<title>High-temperature measurements of reflectivity and heat capacity of metals and dielectrics at 1064 nm</title>

Abstract

High temperature measurements of reflectivity and heat capacity of metals and dielectrics at 1 064 nms.v. Garnov, VI. Konov, 0G. TsarkovaGeneral Physics Institute of Russian Academy of Sciences, Moscow, RussiaF. Dausinger, A.RaiberInstitute of High Power Beam Processing, Stuttgart, GermanyABSTRACTThe information on optical and thermal properties of materials at high temperatures is the base for any theoreticalanalysis of laser matter interaction processes. To evaluate the absolute value of energy deposited in the interaction area andto estimate the laser damage threshold one need possessing the knowledge on reflection/absorbtion coefficients and heatcapacity of material subjected to laser radiation. Because these parameters are strongly dependent on material chemicalcomposition, irradiation and environmental conditions, surface and bulk temperature etc. the task of its direct numericalcalculation becomes very difficult and the obtained theoretical estimations are unreliable. Up to now the only way to get thereliable values of the parameters mentioned is the experimental procedure. Among the other experimental techniquesdeveloped for measuring reflectionlabsorbtion coefficients at high temperatures, the based on an integrating sphere methodis the most suitable, relieble and accurate one'3.The installation for high speed, high temperature measurements of optical (reflectivity) and thermal (heat capacity)properties of metals and dielectric materials is described. The system includes a specially designed photometric sphere(reflected radiation is collected by quartz fibers), a chopped CW Nd:YAG laser with output power up to 250W, which heatssamples and simultaneously serves as a probing beam, and a high speed optical pyrometer. The set-up is fully computerised.The real temperature of targets is determined by a simultaneous measuring of brightness temperature and reflectivity atabout the same wavelengths. Different metals (iron, different steels, cooper and aluminium alloys, etc.), ceramics (SiC,