RHIC D0 INSERTION DIPOLE DESIGN ITERATIONS DURING PRODUCTION. Page: 2 of 3
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straight section of two test coils in order verify the coil
pre-stress and check the field harmonics in the body of the
magnet prior to commencing production. The coils were
collared with the design pole shim and midplane caps.
This section was then measured at room temperature using
a rotating coil to check the field harmonics. The
measurements indicated that the pre-stress was low by
2000 psi and that b2 and b4 were unacceptable. Based on
these results, the sample was disassembled and the
thickness of the midplane caps was increased by 0.005".
The reassembled section was re-measured to determine if
the desired shift in harmonics was achieved.
II. PRODUCTION CROSS SECTION ITERATIONS
Based on the results of the test collaring and warm
measurements some changes were made to the baseline
cross section design. The thickness of the smallest wedge
was increased by 0.004" by adding an additional layer of
Kapton  wrap, the midplane cap thickness was increased
by an additional 0.001", and the pole shim thickness was
increased by 0.001". At this point coil production started,
thereby limiting any future changes to small variations in
pole shim and midplane cap thickness. Cold mass
production of the first magnet was accelerated so that test
data could be analyzed before the second magnet was
assembled. The results of the first magnet confirmed this
iteration. The desired pre-stress was obtained and the body
harmonics at 2000 Amps were within one standard
deviation of ideal values. Fig. 2 shows the relative field
error dBy/B on the x-axis based on these measurements.
The errors are <10-4 within 60% of the coil radius and <4
x 10-4 at 80% of the coil radius. This is the best one
-80 -60 -40 -20 0 20 40 60 80
Percentage of Coil Radius
Figure 2. Geometric Field Errors on x-axis of DRZ101
can expect given the general manufacturing tolerances. Since
the first magnet had the desired coil pre-stress and low field
harmonics in the body of the magnet it has been installed in
the RHIC ring.
The test assembly helped to get the desired geometric
harmonics. However the saturation induced harmonics and the
end harmonics were measured for the first time when the first
magnet tested. The end harmonics could only be measured at
room temperature because the meas. coil for 4.2K tests was not
yet available. The saturation induced harmonics were an order
of magnitude smaller than in the first arc dipole magnet, but
they were still larger than desired. To reduce them in the
following magnets, steel rods were inserted into the saturation
suppression holes in the yoke. To compensate for the end
harmonics observed, the thickness of the midplane caps was
increased by 0.002" for the remaining magnets.
The test results from the next magnet showed that the
desired changes had been obtained both in geometric and
saturation induced harmonics (see Fig. 3). However, the
saturation in the end harmonics, which was being measured for
the first time, was found to be large. This prompted a decrease
in pole shim thickness of 0.004" which was incorporated into
the fifth and sixth cold masses. This geometric change in
cross section was made to give the desired field quality at the
12 - - ------- --
10 _ _--- I-b2(5k)
8 - fl - Body-U(W)
6 - +- Bdy-b2(5kA)
-4 _ _ _ _ _ _
101 102 103 104 105 106 107 108
Magnet Sequence Number
Figure 3. Plot showing b2 and b4 by magnet.
During the planned break in the production after the sixth
cold mass, a change to the stamping die was made to remove
the saturation suppression holes and thereby eliminate the need
to fill the void with steel rods at cold mass assembly. The
computer calculations indicated that this would reduce the b2
saturation. A small integral b2 which was seen in the fifth and
sixth magnets was eliminated in the following magnets. No
further changes are expected for the remainder of the
4 - :- - - ' - - = - - - - - - - - - - - -
2 -- --- ------- -------------,
-23 ----------------------- ---------- -----
-34 - - - - - - - - - - - - - - - - - - -
-4 - - '- - -- - -'- - - - -' - - '
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SCHMALZLE,J.; ANERELLA,M.; GANETIS,G.; GHOSH,A.; GUPTA,R.; JAIN,A. et al. RHIC D0 INSERTION DIPOLE DESIGN ITERATIONS DURING PRODUCTION., article, May 12, 1997; Upton, New York. (digital.library.unt.edu/ark:/67531/metadc734872/m1/2/: accessed March 18, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.