G. Sabbi

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.

An Updated Point Design for Heavy Ion Fusion

Abstract An updated, self-consistent point design for a heavy ion fusion (HIF) power plant based on an induction linac driver, indirect-drive targets, and a thick liquid wall chamber has been completed. Conservative parameters were selected to allow each design area to meet its functional requirements in a robust manner, and thus this design is referred to as the Robust Point Design (RPD-2002). This paper provides a top-level summary of the major characteristics and design parameters for the target, driver, final focus magnet layout and shielding, chamber, beam propagation to the target, and overall power plant.

A First Baseline for the Magnets in the High Luminosity LHC Insertion Regions

The High Luminosity LHC (HL-LHC) project aims at accumulating 3000 fb-1 in the years 2023-2035, i.e., ten times more w.r.t. the nominal LHC performance expected for 2010-2021. One key element to reach this challenging performance is a new insertion region to reduce the beam size in the interaction point by approximately a factor two. This requires larger aperture magnets in the region spanning from the interaction point to the matching section quadrupoles. This aperture has been fixed to 150 mm for the inner triplet quadrupoles in 2012. In this paper, we give a first baseline of the interaction region. We discuss the main motivations that lead us to choose the technology, the combination of fields/gradients and lengths, the apertures, the quantity of superconductor, and the operational margin. Key elements are also the constraints given by the energy deposition in terms of heat load and radiation damage; we present the main features related to shielding and heat removal.

Magnet Design of the 150 mm Aperture Low-

The high luminosity LHC (HL-LHC) project is aimed at studying and implementing the necessary changes in the LHC to increase its luminosity by a factor of five. Among the magnets that will be upgraded are the 16 superconducting low-β quadrupoles placed around the two high luminosity interaction regions (ATLAS and CMS experiments). In the current baseline scenario, these quadrupole magnets will have to generate a gradient of 140 T/m in a coil aperture of 150 mm. The resulting conductor peak field of more than 12 T will require the use of Nb3Sn superconducting coils. We present in this paper the HL-LHC low-β quadrupole design, based on the experience gathered by the US LARP program, and, in particular, we describe the support structure components to pre-load the coils, withstand the electro-magnetic forces, provide alignment and LHe containment, and integrate the cold mass in the LHC IRs.

\beta

In this paper, we outline the present status of the design studies for the high-luminosity Large Hadron Collider, focusing on the choice of the aperture of the inner triplet quadrupoles. After reviewing some critical aspects of the design such as energy deposition, shielding, heat load, and protection, we present the main tentative parameters for building a 150-mm-aperture Nb3Sn quadrupole, based on the experience gathered by the LARP program in the past several years.

Quadrupoles for the High Luminosity LHC

J 2LC02 SC-MAG#773 LBNL-49918 An Approach for Faster High Field Magnet Technology Development R. R. Hafalia, S. Caspi, L. C hiesa, M . Coccoli , D.R. Die tde rich, S. A. Gourlay, A.F. Lietzke, l .W. ONeill, G. Sabbi, and R.M. Scanlan Abstract- The Superconducting Magnet Program at LBNL has developed a magnet design supporting our new Subscale Magnet Program, that facilitates rapid testing of small superconducting racetrack coils in the field range of 10·12 Tesla. Several coils have been made from a variety of NbJSnlCu cables, insulated, wound, reacted, potted and assembled into a small reusable yoke and shell loading structure. Bladder and key technology have provided a rapid, efficient means for adjusting coil pre-stress during both initial assembly, and between thermal cycles. This affords the opportunity to test moderately long cable samples under magnet conditions on a time scale considerably closer to that for traditional short-sample cable tests. We have built and tested four coils with the initial aim of determining the feasibility of reducing overall conductor costs with mixed-strand cables. Details of cost reduction improvements, coil construction, magnet structure, and assembly procedures are reported, along with the relative performance of the mixed-strand coil. II. THE CONDUcrOR The Subscale Magnet Program utilizes superconducting Nb3Sn strands produced by Oxford and lac. T he cables were wou nd with 20 strands ofO.7mm diameter. The nominal cable cross-section used by the Subscale Magnet Program is 7.9mm x 1.3mm. The cable is sheathed in a continuous, woven, fiberglass sleeve. Coil modules are wound in 2 layers in flat racetrack coil configuration around an iron pole-island - each layer having 22 turns each. (Fig. 1). Each double-layer coi l module requires 22m of cable (5 kg). The two baseline coil modules (SCOI & SC02) were used in the inaugural test of the new Subsea Ie Magnet Test Faci lity. They were both wound with Nb3Sn cable - with the same strand as was used in LBLs 14.7 Tesla RD-3B large-scale magnet. The winding and assembly, prior to reacti on, took about 2-3 days. Index Terms- Common Coil Magnet, mixed-strand cable, Nb)Sn, racetrack coil. I. I NTRODUcrlON awrence Berkeley National Laboratory has implemented a Subscale Magnet Program. The new Subscale Magnet Test Facility was fabricated to supporJ the program. The facility includes a 38 lmm-lD x - 1524mm-deep vertical cryostat, wi th supporJ structure and magnet supporJ header. T he program tests the performance of various types of superconducting cables in a medium-to-high field environment as well as investigates magnet structural design modifications, L in small scale, before implementing them into our large-scale program. The magnet structural components were mass- Fig. I . 2 layers wound around iron pole. prod uced and standardized for rapid coil mod ule assembly. Three of the four coil modules initially built (two baseline coils, one mi x.ed strand coil and a comparison coil), have been tested. Presently, two more coil modul es with mi xed Nb3SnlCu strand coil variations have been reacted and are presently being assembled. Also, a coil mod ule with a new woven ceramic insulator is being reacted. Manuscript received August 6, 2002. Thi s was supported by the Director, Office of Energy Research, O ffi ce of High Energy and N uclear Physics, Hi gh Energy Physics D ivision , U. S. Department of Energy. under Contract No. The next coil module (SC03) was wound with a mixed- strand cable consisting of 2 1 strands - 14 Nb3Sn strands cabled with 7 strands of pure copper. Due to the difference in elastic modulus between the SC and the Cu strands, decabling was evident throughout the whole length of the cable. Coil winding tension was cut in half, from 178N to 89N, to minimize decabling. Even with the lower tension, popped strands were observed. DE-AC03--76SFO0098. R.R. Hafalia is with the Lawrence Berkeley National Lab. Berkeley, CA 94720 USA (telephone: 5 10-486-5712, (e-rnail: rrhafalia @Ibl.gov). Coi l module SC04 was wound with 20 Nb3Sn strands and was intended as a comparison to the SC03 mixed strand modul e.

Design Studies for the Low-Beta Quadrupoles for the LHC Luminosity Upgrade

Magnet programs at BNL, LBNL and FNAL have observed instabilities in high J/sub c/ Nb/sub 3/Sn strands and magnets made from these strands. This paper correlates the strand stability determined from a short sample-strand test to the observed magnet performance. It has been observed that strands that carry high currents at high fields (greater than 10 T) cannot sustain these same currents at low fields (1-3 T) when the sample current is fixed and the magnetic field is ramped. This suggests that the present generation of strand is susceptible to flux jumps (FJ). To prevent flux jumps from limiting stand performance, one must accommodate the energy released during a flux jump. To better understand FJ this work has focused on wire with a given sub-element diameter and shows that one can significantly improve stability by increasing the copper conductivity (higher residual resistivity ratio, RRR, of the Cu). This increased stability significantly improves the conductor performance and permits it to carry more current.

An approach for faster high field magnet technology development

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.

Correlation between strand stability and magnet performance

Future upgrades to machines like the Large Hadron Collider (LHC) at CERN will push accelerator magnets beyond 10 T forcing the replacement of NbTi superconductors with advanced superconductors such as Nb3Sn. In support of the LHC Phase-II upgrade, the US LHC Accelerator Research Program (LARP) is developing a large bore (120 mm) Nb3Sn Interaction Region (IR) quadrupole (HQ) capable of reaching 15 T at its conductor limit and gradients of 199 T/m at 4.4 K and 219 T/m at 1.9 K. The 1 m long, two-layer magnet, addresses coil alignment and accelerator quality features while exploring the magnet performance limits in terms of gradient, stress and structure. This paper summarizes and reports on the design, mechanical structure, coil windings, reaction and impregnation processes.

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

The Nb/sub 3/Sn dipole HD1, recently fabricated and tested at LBNL, pushes the limits of accelerator magnet technology into the 16 T field range, and opens the way to a new generation of HEP colliders. HD1 is based on a flat racetrack coil configuration and has a 10 mm bore. These features are consistent with the HD1 goals: exploring the Nb/sub 3/Sn conductor performance limits at the maximum fields and under high stress. However, in order to further develop the block-coil geometry for future high-field accelerators, the bore size has to be increased to 30-50 mm. With respect to HD1, the main R&D challenges are: (a) design of the coil ends, to allow a magnetically efficient cross-section without obstructing the beam path; (b) design of the bore, to support the coil against the pre-load force; (c) correction of the geometric field errors. HD2 represents a first step in addressing these issues, with a central dipole field above 15 T, a 35 mm bore, and nominal field harmonics within a fraction of one unit. This paper describes the HD2 magnet design concept and its main features, as well as further steps required to develop a cost-effective block-coil design for future high-field, accelerator-quality dipoles.