Elsevier

Fusion Engineering and Design

Volume 146, Part B, September 2019, Pages 1703-1707
Fusion Engineering and Design

Constraints on conceptual design of diagnostics for the high magnetic field COMPASS-U tokamak with hot walls

https://doi.org/10.1016/j.fusengdes.2019.03.020Get rights and content

Highlights

  • Main constraints influencing the conceptual design of diagnostics for COMPASS-U were identified.

  • Diagnostic solutions for the hot vacuum vessel, high plasma densities and high heat flux densities are proposed.

  • Spatial constraints at COMPASS-U are reviewed and possible solutions indicated.

Abstract

COMPASS-U, a high magnetic field tokamak with hot walls, will be designed and built at IPP Prague. Unique features of this new device bring noticeable constraints and requirements on plasma diagnostics, which make their development highly demanding. In this paper, the main expected constraints influencing the conceptual design of diagnostic tools for COMPASS-U (high temperature of the vacuum vessel, high plasma density, high heat flux density, strong auxiliary plasma heating, spatial constraints, liquid metals in the divertor) are reviewed and possible solutions are indicated.

Introduction

The project for the design and construction of the high magnetic field COMPASS-U tokamak with hot walls [1] (major radius R = 0.894 m, minor radius a = 0.27 m, plasma elongation 1.8, triangularity less than 0.6, toroidal magnetic field BT on axis 5 T, plasma current Ip = 2 MA for safety factor at the edge q95 = 2.4, 1 s long flat-top at full plasma parameters), started at IPP Prague in 2018. Unique features of this new device caused by a combination of its compactness, plasma parameters linked to a high magnetic field and strong auxiliary heating (4 MW NBI, 2 MW ECRH) and hot walls (300 °C) bring constraints and requirements, which make the development of necessary plasma diagnostics highly demanding. Among the most important features of COMPASS-U leading to consideration of new diagnostic designs there are: a high temperature of the vacuum vessel (VV); a high plasma density (up to 5*1020 m−3); a high heat flux density; cooled copper-based and vertically symmetric magnetic field coils; and finally, the proposed future use of the liquid metal divertor. As a consequence, the diagnostic designs will require dedicated solutions for all in-vessel components. Last but not least, liquid metals proposed to be used in the divertor introduce the question of the material compatibility, mainly at elevated temperatures, and their transport and re-deposition on in-vessel components, including those important for optical diagnostics. Maintenance of installed systems will be ensured using the human access to the vacuum vessel or using their redundancy. In the next sections, the main expected constraints influencing the conceptual design of individual diagnostic tools for COMPASS-U are reviewed and examples of possible solutions are indicated.

Section snippets

Hot vacuum vessel and in-vessel components

The COMPASS-U tokamak, being equipped with a conventional closed divertor made from a solid material, will be able to regulate the amount of wall-stored fuel particles and reach a high recycling regime via an elevated temperature of the VV [2]. Therefore, the VV is designed to withstand 500 °C and all removable parts (plasma facing components, diagnostics) should be able to operate up to 300 °C, being kept at a predefined temperature by an active heating system of the VV. Also, a low recycling

Summary and outlook

The construction of COMPASS-U, a high magnetic field tokamak with hot walls, brings many constraints on plasma diagnostics, which can be also met on either already present or on near future-planned fusion relevant devices. In our short review, the most important problems were named and possible ways, how they can be bridged, were indicated, including necessary future R&D.

Acknowledgments

This work has been carried out within the framework of the project COMPASS-U: Tokamak for cutting-edge fusion research (No. CZ.02.1.01/0.0/0.0/16_019/0000768) and co-funded from European structural and investment funds.

References (45)

  • R. Panek

    Fusion Eng. Des.

    (2017)
  • C. Vorpahl

    Fusion Eng. Des.

    (2013)
  • H. Meister

    Fusion Eng. Des.

    (2017)
  • K.Yu. Vukolov

    Fusion Eng. Des.

    (2017)
  • R.A. Pitts

    Nucl. Mater. Energy

    (2017)
  • R. Chatterjee

    Fusion Eng. Des.

    (2001)
  • R.E. Nygren et al.

    Nucl. Mater. Energy

    (2016)
  • W. Xu

    J. Nucl. Mater.

    (2011)
  • K. Hanada

    Nucl. Fusion

    (2017)
  • D.P. Boyle

    Phys. Rev. Lett.

    (2017)
  • A. Cosler et al.

    Proceedings of the Symposium on Engineering Problems of Fusion Research

    (1979)
  • J.-M. Moret

    Rev. Sci. Instrum.

    (1998)
  • E.J. Strait

    Rev. Sci. Instrum.

    (2006)
  • S.G. Lee et al.

    Rev. Sci. Instrum.

    (2001)
  • E.J. Strait

    Fusion Sci. Technol.

    (2008)
  • S.G. Lee et al.

    Rev. Sci. Instrum.

    (2006)
  • E.J. Strait

    Rev. Sci. Instrum.

    (1996)
  • J. Gernhardt

    Report IPP--1/262

    (1992)
  • J.G. Bak et al.

    Rev. Sci. Instrum.

    (2004)
  • T. Roche

    Rev. Sci. Instrum.

    (2018)
  • S. Entler

    “Prospects for the steady-state magnetic diagnostic based on antimony Hall sensors for future fusion power reactors”, P3.073

    Fusion Eng. Des.

    (2019)
  • I. Duran

    “Status of steady-state magnetic diagnostic for ITER and outlook for possible materials of Hall sensors for DEMO”, P4.061

    Fusion Eng. Des.

    (2019)
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