D. Turrioni

Magnet RaD for the US LHC Accelerator Research Program (LARP)

TUA2OR6 Magnet RD fax: 510-486-5310; e-mail: sagourlay@lbl.gov). G. Ambrosio, N. Andreev, E. Barzi, R. Bossert, V. S. Kashikhin, V. V. Kashikhin, F. Nobrega, I. Novitsky, D. Turrioni, R. Yamada, and A.V. Zlobin are with Fermilab National Accelerator Laboratory, Batavia, IL 3 M. Anerella, A. Ghosh , , R. Gupta, M. Harrison, J. Schmazle, and P. Wanderer are with Brookhaven National Laboratory, Upton, NY.

R&D of Nb/sub 3/Sn accelerator magnets at Fermilab

Fermilab is developing and investigating different high-field magnets (HFM) for present and future accelerators. The HFM R&D program focused on the 10-12 T magnets based on Nb/sub 3/Sn superconductor and explored both basic magnet technologies for brittle superconductors-wind-and-react and react-and-wind. Magnet design studies in support of LHC upgrades and VLHC were conducted. A series of 1-m long cos-theta dipole models based on the wind-and-react technique was fabricated and tested. Three 1-m long flat racetracks and the common coil dipole model, based on a single-layer coil and react-and-wind technique, were also fabricated and tested. Extensive theoretical and experimental studies of electro-magnetic instabilities in Nb/sub 3/Sn strands, cables and magnets were performed and led to a successful 10 T dipole model. This paper presents the details of Fermilabs HFM program, reports its status and major results, and formulates the next steps for the program.

Test Results of the First 3.7 m Long Nb3Sn Quadrupole by LARP and Future Plans

In December 2009 during its first cold test, LQS01, the first Long Nb3Sn Quadrupole made by LARP (LHC Accelerator Research Program, a collaboration of BNL, FNAL, LBNL and SLAC), reached its target field gradient of 200 T/m. This target was set in 2005 by the US Department of Energy, CERN and LARP, as a significant milestone toward the development of Nb3Sn quadrupoles for possible use in LHC luminosity upgrades. LQS01 is a 90 mm aperture, 3.7 m long quadrupole using Nb3Sn coils. The coil layout is equal to the layout used in the LARP Technological Quadrupoles (TQC and TQS models). Pre-stress and support are provided by a segmented aluminum shell pre-loaded using bladders and keys, similarly to the TQS models. After the first test the magnet was disassembled, reassembled with an optimized pre-stress, and reached 222 T/m at 4.5 K. In this paper we present the results of both tests and the next steps of the Long Quadrupole R&D.

Instabilities in transport current measurements of Nb/sub 3/Sn strands

The critical current of Nb/sub 3/Sn strands used in Fermilabs high field magnets was measured at low and high fields under various experimental conditions using the voltage-current (V-I) and voltage-field (V-H) methods. The strands were produced using Modified Jelly Roll, Restacked Rod Process and Powder-in-Tube technologies. V-I characteristics at fields above 10-12 T with a smooth transition from the superconducting to normal phase allowed determining strand critical current. V-I and V-H measurements at low fields showed premature quenches due to magnetic instability in strands with high critical current density and large effective filament size. The results of the strand critical current measurements at low and high fields are herein presented.

Development of Rutherford-Type Cables for High Field Accelerator Magnets at Fermilab

Fermilabs cabling facility has been upgraded to a maximum capability of 42 strands. This facility is being used to study the effect of cabling on the performance of the various strands, and for the development and fabrication of cables in support of the ongoing magnet R&D programs. Rutherford cables of various geometries, packing factors, with and without a stainless steel core, were fabricated out of Cu alloys, NbTi, Nb3Al, and various Nb3Sn strands. The parameters of the upgraded cabling machine and results of cable R&D efforts at Fermilab are reported.

Development and Test of LARP Technological Quadrupole (TQC) Magnet

In support of the development of a large-aperture superconducting quadrupole for the Large Hadron Collider (LHC) luminosity upgrade, two-layer quadrupole models (TQC and TQS) with 90 mm aperture are being constructed at Fermilab and LBNL within the framework of the US LHC Accelerator Research Program (LARP). This paper describes the construction and test of model TQC01. ANSYS calculations of the structure are compared with measurements during construction. Fabrication experience is described and in-process measurements are reported. Test results at 4.5 K are presented, including magnet training, current ramp rate studies and magnet quench current. Results of magnetic measurements at helium temperature are also presented.

Development and Test of a Single-Aperture 11 T

The upgrade of the LHC collimation system foresees installation of additional collimators around the LHC ring. The longitudinal space for the collimators could be provided by replacing some 8.33 T NbTi LHC main dipoles with shorter 11 T Nb3Sn dipoles compatible with the LHC lattice and main systems. To demonstrate this possibility, FNAL and CERN have started a joint program with the goal of building a 5.5 m long twin-aperture dipole prototype suitable for installation in the LHC. The first step of this program is the development of a 2 m long single-aperture demonstrator dipole with a nominal field of 11 T at the LHC nominal current of 11.85 kA and ~ 20% margin. This paper describes the design, construction, and test results of the first single-aperture Nb3Sn demonstrator dipole model.

\hbox{Nb}_{3}\hbox{Sn}

As a first step toward the development of a large-aperture Nb3Sn superconducting quadrupole for the Large Hadron Collider (LHC) luminosity upgrade, two-layer technological quadrupole models (TQS01 at LBNL and TQC01 at Fermilab) are being constructed within the framework of the US LHC Accelerator Research Program (LARP). Both models use the same coil design, but have different coil support structures. This paper describes the TQC01 design, fabrication technology and summarizes its main parameters

Demonstrator Dipole for LHC Upgrades

Fermilab is working on the development of high field magnet systems for ionization cooling of muon beams. The use of high temperature superconducting (HTS) materials is being considered for these magnets using Helium refrigeration. Critical current (Ic) measurements of HTS conductors were performed at FNAL and at NIMS up to 28 T under magnetic fields at zero to 90 degree with respect to the sample face. A description of the test setups and results on a BSCCO-2223 tape and second generation (2G) coated conductors are presented.

Development of TQC01, a 90 mm

Fermilab and CERN started the development of 11 T Nb3Sn dipoles 11 m long to replace a few regular LHC NbTi dipoles and free space for cold collimators in LHC dispersion suppression (DS) areas. An important step in the design of these magnets is the development of the high aspect ratio Nb3Sn cable to achieve the nominal field of 11 T at the nominal LHC operating current of 11.85 kA with 20% margin. Keystoned cables 14.7 mm wide with and without a stainless steel core were made out of hard Cu wires and Nb3Sn strand of 0.7 mm nominal diameter. The cable optimization process was aimed at achieving both mechanical stability and minimal damage to the internal architecture of the Restacked-Rod Process (RRP) Nb3Sn strands with 127 restack design to be used in the magnet short models. Each cable was characterized electrically for transport properties degradation at high fields, for flux jump stability at low fields, and metallographically for internal damage.