P. Schlabach

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.

Field alignment of quadrupole magnets for the LHC interaction regions

High-gradient superconducting quadrupole magnets are being developed by the US LHC Accelerator Project for the Interaction Regions of the Large Hadron Collider. Determination of the magnetic axis for alignment of these magnets will be performed using a single stretched wire system. These measurements will be done both at room and cryogenic temperatures with very long wire lengths, up to 20 m. This paper reports on the stretched wire alignment methodology to be employed: and the results of recent room-temperature measurements on a 2 m model magnet with long wire lengths.

Status of the LHC inner triplet quadrupole program at Fermilab

Fermilab, in collaboration with LBNL and BNL, is developing a quadrupole for installation in the interaction region inner triplets of the LHC. This magnet is required to have an operating gradient of 215 T/m across a 70 mm coil bore, and operates in superfluid helium at 1.9 K. A 2 m magnet program addressing mechanical, magnetic, quench protection, and thermal issues associated with the design was completed earlier this year, and production of the first full length, cryostatted prototype magnet is underway. This paper summarizes the conclusions of the 2 m program, and the design and status of the first full-length prototype magnet.

Passive correction of the persistent current effect in Nb/sub 3/Sn accelerator magnets

Superconducting accelerator magnets must provide a uniform field during operation. However, the field quality significantly deteriorates due to persistent currents induced in superconducting filaments. This effect is especially large for the Nb/sub 3/Sn conductor being implemented in the next generation of accelerator magnets. A simple and inexpensive method of passive correction of the persistent current effect was developed and experimentally verified. This paper describes numerical simulations of the passive correctors and reports the test results.

Field Quality Measurements and Analysis of the LARP Technology Quadrupole Models

One of the US-LHC accelerator research program goals is to develop and prove the design and technology of quadrupoles for an upgrade of the LHC Interaction Region (IR) inner triplets. Four 1-m long technology quadrupole models with a 90 mm bore and field gradient of 200 T/m based on similar coils and different mechanical structures have been developed. In this paper, we present the field quality measurements of the first several models performed at room temperature as well as at superfluid helium temperature in a wide field range. The measured field harmonics are compared to the calculated ones. The field quality of quadrupole models is compared with the NbTi quadrupoles recently produced at Fermilab for the first generation LHC IRs.

Development and test of single-bore cos-/spl thetav/ Nb/sub 3/Sn dipole models with cold iron yoke

Two short Nb/sub 3/Sn dipole models based on a single-bore cos-theta coil with a cold iron yoke were fabricated and tested at Fermilab. This paper summarizes the details of magnet design and fabrication procedure, and reports the test results including quench performance and quench heater studies, and the magnetic measurements.

Field quality in Fermilab-built models of quadrupole magnets for the LHC interaction region

Superconducting quadrupole magnets for the interaction regions of the Large Hadron Collider are being developed by the US-LHC Accelerator Project. These 70 mm bore quadrupole magnets are intended to operate in superfluid helium at 1.9 K with a nominal field gradient of 215 T/m. A series of 2 m model magnets has been built and cold tested at Fermilab to optimize their design and construction and to study the performance of the magnets. Field measurements of the 8 model magnets and comparisons with the required field quality are reported in this paper.

NB 3 SN accelerator magnet technology R&D at Fermilab

Accelerator magnets based on Nb3Sn supercondutor are being developed at Fermilab. Six nearly identical 1-m long dipole models and several mirror configurations were built and tested demonstrating magnet performance parameters and their reproducibility. The technology scale up program has started by building and testing long dipole coils. The results of this work are reported in the paper.

Construction experience with MQXB quadrupole magnets built at Fermilab for the LHC interaction regions

Fermilab is building eighteen full length cold masses for the LHC Interaction Region inner triplets. One prototype and several production assemblies have been completed. This paper summarizes the construction details. Topics include coil fabrication, ground insulation, collaring, instrumentation, electrical testing, and final assembly. In-process measurements are presented and explained. Problems encountered during construction and their solutions are discussed.

Correction of high gradient quadrupole harmonics with magnetic shims

Superconducting quadrupole magnets with 70 mm aperture and nominal field gradient of 215 T/m are being developed by the US-LHC Accelerator Project for the Interaction Regions of the Large Hadron Collider. Due to large beam size and orbit displacement in the final focusing triplet, these magnets are subject to stringent field quality requirements. For this reason, a correction scheme based on design calculations, fabrication issues and tests results involving magnetic shims.