SPIDER 4 ITER: the largest Ion Beam Source in the world has been switched on
There is a big step forward at Consorzio RFX (the fusion research unit in Padova, Italy – partners: CNR, ENEA, INFN, Università di Padova, Acciaierie Venete Spa): SPIDER, the full-scale ITER negative ion beam source prototype has entered into operation. The first pulse was carried out on 11 June 2018, during an international inauguration ceremony which saw the participation of about 360 attendees from Europe, Japan, India and Russia.
The negative ions are electrostatically accelerated to the high energy needed to enter the core of the advanced thermonuclear device ITER. After acceleration, the beam must be neutralised in order to penetrate through the magnetic field confining the hot plasma. At those energies, the cross section for the neutralisation of negative ions is much higher than that for positive ones. Negative Hydrogen ion has, in fact, only one weakly bound state, which allows for a highly efficient neutralisation system. The price to pay for this advantage is the difficulty of producing the negative ions and extracting them from the ionisation chamber. This is the challenge to face in SPIDER.
The aim in ITER is to reach a plasma temperature of 150 million degrees, which asks for the demanding specification of 1 MeV energy and 50 MW power from three injection modules capable of operating for up to 3600 seconds: a big jump from current state-of-the-art injectors developed so far in fusion devices, which has called for a dedicated test bed facility- the Neutral Beam Test Facility – the realisation of which has been entrusted to the Padova Group for Fusion Research, Consorzio RFX, Italy, within the framework of an Europe, Japan and India collaboration.
The NBTF project implies the realisation of SPIDER, the 100keV ion source prototype for the optimisation of negative ion source production, and MITICA, the full-scale ion beam injector prototype.
The first big milestone of the NBTF plant has successfully been reached with the start of SPIDER operation on 11 June 2018; the start of MITICA operation is scheduled for 2022.
2 BOXES
1 – Consorzio RFX: a cradle of competences
In parallel to a long standing (since the 70’s) expertise and achievements in scientific and technological study of ohmically heated self-organized plasma confinement, the RFX laboratory has been deeply involved in neutral beam injection studies for plasma heating for the last two decades. This capacity of diversification comes from physics and engineering competences integrated to advance both in plasma magnetic confinement and fusion technology.
STAFF 160 people: 80 researchers, half of them physicists and half engineers, supported by a team of about 60 technicians and 20 administrative staff.
2 – SPIDER (Source for Production of Ion of Deuterium Extracted from Rf plasma) is devoted to test and develop one of the most critical components of the ITER heating neutral beam injection system: the negative ion source of deuterium (D-) and hydrogen (H-). SPIDER will be equipped with a set of diagnostic systems that will allow a detailed study of the generated beam and its thorough optimisation.
References
- R. N. Hill, “Proof that the H- Ion Has Only One Bound State”. Phys. Rev. Lett. 38, 643 (1977)
- G. Serianni et al., Neutralisation and transport of negative ion beams: physics and diagnostics. New Journal of Physics, 19 045003, (2017).
- R. Lorenzini et al., Self-organized helical equilibria as a new paradigm for ohmically heated fusion plasmas. Nature Physics, vol 5, pag 570-574, (2009).
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