Magnetic and Mechanical Analysis of the HQ Model Quadrupole Designs for LARP

Abstract

Abstract-Insertion quadrupoles with large bore and high gradient are required to upgrade the luminosity of the Large Hadron Collider (LHC). The US LHC Accelerator Research Program is developing Nb 3 Sn technology for the upgrade. This effort includes a series of 1 m long Technology Quadrupoles (TQ), to demonstrate the reproducibility at moderate field, and High-gradient Quadrupoles (HQ) to explore the magnet performance limits in terms of peak fields, forces and stresses. The HQ models are expected to achieve peak fields of 15 T or higher. A coil aperture of 90 mm, corresponding to gradients above 300 T/m, was chosen as the baseline. Peak stresses above 150 MPa are expected. Progress on the magnetic and mechanical design of the HQ models will be reported.

Test Results of the LARP Nb3Sn Quadrupole HQ03a

“…The design concept and main features are described in [3][4][5][6]. The conductor and performance parameters specific to the HQ03a assembly are summarized in Table I. The superconducting cable, which incorporates a stainless steel core to control the dynamic effects, was fabricated as a single production unit using 0.778 mm diameter Nb3Sn strands of the RRP 108/127 design [19].…”

“…Its main goal is to provide a technology basis for the 150 mm aperture low-β quadrupoles (MQXF) that will be installed in the interaction regions of the High Luminosity LHC [2]. The first phase of the HQ program included production of eight coils, and five assembly cycles (HQ01a-HQ01e) [3][4][5][6]. These models, while demonstrating operation well above the HQ target gradient of 170 T/m, were affected by stress degradation, electrical insulation failures, and large dynamic field errors [7][8][9][10].…”

Progress with High-Field Superconducting Magnets for High-Energy Colliders

“…Figure 10 shows the quadrupole models built and tested by LARP, and Table 4 shows the magnet design parameters. The LARP quadrupole models addressed various aspects of the Nb3Sn quadrupole technology, including the shell-type coil design, mechanical structures based on an external aluminum shell preloaded with water-pressurized bladders (TQS series) [44], the collar-based structure with two collar types and collaring techniques (TQC series) [45], the Nb3Sn quadrupole length scale-up (LQS series) [46], and the large aperture and accelerator quality (HQ series) [47]. The LARP quadrupole models were also used to test new Nb3Sn strands and to study quench performance, field quality, and quadrupole quench protection issues.…”

Persistent-Current Magnetization of <inline-formula> <tex-math notation="TeX">$\hbox{Nb}_{3}\hbox{Sn} $</tex-math></inline-formula> Strands: Influence of Applied Field Angle and Transport Current

“…Particular attention will need to be given to differences in parasitic magnetization. (2) The LHC's high luminosity upgrade (High Lumi) calls for the installation by Manuscript [5] and more recently the magnetic properties of strand and cable for the HQ quadrupole. An increasing field applied to a superconducting strand is shielded by a so-called persistent current equivalent to a Beantype magnetization, M sh (one half of the full height of a magnetization loop).…”