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FERMILAB-CON F-06-319-TD
Thermal Analysis of SC Quadrupoles in
Accelerator Interaction Regions
Igor Novitski, Alexander V. ZlobinAbstract-This paper presents results of a thermal analysis
and operation margin calculation performed for NbTi and Nb3Sn
low-beta quadrupoles in collider interaction regions. Results of
the thermal analysis for NbTi quadrupoles are compared with
the relevant experimental data. An approach to quench limit
measurements for Nb3Sn quadrupoles is discussed.
Index Terms- Superconducting quadrupole, interaction
region, operation margin, thermal analysis, temperature margin,
quench limit.
I. INTRODUCTION
The final beam focus in collider interaction regions (IR) is
provided by superconducting low-beta quadrupoles
placed next to the detector on both sides of the interaction
point. The first generation of IR quadrupoles (IRQ) based on
NbTi superconductor are being used in Tevatron [1] and in
LHC [2], [3]. A design study of the second generation IR
quadrupoles for the LHC luminosity upgrade has been started
recently in the framework of U.S. LHC Accelerator Research
Program (LARP) [4]. These magnets will use Nb3Sn
superconductor and provide larger aperture and larger
operation margin to increase the LHC luminosity.
Superconducting low-beta quadrupoles based on NbTi or
Nb3Sn coils are also considered for the ILC IR [5].
Secondary particles coming from interaction point deposit
energy in IR quadrupoles and, in particular, in their coils. This
energy deposition will cause a coil temperature rise and may
lead to a premature magnet quench if coil cooling conditions
are not sufficient. To prevent quenches the coil temperature
has to be kept below the superconductor critical temperature
at given transport current. Moreover, additional operation
margin is usually required for the IR magnets to provide
reliable machine operation.
This paper analyzes and compares the thermal performance
and the operation margin for IR quadrupoles based on NbTi
and Nb3Sn superconductors with respect to radiation heat
deposition. Results of experimental verification of the thermal
calculation for NbTi IR quadrupoles, and possible
measurements of operation margin of Nb3Sn IR quadrupoles
are discussed.
Manuscript received August 28, 2006.
This work was supported by the U.S. Department of Energy.
Authors are with the Fermi National Accelerator Laboratory, Batavia, IL
60510 USA (I. Novitski phone: 630-840-4823; fax: 630-840-3369; e-mail:
novitski @fnal.gov).II. THERMAL ANALYSIS
A. Magnet Design and ANSYS Thermal Model
For a consistent comparison of NbTi and Nb3Sn IR
quadrupoles the thermal analysis was performed for magnets
with equivalent design and performance parameters. These IR
quadrupoles were developed as candidates for the LHC IRs.
Quadrupole cross-sections are shown in Fig. 1. Both magnets
use two-layer coils and were designed for a maximum field
gradient of -250 T/m. The details of magnet designs are
reported in [6, 7].
a) f-- b)
I I I
Fig. 1. 70 mm NbTi MQXB (a) and 90 mm Nb3Sn (b) quad cross-sections.
The NbTi quadrupole coil has a 70-mm bore and is made of
15-mm wide graded cable insulated with Kapton tape. The
Nb3Sn quadrupole coil has a 90-mm bore and uses 15-mm
wide cable insulated with thick S2-glass/epoxy insulation. In
both designs the coil is supported by a stainless steel collar
and surrounded by an iron yoke. The magnet cold mass, which
includes coil, collar and yoke, is cooled with HeII at T=1.9 K.
a) b)
--
" - - - _
Fig. 2. 2D finite element thermal models: a) NbTi IRQ; b) Nb3Sn IRQ.
2D finite element thermal models of the collared coils were
developed using ANSYS for both quadrupole designs. The
models, shown in Fig. 2, are based on the octant symmetry
and include inner and outer coils, interlayer and ground
insulation, aluminum-bronze pole spacer and stainless steel
collars [8].
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Novitski, Igor & Zlobin, Alexander V. Thermal analysis of SC quadrupoles in accelerator interaction regions, article, September 1, 2006; Batavia, Illinois. (https://digital.library.unt.edu/ark:/67531/metadc880956/m1/1/: accessed April 25, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.