LAUSR

In this study, we developed a semi-active method to run a graphite calorimeter in the quasi-isothermal mode under the high-energy x-ray beams. The rate of energy imparted by the beam during irradiation was compensated mainly by removing the electrical heating power based on the pre-calculation and in part by an active automated algorithm as well while the temperature of the calorimeter core was kept constant. Irradiations were performed under the LINAC x-ray beams at 6, 8, 10, 15, and 18 MV. A simple model was applied to analyze the results. The energy imparted to the core was determined with an uncertainty level of 0.2-0.3 %. And the results were reaffirmed by comparing it with that obtained by the quasi-adiabatic mode. The normalized rms deviation of the mean from the quasi-adiabatic mode was 0.11 %, and the associated uncertainty was 0.16 % taking into account the correlation of the uncertainty components. This level of agreement showed that the present method is practical for the high-energy x-ray dosimetry.