The 8-T, 1.1 m bore superconducting solenoid for the 40 T hybrid magnet of the Grenoble High Magnetic Field Laboratory

Abstract

Abstrtlct-The Crenoble High Magneiic Field Lriborrrinryis developing n 4 k T Hybrid Mugiief System io srtpporl resefireh irr sfeody, high nmgneticJelds. Oxford Instruments has bee!] selected tu supply the superconiiticlilrg orifsert system for !he hybrid mngtwl. The scope of siipply includes flie sirpercandtiding magnet, the Iiquejler, a 1.8 IC refrigemtor, ,Ire ttyasrrrt, the poww siipp& nnd the coiriroi-pmtectiolt ,rysietn. Tfic srrpercnnrlrrcfini: magne! is II 8-r, 1.8 m lotig nnd 1.1 m bore NBTi solenoid. It will be operaied in n 1.8 K superfluid keliim hnth (11 IilmospReric presstire. 111 order to deveiop the mngfiet, n speciflc R&Dprogr#m has been curried ofif. This pnper will rlescrihe the prirrclpn/ nsprcls vf the project iricluding the mnin results obfnined fo dflte.This paper describes the main features of the superconducting magnet system to be installed at the Grenoble High Magnetic Picld Laboratory (GHMFL) as part of thc 40 T new Hybrid Magnet. The GHMFL Hybrid Mngnet will produce o field of 40 T in a 34 inm bore; the superconducting magnet outsert itself will producc 8 T iii an 1100 m m cold bore while the 24 MW resistive insert will contribute 32 T. Oxford Instruments (0.1.) has been selected as supplier for the siiperconducting magnet system; thc scope of supply includes:Design and construclion ($the superconducting magnet, clyostuf and cryogenic system Refig~rudion-liy~e~er system 1500 A power supply with +/-I ppm sfabiliQ over 30 minutes Control andprotection sy.stemThe main requirements of the system are the following:Cupubilily of the magnet to with.Ttand a resistive inserf trip wilhout ylrmching, When a powcr failure occurs, the current in the resistivc insert decays with a 0.6 s time constant producing up to 3 T / s magnetic field variation on the outscrt. The fast field variation will produce at the same time current iiicrease and AC loss in the superconducting magnct. As a power 19R3 A.Nijliuis et al., 'I Coupling loss timc caiistaiits in iiill4zc Nb,Sn CIC modcl coltducton for fiision magnets ", ICMC '95 Procccdings M.Ohl ct al.,

Investigation of Ramp-Rate Limitation on the Superconducting Magnet for the Grenoble 40-T Hybrid System

“…The observed performance of the magnet was well below previous results obtained on model coils during the design phase ( [1], [3]). Model coils could be energized with rates of 300 A/s and 400 mT/s at 4.2 K without quenching.…”

“…A detailed description of the superconducting magnet (outsert) design has been previously published in [1]- [3]. The outsert has an inductance of 66.3 H and a stored energy of 60.4 MJ at 1350 A.…”

“…During a ramp of the resistive insert, if the superconducting magnet is disconnected from its power supply and dump resistance, the voltage generated at the ends of the reinforcing strip section j can be calculated as: (1) where , and are the mutual inductances between section j of reinforcing strip and, respectively, resistive insert, quench shield and the shorted turn; while and are the current respectively in the resistive insert and the quenchshield and is the current induced in the shorted turn. In particular , can be calculated from:…”

Resistive magnet technology for hybrid inserts

“…To help accommodate this requirement, the outsert includes a novel feature: a cold-worked oxygenfree copper tube installed at the inner diameter of the superconducting coils. When the insert trips, the magnetic flux transient experienced by the superconducting coils should be slowed from 0.6 to 5.0 s by the presence of the high conductivity cylinder [90].…”

Hybrid and Giga-NMR Projects at the Grenoble High Magnetic Field Laboratory

“…It consists of a 32 T resistive magnet developed at the laboratory surrounded by a platform field of 8 T in a 800 mm room temperature bore obtained by three NbTi coils cooled at 1.8 K. The fabrication of the superconducting part has been subcontracted to the Oxford Company. A technical description of this magnet is given in [1]. The final assembly is now undergoing at the laboratory and 40 T should be available to researchers in 2004 with a 34 mm warm bore diameter.…”