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The effects of bending of the light beam due to density gradients on the interferometric density measurements of dense plasmas with various density profiles are estimated. It is indicated that in spite of the original smooth density profile the bending effects may result not only in quantitative errors but also in apparent density modifications such as dips, plateaus, rippling, and steepening. In laser fusion experiments it is very essential to exactly adjust the imaging optics of the interferometer as well as the laser-irradiation optical system. The errors inevitably introduced are also evaluated. It is experimentally shown that an imaging lens must be properly used even in the density measurement of a plasma focus with relatively low density compared with laser plasmas.

The formation of nap-type structures induced by UV-laser irradiation of renatured gelatin films with various triple helix contents was observed by an atomic force microscope. Surface topography was found to be dependent on degree of helix content (DHC), fluence, and number of applied pulses (PN). The surface roughness (Ra) increased with PN following a hyperbolic curve for the renatured gelatin films with DHC of more than ca. 7%. The increment of Ra tended to be depressed with increasing DHC.

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