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Design of Interaction Region

Design of Interaction Region. Gang Xu Accelerator Physics Group IHEP, Beijing, Oct. 14, 2001. Content. Introduction to BEPCII Requirements to IR design from accelerator physics Detector boundary condition IR beam line layout IR Magnets Background and consideration of new design Summary.

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Design of Interaction Region

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  1. Design of Interaction Region Gang Xu Accelerator Physics Group IHEP, Beijing, Oct. 14, 2001

  2. Content • Introduction to BEPCII • Requirements to IR design from accelerator physics • Detector boundary condition • IR beam line layout • IR Magnets • Background and consideration of new design • Summary

  3. 2-ring collider— factory type machine Synchrotron radiation facility Basic parameters (next page) Introduction to BEPCII

  4. Introduction to BEPCII(continued) Tab. 1 Main parameters

  5. Requirements to IR design from accelerator physics • Rapidly separate the beams into two rings • Squeeze the vertical beta function to 1.5cm • Compensate the coupling from detector solenoid • Connect the two outer rings to provide the synchrotron radiation • Keep the background in the acceptable level • All accelerator components in IR must stay in the space limited by the detector • HOM heating due to the mask and the discontinuity of vacuum chamber should be considered

  6. Boundary condition • Detector geometric condition

  7. Boundary condition(continued) Summary of the main geometric conditions • The first accelerator component must be after 0.5m away from IP • Before 1.15m, the outer aperture of components must be less than Φ384mm • Before 1.9m, the outer aperture of components must be less than Φ756mm

  8. Boundary condition(continued) • Detector solenoid(Bs=1T, new design value 1.2T)

  9. Boundary condition(continued) • Aperture of IR vacuum chamber(Half ) For collision beam 1. 14σx+xoffset+10mm c.o.d.(εx=0.25μm) 2. 14 σy+5mm c.o.d. (full coupling εy=0.125μm) For injection beam 3. 16σx+xoffset+3mm c.o.d. For SR photons(collision beam) 4. Out of the trajectories of SR photons from 10 σ particles

  10. IR beam line layout • Crossing angle θx(mrad)=±11 relative to the detector solenoid axis • Beam comes to IP from outer ring then goes into inner ring • 1st S.C. magnet has combined anti-solenoid(ASOL) and • bending coil(SCB), the latter is used in synchrotron radiation mode • Both electron and positron are off the axis of SCQ • All S.C. coils are in one cryostat • ISPB is a septum type magnet, it will bend the beam in inner ring • OQ1, IQ1, OQ2, IQ2 are special magnets with dual aperture, beam • goes through their axes.

  11. IR beam line layout(continued) βy max<120m(βy *=1.5cm)180m(βy *=1cm), βx max<6m in s=0~1.9m

  12. IR Magnets(Superconducting) • Anti-solenoid ASOL with integral strength 1.42 T·m, 0.6m away from IP, it will be extended onto SCQ to cancel the effect of the solenoid fringe field • SCB placed at the same location as ASOL with integral strength 0.26 T·m • SCQ with strength 17.6T/m and effective length 0.4m, 1.15m away from IP

  13. IR special magnets(Normal)

  14. Background issue and consideration of new design Since the beam coming from outer ring is off axis in the SCQ, this will lead to synchrotron radiation. From the previous plot, the minimum distance between beryllium pipe and the trajectory of the photon is only 7.2mm. This situation must be improved.

  15. 7.2

  16. Three improvement methods • Increase the radius of the beryllium pipe • Add a bending coil on SCQ to cancel(or partially) the bending field due to the off axis for the beam in outer ring, this will lead to BSC increasing from Φ120 to Φ140 • Place SCQ to the center of outer ring beam orbit, this will lead to the equivalent BSC increasing from Φ120 to Φ170

  17. Before doing the improvement, we need to know • What is the acceptable level of the synchrotron radiation? • The more detail boundary conditions in IR • The acceptable heating power of each IR component

  18. Summary • IR design is very preliminary • Due to the background issues we must do more detail IR design • Many items are not taken into account such as background from the loss particle, vacuum, beam diagnostics, …

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