The effects of multiple pulses of a CO2 laser with energy
of 2.5 J and pulse duration of 200 ns on the surface morphology of ion
irradiated CR-39 is investigated in light of the modification in its track
registration properties. For this purpose, a CR-39 was exposed by a
CO2 laser generated hydrogen, argon, cadmium, air molecular
ions (N2 and O2, etc.), high energy (300 KeV) proton
beam from Cock Croft Walton accelerator, and α (5 MeV) from 0.5
μCi Pu239 source. The registered tracks were enlarged after
6 h of 6.25 N NaOH etching. These etched detectors were then exposed to
different number of CO2 laser shots. The etched detectors were
then analyzed by a computer controlled optical microscope (Lexica DMR
series). It was observed that even a single shot of CO2 laser,
irrespective of the registered ions tracks, can change the track
registration properties of CR-39, and can remove the vaporization
resistant skin present on the polymer (CR-39). A significant change in
track density and track shaping regardless of the ions is observed. At the
outside of the focal area, the ion density of different registered tracks
is compared graphically before and after laser irradiation. Laser ablation
of unexposed CR-39 is also done with multiple pulses CO2 laser.
In this regard, the coherent and non-coherent structures, diffraction
patterns, circular fringes with corrugations and ripples, droplets, chain
like structures with cluster formation, chain folded crystallites, and
hole drilling were observed. The irradiation induced ablation of the
polymer is of great importance in electronics industry, lithography,
etc.