IRIS NAPOLI
The objective of this WP is the establishment of an Advanced Instrumentation Laboratory (AIL) to create, test, and validate innovative diagnostics systems based on new instruments and on machine learning techniques.
Testing systems will be used for controlling the assembly and the correct quality of the HTS Cable (green SC line) and HTS Magnet. A civil engineering task is included to create the test site, alongside the infrastructure needed to perform cryogenic tests.
Instruments for Functional Tests will be developed to detect impurities, and structural damage due to twisting and bending that may occur during the cabling of MgB2. The system shall be capable of detecting online resistance variations at µΩ level, and current variations with similar level of accuracy. Machine Learning techniques will be applied to data to detect anomaly thresholds for this testing procedure. Machine Learning is chosen instead of Pre-trained Artificial Neural Networks, due to lack of training data sets.
Another component of the Test System will check the critical current of the HTS cable-pairs, which will be measured to better than 1% precision using a Cryogenic DC Current Transformer (DCCT), capable of measuring critical current at 100kA power levels.
The integrity of the HTS Cable will be controlled by a monitoring system. The technique uses Fibre Bragg Grating sensors and refractive index variation to monitor temperature and strain along the cable length. Machine Learning technique will be used for real time analysis of data to proactively predict impending Quench and/or mechanical damage.
Regularly spaced sensors, inside the cable cryostat, will be connected to a data sending unit, preferably of wireless type with low-power, low-bit rate, long range type. This ensures that data reaches the control station even in presence of a catastrophic event that would impede wired connectivity.
A test system to measure the electrical and magnetic performances of the new generation of magnets will also be designed and built, capable of providing global picture (coil segment impedance, resistance to ground, joint resistance, etc.), and their evolution during various construction and operating phase. The system will also be an up-to-date quench detection and protection unit (but not including the power part of the protection).
A cryogenic test station will be employed to test the superconducting cable samples and the related equipment at operating temperature. The experimental apparatus will consist of a cryostat in which the sample will be inserted, connected through the upper flange to a cryocooler. For greater flexibility, the test station can provide cooling at 77K using liquid nitrogen, or lower temperature, as low as 4K. The test station will allow connecting simultaneously different types of probes for internal measurement, ensuring proper thermal insulation. A key component of the test system is a sensitive control unit to have a tight control of the temperature set point.
In parallel with tests performed on wires, tapes and full cables, mapping of magnetic field penetration in the superconductors critical state will be performed on cm-size samples of cables and tapes, resorting to magneto-optic Kerr effect (MOKE) imaging in applied magnetic field. Our measurements will allow us to correlate the pinning strength, i.e., the critical current of the samples with magnetic field penetration, vortex formation and vortex dynamics. This task will be operated jointly by the CNR-SPIN-NA Unit, which has a well-established tradition in superconductivity, magnetism and cryogenic techniques, and the UNINA-DIFI Unit, in which a long-standing expertise on materials characterization by optical techniques is available. CNR-SPIN-NA will take care of the setup of the apparatus allowing optical access to a cooled superconducting sample in a magnetic field, while measuring its magneto transport properties. UNINA-DIFI will take care of the optical and imaging setup. The three UOs of the WP will work on the joint interpretation of the data collected with the different techniques
INFN - Napoli
NA- DIFI - Università degli Studi di Napoli “Federico II
CIRMIS - Università degli Studi di Napoli “Federico II”
Spin- Na - Consiglio Nazionale delle Ricerche Napoli
