A laser driven plasma wind tunnel using a 2 kW class continuous wave laser was developed as a high speed and high density atomic oxygen generator. Firstly, its operation conditions were examined. Using argon and oxygen as working gases, laser sustained plasma (LSP) was successfully produced in the plenum pressure range from 0.30 MPa to 0.95 MPa, and then the LSP was expanded to the vacuum chamber through the convergent-divergent nozzle. Next, plume characteristics were evaluated by Pitot probe and laser absorption spectroscopy using an absorption line of ArI 772.38 nm. As a result, the Mach number and the specific enthalpy around the center were 5.0 to 6.5 and 3.0 MJ/kg to 5.2 MJ/kg, respectively. The maximum flux density of atomic oxygen was estimated as 2.2×10 21 cm -2 s -1 .

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A novel in situ TEM fracture testing method is developed to elucidate the mechanics dominating crack initiation at an interface edge in nano-structures. The testing system includes a special mechanical apparatus equipped with a piezo-actuated stage and a diamond loading tip attached to a MEMS load sensor, which enables us to control specimen position and perform quantitative load measurement with enough precision. Nano-scale cantilever specimens with interfaces are fabricated from a multi-layered material (Si/Cu/SiN) using FIB process technique. The validity of the testing method is demonstrated by conducting interfacial crack initiation experiments for the specimens with different size. The applied load and the specimen image have been successfully monitored and recorded during the experiments. For each specimen, the crack is initiated from the free-edge of interface between Si/Cu at a maximum load, Pc, and the specimen is instantly separated at the interface. Using the experimental results the stress fields along the Si/Cu interface at the crack initiation are analyzed for each specimen by finite element method. This reveals that the crack initiation of the Si/Cu interface is governed by the normal stress on the interface near the edge.

A continuous wave laser driven wind tunnel has been developed to produce high enthalpy flows to simulate atmospheric reentry environment. As a result of preliminary operation tests, high enthalpy argon/oxygen flows were successfully generated with the input laser power of 800 W, the plenum pressure of 950 kPa and the plume diameter of 15 mm. Next, plume characteristics were diagnosed by laser absorption spectroscopy. Consequently, the radial distributions of the specific enthalpy were measured. It was found that the specific enthalpy of flow was around 4 MJ/kg at the radial position r < 3 mm.