Study On The Key Technologies Of Inductively Coupled Plasma Processing On Fused Silica Optics

Fusion energy with the characteristics of pollution-free and sustainable is the ultimate energy that human can expect.As the main technology to produce fusion energy,one of technical bottlenecks in Inertial Confinement Fusion Technology(ICF)is that the processing problems of large-diameter fused silica optics,which are widely used in high-power systems.Inductively Coupled Plasma Processing(ICPP)is an efficient and damage-free machining method for processing silicon-based material.Since it is essentially a chemical reaction in the plasma environment,the damage layer left by the prior processing on the surface of the silicon-based optical material can be efficiently removed without introducing new processing damage.Therefore,ICPP technology can be introduced into the fused silica optical component process to achieve the efficient processing.At present,the biggest problem in the processing of fused silica components by ICPP is that the thermal effect of processing and the resulting removal function of time nonlinearity.In this paper,the non-linear rule,the key issues of temperature field,thermal effect control,removal function nonlinearity and dwell time are discussed,and the experiment is carried out.The major research efforts include the following parts:(1)Study on temperature field of ICPP.Aiming at the high temperature of inductively coupled plasma and the poor thermal conductivity of fused silica materials,the heat source model of the plasma torch acting on the surface of the fused silica optics was proposed and the thermal differential equation was established.Then,the temperature field was modeled,and the temperature field was simulated and experimentally studied.(2)Parameters and technologies optimization based on thermal effect control.After obtaining the temperature field of the fused silica optics,the influence of different process parameters on the temperature field is studied,and reasonable process parameters are obtained.The effect of different machining paths on the edge effect is compared and the machining path is optimized.(3)The time-varying nonlinear laws of the removal function are studied.As the removal function of ICPP is time-varying,this paper studies the extraction method and time-varying law of inductively coupled plasma removal function.The time-varying nonlinear model of removal function is determined experimentally.(4)The dwell time algorithm of time-dependent removal function is studied.On the basis of removal function time-varying nonlinear model,an algorithm of compensating dwell time based on pulse iteration is proposed in this paper.At the same time,a new method of surface error extension,smoothly fall extension is proposed.Compared with other edge extension methods,this method can get the minimum residuals in a relatively short time.(5)Experimental investigation on the ICPP’s figuring technology.With the new dwell time algorithm,the edge extension method and the machining path,the full-aperture surface errors of a 100 mm square mirror was reduced from RMS 0.854 λ to RMS 0.122 λ in 16.8min.Experimental results verify the effectiveness of the dwell time compensation algorithm and demonstrate the high efficiency of the ICPP’s figuring process.