Pulsed x-ray induced damage to metal and multilayer mirrors

Abstract

The effect of intense pulses of laser-produced x rays upon the reflective and diffractive properties of metal mirrors and multilayered mirrors (artificial crystals) have been inves tigated. Laser pulses from a Nd-glass pulsed laser system of 25 ns pulse width and 50 3 energy were focused onto a copper target to generate the required x-ray pulses. A polished planar sample of nickel was used to reflect the 1.0 to 1.3-keV x rays onto photographic film, The x-ray flux onto the mirror (at grazing incidence angles near 3.5°) was split into two adjacent fields with a beryllium filter over one field and with an equal thickness beryl lium filter placed over the film holder covering the adjacent field. Thin pieces of Kimfol were used as debris shields ahead of the mirror sample. This technique provided an insitu nomalization since both a low intensity and a high intensity irradiation caa he simultane ously achieved on adjacent portions of the sample. A similar technique was used to study reflection by a multilayer sample of carbon-tungsten carbide layering and 19,6A° spacing.Experimental details and the results obtained are presented.;.ij^iy mSM^mmmtmmf

Design of X-UV multilayers for high X-ray flux

“…Kohler et al [11] used a pulsed Nd-glass laser to generate a point source of copper L X-rays (0.980 keV) to study damage degradation in a WC/C multilayer. Their results were consistent with damage occurring at an energy deposition of 0.46 J cm-2.…”

“…Methods of estimating multilayer damage as a function of time during periods of irradiation have been developed [1][2][3][4][5][6][7]. Some experimental damage data has been obtained in X-ray laser experiments [8][9][10], and in experiments specifically designed to make a quantitative measurement of the reflectivity degradation of a multilayer mirror while it was subjected to a short pulse of intense X radiation [3,4,6,7,11].…”

Mechanisms of radiation damage to Sc/Si multilayer mirrors under EUV laser irradiation

“…A correlation in ML stability between thermal and radiation tests was noticed [30]: more thermally stable MLs had higher radiation stability. Depending on the ML, the degradation is observed at power densities of 0.25-2.30 W mm −2 [6,26,30] for synchrotron light and at fluences ranging from 0.05 [27] up to 0.46 [25] J cm −2 for pulsed light. The degradation manifests itself in a shift or broadening of the reflecting maximum, decay of the reflectivity or their combination.…”

“…The resistance of the ML mirrors to intense EUV/x-ray radiation has not been studied in such detail. The first efforts in this direction were made for hard x-rays in connection with the development of a facility to filter white synchrotron light [24] and the construction of a diagnostic instrument to characterize high-intensity sources [25]. Both conventional MLs such as W/C, W/B 4 C, W/Si, Mo/B 4 C, Mo/Si [6,[26][27][28][29] and specially proposed ones (Mo/BN, W/BN [30]) were tested.…”