Vadim V. Kashikhin

Design of HQ—A High Field Large Bore

In support of the Large Hadron Collider luminosity upgrade, a large bore (120 mm) Nb3Sn quadrupole with 15 T peak coil field is being developed within the framework of the US LHC Accelerator Research Program (LARP). The 2-layer design with a 15 mm wide cable is aimed at pre-stress control, alignment and field quality while exploring the magnet performance limits in terms of gradient, forces and stresses. In addition, HQ will determine the magnetic, mechanical, and thermal margins of Nb3Sn technology with respect to the requirements of the luminosity upgrade at the LHC.

{\rm Nb}_{3}{\rm Sn}

In support of the development of a large-aperture Nb3Sn superconducting quadrupole for the Large Hadron Collider (LHC) luminosity upgrade, several two-layer technological quadrupole models of TQC series with 90 mm aperture and collar-based mechanical structure have been developed at Fermilab in collaboration with LBNL. This paper summarizes the results of fabrication and test of TQC02a, the second TQC model based on RRP Nb3Sn strand, and TQC02b, built with both MJR and RRP strand. The test results presented include magnet strain and quench performance during training, as well as quench studies of current ramp rate and temperature dependence from 1.9 K to 4.5 K.

Quadrupole Magnet for LARP

Amongst the magnet development program of a large-aperture Nb3Sn superconducting quadrupole for the Large Hadron Collider luminosity upgrade, six quadrupole magnets were built and tested using a shell based key and bladder technology (TQS). The 1 m long 90 mm aperture magnets are part of the US LHC Accelerator Research Program (LARP) aimed at demonstrating Nb3Sn technology by the year 2009, of a 3.6 m long magnet capable of achieving 200 T/m. In support of the LARP program the TQS magnets were tested at three different laboratories, LBNL, FNAL and CERN and while at CERN a technology-transfer and a four days magnet disassembly and reassembly were included. This paper summarizes the fabrication, assembly, cool-down and test results of the six magnets and compares measurements with design expectations.

Fabrication and Test of LARP Technological Quadrupole Models of TQC Series

The paper describes a method and results of simulation of persistent current effect in high field Nb/sub 3/Sn dipole magnets being developed for the future hadron colliders. Simple and effective techniques of passive correction of the persistent current effect in superconducting accelerator magnets are proposed. Using of these techniques allows a significant reduction of sextupole and decapole field components induced by persistent currents in a coil.

Test Results of LARP Nb3Sn Quadrupole Magnets Using a Shell-based Support Structure (TQS)

A 43.5 mm aperture dipole magnet with a nominal field of 11 T is being fabricated at Fermilab. The design is based on a two-layer shell-type coil structure made of Rutherford-type Nb/sub 3/Sn cable with wind and react technology. The mechanical support structure consists of vertically split iron yoke locked by two aluminum clamps and a 8 mm thick stainless steel skin. This paper summarizes the fabrication details of the first dipole model and test results from a 2110 mm long mechanical model.

Correction of the persistent current effect in Nb/sub 3/Sn dipole magnets

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 Nb3Sn 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.

Fabrication of the shell-type Nb/sub 3/Sn dipole magnet at Fermilab

The paper presents the results of a conceptual design study of double aperture Nb/sub 3/Sn dipole magnets for VLHC based on the cos-theta and common coil geometry with cold and warm iron yoke. The study included an optimization of the iron yoke geometry to achieve the maximum transfer function, small fringe fields and low-order field harmonics as well as an optimization of the coil geometry to correct a quadrupole field component (normal or skew) inevitable for 2-in-1 magnet designs.

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

The final beam cooling stages of a possible Muon Collider may require DC solenoid magnets with magnetic fields of 40-50 T in an aperture of 40-50 mm. In this paper, we study possible solutions towards creating DC fields of that order using available superconductors. Several magnetic and mechanical designs, optimized for the maximum performance are presented and compared in terms of cost and size.

Magnetic designs of 2-in-1 Nb/sub 3/Sn dipole magnets for VLHC

The performance of some superconducting accelerator magnets based on high-Jc Nb3Sn strands suffered from flux jumps in the coils which significantly limited their maximum quench current. Detailed investigation into the possible cause of these performance-limiting quenches showed a correlation between the magnet test results and the properties of the superconducting strands used in the magnet and the magnet design parameters. This paper discusses the effect of flux jumps in Nb3Sn strands and cables on quench performance and on field quality of accelerator magnets

Study of High Field Superconducting Solenoids for Muon Beam Cooling

Several 90-mm quadrupole coils made of 0.7-mm Nb3Sn strand based on the “Restack Rod Process” (RRP) of 108/127 design, with cored and non-cored cables and different cable insulation, were fabricated and individually tested at Fermi National Accelerator Laboratory (Fermilab) using a test structure designed to provide a quadrupole magnetic field environment. The coils were instrumented with voltage taps and strain gauges to study quench performance and mechanical properties. The Nb3Sn strand and cable parameters, the coil fabrication details, the mirror model assembly procedure and test results at temperatures from 4.5 K to 1.9 K are reported and discussed.