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Thermal analysis of the RFX-mod2 operating conditions for the design of the temperature measurement system

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Abstract

High heat fluxes are exchanged in fusion machines (up to 50 MW m−2), thus producing elevated temperature and requiring thermal monitoring and control. The design of a temperature measurement system for the RFX experiment is developed through three-dimensional nonlinear transient finite element simulations of the torus assembly under upgrade from “mod” to “mod2” with enhanced magnetic front-end, vacuum confinement barrier, and first wall. Analyses show how heat fluxes applied at the plasma-facing materials are transmitted, attenuated and delayed, through the machine parts. Results identify the passive stabilising shell as the instrumentable component closest to the plasma boundary able to follow the thermal behaviour by the detection of temperature variations at least of 10 °C during plasma pulses with a response time of about 200 s. Allowable temperature limits of materials are verified simulating a full experimental day with 24 plasma pulses, in particular at the shell supporting rings made of polyamide-imide and at the vessel spacers made of polyether-ether ketone-coated stainless steel. Simulations of the pulse discharge cleaning demonstrated the capability of the system to provide the required power for first wall conditioning (25 kW) and the need to realise a duty cycle (1-h on/3-h off) limiting the average heat flux and the maximum temperature (55 °C) at the vacuum vessel sealing elements in order to minimise differential thermal deformations. Proposed layouts of temperature sensors are able to detect the maximum temperatures expected during operation.

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taken from the pulse file of RFX-mod; high energy pulse considered to simulate pulsed operation (0.5 s duration, 2.0 MA maximum plasma current, 15.5 MJ transferred energy to the plasma, and 1.5 MJ transferred to the vacuum vessel). (Color figure online)

Fig. 4

taken from the pulse file of RFX-mod; disruption considered to simulate locked mode (0.1 s pulse duration, 1.8 MA maximum plasma current, 11 MJ transferred to the plasma, and 2.5 MJ transferred to the vacuum vessel). (Color figure online)

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Acknowledgements

The work leading to this publication is co-funded in the framework of the industrial innovation Project MIAIVO, Granted by Regione Veneto POR-FESR 2014–2020 (Regional Operational Program for the European Regional Development Fund).

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Authors and Affiliations

  1. Consorzio RFX, 4 Corso Stati Uniti, Padova, Italy

    Mauro Dalla Palma, Roberto Cavazzana, Andrea Erculiani, Giulio Gambetta & Simone Peruzzo

  2. CNR - Istituto per la Fisica e Tecnologia dei Plasmi, 4 Corso Stati Uniti, Padova, Italy

    Mauro Dalla Palma

Authors
  1. Mauro Dalla Palma
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  2. Roberto Cavazzana
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  3. Andrea Erculiani
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  4. Giulio Gambetta
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  5. Simone Peruzzo
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Contributions

MDP conceived the presented study, verified results with analytical methods, and wrote the manuscript. AE and GG developed the models and performed the computations. RC supported the identification of accurate thermal loading conditions inferred from past experimental measurements. MDP and SP supervised the findings of this work. SP supported and monitored the activity as project manager.

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Correspondence to Mauro Dalla Palma.

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Dalla Palma, M., Cavazzana, R., Erculiani, A. et al. Thermal analysis of the RFX-mod2 operating conditions for the design of the temperature measurement system. J Therm Anal Calorim 142, 2061–2075 (2020). https://doi.org/10.1007/s10973-020-10351-4

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  • DOI: https://doi.org/10.1007/s10973-020-10351-4

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