1. magnetic confinement - ENEA - Fusione

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3. FUSION TECHNOLOGY
3.4 Magnets
The first topic is mainly interesting for code validation. What is modelled in thermohydraulic
codes is a transition in cooling regime, the so-called well-cooled regime to
ill-cooled regime. Such a change should depend on flow speed and physically
corresponds to situations where, during a heat generation transient caused, for
example, by an EM external disturbance, all the cooling reservoir contained in the
helium can or cannot be absorbed by the strands. If the heat exchange is effective,
then there should be no dependence of the stability on helium speed.
In measuring the stability, no dependence on the helium flow was found, but the
results obtained from the simulation code were different. This means that probably
the transition zone between well/ill-cooled regimes is not well described in the code.
Due to the difficulties in measuring the helium flow, no final quantitative conclusion
can be drawn, but since the experiment is reproducible, other data can be acquired
to solve the uncertainties.
3.4.5 Test in SULTAN of the ENEA Nb 3
Sn magnet (ITER Task M20)
The ENEA 12-T CIC conductor Nb 3 Sn magnet was dismounted from the Pulsed
Field Facility (PuFF) at ENEA Frascati and modified and assembled in the
configuration for testing in the SULTAN facility at CCRP Villigen, Switzerland. The
magnet is now ready to be shipped as soon as the final test schedule is fixed.
3.4.6 Chemical deposition of oxide buffer layers for YBCO-coated
metallic tapes
The Sol-Gel approach was used to deposit buffer layers of Ca,Gd, Y oxides on
textured metallic substrates. The buffer layers have the double role of avoiding Ni
contamination of the YBCO film and inducing its growth in a well-textured structure.
The Sol-Gel approach is attractive as it is scalable to long-length industrial
manufacture.
After extensive development activities, the appropriate parameters for the chemical
deposition of the oxides were defined.
3.4.7 Development of Nb 3
Al strands for high-field applications
Nb 3 Al strands in a Nb matrix have been found to have significant critical
current density at high fields (B>15T). Their good performance is linked to the
formation of stoichiometric Nb3Al A-15 compound, achievable with the so-called
rapid-heating-quenching technique. A strand formed of a Nb matrix with embedded
Nb-Al unreacted filaments is heated up to 2000°C and then rapidly quenched
below 50°C.
A preliminary prototype of a rapid-heating-quenching apparatus was built and
tested. The experience gained will be used to design an updated version of the
system.
The relevant literature was investigated to check the progress in the experimental
data relative to improving the Nb 3 Al transport properties by addition of a third
element.
The technology implemented for chemical deposition of the buffer layers was
successful and produced layers with good microstructural properties, rugosity and
compactness. The next step will be to develop chemical deposition of YBCO thick
films on top of the metallic-tape + buffer-layer structure.