an elongated housing defining an axis and having a proximal end and a distal end a first electrode body disposed at the distal end with a first portion enclosed within the elongated housing and a second portion exposed to outside of the catheter a fluid supply port near the proximal end for supplying a coolant into the elongated housing said first portion being of a shape having a surface area substantially larger than that of said second portion and being in fluid communication with the coolant for exchanging heat therewith said second portion being of a shape having a protruding surface that when disposed to ablate a biological tissue is substantially covered by and in contact with the biological tissue while leaving a minimum surface area not in contact with and uncovered by the biological tissue and an electrical conductor inside the elongated housing coupling the first electrode to a power supply at the distal end during an ablation operation.
