Abstract
A radiation thermopile is described with a flat circular black target 1 cm in diameter over which cw responsivity is almost uniform. It is intended for measuring the energy of radiation pulses as well as cw irradiance and beam power. Rise time for a very short pulse is about 1/4s and cooling time constant 8 s. Typical CW responsivity is 250 mV W-1, and peak-reading pulse responsivity 32 mV J-1, uniform over wavelengths from 0.4 mu m to beyond 10 mu m. Power and energy signal characteristics are closely linear. Design calibration and methods of use, for example in calibrating laser cone calorimeters, are described. With laser pulses, use is limited to about 0.1 J, 1 ms free-running. An alternative model, but with uniform spectral response extending only to 1.2 mu m in the infrared, will withstand free-running pulses up to about 1.5 J, and Q-switched pulses up to about 20 mJ.