[1] [2] [3] Schotanus, P., van Eijk, C. W. E., Hollander, R. W and Pijpelink, J. Development Study of a New Gamma Camera. IEEE Trans. Nuc. Sci. NS-34(1):272-276; 1987, February 1. Levy, P. W., "Overview of Nuclear Radiation Damage Processes: Phenomenological Features of Radiation Damage in Crystals and Glasses," in Radiation Effects in Optical Materials, SPIE 541, Levy, P. W., ed. Bellingham, WA: SPIE, 1985. 2-24. Adams, M. R., Englemann, R., Grannis, P. D., Horstkotte, J., Godfrey, L., Linn, S. L., [4] Woody, C. L., Levy, P. W. and Kierstead, J. A. Slow Component Suppression and Radiation Damage in Doped BaF2 Crystals. To be published in IEEE Trans Nuc. Sci. NS36; 1989, February 1. [5] Levy, P. W. Facilities for Studying Radiation Damage in Nonmetals During Irradiation. Society for the Advancement of Material and Process Engineering (SAMPE) Journal. 21(2): 35-40; 1985, March 1. COMMENTS Question: Answer: Question: Answer: We have found that radiation induced absorption in quartz is a function of the I have a comment about your Mafia principle. In case of glass when you add It originated approximately 30 years ago when people were forced to develop windows for hot cells and at that time a large amount of work was done, just empirical work, to try to find some way of impeding the coloring. What the Cerium actually does in most glasses is at least two things. First of all, it introduces potential centers which have much higher cross sections for capturing the electrons and-or holes then the defects or impurities which color the glass in the visible; most of these new centers are in the ultraviolet. So, in that case, you give away coloring in the ultraviolet to gain transmission in the visible. The other thing that Cerium does is to act as a large recombination cross section material, in other words, it has a large recombination cross section. It traps holes, they then immediately trap electrons and so you short circuit the passage of these electrons and holes to the defects which produce color centers. MANUSCRIPT NOT RECEIVED OPTICAL DAMAGE IN GLASS FROM FOCUSED NANOSECOND RADIATION Evaldas K. Maldutis, Stanislovas K. Balickas, Silvinas V. Sakalauska ABSTRACT In this report the results of complex investigations and the understanding of glass optical damage by interaction with intense laser radiation is presented. The mechanism of glass damage threshold decrease is discussed. Under repeated nanosecond laser radiation when the quantum energy is less than a half of glass matrix ionization energy the changes in SBS intensity, the light absorption and refractive index have been detected. On this account, the main cause of damage accumulation is assumed to be color centers generation in glass resulting in thermal change of the refractive index and a following radiation intensity increase in the successive pulse focal region. The pulse duration, focal region size, radiation wavelength dependence of damage threshold, the accumulation effect and other calculations have considerably proved the presented glass damage model. Manuscript Received The Non-Destructive Prediction of Laser Damage S.E.Clark and D.C.Emmony Department of Physics. Loughborough University of Technology Leics. LE11 3TU United Kingdom We have developed a simple practical technique for the non-destructive prediction of potential damage sites. Excellent correlation is found between the predicted sites and the areas that damage first. The technique is based on using a short pulse dye laser and high resolution video framestore based Schlieren imaging system to record the transient i.e. non-destructive heating of a test surface by an excimer laser. The fluence of the excimer laser is then increased until the damage threshold is reached, whereupon the surface is re-imaged. Computer aided analysis of the transient image allows the areas of anomalous absorption to be found, which are then compared to the locations of areas that actually damaged. On all types of sample tested (metal, semiconductor and dielectric) and for both single and multiple pulse experiments excellent agreement is found between predicted and observed damage sites. Keywords: non-destructive; prediction; laser damage; Schlieren imaging transient heating; anomalous absorption 1. Introduction In The non-destructive prediction of laser induced damage is a process whereby some form of 'transient' non-damaging effect associated with the interaction of the laser beam and the component in question is 'monitored' so that predictions as to where the component will damage can be made. In an ideal world the surface of a component would be completely uniform and would thus damage uniformly over the beam surface interaction area[1,2,3]. reality, where optical quality surfaces are used, residual mechanical stress, strain and surface scratches together with contamination from polishing material and the general surroundings ensures that the samples do not have uniform surfaces. Consequently damage tends to occur in spatially isolated places corresponding to these defects with a factor of 2 or more in damage threshold between areas on the same sample not being uncommon. 2. Review It is generally accepted that for real surfaces, laser induced damage (LID) for large area beams, i.e. larger than a few tens of square microns and pulses longer than a nanosecond, can be attributed to the presence of surface defects which absorb sufficient incident radiation to cause the surface temperature to rise excessively leading to damage via melting, vaporization or mechanical failure of the surface. |