Fusion Science and Technology / Volume 51 / Number 4 / May 2007 / Pages 677-681
A way to make a hole in a resorcinol-formaldehyde (RF) foam shell target is described. A target used in fast ignition (FI) experiments consists of an RF foam shell and a guide cone. The fragile RF foam cannot accept conventional mechanical drilling or laser machining. We used the second harmonics of a Nd:YAG laser (532nm) to bore a hole for the cone by utilizing thermal decomposition of the RF foam.
To optimize the cutting condition, the thermal characteristic and absorption spectrum of the RF foam were measured with a thermo-gravimetric meter and a spectrometer, respectively. Then, using these results, relationships between the laser power and cutting speed were optimized for RF foams with several densities.