in the boundary layer 90 is detected as the pulses supply heat energy into the volume of the tumor 32 the tumor 32 is heated locally basically in the segment shaped zone defined by the beam but also heat is conducted out of the volume of the beam into the remainder of the tumor 32 at a rate dependant upon the characteristics of the tumor 32 itself heating at a localized area defined by the beam is therefore continued until the heat at the boundary layer 90 is raised to the predetermined coagulation temperature on the order of 55 to 65 c once the boundary layer reaches this temperature heating at that segment shaped zone within the disk is discontinued and the fiber is moved either longitudinally to another disk or angularly to another segment or both to move to the next segment shaped zone of the tumor 32 to be heated it is not necessary to predict the required number of pulses in advance since the detection of temperature at the boundary is done in real time and sufficiently quickly to prevent overshoot however predictions can be made in some circumstances in order to carry out the application of the heat energy as quickly as possible by applying high power initially and reducing the power after a period of time it is desirable to effect heating as quickly as possible so as to minimize the.