Alkali metal thermal to electric converter (AMTEC) cells are built with readily available materials. Improvement of the performance of an AMTEC cell requires improvement and development of components as well as cell geometry. The present paper shows parametric results obtained by changing cell geometry to determine the effects of these design changes on the cell performance. In order to improve the cell performance, heat losses, input thermal power, cell's output power and efficiency have been investigated in detail by varying the cell designs. Changing some geometrical dimensions of the cell has proved to be very effective in improving the cell performance. As a result of this overall effort we have been able to demonstrate the improvement in the efficiency of AMTEC cell by 17.5% over the one in operation called Ground Demonstration Converter System at Air Force Research Laboratory, Albuquerque, New Mexico.