Electron beam-pumped excimer lasers are capable of achieving high-power laser output in the extreme ultraviolet (EUV) wavelength range, with the advantage of a broad laser wavelength bandwidth and excellent beam uniformity, making them highly competitive candidate drivers for Inertial Confinement Fusion (ICF). Enhancing the energy deposition efficiency and lifetime of electron beam-pumped excimer lasers is of paramount importance for their application in ICF. This paper analyzes strategies to improve the energy deposition efficiency and lifespan of these lasers from two perspectives: pulsed power drivers and electron beam diodes. It summarizes the research advancements in this field and provides an overview of future research content and methodologies. The study presented herein aims to offer insights and guidance for the design of efficient and highly reliable electron beam-pumped excimer lasers.
The electron beam pumped excimer laser is a competitive candidate for inertial confinement fusion driver. In the excimer laser system, the diode serves as the core component, for its efficiency and reliability of the diode directly impact the laser's lifespan and electro-optical conversion efficiency. But there are no mature design standards for diodes, and many crucial designs rely on researchers' work experience. Particle-In-Cell Simulation is an efficient method to solve that problem. This article presents the mathematical and physical equations governing the transport of electron beams in the vacuum space of a diode, and discusses the application of Particle-in-Cell (PIC) simulation in the design of semiconductor laser diodes. It concludes that the use of PIC simulation allows for the calculation of the trajectory of electron beams, as well as the energy and angular distributions of the beams reaching the anode. Based on the simulation results, the diode can be optimized. It is found that efficient transportation of electrons to the anode surface can be achieved even without the use of guiding magnetic fields, though a drawback is the relatively large angle and dispersed energy distribution of the electron beams reaching the anode. The research offers insights for the efficient design of diodes.
The excimer laser, with advantages of short wavelength, high energy, and tunable repetition rate, serves as an alternative device for inertial confinement fusion (ICF). However, the current bulky size of excimer lasers presents challenges for engineering implementation, leading to significant engineering difficulties. Modularization of diodes proves to be an effective approach for reducing device volume and engineering complexity. The goal of modularization is to achieve higher efficiency and reliability within a smaller footprint, where numerical calculations of electrostatic fields play a crucial role in realizing these objectives. This paper introduces the applications of electrostatic field numerical calculations in diode insulation structure design, suppression of cathode edge emission effects, and mitigation of electron beam scrapping effects, underscoring the scenarios where excimer laser diodes necessitate the utilization of electrostatic field calculations in their design. The research presented herein can serve as a reference for enhancing the efficiency and reliability of electron-beam-pumped excimer laser diodes.
The X-ray properties of Al plasmas were studied experimentally by using the excimer laser facility in the State Key Laboratory of Laser Interaction with Matte. Radiated fluxes were recorded within two X-ray diodes, and the relative spectral distributions were recorded within an X-ray flat-field grating spectrograph, respectively. Experimental results indicated that the major X-ray photons were between 60 eV and 360 eV. By employing the spectral integration method, the measured data were appropriately processed to obtain absolute energies of the X-ray that radiated from Al plasmas.
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
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