The SEHT facility, which was created to generate an 8 T magnetic field in a large volume, uses a solenoid winding with an NbTi conductor assembled from double pancake coils cooled in a superfluid helium bath at 1.8 K and 1.2 bar absolute. The SEHT solenoid is a reconditioned superconducting coil previously used in the 35 T hybrid magnet at LNCMI in Grenoble. The SEHT facility in building 198 has already been used for the ISEULT project to validate experimentally the technological concepts used (1.8 K cryogenics, electrical circuit, instrumentation and control, conductor validation, protection and mechanical resistance of the future magnet under a magnetic field, stabilization and magnetic screening principle).
The 8 T magnetic field offers a large diameter vertical test zone (usable diameter of 587 mm at 300 K), which can accommodate samples or components at room temperature or in a special cryostat.
Following the R1 tests carried out until early 2013 for the ISEULT project (tests on the coil superconducting wire under stress), the associated cryogenic supply system (the CELLO liquefier) was redeployed to the JT-60SA area in building 126, interrupting the use of the facility. However, because of the facility’s stand-alone configuration (it has its own control systems, power supply, protection, 1.8 K pumping system, LN2) and because its helium supply provided by a dedicated satellite cryogenic system is so versatile (from 6 K SHe or from 4.2 K LHe), there are plans for the facility to be brought back into operation using either the 4003 liquefier in the west part of building 198 (short term) or the CELLO liquefier (long term) in building 126.
. In both cases, the liquid helium (LHe) can be transferred by installing a Nexans LHe/GHe coaxial transfer line (e.g. Kabelmetal) to reduce thermal loss over a long distance of tens of meters. SEHT’s cryogenic consumption during 8 T operation is approximately 60 l/hour (excluding LN2 cooling), which is compatible with the capacity of the two nearby liquid helium sources (120 l/hour for CELLO and 70 l/hour for 4003), if the simple LHe supply method is used. The electrical equipment (high-current power supplies), cryogenic systems (LN2, LHe sources, He circuitry), diagnostic equipment (rapid multi-channel acquisition) and handling equipment (10 to 50 metric tonne overhead cranes) available in the SCHEMA area (Building 198 East), where the SEHT station is located, mean that large components could now be tested under magnetic fields up to 8 T. In particular, in the context of R&D programs on superconductors for future cryomagnetic projects, this facility should enable the measurement of performance under strong magnetic fields of single or coiled high critical temperature superconductors and should also allow cold mass tests to be performed on the Nb3Sn magnets in the new high field accelerator magnets.