1. IR Summary M. Sullivan SuperB General Meeting XII
Laboratorie d’Annecy-le-Vieux
de Physique des Particules (LAPP)
d’Annecy-le-Vieux, France
March 16-19, 2010

2. IR Related Presentations
Polarimetry (K. Moffiet)
Beam-Beam Depolarization (C. Rimbault)
Beam-Beam Diffusion (C. Rimbault)
IR Design Update (M. Sullivan)
MDI Issues (M. Sullivan)
Backgrounds (E. Paoloni) (earlier talk)
Be Beam pipe Heating (S. Novokhatski)
Vibration Issues (M. Masuzawa)

3. Spin and Beam-Beam Polarimetry (K. Moffiet)
Beam-Beam Depolarization (C. Rimbault)
Beam-Beam Diffusion (C. Rimbault)
IR Design Update (M. Sullivan)
MDI Issues (M. Sullivan)
Backgrounds (E. Paoloni)
Be Beam pipe Heating (S. Novokhatski)
Vibration Issues (M. Masuzawa)

4. Polarimetry Layout
A little over 80m from the IP

5. Polarimetry Issues

6. Polarimetry Conclusions

7. Beam-Beam and Spin
Two very nice talks showing work started at LAL investigating spin depolarization, spin diffusion and emittance growth from the collision
Further code development is needed for spin depolarization
General conclusions are that these effects are probably small at SuperB

8. Depolarization
Spin Precession induced by the collective EM field of the oncoming beam, described by T-BMT equation (dominant effect at ILC):
Where a= is the coeff of anomalous magnetic moment of electron
Precession angle = ga x deflection angle
Spin-Flip effect during synchrotron radiation: Sokolov-Ternov effect, tends to depolarize in linear collider. Probability for the spin to flip (s-s) at the moment of photon emission, proportional to the photon energy. Very small at SuperB
Those 2 effects are implemented in GUINEA-PIG++ (GP++)

9. Beam-Beam diffusion
Beam-beam diffusion caused by discrete-particle scatterings
with coulomb scattering angle :
(b=impact parameter)
This can leads to:
Reduction of beam life time (particle loss during collision)
Emittance growth
Spin diffusion
Is it a problem for SuperB?
 should be studied because SuperB’s luminosity comes from colliding a small number of particles which are sharply focussed. The small number of colliding particles implies larger statistical effects.
tests comparing kick angle from
gaussian distribution charge (GUINEA-PIG++ simulation)
and discrete point charges

10. Beam-Beam depolarization
Conclusions
Beam-Beam depolarization
Seems that depolarisation due to beam-beam effect very low. (See also BBdiffusion talk tomorrow)
But need more accurate simulations:
 Improve GP++ and combine with spin tracking code (ZGOUBI)
- Add Crab waist
- Add longitudinal field
- Check propagation direction
- Interface between I/O files of the 2 codes is under development
with N. Monseu
Find alternative way to use GP++ as it is : (Center of mass frame studies + boost) ?
Use larger number of macro-particles
Beam-Beam diffusion
Nice accordance between theory and simulation
 Beam life time due to beam-beam diffusion = 292mn
Emittance diffusion time = 14s
Spin diffusion time = 1.4 h
Small effects, should not be a problem for SuperB
Need to be confirmed by other theories and more simulations

11. IR Design Polarimetry (K. Moffiet)
Beam-Beam Depolarization (C. Rimbault)
Beam-Beam Diffusion (C. Rimbault)
IR Design Update (M. Sullivan)
MDI Issues (M. Sullivan)
Backgrounds (E. Paoloni) (earlier talk)
Be Beam pipe Heating (S. Novokhatski)
Vibration Issues (M. Masuzawa)

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

13. Baseline IR Design
Stable since October

14. Machine Parameters

15. New Machine Parameters

16. 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)

17. 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

18. 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.

19. 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)

20. Solenoid compensation
We have recently 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
We will need to revisit our compensation schemes and look at ways of minimizing the fringing fields as well as the total integral

21. To do list SR Revisit solenoid compensation
A more thorough study of surfaces and photon rates
Check dipole SR (for white paper)
More detailed backscatter and forward scatter calculations from nearby surfaces and from the septum
Photon rate for beam pipe penetration (for white paper)
Revisit solenoid compensation

22. 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

23. Resonance
Upsilon 4S
Upsilon 3S
Upsilon 2S
Upsilon 1S
Ecm (GeV)
9.4609
HER
E (GeV)
6.694
6.553
6.343
5.988
QD0 (T/cm)
QF1 (T/cm)
LER
4.18
4.091
3.96
3.737
QD0 ratio
QF1 ratio 
Boost ()

24. 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

25. Super-ferric QD0 and QF1

27. Super-ferric QD0 Constraints Might be able to relax these a little
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

28. 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)

29. 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

30. 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 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

31. Vanadium Permendur Design

32. 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

33. 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 Dy
Ga <120
Fe (scrap) Pb Sn Cu Ni Al
Au ,000 Zn Ag
*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

34. Holmium Design

35. Beta function comparison with V12 baseline
V12 VP Ho
LER x max
HER x max
LER y max
HER y max
Maximum betas are lower in almost all cases

36. 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
Beampipe heating (coming next)
300 mrad angle of acceptance
Cryostat may end up close to that boundary
Cryostat supports
W shielding

37. Flange Drawing

38. Central Chamber

39. Scaled Picture

40. 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?

41. Rapid Access Scenario
Standard Plan View

42. Side view

43. Doors opened

44. Cryostats and SVT slid out of the detector
We need to do more work to study the details, but the general concept looks OK.
Vibrations may be an issue

45. Heating and Vibrations
Polarimetry (K. Moffiet)
Beam-Beam Depolarization (C. Rimbault)
Beam-Beam Diffusion (C. Rimbault)
IR Design Update (M. Sullivan)
MDI Issues (M. Sullivan)
Backgrounds (E. Paoloni) (earlier talk)
Be Beam pipe Heating (S. Novokhatski)
Vibration Issues (M. Masuzawa)

46. Be beam pipe heating

47. Heating summary RF field penetration is reasonably small
We have about 25 cm of beam pipe and two beams so total is about 100 W at full beam current

48. Vibrations at KEK
M. Masuzawa had a very nice and detailed presentation on vibration measurements at KEK
I will only show some of the neat stuff
They can see ocean wave frequencies as well a 1.0 earthquakes

49. ~3Hz : characteristic frequency of the soil
called “Kanto loam” around KEK.
Induced by human activities, mainly vertical
Vibration.Day & night effects and weekend effects
have been observed.
0.2~0.3 Hz: Ocean waves & wind.
Depends on the weather, mainly in horizontal vibration.

50. An example of earthquake (tiny one) during physics run
A good collision condition maintained
by　“iBump” system was lost, resulted
in a beam loss (not beam abort).
Luminosity
Local orbital FB system, max. 1Hz
V beam-beam kick
KEK
SuperKEKB
will be much more sensitive.
“1” in Japanese seismic intensity scale. Tiny earth quake.

51. Vibration Summary KEKB tunnel at the IP vibrates at
QC1RE
QCS-boat
Movable table
KEKB tunnel floor
Belle-stand
B4 floor
KEKB tunnel at the IP vibrates at
~ 0.3 Hz in the horizontal direction (micro-seismic)
~3 Hz in the vertical direction & horizontal
direction (resonance of the “Kanto loam”
soil around KEK)
In addition, magnets, QCS boat and the table vibrate at ~ 8Hz.

52. Vibration Summary ( 2009 data)
Summary table by H.Yamaoka
The vibration amplitude of the IR magnets are much smaller
than the size of the colliding beams (~2mm vertically & ~100mm
horizontally) for KEKB but comparable for SuperKEKB.

53. 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.
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.

54. Summary (2)
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 going to have to be revisited. Solutions will have to be simpler.
We have a very well developed proposal for a polarimeter
Beam pipe heating in the Be chamber has been calculated. We will need to water cool the pipe.

55. Conclusions The IR section for the white paper is about 70% complete
The permanent magnet re-optimization has improved the overall IR design
The new magnet design for QD0 and QF1 greatly improves the flexibility of the IR design (we are even considering a normal quad solution)
As always, there is more to do, but the IR design is looking more and more feasible and able to deliver the luminosity of this SuperB accelerator