Plasma transparency in laser absorption waves in metal capillaries

An experimental investigation was made of the plasma transparency to heating radiation in capillaries when absorption waves propagated in these capillaries as a result of interaction with a CO₂ laser pulse of 5-μs duration. When the length of the capillary was in excess of 20 mm, total absorption of the radiation by the plasma was observed at air pressures of 1–100 kPa. When the capillary length was 12 mm, a partial recovery of the transparency took place. A comparison was made with the dynamics and recovery of the plasma transparency when breakdown of air took place near the free surface.