Distribution of the synchrotron radiation from bending magnets Page: 4 of 12
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2
Figure 2 shows the distribution of the synchrotron radiation on the
vacuum chamber wall when there are no crotches or absorbers. The radiation in
the vertical axis is the integrated value over the vertical opening angle and
per unit length along the vacuum chamber wall in the horizontal direction.
The distance from the storage-ring orbit to the wall in the radial direction
is 23.81 cm.
The distribution of the absorption by crotches and absorbers for the
synchrotron radiation of Fig. 2 is shown in Fig. 3. It is assumed that the
distance from the storage-ring orbit to the edges of the crotches and
absorbers is 3 cm. The radiation from the M1 magnet is absorbed by Cl
(64.5%), Al (25%), and C2 region absorber (7.5%). Due to the slit opening for
the insertion-device (ID) beam near the Cl crotch region, the remaining 3% of
the M1 radiation goes to the ID beam line. (Detailed beam profile at Cl will
be described in Fig. 6.) Here, 100% of the radiation from one BM at 7.0 GeV
and 300 mA is 20.5 kW. The radiation from M1 does not hit the vacuum chamber
directly in the arrangement of the sector shown in Fig. 1.
Because of the straight section (SS) and the extraction of a BM
beam, the absorption of the M2 radiation is somewhat different from that of
the M1 radiation. First, 87% of the M2 radiation will be absorbed by C2
(53.5%), C2 region absorber (8.5%),;A2 (22%), and Cl region absorber (3%).
Another 7.5% of the radiation goes to the BM beam line. The absorption of the
remaining 5.5% of the M2 radiation is dependent on the use of the SS.
(Further details of the BM beam and C2 will be described in Figs. 6 and 7).
When the SS is used for rf cavities or during the initial operation
of'the machine, the wall distance from the storage-ring orbit will be larger
than 7 cm. In this case, the remaining 5.5% of the M2 radiation does not hit
the wall at all. It is absorbed by A3 (4.5%) and A4 (1%).
When the SS is used for an ID, the distance from the storage ring
orbit to the vacuum chamber wall in the present design is 3 cm. The
distribution of the radiation along the ID vacuum chamber for this case is
shown in Fig. 4. With the edge of the A2 absorber 3 cm away from the storage-
ring orbit, the radiation is distributed all over the SS from -2.5 m to 2.7 m,
as shown in Fig. 4. The maximum power density is less than 0.5 W/mm2. The
vertical width of the beam is on the order of 1 mm. The total amount of the
power is 4.5% of the M2 radiation. The remaining 1% is absorbed by A4. The
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Kim, S. Distribution of the synchrotron radiation from bending magnets, report, November 1, 1988; Illinois. (https://digital.library.unt.edu/ark:/67531/metadc679921/m1/4/: accessed March 19, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.