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Project X Reference Design Overview

Project X Reference Design Overview. Sergei Nagaitsev April 12, 2011. Reference Design. Reference Design Capabilities. 3 GeV CW superconducting H- linac with 1 mA average beam current. Flexible provision for variable beam structures to multiple users

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Project X Reference Design Overview

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  1. Project X Reference Design Overview Sergei Nagaitsev April 12, 2011

  2. Reference Design Apr 12, 2011 - S. Nagaitsev

  3. Reference Design Capabilities • 3 GeV CW superconducting H- linac with 1 mA average beam current. • Flexible provision for variable beam structures to multiple users • CW at time scales >1 msec, 15% DF at <1 msec • Supports rare processes programs at 3 GeV • Provision for 1 GeV extraction for nuclear energy program • 3-8 GeV pulsed linac capable of delivering 300 kW at 8 GeV • Supports the neutrino program • Establishes a path toward a muon based facility • Upgrades to the Recycler and Main Injector to provide ≥ 2 MW to the neutrino production target at 60-120 GeV. • Day one experiment to be incorporated utilizing the CW linac • Utilization of a CW linac creates a facility that is unique in the world, with performance that cannot be matched in a synchrotron-based facility. Apr 12, 2011 - S. Nagaitsev

  4. Reference DesignProvisional Siting CW Linac Pulsed 3-8 GeVLinac based on ILC / XFEL technology Pulsed Linac Apr 12, 2011 - S. Nagaitsev

  5. Reference design: accelerator scope 5% duty cycle Pulsed dipole Apr 12, 2011 - S. Nagaitsev Warm cw front end 162.5 MHz, 5 mA (H- ion source, RFQ, MEBT, chopper) 3-GeV cw SCRF linac (325, 650 MHz), 1-mA ave. beam current Transverse beam splitter for 3-GeV experiments 3-8 GeV: pulsed linac (5% duty cycle), 1.3 GHz Recycler and MI upgrades Various beam transport lines

  6. Changes to the reference design since Sep 2010 • Eliminated a 1.3-GHz section from the CW linac (Nov 2010) • Larger aperture, lower stripping losses, fewer cavities, cost neutral • Changed the RFQ frequency to 162.5 MHz (Jan 2011) • Easier chopper, lower RFQ power, larger aperture • Introduced a LEBT chopper (Nov 2010) • Ion source operates at a constant current, 5 mA max (Nov 2010) • Limit the max. cryo loss per cryomodule to 250 W (2K) (Nov 2010) • Per cavity – 25 W • Established pulsed 1.3 GHz linac configuration (Nov 2010) • 25 MV/m gradient • 1 mA beam current in 4.3 ms pulses • 1 Klystron per 16 cavities (2 CM) • 8 ms, 10 Hz Apr 12, 2011 - S. Nagaitsev

  7. Linac beam current Beam to Recycler Apr 12, 2011 - S. Nagaitsev Linac beam current has a periodic time structure (at 10 Hz) with two major components.

  8. Chopping for injection 162 MHz bunches to be removed Recycler RF • RF frequency at injection into the Recycler : ~50 MHz • Chopper needs to provide a kicker gap (~200 ns per 11 µs) and needs to remove bunches that fall into “wrong” phase of ring rf voltage. • 50% of bunches are removed ( ion source at 2 mA) • 80% of bunches are removed ( ion source at 5 mA) Apr 12, 2011 - S. Nagaitsev

  9. Chopping and splitting for 3-GeV experiments 1 msec period at 3 GeV Muon pulses (16e7) 81.25 MHz, 100 nsec at 1 MHz700 kW Kaon pulses (16e7) 20.3 MHz 1540 kW Nuclear pulses (16e7) 10.15 MHz 770 kW Ion source and RFQ operate at 4.2 mA 75% of bunches are chopped at 2.5 MeV after RFQ Separation scheme Transverse rf splitter Apr 12, 2011 - S. Nagaitsev

  10. Beam after splitter 1 MHz pulses 10 MHz bunches 20 MHz bunches Apr 12, 2011 - S. Nagaitsev

  11. Ion source: TRIUMF-typeH- DC ion source Delivery expected: May 2011 LBNL + FNAL will test emittance etc. Apr 12, 2011 - S. Nagaitsev

  12. Proposed LEBT configuration Apr 12, 2011 - S. Nagaitsev LEBT will likely have a chopper to provide 0.5 ms gaps, needed for a switching magnet at 3 GeV

  13. RFQ (162.5 MHz) CW RFQ: Several design studies by LBNL Good experience at ANL and LBNL Apr 12, 2011 - S. Nagaitsev

  14. MEBT design: 5 mA at 162.5 MHz beam 325 MHz warm bunching cavities =0.25 ∙μm; z,n=0.3 ∙μm Apr 12, 2011 - S. Nagaitsev

  15. MEBT chopper Apr 12, 2011 - S. Nagaitsev

  16. RT Bunching CW cavities Apr 12, 2011 - S. Nagaitsev

  17. Effect of longitudinal emittance (L/=0.52) Bunch Length (3) vs. Synch. Phase MEBT SSR0 Apr 12, 2011 - S. Nagaitsev

  18. Prelim Conclusions: Front End Apr 12, 2011 - S. Nagaitsev • Transverse rms (norm) emittance 0.25 mm-mrad • Range of acceptable longitudinal emittances is close to equipartition, z/ ≈ 0.8-1.2, =0.25 ∙μm • No need for using 162.5 MHz cavity (copper) in MEBT. • SSR0 section at 325 MHz works for 162.5 MHz RFQ option • Unanswered issues: • Chopper driver • Beam absorber (10 kW) • Absorber sputtering and blistering rates

  19. SRF LinacTechnology Map Pulsed CW 650 MHz 0.16-3 GeV b=0.11 b=0.22 b=0.4 b=0.61 b=0.9 b=1.0 325 MHz 2.5-160 MeV 1.3 GHz 3-8 GeV Apr 12, 2011 - S. Nagaitsev

  20. 325 MHz spoke cavity families SSR0 – design, prototyping SSR1 – prototyping, testing SSR2 - design Parameters of the single-spoke cavities Apr 12, 2011 - S. Nagaitsev

  21. Focusing Periods in SSR sections: Focusing Period: SSR0: (sol+cav) = 610 mm SSR1: (sol+cav) = 800 mm SSR2: (sol+cav+cav+60 mm) = 1600 mm 800 mm Apr 12, 2011 - S. Nagaitsev

  22. 650 cavities • 650 MHz, 5-cell cavity: • Similar length as for ILC-type cavity; • About the same maximal energy gain per cavity; • The same power requirements; • Benefits compared to 1.3 GHz ILC-type cavity: • Higher accelerating efficiency  smaller number of cavities and RF sources: • Beam dynamics • 2-fold frequency jump instead of 4-fold  easier transition • Smaller beam losses; • Less effect of cavity focusing (~1/ λ) • Trade-offs: • more serious problem with microphonics, but still may be manageable; • Larger diameter (comp to 1.3), higher cost per cavity; • additional rf frequency -> infrastructure. Apr 12, 2011 - S. Nagaitsev

  23. 650 MHz cavities 650 MHz: β=0.61 650 MHz: β=0.9 Apr 12, 2011 - S. Nagaitsev

  24. LE Cryomodules 3238.09 HE Cryomodules 8878.49 3282.03 11325.12 CMs lengths are shown from the first cavity iris to the last cavity iris. Apr 12, 2011 - S. Nagaitsev

  25. 650 MHz Cryomodule(Tesla Style-Stand Alone, 250 W @ 2K) Vacuum Vessel Cold mass supports (2+1) Power MC (8) Beam End Plate Apr 12, 2011 - S. Nagaitsev

  26. Cavity string & 300mm pipe Apr 12, 2011 - S. Nagaitsev

  27. CW linac: Envelopes Apr 12, 2011 - S. Nagaitsev

  28. Energy Gain per Cavity • Single cavity per power source • Solid State, IOT Apr 12, 2011 - S. Nagaitsev

  29. 3 GeV CW LinacCryogenic Losses per Cavity ~42 kW cryogenic power at 4.5 K equivalent Apr 12, 2011 - S. Nagaitsev

  30. Solenoid Magnetic Field Apr 12, 2011 - S. Nagaitsev

  31. Quadrupole (doublet) Gradient Doublet (FD) 100 350 350 Apr 12, 2011 - S. Nagaitsev

  32. Errors and misalignments • Misalignments ±1 mm for all elements (specification ±0.5 mm ) • RF jitter of 0.5 ° x 0.5 % in the front-end & 1 ° x 1% RF jitter in the high-energy part was implemented. • 100 seeds and 1 million macro-particles per seed. • 1 corrector, 1 BPM per solenoid/douplet/quad; BPM resolution=30 μm • Beam centroid is corrected to ±1mm; Emittance increase < 20%. • The uncorrected seeds predict losses above 100 W/m; corrected – no losses Beam Centroid off-set Beam Transverse Emittance The red curves are the 100 seeds without correction and the blue curves are the 100 seeds corrected Apr 12, 2011 - S. Nagaitsev

  33. H- stripping Summary Apr 12, 2011 - S. Nagaitsev • Stripping on residual gas is < 0.1 W/m if pressure is better than 10-8 Torr • Assuming gas contains 50% H2, 25% O2, 25% N2 • Magnetic stripping is well below 0.1 W/m even for unrealistic 5 mm beam offset. • Stripping on blackbody radiation is not an issue for SC linac. • Intra-beam stripping is ~0.1 W/m

  34. 3 – 8 GeV acceleration Apr 12, 2011 - S. Nagaitsev • Pulsed linac based on the ILC technology • 1.3 GHz, 25 MV/m gradient, ≤5% duty cycle • considering 8-30 ms pulse length • ~250 cavities (28 ILC-type cryomodules) needed. • Simple FODO lattice • 1 Klystron per 2 CM’s

  35. Cavity Energy Gain Eacc = 25 MV/m: L=1.038m Apr 12, 2011 - S. Nagaitsev

  36. Envelopes (sigma) Apr 12, 2011 - S. Nagaitsev

  37. Summary of studies for pulsed linac Apr 12, 2011 - S. Nagaitsev • Beam losses are smaller than for CW linac • Intra-beam stripping is well below 0.1 W/m • Magnetic stripping is small for reasonable beam displacement (<20mm) • LLRF control • Simulated for scheme with 1 klystron feed 2 CM • VS control at the level below~0.5 % and 0.5 deg (individual cavity error ~10% and 10 deg) allows to keep energy jitter at 8 GeV below 10 MeV. (needed for injection)

  38. Injection Need to accumulate 26 mA-ms protons in the MI/Recycler For a stationary foil, a single 26-ms pulse would destroy the foil. 6 pulses at 10 Hz give enough time for radiative cooling between pulses Apr 12, 2011 - S. Nagaitsev

  39. Foil efficiency Apr 12, 2011 - S. Nagaitsev

  40. Recycler injection Apr 12, 2011 - S. Nagaitsev

  41. Alternative injection scheme • A possibility to inject in a single 26-ms pulse is highly desirable. • Eliminates the need for Recycler (as an accumulator) • Potentially allows for a lower linac energy (6-7 GeV) • Requires long-pulse linac operation Apr 12, 2011 - S. Nagaitsev

  42. Recycler parameters Apr 12, 2011 - S. Nagaitsev

  43. Phase-space painting Motivation • Gaussian beam G =3 • Single RF harmonic at 53 MHz B =5 DQ= -0.3 • Uniform beam G =1 • Longitudinal painting B =2 DQ= -0.04 Apr 12, 2011 - S. Nagaitsev

  44. Longitudinal painting 162 MHz bunches to be removed Recycler RF B=2.2 Linac long. emittance: 1.3e-4 eV-s Recycler long. emittance: 0.6 eV-s Apr 12, 2011 - S. Nagaitsev

  45. Transverse painting • Transverse painting is designed to: • Minimize the number of secondary passages and foil heating • To make correlated x-y painting (K-V distribution) with radius increase for each next pulse • Injected beam does not move on foil • Closed orbit describes almost a quarter of circle (forward and back) Apr 12, 2011 - S. Nagaitsev

  46. Recycler modifications • New rf systems: • 53 MHz and 106 MHz (fixed frequency) • New injection system • Possibly TiN vacuum pipe coating to mitigate electron cloud Apr 12, 2011 - S. Nagaitsev

  47. MI modifications • New RF systems • 53 MHz and 106 MHz (with freq. sweep for acceleration) • 2.7 MV/turn at 36-degree synch phase • γtjump system • Possibly TiN vacuum pipe coating to mitigate electron cloud Apr 12, 2011 - S. Nagaitsev

  48. Summary • Project X design concept is well developed and has been stable for more than 1 year. • We have an RD&D plan to take us through CD2. Key R&D issues (among others) • Chopper section • Recycler injection • SRF cavities Apr 12, 2011 - S. Nagaitsev

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