High power density laser estimation using quantitative thermal imaging method

The knowledge of the amplitude and the spatial distribution of an excitation flux is of great interest for the quantification of heat sources. In this work, the development of a non-contact imaging powermeter based on the association of a bolometer with an infrared camera is described. This powermeter allows, thanks to infrared thermographic measurements and image processing methods, the quantitative estimation of the spatial distribution of the power of the flux delivered by a high-power laser. First, the experimental setup used is described. Then, the complete model- ling of the heat transfer within the bolometer using the 3D thermal quadrupole formalism is presented. After that, an inverse method based on the Wiener filter in Fourier-Laplace transform spaces to estimate the spatial distribution of the power flux is described. Finally, power estimation results using two metallic plates as a bolometer are presented and discusse

Development of thermal spray alumina coating for high diffuse reflectivity application in Lambertian screen

This study is about material and processes technologies for the realization of diffuse reflective screens supporting high temperatures. The use of high-energy lasers leads to material issues for high temperature diffuse reflective screen applications. Solutions exist for temperatures below 350°C. In this context other technological solutions need to be investigated to produce high temperature resistant screens. Diffuse reflectivity is studied for different alumina coatings obtained by thermal spraying. Plasma and flame processes and different powders (size, microstructure) are selected. The aim is to create various coating microstructures (pore size, porous architecture, nano area) and analyze the influence on diffuse reflectivity. Depending on thermal spray processes (APS, flame, Master Jet), spraying parameters and precursor material (fine powder, nano-agglomerated, flexicord), diffuse reflective values range from 74 to 92%. Best results are obtained by combining the plasma spray process and a nano agglomerated powder. However, a dense coating (porosity lower than 2%) or a too porous one (especially with connected pore columns) are less efficient. T