Thermal modeling and analysis of laser calorimeters

We performed detailed thermal analysis and modeling of the C-series laser calorimeters at the National Institute of Standards and Technology for calibrating laser power or energy meters. A finite element method was employed to simulate the space and time dependence of temperature at the calorimeter receiver. The inequivalence hi the temperature response caused by different spatial distributions of the heating power was determined. The inequivalence between electrical power applied to the front and rear portions of the receiver is ^1.7%, and the inequivalence between the electrical and laser heating is estimated to be <0.05%. The computational results are hi good agreement with experiments at the 1% level. The effects of the deposited energy, power duration, and relaxation tune on the calibration factor and cooling constant were investigated. This article provides information for future design improvement on the laser calorimeters. Nomenclature A = area of the cavity aperture, m2 Ac = cross-sectional area of the wire, m2 b = thermopile responsivity, V/K C = heat capacity, J/K