Lessons learned after three years of SPIDER operation and the first MITICA integrated tests

https://doi.org/10.1016/j.fusengdes.2023.113590Get rights and content

Abstract

ITER envisages the use of two heating neutral beam injectors plus an optional one as part of the auxiliary heating and current drive system, to reach the desired performances during its various phases of operation. The 16.5 MW expected neutral beam power per injector is several notches higher than worldwide existing facilities.

In order to enable such development, a Neutral Beam Test Facility (NBTF) was established at Consorzio RFX, exploiting the synergy of two test beds, called SPIDER and MITICA. SPIDER is dedicated developing and characterizing large efficient negative ion sources at relevant parameters in ITER-like conditions: source and accelerator located in the same vacuum where the beam propagates, immunity to electromagnetic interferences of multiple radio-frequency (RF) antennas, avoidance of RF-induced discharges on the outside of the source. Three years of experiments on SPIDER have addressed to the necessary design modifications to enable full performances. The source is presently under a long shut-down phase to incorporate learnings from the experimental campaign, in particular events/issues occurred during operation, which led to the identification of improvement opportunities/necessities (e.g. RF discharges, local burns, water leaks, other damages, configuration/design upgrades to maximize chances/margin to quest target parameters).

Parallelly, developments on MITICA, the full-scale prototype of the ITER Neutral Beam Injector (NBI) featuring a 1 MV accelerator and ion neutralization, are underway including manufacturing of the beam source, accelerator and the beam line components, while power supplies and auxiliary plants, already installed, are under final testing and commissioning.

Integration, commissioning and tests of the 1 MV power supplies are essential for this first-of-kind system, unparalleled both in research and industry field. 1.2 MV dc insulating tests of high voltage components were successfully completed. The integrated test to confirm 1 MV output by combining invertor systems, DC generators and transmission lines extracted errors/accidents in some components. To realize a concrete system for ITER, said events have been addressed and solutions for the repair and the improvement of the system were developed.

Hence, NBTF is emerging as a necessary facility, due to the large gap with existing injectors, effectively dedicated to identify issues and find solutions to enable successful ITER NBI operations in a time bound fashion. The lessons learned during the implementation on NBTF and future perspectives are here discussed.

Introduction

The ITER Neutral Beam Test Facility (NBTF) is targeted at the development and testing up to nominal performances of the full-scale prototype of the ITER Heating Neutral Beam Injector (HNB) [1], [2], [3].

The NBTF is established in Padova (Fig. 1), integrated in an international framework of responsibility and collaboration among Consorzio RFX, ITER Organization (IO), Fusion for Energy and JADA/QST with the involvement of some European research institutes; it is strictly liaised with the Indian Test Facility (INTF) in charge of the ITER Diagnostic Neutral Beam (DNB) [4].

Two test beds are foreseen on NBTF site: SPIDER features the first prototype of ITER ion source, with strong similarities with DNB configuration, while MITICA is the 1:1 scale prototype of ITER HNB.

In 2021, after three years of operation, SPIDER entered a long shut down phase with the aim of solving issues arising and detected during the first operational phase. MITICA is in the final construction phase of the injector, with all the auxiliary systems installed and with the final integrated tests of the overall power supply underway.

Efforts are being paid in synergy with other experiments worldwide focusing on negative ion based neutral beams, in particular in Japan and India, in relation to their direct involvement in ITER and in the NBTF, and also in Europe, supported by EUROfusion, for the challenging RF source development.

Section snippets

SPIDER

SPIDER experiment (Fig. 2), the third leg in EUROfusion step ladder approach towards ITER source for NB injectors, together with BUG and ELISE at IPP-Garching [5], represents a novelty in the negative ion sources for many aspects related not only to the dimensions. Among the most impacting factors, it is necessary to highlight that, unlike any other existing NBIs, the entire beam source of SPIDER (and MITICA) lies inside the vacuum vessel, so that it is surrounded by the same background gas at

MITICA

MITICA, the one-to-one prototype for ITER HNB, is gradually approaching the start of operation.

Prior to that, three main areas of work are being dealt with in order to complete the whole experiment assembly, testing and commissioning:

  • -

    Last components/plants still under completion [43]

  • -

    Power supply integrated final tests and specific commissioning

  • -

    Preparation for a dedicated campaign of HV holding tests in vacuum

Conclusions

SPIDER is entering the first long shutdown after the first three years of experiments. Interesting results have been obtained at reduced performances, which have also identified necessary modifications, mainly focused on source upgrade, RF generators replacement and enhancement for the vacuum pumping system, in order to quest the target performances during the next operational phase.

MITICA is proceeding towards the end of preparatory activities prior to the start of the first experimental

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgment and disclaimer

This work has been carried out within the framework of the ITER-RFX Neutral Beam Testing Facility (NBTF) Agreement and has received funding from the ITER Organization.

This work has also been carried out within the framework of the EUROfusion Consortium, it has been funded by the European Union via the Euratom Research and Training Programme (Grant Agreement No 101052200 — EUROfusion).

Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the

References (51)

  • M.J. Singh

    R&D status of the Indian test facility for ITER diagnostic neutral beam characterization

    Nucl. Fusion

    (2019)
  • D. Wünderlich

    NNBI for ITER: status of long pulses in deuterium at the test facilities BATMAN Upgrade and ELISE

    Nucl. Fusion

    (2021)
  • E. Sartori

    Influence of plasma grid-masking on the results of early spider operation

    Proceedings for this SOFT congress

    (2023)
  • A. Pimazzoni

    Assessment of the SPIDER beam features by diagnostic calorimetry and thermography

    Rev. Sci. Instrum.

    (2020)
  • M. Barbisan

    First results from beam emission spectroscopy in SPIDER negative ion source

    Plasma Phys. Control. Fusion

    (2021)
  • N. Marconato

    Integration of new sets of magnets for improved plasma confinement in the SPIDER experiment

    Proceedings for this SOFT congress

    (2023)
  • E. Sartori

    First operations with caesium of the negative ion source SPIDER

    Nucl. Fusion

    (2022)
  • C. Gasparrini

    Status of the SPIDER source after 3.5 years operation, proceedings for this SOFT congress A. Luchetta et al., As built design of the control system of the ITER full-size beam source SPIDER in the Neutral Beam Tests Facility - A critical review

    Proceedings for this SOFT congress

    (2023)
  • G. Manduchi

    CODAS for long lasting experiments. The SPIDER experience

    Proceedings for this SOFT congress

    (2023)
  • G. Serianni

    SPIDER real-time data visualization tool

    Proceedings for this SOFT congress

    (2023)
  • L. Grando

    As built design, commissioning and integration of the SPIDER and NBTF central safety systems

    Proceedings for this SOFT congress

    (2023)
  • M. Bigi

    An update of the design of SPIDER Ion Source and Extraction Power Supplies after four years of operation

    Proceedings for this SOFT congress

    (2023)
  • M. Recchia

    Improvement in the electrical design of the SPIDER beam source

    Proceedings for this SOFT congress

    (2023)
  • A. Maistrello

    Overview on electrical issues faced during the SPIDER experimental campaigns

    Proceedings for this SOFT congress

    (2023)
  • R. Zagorski

    2D simulations of inductive RF heating in the drivers of the SPIDER device

    proceedings for this SOFT congress

    (2023)
  • Cited by (0)

    View full text