Investigation of Laser-Surface Interactions Using a Nano- Impulse Balance

A torsional impulse balance has been developed as a new diagnostic tool to study fundamental physical processes in micropropulsi on systems and laser-surface interactions. Of particular interest are the transient forces due to processes of laser ablation and gas desorption from rapidly heated surfaces. With respect to the transfer of momentum, direct measurements of the transient forces can lead to a better understanding and characterization of the efficiency of the thrust that is possible under different configurations. The impulse balance has been designed and tested with a robust calibration system to measure impulsive forces with resolution as low as several nano-Newton-seconds. The behavior of the impulse balance was thoroughly studied and characterized. An analytical model of the balance’s motion was developed from the general equation of motion of an underdamped, harmonically oscillating system. A simple technique has been developed to accurately back out the force as a function of time from the experimental data.