1.1-meter bore, 8-Tesla test facility Page: 3 of 6
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Table 1. Conductor for backing coils.
Conductor
Conductor opecIlIcatIon A B C
axmum field (T) 8 6 3
Current at S K (A) 1000 1000 1000
Conductor size () 2.9 c 0:l 2.9 * 8.1 2.3 x 7.0
eslstiviy ratio In rto field 41s0/1 {1s0/1 4150/1
Nb-TI filament'diameter (v) X0.1 '0.1 '0.1
Twist pitch (mm) '10 50 50
Insolation Nil Nil Nil
Total lergth (ft) 30,000 130,000 38,0i0
Approximate weight (lb) 4.21 . 107 1.P25 x 10 3.66 x l07
Total conductor weight (tonne) 11.750
-0 - ; ' "'i+ '+ 11 1I
+ !
30
20~
I0
10 2
Axis--- '- - ' - - ---- , .
o to 2 40 50 60 70
Axial length -- cm
Center
Isoe BMIN=5.442E-01
BMAX= 8.124E+0)
List of contour welves follow for contours 1, 5, 10 etc.
1 1.000E+00 45 4.500E0
5 5.000E+00 50 5.000E+01
1D 1.000E+0) 55 5.500E+01
15 1.500E+01 60 6.000E+01
20 2.000E+01 65 6.500E+01
25 2.500E+i1 70 7,000+01
30 3.000E+01 75 7.500E+01
35 3.500E+01 80 8.000E+01
40 4.000E+0?
Fig. 2. Magnetic field plot of half of test facility,
with backing coils only.The stability criteria have been based on the
"equal areas" theory of Ref. 3. This theory assumes
that the to ends of a normal region ace in the
nucleate bailing regIoe while the normal region is in
film filing. Becases of the shape of the complete
heac-trunofer curve, there is excess cooling capacity
at the cold ends; therefore, heat flows from the
normal region alonc the conductor to the ends. A
stable condition can exist where the excess hear in
the warm region just equals the excess cooling in
the cold regions. IF the heat generation in the
wire is then slightly reduced, the nucleate boiling
region propagates inward from the coo ends. and the
whole length returns ro nucleate boiling. with a
composite conductor, the conditions are not quie
so simple because the joule hear generated in the
copper decreases as the temperature of the condctor
falls below the critical temperature for the ambient
field and current density, and current begins to
coratate from tha cooper to the superconductor.
Figure 3 shows the heat-generation curve for the
R-T conductor operating at 1000 A snd also shove a
typical heat-transfer curve for bore copper. The
joue heating has been adjusted to give equal areas;
his results in a limiting heat-transfer rate,
q . 0.27 w/cm . The heat-generation curve can he
calculated fairly accurately. I is sore difticulo
to predict the heat-transfer curne, which depends
upon many factors such as conductor surface con-
ditions, conductor insulation, surface orientation,
and cooling-chansol dimensions. The mall temperature
margin available at R T nakes these factors more
critical than at loer fields. Although a layer of
convenuonal enamel insulation on rhe conductor can
improve some of the het-transfer oharactaristice,
the temperature drop through the insulation would
be prohibitive at a T.
Because the preceding heat-transfer calculations
do not cake iso account conduction no a neighboring
turn of cold superconductor, they are probably some-
what peosirmisoic. On the other hand, because the
cooling channels are relatively long (35 cm) and have
a radial depth of only 1.6 so, if a large portion
of a section were to go into film boiling, the coil
would probably quench. The design is thus s
reasonable compromise.-2-
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Nelson, R.; Cornish, D.; Zbasnik, J.; Sackett, S. & Taylor, C. 1.1-meter bore, 8-Tesla test facility, article, November 19, 1975; Livermore, California. (https://digital.library.unt.edu/ark:/67531/metadc870470/m1/3/: accessed May 6, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.