Progress in the Development of the HFML 45 T Hybrid Magnet

Abstract

To extend its user's facilities, the High Field Magnet Laboratory (HFML-EMFL) at the Radboud University is in the process of building a 45-T hybrid magnet. The magnet system will consist of a 22 MW 32.7 T resistive insert and a 600-mmbore 12.3 T superconducting outsert magnet, and the design was significantly adjusted after a thorough design revision in 2011. The HFML hybrid magnet will be operated with separate current sources for the superconducting and resistive coils (20 kA at 10 V and 40 kA at up to 550 V, respectively). The outsert coil is a solenoid layer wound with all-Nb 3 Sn/Cu cable-in-conduit conductor (CICC), cooled by a forced flow of supercritical helium and operated at 20 kA. Similar to the series-connected hybrids for the HZB (Berlin, Germany) and the NHMFL (Tallahassee, FL, USA), the HFML outsert coil contains three grades of conductor. All CICC grades are based on high-current density Nb 3 Sn strand produced by Oxford Superconducting Technology. The CICC production and qualification program has been completed successfully. The coil will be wound at the NHMFL and, after heat treatment and impregnation, sent to Nijmegen for integration into the cryostat. In this paper, the design choices and current status of the program are presented. IndexTerms-CICC, high field magnet, Nb 3 Sn superconductivity. I. INTRODUCTIONT HE High Field Magnet Laboratory at the Radboud University Nijmegen (HFML, partner in the European Magnetic Field Laboratory, EMFL) is developing a 45 T hybrid magnet system, which will consist of a solenoidal 12.3 T Nb 3 Sn-CICC based superconducting outer magnet (outsert) and a 32.7 T Florida-Bitter type resistive inner magnet (insert) with a useful warm bore of 32 mm [1], [2]. After a thorough design review in

High magnetic fields for fundamental physics

“…DC magnetic fields up to about 45 T can be achieved using a hybrid approach, wherein a Bitter-type resistive electromagnet (now the 'insert') is placed within the bore of a large superconducting 'outsert' magnet [150,151]. Using an 11.5 T superconducting outsert and a 33.5 T resistive insert, a 45 T hybrid magnet (32 mm bore) was first demonstrated in 1999 at the NHMFL-Tallahassee.…”

Fabrication of the Nb3Sn/Cu CICC Coil and Cold Mass for the Radboud University HFML 45 T Hybrid Magnet

“…1 on the base plate of the vessel and other cold mass components. A novel bellows system (not pictured) keeps compression on the coil through the thermal cool down and operation [4]. The coil contains five piece lengths of conductor made of three CICC grades.…”

“…The style of the outsert follows the design of the outsert coils of the completed Series-Connected Hybrid magnets (SCH) [2], [3]. The conductors are similar in design although some dimensional improvements have been made [4]. The coils contain the same turns per layer and number of layers as well.…”

A Novel Clamping Method for Resistive Magnets

“…2. Schematic view on the cross-section of the hybrid magnet, from ref [5] showing the coil mounted in its helium-gas filled magnet vessel and connected by a large G10 support ring with the bottom flange of the cryostat. that would result in case there is no cooling.…”