1. Photon collider: ILC configuration and IR issues ( how to make 14mr compatible with gamma-gamma) Valery Telnov Budker INP IRENG07, Sept.18, 2007, SLAC

2. Sept. 18, 2007Valery Telnov, IRENG07, SLAC 2 Contents Introduction Crossing angle Beam dump Laser optics, detector Conclusion

3. Sept. 18, 2007Valery Telnov, IRENG07, SLAC 3  ω max ~0.8 E 0 W γγ, max ~ 0.8·2E 0 W γe, max ~ 0.9·2E 0 α c ~25 mrad ~1-2 mm

4. Sept. 18, 2007Valery Telnov, IRENG07, SLAC 4 Luminosity spectra (decomposed in two states of J z ) Usually a luminosity at the photon collider is defined as the luminosity in the high energy peak, z>0.8z m. L γγ (z>z m ) ~(0.17-??) L e+e- (nom) For ILC conditions The coefficient is for nominal beam emittances. It can be larger, needs optimization of DR for γγ or other injector with even smaller emittances (but cross sections in γγ are larger by one order!)

5. Sept. 18, 2007Valery Telnov, IRENG07, SLAC 5 Physics motivation: summary In ,  e collisions compared to e + e - 1.the energy is smaller only by 10-20% 2.the number of events is similar or even higher 3.access to higher particle masses ( H,A in γγ, charged and light neutral SUSY in γe) 4. higher precision for some phenomena 5. different type of reactions (different dependence on theoretical parameters) One example: 2E 0 =500 GeV For e+e- M H,A (max)~250 GeV (H,A are produced in pairs) For γγ ~400 GeV (single resonance)

6. Sept. 18, 2007Valery Telnov, IRENG07, SLAC 6 So, linear colliders provide a unique opportunity to study ,  e interaction at high energies and luminosities. About 20-25% of all publications on LC physics are related to the photon collider. The opinion of the physics community is expressed in the LC consensus and IFCA scope document: the ILC design should include γγ, γe. The ILC baseline and reference designs did not account the photon collider (in order to reduce the baseline cost), now the GDE has intent to consider it in the EDR.

7. Sept. 18, 2007Valery Telnov, IRENG07, SLAC 7 What is important now. It is important to make design decisions on the baseline ILC project not prohibitive or unnecessarily difficult for the photon collider, which allow to reach its ultimate performance and rather easy transition between e + e - and γγ, γe modes. The PLC needs: the IP with the crossing angle ~ 25 mrad ; places for the special beam dump and the laser system; detector design (s) compatible with gamma-gamma ; R&D on the laser system, IR issues, e.t.c…

8. Sept. 18, 2007Valery Telnov, IRENG07, SLAC 8 2E 0 =200 GeV 2E 0 =500 GeV Crossing angle Disrupted beam with account of the detector field at the front of the quad (blue - without, red –with the field) With account of tails the save beam sizes are larger by about 20 %. L=4m, B=4T Telnov, Snowmass2005

9. Sept. 18, 2007Valery Telnov, IRENG07, SLAC 9 A.F.Zarnecki, LCWS06 at L=4.5 m P quad < 1 W Simulation with account of secondary processes

10. Sept. 18, 2007Valery Telnov, IRENG07, SLAC 10 The radius of the self compensated quad with the cryostat is about 5 cm. (B.Parker, Snowmass 2005) α c = (5/400)*1000 + 12.5 ~ 25 mrad

11. Sept. 18, 2007Valery Telnov, IRENG07, SLAC 11 14mr => 25mr additional angle is 5.5mrad and detector need to move by about 3-4m A.Seryi, LCWS06 1400 m

12. Sept. 18, 2007Valery Telnov, IRENG07, SLAC 12 Possible upgrade 14 mr (e + e - ) to 25 mr (  Tunnel in FF area may need to be wider For transition from e+e- to γγ one should shift the detector by about 0.0055*600=3.3 m as well as to shift 600 m of the upstream beam line or (better) to construct an additional final transformer and doublet, in any case the final doublet should be different. In that case the transition between e+e- and γγ modes will be faster. Two extra 250 m tunnels for γγ beam dump. Somewhat wider experimental hall. Different position of doors.

13. Sept. 18, 2007Valery Telnov, IRENG07, SLAC 13 Remarks (I) The e+e- FF contains two 2.5 mrad bends in opposite directions, for γγ one can use the same signs of the bends and thus to obtain the required 5 mrad without any special bending system. In this case the detector should be shifted only by ~1.75 m. Disadvantages: 1) e+e- and γγ beam dump tunnels are too close (3m between axes) 2) not possible to have independent e+e- and γγ FF beamlines (>1/2 overlap) 2.5 5 mrad

14. Sept. 18, 2007Valery Telnov, IRENG07, SLAC 14 It would be nice by the end of the workshop to produce a preliminary picture of required tunnel modification for 25 mrad crossing angle.

15. Sept. 18, 2007Valery Telnov, IRENG07, SLAC 15 Remarks (II) In principle, one can use the same crossing angle ~25 mrad for e+e- and γγ, but e+e- people want a special extraction line with beam diagnostic (energy, spectrum, polarization), while γγ needs clear way to the beam dump (which is very special). Replacements of beam dumps will be difficult due to the induced radioactivity. So, different crossing angles are even more preferable. However, it is not clear whether e+e- needs such very instrumented extraction line. There are a lot of diagnostics upstream the IP(energy and polarization) and in the detector (acollinearity angles, e+e- pair), which may be sufficient for reconstruction of beam properties. In addition, one can measure easily beam profiles downstream the IP. Such effects as depolarization during the col lision can be accounted by simulation. This needs further study. Also we will not consider at this meeting the two IR designs case.

16. Sept. 18, 2007Valery Telnov, IRENG07, SLAC 16 Beam dump The disrupted beam at the photon collider has 3 components, two are wide and one narrow: 1.e +,e - with the angular spread ~10-12 mrad (need some focusing); 2.beamstrahlung photons with angles up to 3-4 mrad; R~1 m at L=250 m from the IP. 3. Compton photons with angles σ θx ~4·10 -5 rad, σ θy ~1.5·10 -5 rad, that is 1 x 0.35 cm 2 at the distance 250 m. V.Telnov, physics/0512048, Snowmass2005

17. Sept. 18, 2007Valery Telnov, IRENG07, SLAC 17 The angular distribution of electrons If the beam dump is situated at L=250 m, than for particles with θ=7 mrad r~1.8 m, too much. Some focusing of electrons will be useful in order to decrease the radius of the tube and to reduce the energy deposition (rad. activation on the way to the beam dump).

18. Sept. 18, 2007Valery Telnov, IRENG07, SLAC 18 Angular distribution of beamstrahlung photons Large angle photons are radiated by low energy electrons, therefore they are soft For photons the clear angle about 3 mrad will be sufficient, that is 75 cm at L=250 m.

19. Sept. 18, 2007Valery Telnov, IRENG07, SLAC 19 Compton photons

20. Sept. 18, 2007Valery Telnov, IRENG07, SLAC 20 Possible scheme of the beam dump for the photon collider The photon beam produces a shower in the long gas (Ar) target and its density at the beam dump becomes acceptable. The electron beam without collisions is also very narrow, its density is reduced by the fast sweeping system. As the result, the thermal load is acceptable everywhere. The volume with H 2 in front of the gas converter serves for reducing the flux of backward neutrons (simulation gives, at least, factor of 10). In order to reduce angular spread of disrupted electrons some focusing after the exit from the detector is necessary. Needs detailed technical consideration! ~2m Telnov, Snowmas2005 physics/051204

21. Sept. 18, 2007Valery Telnov, IRENG07, SLAC 21 Telnov, Shekhtman, LCWS04, physics/0411253 Max. ΔT in water after one train at 250 GeV photons is 75,50,25 at Ar pressure 3,4,5 atm. ΔT at entrance window is about 40º C. Flux of neutrons at IP is 1.5 10 11 n for 10 7 s. H 2 in front reduces the flux at least by a factor of 10! Previous scheme (was simulated) There is a problem of a large energy deposition in the tube, it should be shielded, needs to be studied carefully.

22. Sept. 18, 2007Valery Telnov, IRENG07, SLAC 22 Laser system The cavity includes adaptive mirrors and diagnostics. Optimum angular divergence of the laser beam is ±30 mrad, A≈9 J (k=1), σ t ≈ 1.3 ps, σ x,L ~7 μm

23. Sept. 18, 2007Valery Telnov, IRENG07, SLAC 23 One example. View of the detector with the laser system (the pumping laser is in the building at the surface) For easier manipulation with bridge crane and smaller vibrations it may be better to hide the laser tubes under the detector. If IR depth is large, the laser room is needed somewhere underground. K.Monig, et al, Zeuthen

24. Sept. 18, 2007Valery Telnov, IRENG07, SLAC 24 Layout of the quad, electron and laser beams at the distance 4 m from the interaction point (IP) Laser beams in the detector

25. Sept. 18, 2007Valery Telnov, IRENG07, SLAC 25 Some problems with laser optics If the final mirror is outside the detector at the distance ~15 m from the center, its diameter is about d~90 cm, very large. Detectors have holes in forward direction ±33-50 mrad (previous slide) while the photon collider needs ±95 mrad, so there should be special removable parts in ECAL, HCAL and the yoke. Alternative solution: pairs of mirrors inside the detector 600-700 cm Then the diameter of focusing mirror is about 20 cm and that of the auxiliary mirror about 11 cm. The dead angle for tracking remains as before about ±95 mrad, but smaller for calorimetry. However, in case mirrors are inside the detector and it is more difficult to adjust optics.

26. Sept. 18, 2007Valery Telnov, IRENG07, SLAC 26 Open angles in detectors LDC SID GLD θ=±45 mrad ±33 mrad±50 mrad that is less than the required ±95 mrad (Very hermetic detectors)

27. Sept. 18, 2007Valery Telnov, IRENG07, SLAC 27 Conclusion (I) The Photon collider imposes very serious requirements to the design if the ILC IR. The RDR layout is not compatible with the PLC. Let us consider for the beginning how to modify the RDR configuration in order to satisfy PLC requirements (α c ~25mrad). Other geometries (two IRs, 25 mrad for both e + e - and γγ) should not be rejected. They have some advantages. The muon wall should have an additional hole to the γγ case. The laser optics (100 m loop) and the laser itself need a space in the experimental hall. It influences also detector designs.

28. Sept. 18, 2007Valery Telnov, IRENG07, SLAC 28 Conclusion (II) The beginning of the LC construction continuously delays and the cost grows: 7 B$ according to RDR and 15-28 B$ (total) according to the Chicago Tribune. Such expensive project can be approved only if it ambitious enough and has rich experimental program! It is obvious that beside e + e - it should include e - e -, γγ, γe, fixed target etc. The End

29. Sept. 18, 2007Valery Telnov, IRENG07, SLAC 29 Some additional slides (not shown)

30. Sept. 18, 2007Valery Telnov, IRENG07, SLAC 30 Conventional Facilities Components ILC - Global Design Effort, Barish, LCWS07 Σ Value = 6.62 B ILC Units

31. Sept. 18, 2007Valery Telnov, IRENG07, SLAC 31 Barish,HEPAP,22Feb07

32. Sept. 18, 2007Valery Telnov, IRENG07, SLAC 32 Single IR, push-pull : cost Cost difference of two IR versus single IR push-pull as reported to CCB on Dec.15 (based on Valencia wbs): –baseline 14/14: 100% –estimate for single p-p IR: 69.1%, with further updates 67.6% Estimation of saving, in Value cost, is 31-32% of BDS cost Using single push-pull IR saves about one third of two IR BDS cost, or in other words the two IR BDS is by about 50% more expensive than single push-pull IR BDS Estimation of additional hardware that is needed to make push-pull feasible is small fraction of the savings BDS Area leaders Deepa Angal-Kalinin, Andrei Seryi, Hitoshi Yamamoto ILC MAC meeting, January 10-12, 2007

33. Sept. 18, 2007Valery Telnov, IRENG07, SLAC 33 Beam Delivery System, 2x14 mrad, Valencia, Nov.2006 ( BDS Area leaders) IP2 IP1 10m 1km beam dump service hall alcoves 9m shaft for BDS access polarimeter laser borehole muon wall tunnel widening

34. Sept. 18, 2007Valery Telnov, IRENG07, SLAC 34 Beam Delivery System tunnels for 2x14 mrad (Valencia)

35. Sept. 18, 2007Valery Telnov, IRENG07, SLAC 35 RDR Baseline Layouts for Interaction Region