1. 1/18 The Distribution of Synchrotron Radiation Power in the IR C. H. Yu IR Overview SR Distribution in the IR The Protection of SR Power

2. 2/18 IR Overview Top view of IR vacuum chamber Top view of IR vacuum chamber The central part is Be pipe with the length of 0.3m and inner diameter of 63mm. The central part is Be pipe with the length of 0.3m and inner diameter of 63mm. The Be pipe is welded to a copper cylinder with the length of 0.55m and inner diameter of 63mm. The Be pipe is welded to a copper cylinder with the length of 0.55m and inner diameter of 63mm.

3. 3/18 SR Distribution in the IR 1. Formula for the SR Calculation Synchrotron radiation is produced when an electron (or positron) trajectory curves in the magnetic field of a dipole or quadrupole. Photons are emitted in a direction tangential to the particle instantaneous trajectory with differential power: Synchrotron radiation is produced when an electron (or positron) trajectory curves in the magnetic field of a dipole or quadrupole. Photons are emitted in a direction tangential to the particle instantaneous trajectory with differential power: Where  is the local radius of curvature and d  is the deflection angle.

4. 4/18 Since the BEPCII will be operated with colliding mode and SR mode, which have different synchrotron radiation sources and synchrotron radiation fan distributions, the situation of SR must be studied separately. Since the BEPCII will be operated with colliding mode and SR mode, which have different synchrotron radiation sources and synchrotron radiation fan distributions, the situation of SR must be studied separately.

5. 5/18 SR Distribution in the IR 2. Colliding Mode The colliding mode will be operated at energy range 1.0GeV to 2.1GeV. However the case with maximum SR power distribution is 1.89GeV as well as beam current of 0.91A. The colliding mode will be operated at energy range 1.0GeV to 2.1GeV. However the case with maximum SR power distribution is 1.89GeV as well as beam current of 0.91A. For the e- beam, synchrotron radiation fans in the IR are mainly generated from the final bending magnet R4OWB and from the IR quadrupoles due to the crossing angle trajectory. For the e- beam, synchrotron radiation fans in the IR are mainly generated from the final bending magnet R4OWB and from the IR quadrupoles due to the crossing angle trajectory. The synchrotron radiation generated by e+ beam is symmetrical with e- beam. The synchrotron radiation generated by e+ beam is symmetrical with e- beam.

6. 6/18 SR Distribution in the IR 2. Colliding Mode (Continued) The SR fans in the IR produced by e- beam. The SR fans in the IR produced by e- beam. The shading density indicates the relative power of each fan. The darker shading means higher power density.

7. 7/18 SR Distribution in the IR 2. Colliding Mode (Continued) As the e- beam travels through the final bending magnet R4OWB (13.4m from the IP) and enters the IR, it generates SR fan with the total power 396W (E c =0.7keV). The SR fan of center beam passes through the IP and spreads horizontally up to 0.5m from the IP. It contributes about 3.0W of SR power on the 0.5m~0.7m beam pipe from the IP. As the e- beam travels through the final bending magnet R4OWB (13.4m from the IP) and enters the IR, it generates SR fan with the total power 396W (E c =0.7keV). The SR fan of center beam passes through the IP and spreads horizontally up to 0.5m from the IP. It contributes about 3.0W of SR power on the 0.5m~0.7m beam pipe from the IP.

8. 8/18 SR Distribution in the IR 2. Colliding Mode (Continued) There are 6 quadrupoles between R4OWB and the IP. Among them R4SCQ magnet is the largest radiation source due to its off-axis installation. The total SR power generated by the R4SCQ magnet is 95.2W (E c <0.7keV). The SR fan of center beam also can reach 0.5m from the IP. About 19.2W of SR power from R4SCQ can strike on the 0.5m~0.7m beam pipe from the IP. The rest of SR fans travels out of the near IR and is absorbed on the surface at 3m~4m from the IP. There are 6 quadrupoles between R4OWB and the IP. Among them R4SCQ magnet is the largest radiation source due to its off-axis installation. The total SR power generated by the R4SCQ magnet is 95.2W (E c <0.7keV). The SR fan of center beam also can reach 0.5m from the IP. About 19.2W of SR power from R4SCQ can strike on the 0.5m~0.7m beam pipe from the IP. The rest of SR fans travels out of the near IR and is absorbed on the surface at 3m~4m from the IP.

9. 9/18 SR Distribution in the IR 2. Colliding Mode (Continued) Most of the synchrotron radiation power (521.3W) generated by R3SCQ and ISPB (E c =1.0keV). magnets hits the beam pipe at 3.0m~4.4m from the IP. Most of the synchrotron radiation power (521.3W) generated by R3SCQ and ISPB (E c =1.0keV). magnets hits the beam pipe at 3.0m~4.4m from the IP. In the proposed design, the photons with about 0.5W of SR power contributed by both e+ & e- beams within 10  x of beam size will hit directly on the detector beryllium pipe. In the proposed design, the photons with about 0.5W of SR power contributed by both e+ & e- beams within 10  x of beam size will hit directly on the detector beryllium pipe.

10. 10/18 SR Distribution in the IR 2. Colliding Mode (Continued) During the operation if there is extreme case such as 5mm orbit and 2mrad angle distortion. The SR power on beam pipe beside Be pipe is 61W and Be pipe is 10.1W. During the operation if there is extreme case such as 5mm orbit and 2mrad angle distortion. The SR power on beam pipe beside Be pipe is 61W and Be pipe is 10.1W. The SR distribution caused by the final bending magnet R4OWB and R3OWB are sensitive to the beam orbit distortion. They are the only SR source which is sensitive to orbit distortion. The SR distribution caused by the final bending magnet R4OWB and R3OWB are sensitive to the beam orbit distortion. They are the only SR source which is sensitive to orbit distortion.

11. 11/18 SR Distribution in the IR 3. SR Mode The SR mode will be operated at energy of 2.5GeV. The maximum beam current is 250mA. The SR mode will be operated at energy of 2.5GeV. The maximum beam current is 250mA. The SR power in the IR mainly generated by the final bending magnet R4OWB and the superconducting bending magnet R4SCB/R3SCB nearby the IP. The SR power in the IR mainly generated by the final bending magnet R4OWB and the superconducting bending magnet R4SCB/R3SCB nearby the IP. For the SR mode, only e- beam is employed. For the SR mode, only e- beam is employed.

12. 12/18 SR Distribution in the IR 3. SR Mode (Continued) The SR fans in the IR produced by e- beam. The SR fans in the IR produced by e- beam. The shading density indicates the relative power of each fan. The darker shading means higher power density.

13. 13/18 SR Distribution in the IR 3. SR Mode (Continued) As the e- beam travels through the final bending magnet R4OWB and enters the IR, it generates SR fan with the total power 333W (E c =1.7keV). The SR fan of center beam passes through the IP and spreads horizontally up to 0.5m from the IP. It contributes about 2.5W of SR power on the 0.5m~0.7m beam pipe from the IP. As the e- beam travels through the final bending magnet R4OWB and enters the IR, it generates SR fan with the total power 333W (E c =1.7keV). The SR fan of center beam passes through the IP and spreads horizontally up to 0.5m from the IP. It contributes about 2.5W of SR power on the 0.5m~0.7m beam pipe from the IP.

14. 14/18 SR Distribution in the IR 3. SR Mode (Continued) The total power of the SR fan generated by R4SCB is 223W (E c =2.3keV). The SR fan of center beam also can reach 0.5m from the IP. About 25.3W of SR power from R4SCB can strike on the 0.5m~0.7m beam pipe from the IP. The rest of SR fan from R4SCB travels out of the near IR and is absorbed on two surfaces, one is a mask placed in front of the ISPB septum, the other is the beam pipe at 3m~4m from the IP. The total power of the SR fan generated by R4SCB is 223W (E c =2.3keV). The SR fan of center beam also can reach 0.5m from the IP. About 25.3W of SR power from R4SCB can strike on the 0.5m~0.7m beam pipe from the IP. The rest of SR fan from R4SCB travels out of the near IR and is absorbed on two surfaces, one is a mask placed in front of the ISPB septum, the other is the beam pipe at 3m~4m from the IP.

15. 15/18 SR Distribution in the IR 3. SR Mode (Continued) About half of the SR power 223W generated from R3SCB hits the mask placed in front of the ISPB septum. The remainder mainly strikes the beam pipe between the R3Q1a and R3Q1b. About half of the SR power 223W generated from R3SCB hits the mask placed in front of the ISPB septum. The remainder mainly strikes the beam pipe between the R3Q1a and R3Q1b. In the proposed design, the photons with about 0.2W of SR power within 10  x of beam size will hit directly on the detector beryllium pipe. In the proposed design, the photons with about 0.2W of SR power within 10  x of beam size will hit directly on the detector beryllium pipe.

16. 16/18 SR Distribution in the IR 3. SR Mode (Continued) During the operation if there is extreme case such as 5mm orbit and 2mrad angle distortion. The SR power on beam pipe beside Be pipe is 59W and Be pipe is 4.3W. During the operation if there is extreme case such as 5mm orbit and 2mrad angle distortion. The SR power on beam pipe beside Be pipe is 59W and Be pipe is 4.3W. Final bending magnet is the only SR source which is sensitive to orbit distortion. Final bending magnet is the only SR source which is sensitive to orbit distortion.

17. 17/18 The Protection of SR Power We have designed the water cooling structure in the beam pipe 0.5~0.7m from the IP, the crotch beam pipe and the beam pipe 3.0~4.0m from the IP to avoid the heat problem in these region. We have designed the water cooling structure in the beam pipe 0.5~0.7m from the IP, the crotch beam pipe and the beam pipe 3.0~4.0m from the IP to avoid the heat problem in these region. Except Be pipe, the material of vacuum chamber within  3.5m is chosen as copper for its low coefficient of photon-induced gas desorption, high thermal conductivity and large photon absorption coefficient. Except Be pipe, the material of vacuum chamber within  3.5m is chosen as copper for its low coefficient of photon-induced gas desorption, high thermal conductivity and large photon absorption coefficient.

18. 18/18 Summary The SR power distribution of colliding mode and SR mode have been estimated. The water cooling structure has been designed in the region with heat problem. The SR power distribution of colliding mode and SR mode have been estimated. The water cooling structure has been designed in the region with heat problem. It’s difficult to stop both direct and once- scattering photons emitted within 10  x of beam size at all magnets hitting on the Be pipe. It’s difficult to stop both direct and once- scattering photons emitted within 10  x of beam size at all magnets hitting on the Be pipe.