Mon-Af-Po1.01-05 1 Design and Fabrication of the 1.9 K Magnet Test Fa- cility at BNL, and Test of the First 4 m-Long MQXF Coil J. Muratore, M. Anerella, P. Joshi, P. Kovach, A. Marone, P. Wanderer Abstract— The future high luminosity upgrade of the Large Had- vertical superconducting magnet test facility of the SMD at ron Collider (LHC) at CERN will include twenty 4.2 m-long BNL has been upgraded to perform testing in superfluid He at Nb3Sn high gradient quadrupole magnets which will be compo- 1.9 K and 1 bar, the operational condition at the LHC. This nents of the triplets for two LHC insertion regions. In order to test these and four pre-production models, the vertical supercon- has involved extensive modifications of the 40-year old, 4.5 K ducting magnet test facility of the Superconducting Magnet Divi- cryogenics plant and vertical test facility at the SMD. These sion (SMD) at Brookhaven National Laboratory (BNL) has been upgrades include new piping, compressors, and other critical upgraded to perform testing in superfluid He at 1.9 K and 1 bar, components; a new vertical test cryostat with a top plate and the operational condition at the LHC. This has involved extensive hanging fixture which can accept larger diameter and longer modification of the 4.5 K cryogenics plant, including piping, magnets, up to an actual length of 5 m; a 1.9 K heat exchang- compressors, and other upgraded components; a new vertical test cryostat which can accept larger diameter magnets; a modern- er; a newly designed warm bore tube; and a lambda plate de- ized power supply system upgraded with IGBT switches and fast signed with a novel sealing scheme to provide for both shutoff capability, and that can supply 24 kA to test high field strength and minimum heat loss. In addition, the former short Nb3Sn magnets; and completely new data acquisition, signal sample cable test facility 30 kA power supply has been up- analysis, and control software and hardware, allowing for fast, graded with an energy extraction system using IGBT switches high precision, large volume data collection. This paper reports and fast shutoff capability, and new high energy dump resis- on the design, assembly, and commissioning of this upgraded test tors, and has been reconfigured to supply 24 kA to test high facility, and presents results of the first magnet test performed. field Nb3Sn magnets. Index Terms—accelerator magnet, superconducting coils, We have also assembled completely new data acquisition, quench protection, test facilities signal analysis, and control software and hardware, allowing for faster, higher precision, and larger volume data collection. This paper describes the design, assembly, and commis- I. INTRODUCTION sioning of the upgraded test facility, and reports on the first he future high luminosity (HiLumi) upgrade of LHC at magnet test performed, on a mirror model, which consists of a single coil quadrant and an iron yoke which fills the space of T CERN will include twenty 4.2 m-long Nb3Sn high gradi- ent quadrupole magnets which will be components of the Q1 the other three quadrants. The test facility and its upgrades can and Q3 triplets for two insertion regions of the LHC. These be discussed in four general areas: 1) cryogenics facility, magnets, denoted as MQXFA, will be supplied by the US Ac- 2) vertical test cryostat and magnet fixture, 3) power supply celerator Upgrade Project (AUP), a collaboration of BNL, system with quench protection, and 4) data acquisition, con- Fermi National Accelerator Laboratory, and Lawrence Berke- trol, and analysis hardware and software. ley National Laboratory. Each magnet will have four two- layer coils wound with 40-strand Nb3Sn Rutherford cable in TABLE I order to generate the high field gradients necessary for the REQUIRED OPERATIONAL PARAMETERS FOR MQXFA TESTS LHC HiLumi upgrade. Table I shows required operational pa- Coil inner aperture D = 150 mm rameters for these magnets, which include operating at cur- Coil magnetic length l = 4.2 m rents up to 17.89 kA, known as the ultimate current. More in- Coil actual length l = 4.523 m formation about the MQXFA magnets and the test require- Total magnet length l = 5 m (nom) ments can be found in [1], [2]. Operational temperature T = 1.9 K In order to test these and four pre-production models, the LHC nominal operating current (1.9 K) Inom = 16.470 kA LHC ultimate operating current (1.9 K) Iult = 17.890 kA This work was supported by the U.S. Department of Energy, Office of Sci- ence, Office of High Energy Physics, through the US LHC Accelerator Re- Conductor limit at 1.9 K Iss = 21.600 kA search Program and by the High Luminosity LHC project at CERN. The U.S. Conductor limit at 4.5 K Iss = 19.550 kA Government retains and the publisher, by accepting the article for publication, acknowledges that the U.S. Government retains, a non-exclusive, paid-up, ir- Magnet inductance (at 1.9 and 1 kA) L1 = 40.9 mH revocable, world-wide license to publish or reproduce the published form of Magnet inductance (at 1.9 and Inom=16.5 kA) L16.5 = 32.8 mH this manuscript, or allow others to do so, for U.S. Government purposes. Operating stored energy (at Bnom, Inom) Emax = 4.5 MJ The authors are with the Superconducting Magnet Division, Brookhaven National Laboratory, Upton, NY 11973 USA (e-mail: [email protected]). Dump resistor (energy extraction) options RD = 30, 37.5, 50, 75, 150 mΩ 2 II. CRYOGENICS FACILITY 0.0837 bar and it delivers 2.7 g/s at 1.9 K. Vapor pressure in The cryogenics facility with its large infrastructure and the heat exchanger is 16 mbar. Cooling capacity is 40 W. Out- multiple vertical test cryostats at the SMD has been used since dated control and diagnostic programming has been replaced the 1970’s to test superconducting magnets at 4.5 K (nominal) with more efficient LabVIEW software. As with the other and up to 10 kA current for magnets mostly wound with NbTi components of the cryogenics system, the vacuum pump has conductor, and it has supported such projects as SSC, RHIC, been refurbished with many new parts and critical spares have and the present LHC insertion region dipole magnets. For use been purchased. in the present HiLumi project, the facility had to be modern- Warm Helium Return ized and upgraded to test at 1.9 K and 1 bar, and up to 24 kA 4.5 K Helium Input current for the state-of-the-art Nb3Sn MQXFA quadrupoles. BNL management funded the purchase of new parts and criti- Liquid Helium 4.5 K Storage Dewar 16 mbar 10000 L cal spares, preventive maintenance of critical components, and 1 bar installation of backup systems to improve reliability and miti- Nash 1.9 K Vacuum 1.9 K Buffer Tank Station to Helium Gas gation of risks inherent in a 40-year old facility. Fig. 1 shows a Storage flow chart of the cryogenics facility and its components. 2-Stage CVI/Magcool Purifier A & B 1.9 K Test Cryostat High Pressure Helium Gas High Pressure Mycom 800 hp Sullair 500 hp Sullair 350 hp Sullair 100 (75 kW) Helium Gas Compressor Compressor Compressor @ 8K (2 Stages) (Single Stage) (Single Stage) 160 g/s 80 g/s 51 g/s Buffer Tank Reciprocating to Suction CS4 Helium Expander CTI Model 4000 Buffer High Pressure Helium 1500 W Tank CS4 Refrigerator/ CVI – Magcool Gas Storage Liquifier Precooler/Subcooler 8.5 x 106 L @ 15.5 bar (Cold Box) Fig. 2. 1.9 K Process Flow Chart for Cryogenics Facility at SMD Liquid Helium Helium Wet Expander Koch Model 1600 Warm Return The SMD has five vertical test cryostats, of which the Warm Return Liquid 6.1 m-deep Test Cryostat 2 was modified by inserting a new, Helium Turbo-Expander 4.5 K Lambda redesigned inner He vessel, with 4.5 K heat shield, and which High Pressure Helium Dual Plate Helium Gas Liquifier Turbines 1 bar CVI/Air Liquide Cryenco is rated at 5.86 bar, into the existing outer dewar and which 1000 W Cryenco Gardner 10000 L 1.9 K 3785 L 3785 L Storage Dewar extended the useful length by 200 mm, in order to accommo- Storage Storage Dewar Dewar Cryenco date wider and longer magnets, up to 5 m long, and can there- Inline Purifier fore accept the MQXFA quadrupole magnets, which are close 1.9 K Test Cryostat 2 Fig. 1. SMD Cryogenics Facility Main Process Flow Chart to 5 m. In addition, a new top plate assembly (76.2 mm-thick 304 The main source of liquid helium is a 1500 W CTI Model stainless steel) has also been built with enough connector trees 4000 Refrigerator/Liquefier with two reciprocating expansion to accommodate the large amount of MQXFA instrumenta- engines rated at 250 rpm. With both expansion engines and a tion, including voltage taps, quench protection heaters, strain Koch Model 1600 Wet Expander, rated at 60 rpm, running, the gauges, temperature sensors, and level probes. The top plate liquefaction capability is 320 L/hr, with up to 17570 L storage assembly also includes a G10-stainless steel bilaminar lambda capacity. Refrigerator upgrades included a new liquid nitrogen plate, 24 kA vapor-cooled copper leads, two 1 kA NbTi leads heat exchanger, doubling the number of inline purifiers to for the CLIQ (coupling loss induced quench) protection sys- four, rebuilding of expansion engines and wet expander, and tem, a 1.9 K heat exchanger, and multiple liquid helium fill new diagnostic and control software written in LabVIEW.