Abstract
A radiometric calorimeter is described in which the energy absorber works at the same time as a temperature sensor so that thermal equilibrium for the entire volume of absorber is not required before measuring an incident energy. The achievable frequency response is therefore quite high, and this is not offset by the size and/or damage threshold of energy receiver. The device, formerly called Rat’s Nest Calorimeter (RNC), has been found quite useful for measuring the total energy of modern pulsed lasers with a large beam cross section. The aperture (presently 6 cm) can be increased arbitrarily without degrading the rise time. Excellent stability and high damage threshold (≫439 MW/cm2) result when a thick wire bolometer and amplifier combination is used. Response time (∼9 μs) and spectral flatness are much better than previously reported. Potentials of the RNC for measuring any energy which it absorbs up to 2 kJ at the rise time 60 ns (∼10 MHz) are discussed. The maximum sensitivity of the model 3.5 mJ/cm2 is sufficient to detect the radiative energy emitting from today’s fusion test plasmas.
Published Version
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