D.R. Chichili

Investigation of cable insulation and thermo-mechanical properties of epoxy impregnated Nb/sub 3/Sn composite

Within the framework of the Fermilab high field magnet program, cable insulation and thermo-mechanical properties of epoxy impregnated Nb/sub 3/Sn composite were studied. As a part of cable insulation development, a new wrappable ceramic insulation was investigated to understand its mechanical properties and its influence on magnet fabrication technology. Measurements of modulus of elasticity and Poissons ratio of Nb/sub 3/Sn composite made out of ten-stack samples were performed under compression at room temperature and at 4.2 K. The results from both monotonic and cyclic loading tests are presented. Finally, measurements of the coefficient of thermal contraction for the composite using strain gauges is discussed.

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.

Fabrication of Nb3Sn Shell‐Type Coils with Pre‐Preg Ceramic Insulation

Insulation is one of the critical components for high‐field Nb3Sn magnets that follow wind‐and‐react approach. The insulation material has to withstand high bending stresses while winding the coil and high heat‐treatment temperatures under pressure during coil reaction. At Fermilab we have developed a procedure and tested successfully the dry ceramic insulation tape with inorganic liquid binder to wind and cure the coils. Recently we have extended this to a pre‐preg ceramic insulation tape, which would minimize and control the amount of binder in the coil. Several coils with various insulation patterns have been fabricated and tested at Fermilab. This paper discusses the fabrication issues of the coils with different types of cable insulation including the pre‐preg ceramic insulation.

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

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.

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.

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.

Superconductor and cable R&D for high field accelerator magnets at Fermilab

This paper presents past results and future goals of the Nb/sub 3/Sn strand and cable R&D being performed within the High Field Magnet program at Fermilab. Research tools include a reaction site for Nb/sub 3/Sn, a Short Sample Test Facility, a Scanning Electron Microscope, and a 28-strand cabling machine. Strands of various designs and diameters produced with the Internal Tin, Modified Jelly Roll, and Powder-in-Tube methods, and several Rutherford-type cables were studied.

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.

Conceptual design study of Nb/sub 3/Sn low-beta quadrupoles for 2nd generation LHC IRs

Conceptual designs of 90-mm aperture high-gradient quadrupoles based on the Nb/sub 3/Sn superconductor, are being developed at Fermilab for possible 2nd generation IRs with the similar optics as in the current low-beta insertions. Magnet designs and results of magnetic, mechanical, thermal and quench protection analysis for these magnets are presented and discussed.

Volume expansion of Nb-Sn strands and cables during heat treatment

In the recent years, Nb3Sn has been widely used for the development of high field superconducting magnets. It is known that the unreacted Nb-Sn composite undergoes a volume expansion during heat treatment due to the formation of the Nb3Sn phase. In an as-received strand this expansion is isotropic. However, an anisotropic volume expansion was observed in the Rutherford-type cable samples. A systematic study was undertaken to investigate this phenomenon and to check the hypothesis that the plastic deformation of the strands during cabling process is responsible for this behavior. Nb-Sn strands from various manufacturing technologies were rolled down to different sizes, and the resulting thickness and width of the deformed strands were measured before and after heat treatment. The results obtained on the deformed strands were then compared with those obtained from cables. A good consistency was achieved in most of the cases.