Surface Scattering Test Of Stray Light Suppression Materials In Thomson Scattering

The surface scattering of light has a direct relationship with the roughness of the surface of the materials,so the scattering light will carry information about the surface characteristics of the materials.Therefore,according to the scattering distribution,it can be used to measure the surface roughness,or to detect defects and unevenness of the surface.Light scattering technology has a wide range of applications in manufacturing or test environments.On the other hand,the scattering distribution of the surface can be analyzed by the theory of the bidirectional reflection distribution function.The surface of the BRDF can be given by scattering light measurement,which can be used in the field of computer graphics such as rendering images.Therefore,we hope that through studying the scattering light distribution of materials,we can study the surface properties of materials,such as surface roughness,and can provide data support for BRDF modeling based on the measured scattering distribution.Based on the theoretical basis of BRDF and the actual measurement basis,this paper designs and optimizes the scattering light distribution measurement system on the surface of materials.The measured scattering distribution data combined with the surface roughness can characterize the surface properties of the materials,and the surface BRDF of the materials can be obtained from the scattering distribution.The scattering light distribution of the absorbing materials were measured under the premise of applying Thomson scattering stray light suppression.Through the experimental measurement of the scattering light distribution,the effect of absorbing light on stray light was studied and analyzed,which provided a data reference for the selection of absorbing materials for Thomson scattering diagnosis.Using a scattering measurement system to test,including mirrors,standard whiteboard,A4 white paper,stainless steel,aluminum alloy,black aluminum oxide,graphite,black paper,Thorlabs' black aluminum foil,Thorlabs' black flannel,Avian Black-S black paint and Acktar's Metal VelvetTM coated Foil Roll black foil and Thorlabs' light barriers distribute light across a dozen materials.Through the measurement of scattering light from these materials,the reliability of the scattering measurement system we designed was first verified.The measured scattering light distribution of the materials were analyzed,and the ability to absorb stray light of each materials were studied in detail.It is known that A4 white paper is like a standard whiteboard,the surface is a difftuse reflection surface;Optical components such as mirrors and stainless steel,aluminum alloy and other metal parts are the main sources of stray light in Thomson scattering;while graphite,black paper and Thorlabs black aluminum foil can only be reduced by one order of magnitude of stray light,and also produces specular stray light;Thorlabs' black flannel does not produce strong specular light,but does not absorb 1064nm laser;Avian Black-S black paint and Acktar's Metal VelvetTM coated Foil Roll black foil can reduce the stray light level by at least 2 orders of magnitude.These two materials are good for absorbing stray light materials;Thorlabs' light block can reduce stray light levels by at least 3 orders of magnitude.Blackening and blackening aluminum foils are more practical,considering the scope of application.The ability to shield stray light from these absorbing materials under grazing incidence were investigated.Only Avian Black-S black paint can reduce at least two orders of stray light levels under grazing incidence.Finally,the Thomson scattering diagnosis carried out on the KTX device analyzes the source of stray light by measuring the scattering light distribution of optical components such as mirrors and metal materials such as stainless steel,and selects appropriate absorbing materials by measuring the scattering of the absorbing material.The stray light is absorbed to the greatest extent.In the measured Thomson scattering signal,the stray light has been suppressed to the level of the noise floor,and the signal-to-noise ratio of the Thomson scattering signal is significantly improved.