Assembly and Tests of SQ02, a Nb3Sn Racetrack Quadrupole Magnet for LARP Page: 4 of 4
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During excitation, the electromagnetic forces in the coil
straight sections push the conductors toward the mid-planes,
unloading the island pole, and producing an increase of
azimuthal tension in the shell (within 1 MPa). In the end
regions, the longitudinal Lorentz force tend to elongate the
coils in the axial direction, thereby increasing the rods tension
Fig. 9 Strain gauge location on coils SC15-SC16. by about 4 MPa. As shown in Fig 10, the increase is well
reproduced by the 3D finite element model predictions, as long
12 as a friction factor p = 0.1 between the coils and the
Shell measurements components is included.
10 --o- Model without friction (rods) All coil strain gauges exhibited a decrease of the
9 --- Model with friction (rods) r
c -Model without friction (shell) bidirectional strain (8_ - 8/) both in the straight section and in
7; -f-Modelwithfriction(shell) the end regions (Fig. 11). The variation can be explained
pointing out that the Lorentz forces tend to push outwardly the
6 -coil, i.e. separating it from the island pole. This effect
4 determines, both on straight sections and ends, a turn-to-turn
3 compression (negative c1) and a stretching in the coil winding
2 +,= direction (positive 8/). As already observed in the rods, the
1 results of the 3D model are in better agreement with the
measurements when friction is included. In particular, the
-'1 model reproduces the strain response of the coil straight
0.00 0.20 0.40 0.60 0.80 1.00 section well, but it underestimates it at the coil ends.
Fig. 10. Variation of tension in the shell and in the rods during magnet
excitation as a function of the fraction of Lorentz force with respect to the
4.5 K short sample value.
-9 Coil straight seaction meas. t
11 Coil end meas
> -1100 -c- Model without friction (ss)
Fig. 11. V
to the 4.5
to the alum
and two ne
The Nb3Sn subscale quadrupole magnet SQ01 has been
disassembled, visually inspected, reassembled, and retested as
SQ01b after minor modifications in the end pre-load. The
magnet performed similarly, achieving a slightly higher
maximum current, compared to the first test. Ramp-rate and
temperature dependence studies were conducted: at 2.2 K, a
drop in quench current was observed in the MJR coils.
Magnetic and strain gauges measurements were collected,
analyzed and found consistent with numerical predictions.
-Q- Model with friction (ss)  A. Devred, S. A. Gourlay, and A. Yamamoto, "Future accelerator
0 -- Model without friction (end) magnet needs", IEEE Trans. Apple. Superconduct., Vol. 15, no. 2, pp.
- - Model with friction (end) 1192-1199, June 2005.
 S. A. Gourlay. "Magnet R&D for the US LHC Accelerator Research
0.00 0.20 0.40 0.60 0.80 1.00 Program", presented at 19h International Conference on Magnet
(1/1", Technology, Genoa, Italy, September 18-23, 2005.
 R. C. Bossert, et al., "Development of a 90-mm Nb3Sn technological
variation of bidirectional strain in the coil end regions during quadrupole for LHC upgrade based on SS collars", presented at 19'h
action as a function of the fraction of Lorentz force with respect International Conference on Magnet Technology, Genoa, Italy,
K short sample value: s1 and cg are respectively the strains September 18-23, 2005.
r and parallel to the wide surface of the cable.  S. Caspi, et al., "Design and construction of TSQ01, a 90 mm Nb3Sn
quadrupole model for LHC luminosity upgrade based on a key and
iinum rods to measure their axial tension. Moreover, bladder structure", presented at 19'h International Conference on
coils were instrumented with four full-bridge strain Magnet Technology, Genoa, Italy, September 18-23, 2005.
ced directly over the turns and impregnated wit  P. Ferracin, et al., "Development of a large aperture Nb3Sn racetrack
quadrupole magnet", IEEE Trans. Appl. Superconduct., Vol. 15, no. 2,
9). A coil trace overlay  was used to connect the pp. 1132-1135, June 2005.
ges to the coils and to secure their position. Two  B. Bordini, et al., "SQ01b test summary", Fermilab Technical Division
re located near the middle of the straight sections Note TD-05-017, January 2005.
ar the middle of the coil ends. The resulting signal  S. Caspi, et al., "The use of pressurized bladders for stress control of
superconducting magnets", IEEE Trans. Appl. Superconduct., vol. 11,
rtional to the difference between the turn-to-turn no. 1, pp. 2272-2275, March 2001.
and the strain in the cable winding direction (c).  A. F. Lietzke, et al., "Voltage Spike Observations in LARP Nb3Sn Coil
10 the stress (tension) variations as a function of Tests", presented at 19'h International Conference on Magnet
n of Lorentz force with respect to the 4.5 K short Technology, Genoa, Italy, September 18-23, 2005.
lu (/"2),btfo th shl(ith azm hl  S. Caspi, et al., "Measured strain of a Nb3Sn coil during excitation and
[ue ((I/Iss)2), both for the shell (in the azimuthal quench", IEEE Trans. Appl. Superconduct., vol. 15, no. 2, pp. 1461-
and the rods (in the axial direction), are plotted. 1464, June 2005.
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Ferracin, Paolo; Ambrosio, G.; Barzi, E.; Caspi, S.; Dietderich, D.R.; Feher, S. et al. Assembly and Tests of SQ02, a Nb3Sn Racetrack Quadrupole Magnet for LARP, article, June 1, 2007; Berkeley, California. (https://digital.library.unt.edu/ark:/67531/metadc893584/m1/4/: accessed April 23, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.