A drill for concrete and rocks is being developed using a laser-based hybrid technique. The design locates the outlet hole
of laser beam and drill blades on a common rotational axis. The laser beam weakens the concrete, and the blade breaks
the weakened layer. The target performance is a drilling speed of 30 mm/min at a sound level less than 70 dB using 1-2
kW laser power to produce a φ20 mm × 300 mm hole.
A laser-based hybrid technique is shown to be effective for cutting concrete and drilling rock. Experimental conditions
used included a laser power of 1-10 kW, 10 mm laser beam diameter and 1.25-50 mm/s scanning speed. The results of
surface scanning tests and 100 mm deep cut tests indicated that the shortest operation time was about 3.5 hr/m<sup>2</sup> for plain
concrete and 4.5 hr/m<sup>2</sup> for heavy concrete. The specific energy for the rocks (the amount of energy required to remove a
unit volume of rock), which were granite and sandstone, was as same as that for heavy concrete. Thermal decomposition
was observed for limestone. The specific energy of limestone was more than 1.5 times higher than that for granite and
Mist singlet oxygen generator (Mist-SOG) has been developed in order to increase the BHP utilization. On the other hand, Mist-SOG generates much more water vapor than conventional SOG because the heat capacity of the BHP is small. It is well known that the water vapor deactivates the excited iodine. In order to remove the water vapor, we developed a jet-cold trap. In this method, a nozzle sprayed a chilled H<sub>2</sub>O<sub>2</sub> at 238K with a thin layer form to the gas flow directly in order to get the large specific surface for the water vapor. As a result of experiment, Water vapor partial pressure reduced from 3.3 Torr at the BHP flow rate of 2.2 ml/s and Cl<sub>2</sub> flow rate of 3.5 mmol/s for the 65µm BHP droplets.
New type mist singlet oxygen generator (Mist-SOG) for the chemical oxygen-iodine laser (COIL) has been developed. This SOG is devoted to make the liquid recirculation unnecessary with the complete reaction through a single pass of basic hydrogen peroxide (BHP). 75% of Cl2 utilization and 76% of O2(1Æ) yield were obtained with Cl2 molar flow rate of 3.0 mmol/s. H2O2 utilization in the BHP was achieved as high as 12.3%. This value is about 24 times larger than that obtained by the liquid-jet SOG.