I n s i t u measurement of micromass of the fuel in a cryogenic foam target for laser fusion research

Abstract

We have presented a novel in situ method which is simple and sensitive, to measure the micromass of the fuel layer in a cryogenic foam target. In this method, a foam shell is mounted on a flexible polyester fiber 7 μm in diameter and 800 μm in length. The fiber is suspended with a stalk which is mechanically vibrated at any given frequency. The resonant frequency of the elastic vibration of a foam-fiber system is measured before and after fuel loading. The mass of the fuel can be determined from the change in the resonance frequency in the range from submicrograms to submilligrams. The resolution of this system, which is limited by the Q factor of the foam-fiber system, is better than 0.2 μg corresponding to the measurement accuracy of 0.1%.