclotron on the filament's lifetime is studied for solving the lifetime problem of the MGC-20 cyclotron's ion source.The new types of the filaments were machined from wires, 2.5 mm in diameter, to take the same shape and dimensions as the original tantalum (Ta) filament. The three types of filaments were used, in turn, in the cyclotron operation. Each filament is operated for successive five-hour intervals until it breaks down. The ion source operation parameters, such as the value of the vacuum, the filament heating current, the arc-voltage, and the arc-current, were also recorded regularly during each of these five-hour intervals. It was found that the molybdenum (Mo) filament broke down after 20.8 hours and the tantalum filament broke down after 27.8 hours. The tungsten (W) filament appeared to last longer and a preliminary experiment showed that it stayed in operation for more than 100 hours. By recording the original weight of the filament and re-weighing it at the end of each interval, and after it breaks down in the case of Mo and Ta, both the differential and integrated mass loss rates were calculated. To compare the behavior of the three filaments, the integrated mass loss rate for the three materials in the first 20 working hours was calculated. The ratio was found to be 1.3: 5.595: 8.395 mg/h for W: Ta: Mo respectively. The theoretical lifetime were calculated for the three filaments and were found to be 328.9, 27.6, and 21.7 hours for Mo, Ta, and W, respectively. The first two values are in good agreement with the actual lifetime while the lifetime of tungsten seems to be reasonable with respect to its observed low mass loss rate.The temperature distribution along the filament length was studied using the numerical capabilities of the ANSYS 5.4 program. The results were presented in the form of color coded graphs and in the form of tables. The temperature distribution was calculated twice for each of the three filament materials; the first of them by considering the heat load due to the filament electric heating power only, and the second one by considering the extra power due to the formation of the arc. It is noted that; the first case maximum temperatures of the three filaments were almost the same as the calculated filaments temperatures by the Newton-Raphson Technique.