A Tubular Calorimeter for High Power Laser Pulses

An isoperibol calorimeter employing a 72 junction thermopile and a massive metal jacket is described. The receiver consists of a nickel‐plated copper tube; the beam enters at an angle of 45° and travels through the interior, undergoing multiple partial reflections. The aperture is 16 mm; the detection limit for small pulses is 1 mJ and the precision for large energies is 0.1%. Measurements have been made with 100 nsec, 500 mJ cm−2 pulses. The instrument has a number of advantages over cone calorimeters.