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IR Summary

IR Summary. M. Sullivan for the IR and MDI teams SuperB General Meeting XIII La Biodola Isola d’Elba, Italy May 31-June 4, 2010. IR Related sessions. IR (accel.) IR Design Update (M. Sullivan) Solenoid compensation (K. Bertsche) HOM damped bellows (S. Novokhatski)

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IR Summary

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  1. IR Summary M. Sullivan for the IR and MDI teams SuperB General Meeting XIII La Biodola Isola d’Elba, Italy May 31-June 4, 2010

  2. IR Related sessions • IR (accel.) • IR Design Update (M. Sullivan) • Solenoid compensation (K. Bertsche) • HOM damped bellows (S. Novokhatski) • MDI Issues (E. Paoloni) • Backgrounds (E. Paoloni)

  3. IR Design Topics • IR update • White paper baseline • PM update • Panofsky Style QD0 and QF1 • Design changes for SR reasons • Solenoid Compensation • IR Interface • Thin Be beam pipe • Rapid access to Central Region • Flanges and bellows • White paper status • Summary and Conclusions

  4. Baseline IR Design Stable since October

  5. Machine Parameters

  6. General IR Design Features • Crossing angle is +/- 33 mrads • Cryostat has a complete warm bore • Both QD0 and QF1 are super-conducting • PM in front of QD0 • Soft upstream bend magnets • Further reduces SR power in IP area • BSC to 30 sigmas in X and 100 sigmas in Y (7 sigmas fully coupled)

  7. SR backgrounds • No photons strike the physics window • We trace the beam out to 20 X and 45 Y • The physics window is defined as +/-4 cm for a 1 cm radius beam pipe • Photons from particles at high beam sigmas presently strike within 5-6 cm downstream of the IP • However, highest rate on the detector beam pipe comes from a little farther away • Unlike PEP-II, the SuperB design is sensitive to the transverse beam tail distribution

  8. Beam Tail Distribution These tail distributions are more conservative than those used for PEP-II. The SuperB beam lifetime is shorter by about a factor of 10 so the tail distributions can be higher. But we will probably collimate at lower beam sigmas than shown here.

  9. New beam tails from Touschek Manuela has been working on getting a beam tail distribution from BGB and Touschek. This is from the LER at -2 m from the IP. This will be a first as far as getting a real distribution for the beam tails for SR. More on this on Thursday.

  10. On the airplane comparison Comparison shows that the guessed at X distribution is not so unreasonable for  > 10. However, it looks like we need to add more particles in the 4-10 range. The comparison is off a bit. Manuela says 4cm should be more like 35.

  11. Estimate of the photon rate incident on the detector beam pipe LER HER 0.24 0.07 10 13 111 13 8 9 968 105 Backscattering SA and absorption rate (3% reflected)

  12. How do we change the beam energies? • For the baseline QD0 and QF1 magnets we need to keep the ratio of the magnetic field strengths constant in order to maintain good field quality • We want the * values to remain constant to maintain luminosity • We need to match the lattice functions to the rest of the ring • No changes to the permanent magnets • Solutions found for all Upsilon resonances

  13. Energy Changes • The 2S and the 3S LER energies would have very little polarization • It should be straightforward to develop a procedure to perform an energy scan • To go to the Tau-charm region (Ecm ~4 GeV) we will need to remove most if not all of the permanent magnets • With the air-core super quads we would need to approximately preserve the energy asymmetry • We should be able to change the boost by using the PMs to change the actual beam energies

  14. Super-ferric QD0 and QF1

  15. Super-ferric QD0 Vobly had a 2 T limit but we need 10% headroom for any above 4S energy scan • Constraints • Maximum field of no more than 1.8 T at the pole tips (we assume this is the same as the half width – should probably lower this limit another 10%-20% because the pole tip is on the diagonal) • Equal magnetic field strengths in each twin quad • Square apertures • Might be able to relax these a little • If we have room between the windings to add Fe then we can have some magnetic field difference • Might be able to make the apertures taller than they are wide – means the windings get more difficult • For now assume constraints are there and then see what we can do

  16. Permanent Magnets • Upon embarking on the task of looking at the Super-Ferric design we realized we could significantly improve the IR design by re-optimizing the permanent magnet part of the design • Give up some vertical aperture in order to go back to circular magnet designs (~1.4 stronger field) • Open up the crossing angle 10% to get more space for permanent magnet material (60  66 mrad) • Add a couple of permanent magnet slices in front of the septum (shared magnets but close to the IP and hence minimal beam bending) • LER beam 1.864 mrad • HER beam 1.164 mrad

  17. Permanent Magnets (2) • Moved some of the slices previously used on the HER to the LER in order to get more vertical focusing to the LER • We now have more equal vertical beta maximums • The beam pipe inside the magnets is 1 mm smaller in radius • 6 mm from 7 mm • The magnetic slices are now only 1 cm long and are perpendicular to the beam line instead of the detector axis • Better packing and better magnetic field performance for each beam

  18. Vanadium Permendur Design • We use the above redesigned permanent magnet slices • The twin quad QD0 face is 55 cm from the IP. If we move in closer the field strength gets too high. In addition, we lose space for the stronger PM slices • We start by setting the LER side of QD0 and QF1 • We impose the beta function match requirements for the LER (* and the match point at 16.17 m) and we also try to get the maximum field close to 1.8 T • We keep the L* value constant but are allowed to change the separation and the lengths of QD0 and QF1 • These set the QD0 and QF1 strengths for the HER • We then add HER only quads behind QD0 and QF1 to finish the final focusing for the HER

  19. Vanadium Permendur Design

  20. Latest New Idea • We have discovered there are several rare earth metals that have very high magnetization curves • Holmium • Dysprosium • Gadolinium • Holmium has the highest magnetic moment of any element and is reputed to have a magnetization curve up to 4 T (Vanadium Permendur is about 2.4 T) • Curie temperatures • Ho is 20 K • Dy is 85 K • Ga is 289 K

  21. Some properties of these metals* • Den. Young’s Shear Bulk Possion Vickers Brinell Cost • Elem. g/cc Mod. Mod. Mod. Ratio Hard. Hard. $/kg • Ho 8.80 64.8 26.3 40.2 0.231 481 746 1000 • Dy 8.55 61.4 24.7 40.5 0.247 540 500 120 • Ga 7.90 54.8 21.8 37.9 0.259 570 --- <120 • Fe 7.87 211 82 170 0.29 608 590 0.4 (scrap) • Pb 11.35 16 5.6 46 0.44 --- 38.3 2 • Sn 7.31 50 18 58 0.36 --- 51 18 • Cu 8.96 120 48 140 0.34 369 874 15 • Ni 8.90 200 76 180 0.31 638 700 18 • Al 2.70 70 26 76 0.35 167 245 21 • Au 19.30 120 27 180 0.44 216 --- 34,000 • Zn 7.13 108 43 70 0.25 --- 412 2 • Ag 10.50 83 30 100 0.37 251 25 530 • *Wikipedia, Metalprices.com and VWR Sargent Welch These elements appear to be somewhere between Tin and Aluminum in hardness and strength with a density of Ni or Cu

  22. Holmium Design

  23. Beta function comparison with V12 baseline • V12 VP Ho • LER x max 316 309 221 • HER x max 388 480 328 • LER y max 1562 1424 1300 • HER y max 1266 1208 1111 Maximum betas are lower in almost all cases

  24. SR backgrounds • We have been struggling to get a solution for the SR backgrounds • So far, NONE of the new designs work as well as the previous baseline design (concentrating on the HER so far) • Why? It looks like a combination of things • Opening the crossing angle to 66 mrad from 60 mrad costs us 3 mrad • The shared quads costs 1.1 mrad for the HER • Sloping the QD0 to match the beam angle in order to minimize the aperture costs some free QD0 bending • Moving QF1 closer to QD0 costs leverage. Offsetting QD0 is less effective. • The QF1 beta X max is reduced by moving in closer but apparently the leverage loss is a bigger effect • Strengthening PM reduces the strength of QD0 forcing a bigger offset for the same effect • Net result is that even with a beam bend angle of 10 mrad in QD0 we are not able to steer all of the SR away from the detector beam pipe (previous baseline was successful with a 1.6 mrad bend in QD0)

  25. SR backgrounds (2) • What to do? • Suggest the following compromises: • Remove the shared quads • Reduce the crossing angle back to 60 mrad • This hurts a little because we gained a lot by increasing the strength of the PMs. We would still have most of the improvement. • Set a maximum bend angle of 3-4 mrad in the incoming QD0 magnets • We will want to have a zero bend angle in the outgoing QD0 and QF1 magnets • This favors the panofsky style quads for the outgoing beams • We presently scan out to 20  in x. We scanned out to 10  for PEP-II. Propose scanning out to 12-15  in x. Use this only if we can’t make it any other way.

  26. Solenoid compensation • We have found out from our colleagues at KEK that we must pay much more attention to the fringe field of the detector solenoid • The radial part of the field causes emittance growth • This also means that we want to minimize the fringing fields of the compensating solenoids • K. Bertsche had a presentation on solenoid compensation

  27. HOM power • Sasha presented general information on HOM generation and absorption • He showed many PEP-II cases • Experience with wake fields from collimators • Effects of shortening the beam bunch

  28. A List of Topics at the Interface • Physics Beampipe • Inside radius is 10 mm • As thin a Be wall as possible but water cooled • Assembly and removal (Flanges and bellows) • Shared permanent magnets (now removed) • Beampipe heating (coming next) • 300 mrad angle of acceptance • Cryostat may end up close to that boundary • Cryostat supports • W shielding

  29. Flange Drawing

  30. Central Chamber

  31. Scaled Picture

  32. L0 and Be beam pipe • F. Bosi has been working on integrating the L0 layer with the Be beam pipe Be water-cooling L0 water-cooling

  33. L0 mounted on the Be beam pipe Room for a bellows?

  34. Supports and Shielding • Cryostat supports and rapid access • The cryostats must be rigidly supported • We also want rapid access to the SVT and PMs • Working toward an access time of a couple of days • Drift chamber needs significant shielding • Who is supporting all of this weight?

  35. Summary • The general Interaction Region design has held steady • The baseline design can run on all of the Upsilon resonances and perform an energy scan (and, of course, run off resonance) without any change in hardware • We have re-optimized the permanent magnet part of the IR and have significantly improved the IR design. Further optimization looks possible.

  36. Summary (2) • We have a different way of making QD0 and QF1. QD0 has always been one of the most challenging aspects of the IR design. The new design looks quite promising. • Currently the three new IR designs using the Panfosky style quads have proven to be difficult in the control of the SR generated by the FF magnets • We believe we understand how this happened and will back out some of the “improvements” we made to the design in the next iteration

  37. Summary (3) • Rapid access schemes are being investigated and are looking conceptually feasible. This would also be the way you initially assemble things. Vibration control may be an issue. • Magnetic field compensation schemes are being pursued that satisfy the accelerator requirements • Good progress is being made toward integrating the Be beam pipe and L0 of the SVT

  38. Conclusions • The permanent magnet re-optimization has improved the flexibility of the overall IR design • The new magnet design for QD0 and QF1 further improves the flexibility of the IR design • We have been struggling with the control of the SR from the FF magnets • Finding an edge in the design is in a sense reassuring. We have moved in one direction a little too far and now need to pull back a bit. • The IR design is still robust and will emerge a better design once we figure out how to control the FF SR

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