1. Status on SuperB effort Daresbury, April 26, 2006 P. Raimondi

2. Outline Basic Concepts (March-Sept,2005) Parameters and layout optimization based on a High-Disrupted regime (Nov, 2005) Parameters and layout optimization for a Minimal-Disrupted regime (Jan, 2006) Layout for a Ring Collider with Linear Collider Parameters (Mar, 2006) Conclusions

3. Basic concepts SuperB factories based on extrapolationg current machines require: Higher currents Smaller damping time (weak function ^1/3) Shorter bunches Higher power SuperB gets very expensive and hard to manage, expecially all the problems related to the high current => look for alternatives

4. Basic Idea comes from the ATF2-FF experiment In the proposed experiment it seems possible to acheive spot sizes at the focal point of about 2  m*20nm at very low energy (1 GeV), out from the damping ring Rescaling at about 10GeV/CM we should get sizes of about 1  m*10nm => Is it worth to explore the potential of a Collider based on a scheme similar to the Linear Collider one Idea presented at the Hawaii workshop on Super-B factory on March-2005

5. LinearB scheme IP LER Bunch compressor and FF HER Bunch compressor and FF LER HER Overall rings lenght about 6Km, Collision frequency about 120Hz*10000bunch_trains=1.200MHz Bunch train stays in the rings for 8.3msec, then is extracted, compressed and focused. After the collision is reinjected in its ring LER injectionHer injection

6. Scaling laws to optimize the IP parameters Disruption: Luminosity Energy spread: Decrease  z + decrease N Increase spotsize Increase N Decrease spotsize Increase  z + decrease N Increase spotsize Contraddicting requests!

7. A lot of homework done in collaboration at SLAC and at the LNF for a few months. Explored the parameters phase in order to maximize the luminosity per crossing Laid down all the other possible advantages (e.g. less current through the detector, smaller beams, smaller beam pipe etc) Leading to a workshop held on Nov,11-12 2005 in Frascati to investigate and optimize the scheme and the feasibility of the different subsystems

8. Horizontal Collision Vertical collision Effective horizontal size during collision about 10 times smaller, vertical size 10 times larger Simulation by D.Schulte First attempt

9. Horizontal phase after the collision Vertical phase after the collision IP Parameters set considered at the workshop caused large increase of the emittance due to the collision:  x_out /  x_in =12  y_out /  y_in =300 M. Biagini studies

10. Linear Super B schemes with acceleration and energy recovery, to reduce power e- Gun 2GeV e+ DR IP 5GeV e+ SC Linac e- Dump 7GeV e+ 4 GeV e- 4GeV e- SC Linac 2 GeV e+ injection 2 GeV Linac1.5 GeV Linac Linac Damping Rings 2 GeV Linac e + Gun e - Gun Use SC linacs to recover energy Use lower energy damping rings to reduce synchrotron radiation No electron damping ring Make electrons fresh every cycle –Damping time means time to radiate all energy –Why not make a fresh beam if storage time is greater than 1 damping time

11. Progress in design optimization after the 1° SuperB workshop Between December-2005 and March-2006 a lot of studies have been made in order to understand what are the sources of the blow-ups in the collision and how to minimize then. Power requirements could be greatly reduced if collision is less disruptive Search for a trade off between luminosity delivered in one collision and power spent for each collision Search for the simplest and more economic solution

12.  x =10  m  y =10nm  z =250um  x =33mm  y =1mm  x =3.3*10 -9  y =10 -13 L norm =Ld/log(  y_out /  y_in )=2.27 at N part =2.5*10 10 Introduced the luminosity merit function: Lnorm=L/log(ey_out/ey_in) => Luminosity per energy cost Luminosity vs bunch charge for a given set of IP parameters Outgoing/incoming emittances ratio vs bunch charge for a given set of IP parameters

13. Ey_after collision increases fast with current and 1/  x: with Npart=2*10^10 Lnorm=2.27 Cure 1: decrease  y from 1mm to 250um =>  y_in =4*10 -13  y_out =23.4*10 -13  y_out /  y_in =6 instead of 24 Ld drops from 7.22*10 32 to 5.6*10 32 (hourglass) Lnorm=3.12 Cure 2: travelling focus (waist position is shifted by z wrt the IP for the slice ‘z-z+dz’=> Ld goes back up to 7.01*10 32 Lnorm=3.91 Cure 3: further decrease  y from 250um to 100um and use the pinch to keep the beams from diverging rather than to disrupt them with overfocusing=> BB FOCUS COMPENSATION CONCEPT !!!!!!!!!  y_in =10*10 -13,  y_out (slice)=15.0*10 -13,  y_out /  y_in =1.5 instead of the initial 24 Ld drops to 5.77*10 32 Lnorm=14.1 !!

14. With travel focus Without travel focus Horizontal collisions in a round beam case

15. 3 planes slice emittances after the collision (round beams case), each color is a different slice: red head of the bunch, black tail Without Travel Focus  y_out/  y_in =3 With Travel Focus  y_out/  y_in =1.1

16. In summary, the small disruption regime requires: small  z (=> large  e from compressor) big  x small  y (for luminosity) and  y BB-compensation by traveling focus all the requirements do fit togheter with the horizontal monocromator: betatron  x small, and made large by adding horizontal dispersion with opposite sign for the 2 beams. High energy particles of first beam collide with low energy particles of the sencond one it simultaneneously enlarge  x and decrease the luminosity energy spread moreover since the natural horizontal emittance is small, the emittance ratio of about 0.5% ensures the small  y

17. Single pass Collider Ring with compressor Ring without compressor Sigx*  m 30 (2 betatron)18 (2 betatron)2.67 Etax mm+-1.5+-5.00.0 Sigy nm12.663.212.6 Betx mm5.0 9.0 Bety mm0.0800.5000.080 Sigz_IP mm0.1000.6006.0 Sige_IP2.0e-23.5e-31.3e-3 Sige_Lum1.0e-3 0.9e-3 Emix nm0.8 Emiy nm0.0020.0080.002 Emiz  m 2.0 8.0 Cross_angle mradOptional>2*122*25 Sigz_DR mm4.0 6.0 Sige_DR0.5e-3 1.3e-3 Np 10e107.02.02.3 Nbunches12000 DR_length km6.0 Damping_time msec20 Nturns_betwe_coll5011 Collision freq MHz12.0600 L singleturn 1e361.51.71.2 L multiturn 1e361.10.91.0

18. Single pass Collider with Np=7*10 10 N bunches =12000 (6Km ring) Travel focus in vertical plane  x =1.5mm (opposite sign for the two beams),  x *=30  m  z =100  m  z =4mm in DR  e =100MeV  e /e=2*10 -2  e /e=5*10 -4 in DR  e_Luminosity =7MeV  x =0.8nm  x_norm =8  m  y =0.002nm  y_norm =20pm  z =2.0  m Stored time between collision=1msec=50turns Lmultiturn=0.9*10 36 (Lsingleturn=1.5*10 36 ) FF with large energy spread tricky

19. Multiturn Simulation for flat case 6Km ring,Np= 7*10 10 coll_freq=1Khz*12000 L multiturn =0.9*10 36

20. Compressor Decompressor DeCompressor IP Optional Acceleration and deceleration Optional Acceleration and deceleration FF ILC ring with ILC FF ILC compressor Colliding every 50 turn Acceleration optional Crossing angle optional Now the acceleration is not needed anymore in order to reduce the power Simplified layout in the Small Disruption Regime

21. Equilibrium Emittance Vertical blowup about 60% Blowup as function of beam currents almost linear Blowup as function of damping time goes like Tau 1/3 Reducing the bunch charge by a factor 6 (10 10 ), the blowup at the equilibrium decreases to 10% Reducing the damping by a factor 50 (collision every turn) equilibrium blowup increases by a factor 4 (50 1/3 ) Final Blowup in this case is about 40% Geometric Luminosity decreases by a factor 36 due to less charge and increases by a factor 50 for increased collision rate With the same parameters but colliding in the ring (bunch compressor and FF in the ring), we get: L=10 36 with Npart=10 10 and L=4*10 36 with N=2*10 10 => overhead in luminosity Possible to reoptimize the parameters in this scenario Scaling the parameters to a Ring Colliding Machine

22. Ring Collider Compressed Bunches With proper tunes choice (.503,.55) the BB compensation with travel focus is not needed  e =16MeV  e /e=3.5*10 -3  e_Luminosity =10MeV  x =0.8nm  y =0.008nm  z =2.0  m L multiturn =0.84*10 36 (L singleturn =1.7*10 36 ) with N part =2*10 10 FF with large energy spread tricky Bunch compressor (  z 4mm=>0.6mm) in the ring tricky: 150MeV 1.3GHz

23. Betx_dyn=3.0mm sigx_dyn=2um sigxp_dyn=0.7mrad Emix_dyn=1.5nm Etax_dyn=+-5mm Sigx_eta=18um Sigz_dyn=0.57mm Sige_dyn=5*10-3 Bety_dyn=0.5mm Sigy_dyn=93.0nm Sigyp_dyn=0.2mrad Emiy_dyn=0.020nm Betx=5.0mm sigx=2um sigxp=0.4mrad Emix=0.8nm Etax=+-5mm Sigx_eta=18um Sigz=0.6mm Sige=3.5*10-3 Bety=0.5mm Sigy=63.2nm Sigyp=0.11mrad Emiy=0.008nm L0=1.7*10^36, Ldyn=0.84*10^36, sige_lum=11MeV Npart=2*10^10, fcoll=600MHz

24. Compressor Decompressor IP FF ILC ring with ILC FF ILC Compressor, 0.4GeV S-Band or 1GeV L-Band Crossing angle optional Simplified layout in the Small Disruption Regime Collisions every Turn

25. Do we need to compress the bunches? Sz Sx Both cases have the same luminosity, (2) has longer bunch and smaller  x 1) Standard short bunches 2) Crossing angle Overlapping region Sx Sz Overlapping region

26. Colliding every turn very promising but requires a bunch compressors and a decompressor in the ring In principle not needed to compress the beams if we collide with a crossing angle such as:  z *x cross =24  m (same projected horizontal size)  x /x cross =100  m (same effective longitudinal interaction region)  y =12.6nm,  y =80um like in the compressed case These parameters gives the same geometric luminosity like the compressed case: If  z =4mm we need: x_cross=6mrad,  x =0.6um However now beam-beam worsened because the beams see each other also at non-minimum betay locations Scaling the parameters for an every-turn colliding machine, with Uncompressed Bunches

27. With large crossing angle X and Z quanties are swapped Very important!!! Sz Sx  z x Sx/  Sz*  e- e+

28. Easy way to decrease the ‘Long Range Beam Beam’ is to increase the crossing angle by a factor 4 at a direct luminosity cost of a factor 4: x crossing_angle =2*24mrad  x =2.4  m This still gives a luminosity of 1.2*10 36 with N=2*10 10 if the vertical blowup were none Unfortunately the blowup is still large and  y at the equilibrium is about 6 times larger: L mutiturn =0.4*10 36 Overall a factor 10 loss in luminosity w.r.t. full compressed bunches (with all the other parameters the same)

29. Second way to decrease the ‘Long Range Beam Beam’ is to apply the travel focus idea, but now has to be applied in the transverse plane since x and z are swapped. Vertical waist position in z is a function of x: Zy_waist(x)=x/2  Crabbed waist All components of the beam collide at a minimum  y => - the ‘hour glass’ is reduced - the geometric luminosity is higher - the bb effects are reduced  y blowup at the equilibrium less than a factor 2

30. Vertical waist has to be a function of x: Z=0 for particles at –  x (-  x /2  at low current) Z=  x /  for particles at +  x (  x /2  at low current) 2Sz 2Sx  z x 2Sx/  2Sz*  e- e+ YY

31. Emittance blowup due to the crossing angle Colliding with no crossing angle and  x =100  m,  z =100  m:  y (single pass)=4*10 -4 L=2.1*10 27 Colliding with crossing angle=2*25mrad and  x =2.67um,  z =4mm (  z *  =100um,  x /  =104um):  y =4*10 -3 (single pass) L=2.14*10 27 Same geometric luminosity but 10 times more emittance blowup Adding the “Crab-waist”, Zy_waist(x)=x/2  :  y =1.5*10 -3 (single pass) L=2.29*10 27 - the ‘hour glass’ is reduced, the geometric luminosity is higher: small effect about 5% more luminosity - the main effect: blowup due the the beam-beam is reduced, about a factor 2.4 less  y (3.8 times the nocross)

32. Colliding with an angle requires just the ILC DR and the ILC FF. No compression needed Crabbed y waist is achieved by placing a sextupole upstream the IP (and symmetrically downstream) in a place in phase with the IP in X and at  /2 in Y (much easier than the longitudinal travel focus). Only natural energy spread in the beams Angular divergences about 150  rad in both planes Crossing angle so large makes the IR (and the FF) design very easy Low energy spread makes the FF very easy Beam currents around 1.9Amps, possible better trade off current  damping time

33. Collisions with uncompressed beams Crossing angle = 2*25mrad Relative Emittance growth per collision about 1.5*10 -3  yout /  yin =1.0015 Horizontal PlaneVertical Plane

34. Y bb_scan

35. with 40um horizontal separation Y field linear and much smaller kick: 1.5  rad instead of 150  rad No X separation y-scan

36. Ring Collider Uncompressed Bunches Crab focus on in vertical plane X crossing_angle =2*25mrad  z =6mm  e =6MeV  e_Luminosity =9MeV  x =0.8nm  y =0.002nm  z =8.0  m Collision_frequency=600MHz L multiturn =1.0*10 36 (L singleturn =1.2*10 36 ) with Np=2.3*10 10 Vertical tune shift like in PEP!!! (similar currents,100 times more luminosity, 100 times smaller betay) Projected Sigmax=Sigmaz*Cross_angle=100  m, like in PEP! Possible to further increase the luminosity with: - more current: L=1.8*10 36 with Np=4*10 10 - further simultaneuos  x and  y squeeze -  z shortening

37. Vertical beam size vs crab focus K2=sextupole strength Luminosity vs crab focus K2=sextupole strength With k2=8 the vertical emittance blowup is < 20% Luminosity gain about 70% Vertical size rms reduction about a factor 2.5, large tails reduction Luminosity in excess of 1e36 is achievable Ohmi simulations

38. Beam-Beam Tails (D.N. Shatilov) Without Crab FocusWith Crab Focus

39. Tune shift and luminosity with crossing angle Very small:  z *  =100  m  =25mrad  x =9mm

40. X-Z Coupling smaller then KeK:  z *  =100  m  =25mrad  x =9mm Kicks that a particle receives while passing through the other beam

41. Multiturn simulations for uncompressed beams 6Km ring, 12000 bunches Coll_freq=600MHz Bunch_charge=2*10 10  e =4mm, X crossing =2*25mrad  y0 =2pm  x0 =400pm

42. IP FF ILC ring & ILC FF Simplified layout in the Small Disruption Regime Collisions every Turn Uncompressed bunches Crossing angle = 2*25 mrad Crabbed Y-Waist

44. 35m long FF A.Seryi

45. Conclusions (1): - Rapid progress in the optimization of the SuperB parameters and layout - First workable parameters set requires: - ILC damping ring, - ILC bunch compressor, - ILC Final Focus - No energy acceleration -Same parameters set but with increased collision rate and reduced beam current gives more and more luminosity -The optimal collision rate is every turn.

46. Solution with ILC DR + ILC FF and no compression seems extremely promising: - Crossing angle of about 25mrad - Requires virtually no extra R&D - Uses all the work done for ILC - Ring and FF layouts virtually done, 6km (down to 2km should be possible) circunference rings - 100% Synergy with ILC - IR extremely simplified - Beam stay clear about 20sigmas supposing 1cm radius beam pipe - Beam Currents around 2.0Amps - Background should be better than PEP and KEKB - Possibly to operate at the  energy with L=10 35 - Total cost less than half of the ILC e+ DRs (2 e+ 6km rings in ILC) - Power around 40MW, further optimization possible - Possible to reuse PEP RF system, power supplies, Vacuum pumps, etc., further reducing the overall cost - Needs the standard injector system, probably a C-band 7GeV linac like in KEKB upgrade (around 100ME) Conclusions (2)

47. Conclusions (3) Possible fall back on the existing factories The crabbed waist potentially beneficial also for the current factories Possibility to simultaneously boost the performances of the existing machines and do SuperB R&D