High‐speed pellet injection with a two‐stage pneumatic gun

Reggiori, A.; Carlevaro, R.; Riva, G.; Daminelli, Giambattista; Scaramuzzi, F.; Frattolillo, A.; Martinis, L.; Cardoni, P.; Mori, Luan Miranda

doi:10.1116/1.575546

Cited by 5 publications

(1 citation statement)

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“…The ENEA Frascati team has been at the forefront in the development of high-speed pellet injectors, based on the TSG technology, since 1984. A compact and reliable design of the TSG was developed [8], [9], [10], while different techniques for the formation of cryogenic pellets were investigated, with the aim of improving the mechanical strength of D2 ice to better withstand the huge stress during acceleration. In particular, the "in-situ" pellet formation process was optimized to provide accurate control of deuterium freezing parameters; temperatures need to be carefully controlled during pellet formation under a constant D2 gas pressure, and then smoothly lowered to ~7 K and kept stable to ensure good resistance of cryogenic projectiles.…”

Section: The Enea-ornl High-speed Pellet Injectormentioning

confidence: 99%

Core Fueling of DEMO by Direct Line Injection of High-Speed Pellets From the HFS

Frattolillo

Baylor

Bombarda

et al. 2018

IEEE Trans. Plasma Sci.

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Pellet injection represents to date the most realistic candidate technology for core fueling of a DEMO tokamak fusion reactor. Modelling of both pellet penetration and fuel deposition profiles, for different injection locations, indicates that effective core fuelling can be achieved launching pellets from the inboard high field side at speeds not less than 1 km/s. Inboard pellet fueling is commonly achieved in present tokamaks, using curved guide tubes; however, this technology might be hampered at velocities  1 km/s. An innovative approach, aimed at identifying suitable inboard "direct line" paths, to inject high-speed pellets (in the 3 to 4 km/s range), has been recently proposed as a potential complementary solution. The fuel deposition profiles achievable by this approach have been explored using the HPI2 simulation code. The results presented here show that there are possible geometrical schemes providing good fueling performance. The problem of neutron flux in a direct line of sight injection path is being investigated, though preliminary analyses indicate that, perhaps, this is not a serious problem. The identification and integration of straight injection paths suitably tilted may be a rather difficult task, due to the many constraints and to interference with existing structures. The suitability of straight guide tubes to reduce the scatter cone of high-speed pellets, is therefore of main interest. A preliminary investigation,, aimed at addressing these technological issues, has been recently started. A possible implementation plan, using an existing ENEA-ORNL facility is shortly outlined. Index Terms-DEMO tokamak fusion reactor, HFS highspeed pellet injection, straight guide tubes Manuscript received June 2017. This work has been carried out within the framework of the EUROfusion Consortium and has received funding from the Euratom research and training programme 2014-2018 under grant agreement No 633053. The views and opinions expressed herein do not necessarily reflect those of the European Commission.

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Section: The Enea-ornl High-speed Pellet Injectormentioning

confidence: 99%

Core Fueling of DEMO by Direct Line Injection of High-Speed Pellets From the HFS

Frattolillo

Baylor

Bombarda

et al. 2018

IEEE Trans. Plasma Sci.

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Pellet injection technology

Combs

1993

Review of Scientific Instruments

141

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During the last 10 to 15 years, significant progress has been made worldwide in the area of pellet injection technology. This specialized field of research originated as a possible solution to the problem of depositing atoms of fuel deep within magnetically confined, hot plasmas for refueling of fusion power reactors. Using pellet injection systems, frozen macroscopic (millimeter-size) pellets composed of the isotopes of hydrogen are formed, accelerated, and transported to the plasma for fueling. The process and benefits of plasma fueling by this approach have been demonstrated conclusively on a number of toroidal magnetic confinement configurations; consequently, pellet injection is the leading technology for deep fueling of magnetically confined plasmas for controlled thermonuclear fusion research. Hydrogen pellet injection devices operate at very low temperatures (≂10 K) at which solid hydrogen ice can be formed and sustained. Most injectors use conventional pneumatic (light gas gun) or centrifuge (mechanical) acceleration concepts to inject hydrogen or deuterium pellets at speeds of ≂1–2 km/s. Pellet injectors that can operate at quasi-steady state (pellet delivery rates of 1–40 Hz) have been developed for long-pulse fueling. The design and operation of injectors with the heaviest hydrogen isotope, tritium, offer some special problems because of tritium’s radioactivity. To address these problems, a proof-of-principle experiment was carried out in which tritium pellets were formed and accelerated to speeds of 1.4 km/s. Tritium pellet injection is scheduled on major fusion research devices within the next few years. Several advanced accelerator concepts are under development to increase the pellet velocity. One of these is the two-stage light gas gun, for which speeds of slightly over 4 km/s have already been reported in laboratory experiments with deuterium ice. A few two-stage pneumatic systems (single-shot) have recently been installed on tokamak experiments. This article reviews the equipment and instruments that have been developed for pellet injection with emphasis on recent advances. Prospects for future development are addressed, as are possible applications of this technology to other areas of research.

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