Photocalorimetric measurement of power distribution in multipole-wiggler radiation

This paper presents a photocalorimetric method to measure intensity of high-power synchrotron radiation with the experimental results. The calorimetric device consists of a photoabsorber, a heat conductor, both are monolithically made from a copper block, and a water-cooled heat sink. Based on the temperature gradient along the heat conductor measured at a stationary state the incident power was evaluated. Power density distribution in multipole-wiggler radiation was measured on the beamline BL-28 of the Photon Factory. The beamline had neither beryllium nor graphite windows, which allowed exact comparison between measured powers and calculated values using Kim's formula for undulator radiation. Although the measured density was lower by on an average 20% at the peak density, it was ascertained that Kim's formula gives the power density of multipole-wiggler radiation. Besides, the photocalorimetry was found to be useful means for measuring high-power x-radiation. (author)