Excimer lasers driven by linear transform driver (LTD) are expected to be used in inertial confinement fusion (ICF). The main problem of LTD in excimer lasers is synchronous triggering on multiple circuits, gas spark switches are important for synchronous triggering, which are required to be fired with low prefire probability and jitter. Multi-gap switch, as a kind of the gas spark switches, is always used in LTD. In this paper, a comparison study of corona discharge current of a multi-gap switch for LTD from the aspects of self-breakdown voltage and jitter is presented. The length of equalizing voltage needle was optimized by the electrical strength simulation. Using the optimized needle, the corona currents of the two gaps were measured, then it was found that the corona currents differ when the lengths of the corona needles were equal. To study if the difference of current in each gap affects the breakdown voltage and jitter of the switch, the length of the needle was adjusted to make the corona current the same. Then the breakdown voltage and jitter were measured under the two conditions of equal and unequal corona currents. It can be found that smaller the difference of current in each gap, higher the breakdown voltage and lower the jitter of the switch. It can be concluded that the corona needle can be adjusted to make corona current of each gap equal, which can be beneficial to increase the breakdown voltage and lower the jitter of the switch.
In the high-power laser device, through precisely positioning the target and pointing multiple laser beams at a very small area on the target surface, the laser power density coupled with the target can be greatly improved and is conducive to the research of laser-induced plasma experiments. This paper proposes a set of target positioning and laser beam pointing system, which has advantages of high experiment efficiency, high target positioning and laser pointing accuracy. This system can automatically correct the attitude and position of targets, and make all laser converge together by adjusting their incident directions. It was verified that the target positioning error is 14.83 µm and the beam guidance accuracy is 9.70 µm.
The square pulse output of Linear transformer driver (LTD) is of great interest for excimer lasers, where the efficiency can be greatly improved in this way. The design of square pulse output LTD within the single cavity was presented, then the influence of jitter and loop inductance on square pulse output was studied, it can be found that the higher the value of the jitter and loop inductance, the more the risetime of the voltage pulse, which hinders the shaping of the square pulse output. Then the method to change the square pulse width by varying the triggering times was presented, through the simulation, it is found that when the triggering interval is set to 15s, the square pulse characteristics of the voltage output are more obvious, the flat top is flat, and the pulse width is wider. The bricks within the single cavity can be designed by two methods, where the one is using the same sized capacitors, the other is using the different sized capacitors to synthesize a flat voltage pulse, the choice of the two methods should be based on the cost and requirements of the excimer laser, including the amplitude of the output voltage, the pulse width and the laser beam quality. The reference of designing the square pulse LTD can be provided by this paper
A theoretical model based on rate equations for actively Q-switched Er3+-doped ZBLAN fiber laser is built. The operation behaviors and output characteristics of the actively Q-switched fiber laser at 2.8 μm are analyzed. Effects of some important laser parameters, such as pump power levels, reflectivity of the laser output coupler, fiber lengths, Er concentrations, etc., on laser output were investigated. The model and simulating results are useful for design and optimization of actively Q-switched fiber laser at 2.8-μm region.
We report a continuous wave (CW) all-solid-state Cr:LiSAF laser with a prism-controlled coupled-cavity. Broad-band tuning of 198 nm from 784 nm to 982 nm is demonstrated. The output power is always above 14 mW tuned from 825 nm to 975 nm and reaches the maximum value of 21.4 mW at 900 nm. Dual-wavelength operation is observed at the edge of the tuning range. The coupled-cavity passive loss is discussed and calculated to be 18%.
The investigations of the XeF laser bumped by ultraviolet radiation have been studied for more than 20 years in Northwest Institute of Nuclear Technology (NINT Xi’an China). Up to now, several XeF laser devices were developed and an integrative experimental system has been set up which is comprised of a laser device, an electrical power supply, a high voltage trigger generator and a mixture gas supply device. Many key technologies were studied in detail and have been applied now. These technologies include section surface discharge, XeF2 photodissociation, synchronal trigger generating, double-sides optical pumping from opposite directions, active mixture gases supplying in real time, gases circulation, and so on. The XeF laser system operating on pulse repetition frequency (PRF) is up to 10 Hz. Two kinds of operating modes were applied. For the open gas flowing mode, the pulse energy of 3.2 J and the average power of 32 W at 10Hz is obtained. For the gases circumrotate mode, the average energy of 20 laser pulses is more than 0.5J.
SF6 and C2H6 are the working gas mixture of non-chain HF laser. In our work, we use a simple pumping circuit to study the influence of the electric field uniformity on the discharge characters. Three groups of electrodes with different designs have been manufactured, and different discharge characters have been got. We have analyzed the results qualitatively, and find that without preionization, uniform electric field is not the best choice to form a large volume discharge in strong negative gas such as SF6-based mixture; approximate uniform electric field may be its substitution. In such electric field the gap breakdown voltage decreases and discharge can perform much easily. The discharge channels away from the cathode surface can also diffuse together to form a large volume discharge to deposit the electric energy into the laser working gas.
A 3A molecular sieve separation device was designed and mounted in a closed-cycled non-chain HF laser to separate the ground state molecule being produced in discharge region from gas stream in order to improve the stability of laser output energy. Experiments were carried out with several different discharge voltages and gas flow velocities, and the preliminary results show that the molecular sieve separation device could dramatically decrease the decay of output energy of HF laser while improving the laser energy stability.
A general model has been developed for the optimization of the end-pumped solid-state lasers by including the effect of beam quality of the pump, and ellipticity of pump and oscillation beam into the overlap integrals. Previous models of mode-matching between oscillation and pump beam just consider of the ellipticity of pump beam, and assume the Gaussian oscillation beam to be circle TEM00 mode. Our model of mode-matching considers not only the ellipticity of the pump and oscillation beam, but also the angle of the long axis of the pump and oscillation beam. To illustrate the utility of the present model, an end-pumped Cr:LiSAF laser pumped is considered and the experimental results fit well with the theoretical results.
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