# Presentation: 714139

## IR Design Status

**M. Sullivan**
**For**
** ****M. Boscolo, K. Bertsche, E. Paoloni, S. Bettoni, **
**P. Raimondi,  et al.**
** ****SuperB Workshop **
**LAL, Orsay, France**
**Feb 15-18, 2009**

## Outline

**Present Design**
**Improvements over July 2008**
**Layout**
**Parameters**
**SR summary**
**Detector Solenoid**
**More to do**
**Summary**

## Present Design

**After some iterating we have....**
**Increased the crossing angle to +/- 30 mrads**
**Cryostat now has a warm bore**
**Both QD0 and QF1 are super-conducting**
**PM in front of QD0 for the LER only**
**LER has the lowest beta Y***
**Soft upstream bend magnets**
**Further reduces SR power in IP area**
**Increased BSC to 30 sigmas in X and 140 sigmas in Y**
**Using the highest luminosity design parameters **
**Lowest beta* values and highest emittances **

**Do NOT want to design out upgrades**

## Present Design

## Same scale as previous slide

**Same scale as previous slide**

**Comparison to PEP-II**

## Inside the detector

## Some more details

**Longer QD0**
**QD0 strength was getting too high**
**Maintaining the gradient below 1.2 T/cm**
**Increased the space for the QF1 cold mass ( 1.75 times)**
**Added a shared quad as part of QD0**
**Starting parameter for a warm bore design is that 5 mm is enough radial space between the cold mass and room temperature (needs engineering confirmation)**
**BSC in X is 30 ******** uncoupled (all of the emittance in the X plane) and in Y we use 20% of the total emittance which is about 140 ********s**

**Simona Bettoni will talk on this**

## Parallel axis QD0 and QF1

**Presently the axes of the QD0 twin quads are parallel as are the axes of the twin quads of QF1**
**The beams are bent by these quads because the beam goes through at about a 30 mrad angle**
**Depends on where the quad axis is w.r.t. the beam trajectory**
**Have studied on axis QD0 and QF1 magnets for SR backgrounds. About as good as this design.**

## Close up of beam orbits in QD0 

**We have a double or “S” bend**

**The SR bending power from QD0 is 2x8793 W for a 2A beam **

**The net bending angle is 1.85-4.25=-2.40 mrads**

**QD0 axis**

**HER coming into the magnet**

**HER outgoing**

## Close up of QD0 beam orbits 

**The SR bending power from QD0 is 2x1084 W for a 2A beam **

**The net bending angle is 5.84-0.43=5.40 mrads**

**QD0 axis**

**LER coming into QD0**

**LER outgoing**

## Permanent Magnets 

**The permanent magnets start the vertical plane focusing for the LER**
**With the larger crossing angle the beams are far enough apart at 0.35 m from the IP to have enough space to install a PM that can work on the LER**
**The PM quadrupole slices have an elliptical aperture to give us more vertical space**
**Dimensionally the slices are small**
**The chosen remnant field is high but not the highest**

**Kirk Bertsche designed the PM slices**

## Vertical View

## Beam parameters used

**Parameter****	****	****	****           HER****	****           LER**
**Energy (GeV)****	****	****	****   7****	****	****   4**
**Current (A)****	****	****	****           2.00              2.00**
**Beta X (mm)****	****	****	****	****  20****	****	****  35**
**Beta Y (mm)****	****	****	****	****  0.27****	****	**** 0.16**
**Emittance X (nm-rad)****	****	****  1.6****	****	**** 2.8**
**Emittance Y (pm-rad)****	****	****  4.0****	****	**** 7.0**
**Sigma X (********m)****	****	****	****  5.7  ****	****	**** 9.9**
**Sigma Y (nm)****	****	****	****  33****	****	****  33**
**Crossing angle (mrad)****	****	****	****+/- 30**

## Magnet parameters

**Quad       G (kG/m)    L(m)     from IP (m)**
**QD0L   ****	****    -522       0.40           0.58**
**QD0H       -1192       0.40           0.58**
**QF1L           399       0.30           1.60**
**QF1H          726        0.30           1.60**
**Dipole      B (kG)     L(m)     from IP (m)**
**B0L            -0.77       2.0           6.346**
**B0H           -1.35        2.0           6.346       **

## SR backgrounds

**No photons strike the physics window**
**Trace the beam out to 20******** X and 45******** Y**
**+/-4 cm for a 1 cm radius beam pipe**
**Unlike in PEP-II, we are sensitive to the transverse beam tail distributions**
**Photons presently strike 10 cm upstream and  downstream of the IP**

## SR fans from upstream bends

## SR from the upstream bends

## SR to do list

**More thorough study of surfaces and photon rates**
**Backscatter calculations from nearby surfaces and from septum**
**Photon rate for beam pipe penetration**
**Orbit deviation study**
**Beam tail distribution study**

## Detector solenoid compensation

**Just starting to look at detector  solenoid effects on the beams**
**The large crossing angle increases the detector field influence**
**Starting point is to use the compensating solenoids to correct the beam orbits**
**Some results for the LER incoming beam**

## BaBar detector field

**Bz along the Z axis**

## Compensating solenoids

**Plots are scaled to 10 KG (1 T) peak field**

## Orbit before any correction

**This study starts the beams at the IP. Detector field-off orbit is a straight line at zero.**

**Incoming LER**

**Outgoing HER**

**Right side of the detector field.**

## Incoming LER corrected with compensation solenoids and added VCOR

**Uncorrected detector at   -15.6 kG**

**1st anti at +15kG**

**1st & 2nd at +15kG**

**1st at +20kG & 2nd at +15**

**1st at +20kG & 2nd at +15 & vcor at 2.8m**

**Maximum orbit deviation is about 1.5 mm. We want to get this below a mm.**

**Very**
**Preliminary**

## More tuning options

**Can make the compensating solenoids stronger**
**However we want to keep the field around QD0 and QF1 to a minimum**
**Extend the second compensator**
**Cover more of the fringe from the detector field**
**Adds more integrated compensator field strength**
**Put a vcor inside the cryostat**
**Catch the orbit deviation earlier**

## More to do...

**Solenoid compensating windings are shared with both beams**
**Need to check both beams and find the best compromise setting**
**The right side is not equal to the left side – must do the incoming HER and outgoing LER as a separate correction from incoming LER and outgoing HER**
**Detector field is not symmetric (see detector field plot)**
**Coupling correction is also different on each side of the IP**
**Coupling correction may want a yet different setting – need to check coupling against orbit correction setting**
**Will have to include skew quads in the cryostat**

## Engineering to do list

**How do we build QD0?**
**How do we build QF1?**
**Transition space from warm bore to cold bore**
**Magic flange locations (CESR, KEK and BEPCII have done it)**
**Bellows location to relieve stress on detector Be beam pipe**
**Magnet supports**
**Vacuum supports**
**Where can we put pumping?**

## Summary

**The present IR design has improved since the July machine advisory review**
**All the magnets inside the detector are now either PM or SC**
**The beam pipes inside the cryostats are now warm**
**We now have a 30s BSC in X and 140s BSC in Y**
**Synchrotron radiation backgrounds look ok, but need more study**
**Radiative bhabha backgrounds should be close to minimal**
**Designing to the most aggressive machine parameters in order to NOT design them out**

## Conclusion

**Good progress has been made**
**Much more to do but the design is firming up**
**SR backgrounds need more study**
**Solenoid compensation needs more work**
**Very close to starting a first engineering design**
**Onward!**