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MRI Magnets
Published in David A. Cardwell, David C. Larbalestier, Aleksander I. Braginski, Handbook of Superconductivity, 2022
Michael Parizh, Wolfgang Stautner
As of now, Iseult (Figure H1.3.57) is the only actively shielded, 900 mm aperture, 500 MHz MRI magnet. Multiple challenging design options of an ultra-high-field MRI magnet have been reviewed with the engineering background of high energy physics (CERN) and thermonuclear fusion magnet (Tore Supra). This work has led to a non-traditional design [45, 133]. The section is summarizing the main technical challenges and design solutions developed. The main parameters of the scanner are shown in Table H1.3.12. The magnet parameters are given in Table H1.3.13.
The Development and Testing of a Digital ITER-Type Mock-Up Based on Virtual Reality Technology
Published in Fusion Science and Technology, 2021
Jin-Yang Li, Long Gu, Hu-Shan Xu, You-Peng Zhang, Cun-Feng Yao, Da-Jun Fan, Guan Wang, Xin-Kang Su
With the development of computer-aided geometric design and graphics rendering technology, the virtual reality (VR) method in scientific research work has received wide attention and has been applied in visualization of complicated experiment facilities with numerical simulation results,6 which can achieve real-time roaming and inspecting in the corresponding environment and execute online analysis and fault diagnosis with the demonstration of scientific datasets. Many research groups have proved that VR technology has the potential to tackle budgetary pressure and to make cooperation work more efficient. For example, the real-time visualization system for the radiation dose field of the Joint European Torus (JET) has been established in combination with Visual ToolKit (VTK) for the purpose of minimizing the dose and prolonging the lifetime of the corresponding vital components.7 Additionally, a remote-handling virtual environment has been developed and applied in the operation cycle and design progress for the Aditya tokamak device in order to tackle various difficulties in the complicated in-vessel radiation environment.8 Moreover, the welding task simulation and assessment of the maintenance feasibility for the fusion components in the Tore Supra tokamak have been analyzed in combination with the VR technology and the dynamic biomechanical feedback method to solve the limitations in the very tight and confined operation environment.9
Pellet-Injector Technology—Brief History and Key Developments in the Last 25 Years
Published in Fusion Science and Technology, 2018
Before the benefits from HFS pellet injection on tokamaks were known (discussed in Sec. III), a significant amount of development was ongoing around the world to produce speeds greater than 2000 m/s. The three advanced techniques that seem to still be the most promising are (1) the two-stage light gas gun, (2) the electro-thermal accelerator, and (3) the electro-magnetic rail gun. While all of these techniques have been used to accelerate cryogenic pellets in the lab, two-stage guns have even been used to inject pellets into fusion plasmas.3 The highest speed reported with “bare” D2 pellets was over 4000 m/s with a two-stage gas gun on the Tore Supra tokamak.51 To be useful for plasma fueling of large and future fusion experiments, pellet injectors must be capable of operating repetitively for long pulses. Of the three leading candidates, the two-stage gas gun is the only one that has demonstrated repetitive operation with D2 pellets. Frattolillo et al.52,53 reported speeds of up to 2500 m/s at a repetition rate of 1 Hz with 2.7-mm D2 pellets in lab experiments; a batch extruder like that shown in Fig. 5 was used to supply the solid material. Any acceleration method would need to be able to perform reliably at higher pellet rates (>5 Hz) to be considered for plasma fueling applications on most present and future fusion experiments. More information on pellet acceleration with centrifuges and advanced techniques is readily available in the literature (most of the early work is referenced in the review papers previously called out).3,4,45
Thermal Analysis on Various Design Concepts of ITER Divertor Langmuir Probes
Published in Fusion Science and Technology, 2018
L. Chen, W. Zhao, G. Zhong, C. Watts, James P. Gunn, X. Liu, Y. Lian
The LPs have been successfully utilized in nearly every tokamak in the world, such as JET (Ref. 2), DIII-D (Ref. 3), Tore Supra,4 ASDEX-U (Ref. 5), EAST (Ref. 6), and HL-2A (Ref. 7). In all cases, the LPs are designed to withstand either short-pulse high heat flux and then allowed to cool between discharges, or else suffer long duration but lower heat flux. The ITER LPs, on the other hand, will be required to withstand high power, long pulses up to 1000 s, which presents a number of challenges predominantly associated with extreme heat loads. These include severe incident heat flux (plasma, photons, and energetic neutrals emanating from charge exchange reactions) on its plasma-facing tips, irradiation from neutral particles and photons to the sides (Fig. 1), and volumetric nuclear heating due to neutron irradiation. To make matters worse, the LPs cannot be equipped with an active cooling system and must instead rely on passive cooling through attachment to the divertor targets. This results in limited heat removal by the divertor, which makes thermal damage a big obstacle to the design. For the original conceptual design, the LPs were bolted to the divertor target monoblock. (Monoblocks are the tungsten plasma-facing elements of the divertor targets which are strung along and bonded to a copper pipe to provide active divertor cooling.8) Thermal analysis results indicate that there is a high risk of damage to the LPs due to the heat transfer resistance of the bolted interface. Recently, three alternative options have been proposed during the Preliminary Design Review (PDR) phase. In this technical note the power-handling capability, damage risk, and interface challenges of these options are compared.