D J Biswas
Articles written in Pramana – Journal of Physics
Volume 75 Issue 5 November 2010 pp 757-758
Volume 75 Issue 5 November 2010 pp 889-894 Conributed Papers
The repetition rate capability of self-switched transversely excited atmosphere (TEA) CO2 laser was studied for different gas flow configurations. For an optimized gas flow configuration, repetitive operation was achieved at a much smaller gas replenishment factor between two successive pulses when compared with repetitive systems energized by conventional pulsers.
Volume 75 Issue 5 November 2010 pp 901-906 Conributed Papers
The work presented in this paper deals with the triggering aspect of a switch-less laser. Many methods were utilized to affect the operation of two switch-less lasers in the oscillator–amplifier configuration. Most satisfactory performance in terms of the range and reliability of the delay was obtained with the LC inversion-based triggering option.
Volume 75 Issue 6 December 2010 pp 757-758
Volume 75 Issue 6 December 2010 pp 1087-1097 Invited Papers
Pulsed laser-assisted removal of particulates from substrates has decided advantages over the conventional methods of cleaning. Experiments conducted with loose contamination on metal and transparent dielectric surfaces proved conclusively the dominant role played by the absorption of the incident radiation by the surface towards the generation of the cleaning force as against the absorption in the particulates alone. Further, the presence of transparent/semi-transparent particulates on a metal surface was found to result in an increased absorption of the incident radiation by the substrate. This effect, identified as field-enhanced surface absorption was found to increase with reduction in the average particulate size.
Volume 82 Issue 1 January 2014 pp 1-2
Volume 82 Issue 2 February 2014 pp 1-2
Volume 82 Issue 2 February 2014 pp 237-242 Contributed Papers
Removal of a thin oxide layer from a tungsten ribbon and ThO2 particulates from zircaloy surface was achieved using a pulsed Nd:YAG laser. The removal mechanism of the oxide layer from the tungsten ribbon was identified as spallation or sublimation depending on the wavelength and fluence of the coherent radiation. The oxidized and cleaned surfaces were analysed by scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDS) and atomic force microscopy (AFM). Laser-cleaned tungsten ribbons were used in a thermal ionization mass spectrometer (TIMS) to determine isotopic composition of neodymium atoms. The fundamental (1064 nm) and the third harmonic (355 nm) radiations were found to be the most effective in removing ThO2 particulates from the zircaloy surface. Decontamination efficiency was found to be critically dependent on the wavelength of the coherent radiation and number of exposures. The mechanism of cleaning of ThO2 particulates from the zircaloy surface at different wavelengths of the incident radiation has been explained qualitatively.