1. December 5, 2007 1 Chuck Ankenbrandt Fermilab Muon Collider Design Workshop @BNL Project X as a Hi-Rep-Rate Driver for a Muon Collider Chuck Ankenbrandt and Milorad Popovic Fermilab December 5, 2007

2. 2 Chuck Ankenbrandt Fermilab Outline  Introduction  What’s Project X?  There are various ways to use Project X to drive a muon collider –High repetition rate or low repetition rate –8 GeV protons or 50 GeV protons –Use/don’t use Main Injector –To drive a low/high emittance muon collider –My talk / Dave Neuffer’s  A high rep. rate, 8 GeV front end based on Project X  Summary

3. December 5, 2007 3 Chuck Ankenbrandt Fermilab Muon Collider & Ionization Cooling Issues - Y. Alexahin, FNAL December 5, 2006 Muon Collider parameters Low Emitt. High Emitt. Energy (TeV) 0.75+0.75 (  =7098.4) Average Luminosity (1e34/cm^2/s)2.71 Average bending field (T)108.33 Mean radius (m)361.4363.8 Number of IPs4 (350m/2 each)2 (200m each) P-driver rep.rate (Hz)6560 Beam-beam parameter/IP,  0.0520.1  (cm)0.53 Bunch length (cm),  z 0.52 Number of bunches/beam, n b 101 Number of muons/bunch (1e11), N  112 Norm.transverse emittance (  m),   N 2.113 Energy spread (%)1 0.1 Norm.longitudinal emittance (m),  ||N 0.35 0.14 Total RF voltage (GV) at 800MHz406.6  10 3  c 0.26  10 3  c RF bucket height (%)23.90.6 Synchrotron tune0.723  10 3  c 0.02  10 3  c  +  - in collision / proton0.15 /20.15 8GeV proton beam power (MW)1.10.6  Low emittance option (advanced): owing to ideas by Yaroslav Derbenev (HCC, PIC) much lower 6D emittances seem to be feasible than previously thought of.  High emittance option (baseline): conceptually follows 1999 PRSTAB Muon Collider Collaboration report

4. December 5, 2007 4 Chuck Ankenbrandt Fermilab Introduction to Project X  The heart of Project X is an 8-GeV H - linac based on ILC technology.  Project X will stack beam into the Recycler to allow Main Injector to accelerate 2.2 MW of beam to 120 GeV.  Excess beam cycles will be available at 8 GeV.  http://www.fnal.gov/directorate/Fermilab_AAC/AAC_July_07/ http://www.fnal.gov/directorate/Fermilab_AAC/AAC_July_07/ http://www.fnal.gov/directorate/Fermilab_AAC/AAC_July_07/Agenda_Aug_07_Rev4.htm

5. December 5, 2007 5 Chuck Ankenbrandt Fermilab Overview of Project X 120 GeV fast extraction spill 1.5 x 10 14 protons/1.4 sec 2 MW 8 GeV H - Linac 9mA x 1 msec x 5 Hz 8 GeV extraction 1 second x 2.25 x 10 14 protons/1.4 sec 200 kW Stripping Foil Recycler 3 linac pulses/fill Main Injector 1.4 sec cycle Single turn transfer @ 8 GeV 0.6-8 GeV ILC Style Linac 0.6 GeV Front End Linac From Dave McGinnis’ talk

6. December 5, 2007 6 Chuck Ankenbrandt Fermilab Possible site layout of Project X

7. December 5, 2007 7 Chuck Ankenbrandt Fermilab H- Injection – Transverse painting (Dave Johnson) End 1 st injection End 2 nd injection End 3 rd injection Foil (injected beam) Closed orbit movement Move off foil Start injection Stripping foil Closed orbit Final distribution after painting to 25  at  H of 70 and  V of 30 (STRUCT) H- Foil H+ inj abs painting Chicane (DC) Cartoon of phase space painting with 3 linac pulses Horizontal orbit motion during painting Painting waveform for Recycler Injection Aug 8, 2007 AAC meeting D. Johnson

8. December 5, 2007 8 Chuck Ankenbrandt Fermilab Outline, revisited  Introduction  What’s Project X?  Ways to use Project X to drive a muon collider 

9. December 5, 2007 9 Chuck Ankenbrandt Fermilab Project X: Possible 8 GeV Upgrades The last column has about the same Recycler intensity as when the baseline Project X accumulates 3 cycles for the Main Injector.

10. December 5, 2007 10 Chuck Ankenbrandt Fermilab Using Project X to make muons for a collider  Proton beam power of 2 MW may be enough to drive a high-luminosity, low-emittance muon collider.  The challenge is to “repackage” the protons into a useful form for a muon collider.  It’s not clear what will work best for a muon collider or a neutrino factory, so flexibility would be nice at the conceptual design stage. –The rms bunch length should be 3 nsec or less. (Really?) –A repetition rate of 60 Hz would match the muon lifetime at 750 GeV. (However, we may end up at a different energy.) –Will we use one or two proton bunches to make each pair of muon bunches? Or to make multiple pairs? –How many pairs of muon bunches will we make at a time?  “Buffer rings” (two 8 GeV storage rings with large acceptances and small circumferences) could provide the needed flexibility.

11. December 5, 2007 11 Chuck Ankenbrandt Fermilab A specific hi rep. rate, 8 GeV example  Use Accumulator(-like) and Debuncher(-like) rings.  Acc and Deb are leftovers from Fermilab’s Antiproton Source  They are not very deep underground; maybe move to new tunnel?  Paint to large (~200 pi) transverse emittances in rings with small circumference to control space charge.  Could strip directly into “Accumulator” or do multi-turn transverse stacking from Recycler to “Accumulator”.  Small circumference means more favorable bunching factor.  Scale from space charge tune shift (~0.04) in Recycler ring.  Use h=12 and h=24 rf to make 12 ~rectangular bunches.  (Note possible constraints on h 1, h 2 : Circumference ratio)  Transfer two bunches at a time to the “Debuncher”.  Do a bunch rotation in the “Debuncher”.  Deliver two bunches at a time to the target at 60 Hz.

12. December 5, 2007 12 Chuck Ankenbrandt Fermilab Picture of the concept

13. December 5, 2007 13 Chuck Ankenbrandt Fermilab ESME-One bunch

14. December 5, 2007 14 Chuck Ankenbrandt Fermilab Twelve bunches in Accumulator

15. December 5, 2007 15 Chuck Ankenbrandt Fermilab Shorter bunches in Accumulator

16. December 5, 2007 16 Chuck Ankenbrandt Fermilab Longitudinal emittance scaling  In the Recycler, beam will be painted to a longitudinal emittance of about 0.25 eV sec per bunch  After transfer via transverse stacking to the Accumulator, the total longitudinal emittance will be ~ 84 times 0.25  If we form 12 bunches, each will have 84(0.25)/12 = 1.75 eV sec.  If we reduce the bunch length to a total  t of about 10 nsec, then  E will be about 0.175 GeV = +/- 0.09 GeV  So  E/E = +/- 1%, well within the momentum aperture.

17. December 5, 2007 17 Chuck Ankenbrandt Fermilab Space-charge tune shift scaling  Scale from incoherent tune shift of 0.04 in Recycler  The energy (8 GeV) and the total number of protons are the same in the Recycler and the Debuncher.  The transverse stacking into the Debuncher raises the transverse emittances by a factor of eight.  The bunching factor goes down by a factor of nine.

18. December 5, 2007 18 Chuck Ankenbrandt Fermilab Flexibility  Above example was for 60 Hz; however…  Could form fewer bunches in rings  Could combine bunches externally (cf. next slide)  Rep rate as low as 10 Hz (once per linac cycle) may be feasible  Analogy: Tevatron Collider  Started with one pair of bunches at design luminosity of 10 30  Went to 3x3, mainly to reduce events per crossing  Implemented electrostatic separators and went to 6x6  Now at 36x36

19. Very High Rep Rate via CW Linac  For a muon collider rep rate of 65 Hz with ten bunch pairs, the front end might run at 650 or 1300 Hz.  A 50-GeV neutrino factory might also run at ~ 1 kHz.  Those rates might best be delivered via a CW linac.  Rol Johnson, CA and MP wrote a letter to the Fermilab Steering Group suggesting that possibility.  Arguments for a CW linac:  It’s easier to operate a superconducting linac CW (no transients)  Low peak rf power => lots of inexpensive klystrons  Jlab is existence proof  Could be a multipurpose facility December 5, 2007 19 Chuck Ankenbrandt Fermilab

20. December 5, 2007 20 Chuck Ankenbrandt Fermilab An external combiner to reduce rep rate at target Several bunches enter Bunches converging upon exit

21. December 5, 2007 21 Chuck Ankenbrandt Fermilab Summary: Project X for Muon Collider  A flexible way to deliver short intense 8-GeV proton bunches from Project X to a muon collider target station at various rep rates has been found.  The scheme uses the full 8-GeV capability of Project X upgraded to 2 MW of beam power.  The scheme uses Accumulator-like and Debuncher-like storage rings.  A CW linac could provide even higher rep rates.  Dave Neuffer will talk about using the Main Injector as part of the strategy.

22. December 5, 2007 22 Chuck Ankenbrandt Fermilab Backup Slides

23. December 5, 2007 23 Chuck Ankenbrandt Fermilab Pros and Cons

24. December 5, 2007 24 Chuck Ankenbrandt Fermilab Muon Collider & Ionization Cooling Issues - Y. Alexahin, FNAL December 5, 2006 Muon Collider parameters Low Emitt. High Emitt. Energy (TeV) 0.75+0.75 (  =7098.4) Average Luminosity (1e34/cm^2/s)2.71 Average bending field (T)108.33 Mean radius (m)361.4363.8 Number of IPs4 (350m/2 each)2 (200m each) P-driver rep.rate (Hz)6560 Beam-beam parameter/IP,  0.0520.1  (cm)0.53 Bunch length (cm),  z 0.52 Number of bunches/beam, n b 101 Number of muons/bunch (1e11), N  112 Norm.transverse emittance (  m),   N 2.113 Energy spread (%)1 0.1 Norm.longitudinal emittance (m),  ||N 0.35 0.14 Total RF voltage (GV) at 800MHz406.6  10 3  c 0.26  10 3  c RF bucket height (%)23.90.6 Synchrotron tune0.723  10 3  c 0.02  10 3  c  +  - in collision / proton0.15 /20.15 8GeV proton beam power (MW)1.10.6  Low emittance option (advanced): owing to ideas by Yaroslav Derbenev (HCC, PIC) much lower 6D emittances seem to be feasible than previously thought of.  High emittance option (baseline): conceptually follows 1999 PRSTAB Muon Collider Collaboration report

25. December 5, 2007 25 Chuck Ankenbrandt Fermilab The Primary Matrix Left wingCenterRight wing Hillary Rudy Barack Mitt John Ankle-biters

26. December 5, 2007 26 Chuck Ankenbrandt Fermilab Choices  Hi rep rate or low rep rate?  8 GeV or 50 GeV?  Ankenbrandt or Neuffer?

27. December 5, 2007 27 Chuck Ankenbrandt Fermilab Rep. RateHigh Low  High EpEp 8 GeV 50 GeV The Front End Matrix

28. December 5, 2007 28 Chuck Ankenbrandt Fermilab Introduction  Young-Kee’s Steering Group likes Project X.  Pier asked: Can Project X be used for a muon collider?  We can and should provide an affirmative, simple, flexible response to Pier and the Steering Group.