Overview and Issues of the MEIC Interaction Region

1. Overview and Issues of the MEIC Interaction Region M. Sullivan MEIC Accelerator Design Review September 15-16, 2010

2. Interaction Region Design Concerns Accelerator Concerns Detector Concerns MEIC IR and detector Summary Outline

3. There are several conflicting constraints that must be balanced in the design of an Interaction Region The design must accommodate the requirements of the detector in order to maximize the physics obtained from the accelerator At the same time, the design must try to maximize accelerator performance which usually means having the final focusing elements in as close as possible to the collision point (minimize L*) Interaction Region Design

4. Beam related detector backgrounds must be carefully analyzed and mitigation schemes developed that allow the detector to pull out the physics For electron (positron) beams this means controlling synchrotron radiation backgrounds and lost beam particles For proton (ion) beams this means primarily controlling the lost beam particles Interaction Region Design (2)

5. An adequate beam-stay-clear must be defined If possible, the definition should permit beam injection while the detector is taking data (for the electron beam) Modern light sources, the B-factories and (of course) the super B-factory designs use continuous injection Machine performance with continuous injection is vastly improved Interaction Region Design (3)

6. The detector acceptance for the physics is a very important constraint Usually all detectors want 4 solid angle coverage This wish has to be tempered with the needs of the accelerator and the requirements of the final focusing elements Interaction Region Design (4)

7. The MEIC Interaction Region Features 50 mrad crossing angle Detector is aligned along the electron beam line Electron FF magnets start/stop 3.5 m from the IP Proton/ion FF magnets start/stop 7 m from the IP MEIC Interaction Region Design

8. Electron beam Energy range 3-11 GeV Beam-stay-clear 12 beam sigmas Emittance (x/y) (1.02/0.20) nm-rad Betas x* = 100 cm x max = 435 m y* = 2 cm y max = 640 m Final focus magnets Name Z of face L (m) k G (11 GeV) QFF1 3.5 0.5 -1.7106 -62.765 QFF2 4.2 0.5 1.7930 65.789 QFFL 6.7 0.5 -0.6981 -25.615 Table of Parameters (electrons)

9. Proton/ion beam Energy range 20-60 GeV Beam-stay-clear 12 beam sigmas Emittance (x/y) (2.25/0.45) nm-rad Betas x* = 100 cm x max = 2195 m y* = 2 cm y max = 2580 m Final focus magnets Name Z of face L (m) k G (11 GeV) QFF1 3.5 0.5 -1.7106 -62.765 QFF2 4.2 0.5 1.7930 65.789 QFFL 6.7 0.5 -0.6981 -25.615 Table of Parameters (proton/ion)

10. Ultra forward hadron detection Small angle hadron detection Central detector with endcaps Low-Q2 electron detection ion quads dipole Large aperture electron quads IP dipole dipole Small diameter electron quads ~50 mrad crossing Solenoid yoke + Muon Detector Solenoid yoke + Hadronic Calorimeter RICH Tracking RICH Muon Detector EM Calorimeter EM Calorimeter Hadron Calorimeter HTCC Interaction Region and Detector Courtesy Pawel Nadel-Tournski and Alex Bogacz 5 m solenoid

11. 4 3 Tesla 2 1 QFFP QFFP QFFL QFF2 QFF1 QFF1 QFF2 QFFL ~2 kG Estimate of the detector magnetic field (Bz) The detector magnetic field will have a significant impact on the beams. Some of the final focusing elements will have to work in this field.

12. Both beam energies have a fairly large energy range requirement The final focus elements must be able to accommodate these energy ranges An attractive alternative for some of the final focusing elements (especially the electron elements) is to use permanent magnets – they have a very small size and do not need power leads However, any PM design has to be able to span the energy range Energy range

13. First look at backgrounds 50 mrad Synchrotron radiation photons incident on various surfaces from the last 4 electron quads 38 P+ 8.5x105 2.5W 4.6x104 240 2 e- 3080 Rate per bunch incident on the surface > 10 keV X Beam current = 2.32 A 2.9x1010 particles/bunch Rate per bunch incident on the detector beam pipe assuming 1% reflection coefficient and solid angle acceptance of 4.4 % Z M. Sullivan July 20, 2010 F$JLAB_E_3_5M_1A

14. Initial look at synchrotron radiation indicate that this background should not be a problem Need to look at lost particle backgrounds for both beams Generally one can restrict the study to the region upstream of the IP before the last bend magnet A high quality vacuum in this region is sometimes enough Backgrounds

15. The IR is one of the more difficult regions to design There are multiple constraints, however, balancing the various requirements to maximize the physics should be the primary goal of any design The MEIC IR design shows good promise and initial studies of SR backgrounds show that this background looks ok Summary

16. The MEIC IR design has tried to accommodate the requirements of the detector and the requirements of the accelerator The design has benefited from input from both the accelerator and the detector community A reasonable compromise has been struck and the design can deliver the needed accelerator performance while allowing the detector to collect the important physics Conclusion