LNF:Estudios del confinamiento mejorado y de impurezas en los Stellarators TJ-II y W7-X mediante inyección de pastillas criogénicas (Pellets) y encapsulados de impurezas (TESPEL)
LNF - Nationally funded project
Title: Estudios del confinamiento mejorado y de impurezas en los Stellarators TJ-II y W7-X mediante inyección de pastillas criogenicas (Pellets) y encapsulados de impurezas (TESPEL)
Reference: PID2023-148697OB-I00
Programme and date: Proyectos de Generación de Conocimiento 2023
Programme type (Modalidad de proyecto): Proyectos investigación orientada
Area/subarea (Área temática / subárea): Energy & Transport / Energy
Principal Investigator(s): Isabel García-Cortés Kieran Joseph McCarthy
Project type: Proyecto individual
Start-end dates: 01/09/2024 - 31/08/2027
Financing granted (direct costs): 130.000 €
Description of the project
The aim of this project, which falls within the realm of magnetic confinement fusion, is to continue and broaden the research initiated in projects ENE2013-48679-R, FIS2017-89326-R and PID2020-116599RB-I00 on fuelling and impurity control in plasmas created in the stellarators TJ-II (Ciemat, Madrid), W7-X (Greifswald, Germany) and LHD (Toki, Japan). This research aims to investigate issues related to these two issue which are critical for achieving steady-state operation of helical-type fusion reactors. In particular, it is necessary to identify operational scenarios that ensure adequate plasma fuelling and short impurity confinement times, in particular, for heavy ions. It is intended that this work will support the European stellarator programme and contribute to the development and scientific exploitation of stellarators, a priority highlighted in the document "Fusion Electricity: a roadmap to the realization of fusion energy" (EFDA 2012).
1. The first aim is to investigate aspects of plasma fuelling that are still not fully understood and the effects of fuel pellets on plasma magnetic activity, plasma turbulence and plasma performance. For this, the medium-sized heliac TJ-II will be used. It is equipped with a cryogenic pellet injector (PI) for producing solid hydrogen pellets that can be injected at high velocity into the plasma. It is intended to investigate pellet fuelling as a means to enhance plasma confinement (higher stored energy, longer particle confinement) and to identify and explore new pellet phenomena. While TJ-II is equipped with a large number of modern diagnostics, it is proposed to develop a new system to measure pellet cloud density and temperature to extend knowledge of pellet physics.
2. The second aim is to continue to support impurity transport studies in TJ-II, W7-X and LHD. Under the umbrella of a trilateral collaboration (2020-2029) with the National Institute for Fusion Science (Japan) and IPP-Max-Planck (Greifswald, Germany), the Tracer-Encapsulated Solid Pellet (TESPEL) method is now employed on TJ-II, W7-X and LHD. TESPELs are polystyrene spheres (diameter <1 mm) loaded with small quantities of selected impurities (atomic elements other than fuel). Thus, TESPEL allows delivering a precise quantify of tracer to a preselected location in the plasma core, after which its transport can be studied. An important aspect of previous projects was the establishment of a laboratory to fabricate TESPELs at Ciemat. Thus, key parts of this current project are to continue TESPEL fabrication at this laboratory, thereby allowing Ciemat to maintain its fruitful collaborations with W7-X and LHD. Finally, during recent experiments with TESPEL at LHD, project members observed that mid-/high- Z atomic ions can be flushed out of the high-density plasmas if Li-granules are dropped continuously into the plasma edge. Compared to reference plasmas, confinement times of high-Z ions were reduced by a factor 4 or more. Further work will be done here to explore this new operational scenario for stellarators.
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