![]() The complete laser will meet required specifications of the LICS, with the added advantage of an ultra-compact design that is suitable for use in a typical experimental tokamak facility. In Phase II, a complete laser system will be constructed, incorporating design modifications to allow pulse energies greater than 1 J at the desired repetition rate. Work in Phase I will utilize the existing system to determine precise constraints on the peak intensity and to demonstrate the beam characteristics required for damage free amplification. In order to achieve pulse energies greater than 1 J at such short pulse durations, innovative temporal and spatial pulse shaping methods will minimize the peak intensity in the solid material. The limiting factor in the proposed system is the damage threshold of the Nd:YAG amplifier rod in the perspective of the maximum commercially available diameter of rods, 1 inch. The proposed work will include development of an amplifier stage which will increase the pulse energy to the multi-J-per-pulse level with an expected repetition rate of greater than 20 Hz. The existing system is ultra-compact, having a table footprint of less than 1 by 4 feet. The demonstrated body of work includes an innovative 200 mJ, 80 ps laser at 1.064 microns with a repetition rate of 1 kHz, developed under an existing Phase II SBIR program. This work will demonstrate the needed laser by building upon, and extending, the 1-kHz repetition rate laser system developed under SBIR funding. The second required system for LICS implementation is a high repetition rate, > 20-Hz, laser with energies-per-pulse exceeding ~1 Joule within the 80-ps detection gate time. ![]() The detection system, an 80-ps gated x-ray imaging camera, has been developed and demonstrated as part of the Inertial Confinement Fusion program. Two key hardware systems are needed to implement LICS. Laser Inverse Compton Scattering (LICS), with time-gated detection of incident laser light up- scattered by high energy electrons into the soft x-ray regime, meets this requirement. To mitigate the shortcoming of present diagnostics, a new diagnostic with adequate temporal and spatial resolution of the runaway electron’s velocity distribution is needed. A proper diagnosis of these runaway electrons is critical to mitigating their formation. Multi-MeV, “runaway” electrons pose a serious risk in tokamak plasmas, capable of inflicting catastrophic damage to the armor and vessel walls.
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