Based On Electrical Calibration Of Large-caliber High Power Laser Energy Measurement Techniques

In the past two decades, the study on the ICF driver has gained rapid improvement. In order to achieve energy equilibrium among different beams, we need to achieve real-time precise measurement for large-aperture laser energy. Volume absorbing laser detectors are known for their wide wavelength range, high damage threshold, long-term stability and overall accuracy, have widely been used in laser testing. For peak-power, single-pulse laser energy detecting, this method is also used. However, for its calibration, there is no standard facility for high-power laser, we can only make an indirect transmission for the standards. The uncertainty of laser energy measuring increases in the process of transmission. This work aims at studying the electrical calibration technology of large-aperture laser energy measurement, a new design of electrical calibration set in laser detector is proposed, the research and achievements are as follows:1.A new laser energy detector with electrical calibration device is proposed based on equivalent thinking between electrical heating and laser heating, the principle of this detector and the thermodynamic boundary conditions are studied;2.The effects of absorption coefficients and two-photon absorption on energy measuring are studied. The temperature histories for single-pulse heating are predicted using a three-dimensional model with different absorption coefficients in infinite element method. The results show that:For the large-aperture(400mm X 400mm) single-pulse(3ns) laser energy measurement, for 5 mm thickness, absorbers with absorption coefficient between 400 600m-1 is most appropriate; simulation of the two-photon absorption in the energy measurement showed that:two-photon absorption can compress the volume absorbing effect into surface absorption and result in a very high peak temperature on the glass surface. This is very harmful for the laser detecting. The performances of the thermocouple are studied, the results show that:The Seedback coefficient is 13mV/℃with a standard deviation of 0.13%; Voltage-current relationship can be described as U=2.05792*I-0.03684;3.The response of the detector to electrical energy and laser energy are simulated and experimentally studied. The simulation results show that:in the proposed detector, the temperature of temperature-detecting area increases linearly with the laser and electrical energy; The experimental results show that:the laser detector has a linear response with the laser energy, only a partial linear response with the electrical energy, the causes are under further studying;4.A design of large-aperture laser energy measurement system with electrical-calibration device is proposed, the calibration platform circuit diagram, measurement and calibration software process are given.