1. An SLC-Style Higgs Factory (and some comments on NLC technology) Tor Raubenheimer ICFA Higgs Factory Workshop November 14 th, 2012

2. Goal and Outline Can we reduce ILC cost by factor of 4 and still do physics? -What about a gamma-gamma collider? Eliminate complicated damping rings, e+ source and lowers energy -What about the SLC configuration? Further reduce center-of-mass (cms) energy to ~85 GeV 2 Higgs Factory Workshop, 11/14/12 500 GeV ILC RDR Cost Distribution 5% 8% 10%

3. 3 Synchrotron Radiation Limitations Very strong synchrotron radiation presents severe limitation on center-of-mass energy in SLC configuration Higgs Factory Workshop, 11/14/12  E ~ 6 GeV / turn at 85 GeV with 1-km radius   ~ 0.2% / turn at 85 GeV with 1-km radius  ~ 1 mm-mrad / turn at 85 GeV with 1-km radius and 5-m cell Requires ~3.5 km radius at 240 GeV cms

4. Gamma-Gamma Higgs Factory Concept Lots of people have discussed a  Higgs factory -Significant write-ups for NLC ZDR, TESLA and ILC -Good discussion from D. Asner (2001), arXiv:hep-ex/0111056 -Polarized e-/e- beams and intense lasers becoming more realistic SAPPHIRE design paper is a good reference -S. Bogacz, et. al., arXiv:1208.2827 [physics.acc-ph] (2012). arXiv:1208.2827 Advances in tapered FELs makes laser sources more reasonable Higgs Factory Workshop, 11/14/12

5. 5 Gamma-gamma collider Lack of beamstrahlung allows different optimization of LC parameters  focus on high charge, round beams Relaxes location of conversion point, jitter tolerances, etc From an rf gun emittance tends to scale as less than N  gain by going to higher charge Higgs Factory Workshop, 11/14/12

6. 6 Inverse Compton Scattering Inverse Compton Physics x = 4.8 to avoid pair production laser ~ 350 nm and  m ~ 0.8 E 0 implying 80 GeV e- beams for 130 GeV cms  Need 1.2 J per laser pulse in 1-ps and a 1 um spot 4 mm from IP to get 80% conversion Higgs Factory Workshop, 11/14/12

7. 7 Laser Beam Source Significant progress in optical cavities but UV is more difficult Seeded FEL’s have demonstrated strong tapering Higgs Factory Workshop, 11/14/12 G.Klemz, et al (2005), arXiv:physics/0507078 T. Orzechowski et al. PRL (1986) SASE + Tapering at 10cm wavelength Recent seeding studies in hard x-ray regime support simulation studies  J-class pulses are thought possible with ~10% extraction efficiency

8. 8 Polarized Rf Gun Have to get rid of the damping rings because they are expensive and have very poor longitudinal emittance causing expensive bunch compression system -DR’s plus BC’s are ~20% of ILC cost! SCRF gun development has made great progress. Options at frequencies from 112 MHz up to 1.3 GHz -704 MHz gun is designed for 5 nC at 5 mm-mrad -Lower frequency would likely be better for high bunch charges -Simulations of 5 mm-mrad at 10 nC with 112 MHz gun 112 MHz QWT SCRF gun

9. 9 Acceleration Limitations Sapphire assumes a 4x recirculation in two 11 GeV CW linacs an average current of 0.32 mA and an average gradient of 10 MeV/m and a 200 kHz bunch rate -Jlab model for the linacs  25 MW per beam! Another option is the ILC SCRF scheme using KEK-style couplers, 10 mA beam current at the IP (40 mA in the linac), a 45 GeV linac with 2x recirculation (some issues here) and a 10Hz rep. rate or a single pass in an 85 GeV linac with 20 mA -ILC model for the linacs  7 MW per beam and recover luminosity with collision format Higgs Factory Workshop, 11/14/12

10. 10 High Power Coupler Design Linac current limited by couplers. KEK large aperture coupler design has higher power capability. Higgs Factory Workshop, 11/14/12 Warm Window Vacuum Port Cold Window 80K 5K Beam Pipe Monitor Port Low loss 0.2W to 5K Higher Static loss 1W to5K No Tuning TRISTAN type ceramic window Qext = 2.0 x 10 6 Prf = 350 kW 82.4 mm

11. 11 Arcs Considerations Strongly limited by synchrotron radiation Biggest impact is on beam emittance Could consider high brightness lattices like light sources TME lattice has minimum emittance of: but one problem is poor lattice packing Requires ~600 cells with 11 kG bends and F m ~ 25% to keep  ~ 10% Higgs Factory Workshop, 11/14/12

12. 12 Arc Considerations (2) Another option is a combined function lattice similar to SLC 1 km average bending radius with  ~ 5e-7 -4.5 meter cell with 2 meter bends  roughly 700 cells -B’ ~ 14 kG/cm; B0 ~ 3.2 kG Not clear if this would be cheaper and simpler than TME-style lattice Higgs Factory Workshop, 11/14/12

13. 13 SLC-ILC-Style (SILC) Higgs Factor Some challenges with 2-pass design! Higgs Factory Workshop, 11/14/12 1 km radius 45 GeV, 1.5 km or 85 GeV, 3 km Final focii ~ 300 meters in length Laser beam from fiber laser or FEL Upgrade with plasma afterburners (what cms energy is possible?) 250 m

14. 14 Primary Parameters ParameterCLIC-HiggsSapphireSILC cms e- Energy160 Gev160 GeV Peak  Energy 128 GeV 130 GeV Bunch charge4e91e105e10 Bunches/train169011000 Rep. rate100200 kHz10 Hz Power per beam9.6 MW25 MW7 MW  x /  y [um] 1.4 / 0.055 / 0.56 / 5  x /  y at IP [mm] 2 / 0.025 / 0.10.5 / 0.5 sx / sy at IP [nm]138 / 2.6400 / 18140 / 125 L_geom4e342e341e34 L_gg (E  > 0.6 Ecms) 3.5e33 2e33 CP from IP1 mm 4 mm Laser pulse energy2 J4 J1.2 J Higgs Factory Workshop, 11/14/12

15. 15 Upgrade with Plasma Afterburner The goal is to upgrade the Higgs machine in energy using PWFA afterburner to double beam energy. Could also increase electron beam energy 80  100 GeV from the arcs. Would require a more complex arc cell like a TME optics. Alternately would be to develop a shaped bunch for higher transformer ratio! Challenging to achieve desire luminosity. Simple idea would be divide bunch 2/3 = drive, 1/3 = production but luminosity drops by 4.5. Looking at other approaches to boost energy. Higgs Factory Workshop, 11/14/12

16. 16 Plasma Wakefield Afterburner Higgs Factory Workshop, 11/14/12 Erik Adli

17. 17 Cost Guestimate Assumptions: Laser system is donated by LLNL! Linac costs scaled from ILC costs Arc costs scaled from ILC and SLC Higgs Factory Workshop, 11/14/12 45 GeV linac versus 490 GeV (rf power increases by 4x but small % of linac costs)  20% or 0.8 B$ value BDS reduced in half  0.2 B$ DR, RTML, and e+ = 0 Rf gun = 0.05 B$ value Arc = 2km C&C tunnel and 8 km of arc magnets & vacuum (100 k$ / meter beamline or 40 k$ / meter in value units)  0.4 B$ value Other costs ~ 0.15 B$  1.6 B$ value ~25% ILC 500 GeV ILC RDR Cost Distribution 5% 8% 10%

18. 18 Summary – SLC-style linear collider SLC-style option (arcs) is very limited by synchrotron rad. Options include 80 GeV beams with 1 km radius, 120 GeV beams with 3.5 km radius, … A combination of the SLC LC concept with ILC technology, gamma-gamma and high power lasers/FELs may provide a cost effective and politically acceptable path to a Higgs factory. It would engages almost all partners with: -Challenging beam dynamics (everybody), -High power SCRF (Cornell and FNAL), -SCRF guns (BNL), -Lasers (LLNL, LANL and SLAC), -Recirculating linacs (Jlab), -and physics (the world)! Higgs Factory Workshop, 11/14/12

19. NCRF versus SCRF? NCRF is believed (at least be me) to be cheaper per GeV -Costs are not fully developed and industrialization scaling is guess -Fabrication infrastructure can be developed quickly as demonstrated by Fermilab in early 2000’s SCRF is cheaper per MW -Solid cost basis from XFEL -Major investments in fabrication infrastructure in US (200 M$), Asia and Europe -SCRF LC has large zero energy cost due to large injector complex PWFA concept is still attractive but do not yet understand infrastructure costs  comparable to NCRF 19 Higgs Factory Workshop, 11/14/12

21. Simplified Layout of NLC/GLC RF System (Efficiencies & Powers in Parentheses) Beam / Wall Plug = 6.5%

22. X-Band Pulse Compression Revisited! Dual-moded transmissive delay line. →No tuning needed (use LLRF phase). → Intrinsic efficiency is 100%. 1 unit delay (200 ns) 4  85 MW  600 ns 3  340 MW  200 ns CP 123 TE 12 (340 MW) TE 01 (680 MW) ~30 m Four klystrons are combined through a cross potent superhybrid. During the 1 st time bin, power combines through path 1 into the delay line. Upon returning through the second pipe of the delay line, the power is combined with that of the 2 nd time bin, coming along path 2, and sent through the delay line again in a different mode. The returning power is then split and feeds the accelerator simultaneously with the 3 rd time bin power directed along path 3. 526 kV, 1.08 kA, 600 ns C r = 3  i = 1 C. Nantista ’08

23. If the efficiency of the PC/PDS is 90%, we have ~918 MW / RF system. If the accelerating structure power requirement is 100 MW/m and the packing fraction is 90%, we can then feed ~10 m* of the linac physical length per RF system. Delay lines from 3 RF stations will overlap, for a cross-sectional footprint of 6 pipes. Delay Line Packing * fifteen 60cm structures. 6.7% more klystrons (@ 113% peak power & 75% pulse width) 47% fewer modulators (@ 105% voltage, 216% current & ~173% pulse energy) 6.7% more delay line (with no moving tuners!) Intrinsic compression efficiency: 1 vs. 0.86 Comparison With Dual-Moded SLED-II Higgs Factory Workshop, 11/14/12

24. 24 NCRF versus SCRF layouts and costs ILC RDR Costs 31 km for 500 GeV

25. Simplified/Unified ILC and NLC Linac Costs NLC damping rings and sources significantly less expensive than ILC 300 meter versus 3000 meter circumference; 2 GeV versus 5 GeV, etc. Higgs Factory Workshop, 11/14/12

26. 1 TeV PWFA Concept for PWFA-based on LC developed in 2009 -Options for NCRF or SCRF drive linac -No optimization; cost dominated by turn-around arcs -Re-optimize to lower turn-around energy or co-linear layout

27. 27 Summary – NCRF Options NCRF may be more cost effective than SCRF for a low energy (Higgs Factory) LC -In general SCRF has greater capability than NCRF but the higher power capability may not be necessary for LC World (HEP) accelerator community is developing SCRF as next generation accelerator technology -Light source community is more driven by cost limitations Topic may be re-examined if a project is formed but hard to make progress at this time Higgs Factory Workshop, 11/14/12