Solenoid Compensation for the SuperB Interaction Region Page: 2 of 3
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ends of the quadrupoles. Additional coils (or higher
winding density) would be needed at the ends of these
compensation solenoids. In addition, the baseline design
cannot satisfy Eq. 1, so cannot remove x-y coupling.
An improved set of compensation solenoids for the
baseline design is presented in Fig. 2. The solenoids of
Fig. 1 have been shortened, additional small trim coils
have been added at some solenoid ends, and large
solenoids have been added between quadrupoles to over-
compensate the detector solenoid and satisfy Eq. 1. Some
of the coil excitations are fairly high, but are not
unreasonable for realistic superconducting solenoid
designs in the available space.ZUU
100
mm
0
-100-3 -2 -1 0 cm 1
2.
Figure 2: Compensation solenoids added to baseline IR
design. Coil excitations are given in kA-turns.
The magnetic fields due to this compensation approach
are shown in Fig. 3. The largest curve (red) shows Bz on
axis. The smaller curves show the B. along the beam
trajectory in the detector solenoid coordinate frame
(green) and in the beam coordinate frame (blue), which
has a crossing angle relative to the detector solenoid
frame.
Magnetic Fields
10000
1000
-300 -200 - 00 0 1 2 30; B i
deetrslni n cometon soleoids
-5o000
-000
-25000
x (cm)
Figure 3: Magnetic fields in IR due to combination of
detector solenoid and compensation solenoids.
Solenoid compensation has reduced Bz in the body of
the quadrupoles to < 1.5 kG, less than 10% of the nominal
detector field. The Bz near the quadrupole ends is not verysmooth; this can be improved by a gradually varying the
winding density of the trim coils that were added at the
ends of the compensation solenoids.
Beam Offsets and Angles
The transverse B. fields kick the beam in the y-
direction. The resultant offsets and angles for the LEB are
shown in Fig. 4. Offsets do not exceed 1 mm, which is
acceptably small. The higher energy HEB will have
proportionately smaller offsets and angles in the IR. By
virtue of satisfying Eq. 1, the beams are forced to have no
offset or angle where they cross, at the IP.
Y Behavior: 4 GeV BeamcO 200 o 300 V1"m'
Figure 4: LEB offsets and angles in IR.
The offsets and angles shown in Fig. 4 do not include
quadrupole kicks. The quadrupoles will introduce kicks,
but these will be small and easily correctable. (The
quadrupoles would not introduce kicks if they were offset
and rolled slightly. But this would add complexity and
asymmetry to the IR design, so is not planned.)
Detector Field Distortion
The implementation of compensation solenoids slightly
distorts the detector field near the IP, and reduces its
magnitude by about 200 G (Fig. 5). If necessary,
additional trim solenoids could be added over the PM
quads to reduce this perturbation.Detector Bz On Axis
)5100
1500014900
14!004600-
1500
-25 15-- - Uncompensoted
-Compensated15 25
("I
Figure 5: Effect of solenoid compensation on detector
field near IP.PEP-I 30 mradS
Support tube Solenoids
20 m d
HER . P
LE
_QF1 8 Ilo oV e IQF1 _
020 100 o
1521_
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Bertsche, Kirk & Sullivan, Michael K. Solenoid Compensation for the SuperB Interaction Region, article, August 25, 2010; United States. (https://digital.library.unt.edu/ark:/67531/metadc833025/m1/2/: accessed April 18, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.