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Making More Muons

Making More Muons. mu2e Conversion and higher intensity beams Project X Physics Workshop. Chuck Ankenbrandt Fermilab November 17, 2007. Game Plan for this Talk. My title (from the organizers) suggests three topics: Delivering protons from Project X to mu2e

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Making More Muons

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  1. Making More Muons mu2e Conversion and higher intensity beams Project X Physics Workshop Chuck Ankenbrandt Fermilab November 17, 2007 Chuck Ankenbrandt Fermilab

  2. Game Plan for this Talk My title (from the organizers) suggests three topics: • Delivering protons from Project X to mu2e • I will discuss this only briefly unless there are questions. • Providing more/better muons than MECO • This is the main topic of my talk. • I will present preliminary ideas to induce brainstorming. • Upgrading the detector for higher rates • This is under active consideration by the collaboration. • I will not discuss it here. Chuck Ankenbrandt Fermilab

  3. Delivering the Protons • From the Booster: Cf. Jim Miller’s mu2e presentation • At similar intensities (~30 kW), but from Project X: • Cf. Letter to Steering Group: “Using an ILC-Style 8 GeV H- Linac for a Muon to Electron Conversion Experiment” by C. Ankenbrandt, S. Geer, and E. Prebys (also backup slides) • Up to ~ 200 kW (full Project X 8-GeV beam power): Extract one complete Recycler fill (1 to 4 Linac squirts) in a single turn at MI52 and transmit it via P150 line to the Accumulator. Inject the beam into the Accumulator using multi-turn (7-turn) transverse stacking in both transverse planes. That should be feasible because the transverse acceptances in the Accumulator are each about an order of magnitude larger than those of the Recycler. Chuck Ankenbrandt Fermilab

  4. Muon Beam Introduction • Muon Beams would be useful for … • National or International Lepton Colliders (NLC or ILC!) • Neutrino Factories • Precision Physics beyond the Standard Model • Muon g-2 • Muon EDM - m->e + g • Muon to electron conversion (mu2e): (focus of this talk) • Muons, Inc/Fermilab recently got an SBIR grant to explore whether innovations in muon cooling can be used to improve Stopping Muon Beams, particularly for mu2e. Chuck Ankenbrandt Fermilab

  5. Intro., continued: Approximate rates • An 8-GeV proton beam on an optimized target produces about one charged pion of each sign per proton. Chuck Ankenbrandt Fermilab

  6. Stopping Muon/proton ratio • Reaction of muon collider community: “Why is the ratio so small?” • Reaction of stopping muon community: “How does MECO get such a large ratio?!” Chuck Ankenbrandt Fermilab

  7. More intro.: Comparison of Front Ends Those familiar with muon colliders should realize that stopping muon beams have very different requirements. (If and when a muon collider exists, a stopping muon program could use the cold muon beam when the collider is not operating.) Chuck Ankenbrandt Fermilab

  8. MECO Chuck Ankenbrandt Fermilab

  9. Stopping Muon Beams 101 • p + A -> p + X • ~One charged pion of each sign per 8-GeV proton • Pion decay length is 7.8 meters for p = mc • p -> m + n decay kinematics in lab: • Less than 29 MeV/c of transverse momentum • Longitudinal momentum distribution of muons is uniform between about 60% and about 100% of pion momentum • Polarization correlates completely with longitudinal momentum • Passing the muons through material causes the momentum spread to grow (dE/dx causes longitudinal heating) • Where the pions are: cf. next slide Chuck Ankenbrandt Fermilab

  10. Momentum vs. Cosine of production angle (from C. Yoshikawa)

  11. Momentum vs. Cosine of production angle (from C. Yoshikawa) Alt. B MECO Alt.A

  12. Concepts • (a) p/m production (b) momentum evolution • SBIR Cooling Concept: • 6D particle density increase • Absorber density decrease b) a) HCC acceptance MECO acceptance (From Mary Anne Cummings) Chuck Ankenbrandt Fermilab

  13. However, … • Above example used collider target solenoid (20 T) • Not a fair comparison with MECO (5 T) • Perhaps not practical for mu2e • Also, collaborators dislike proton beam pointed at detector • Ergo, explore other concepts: Chuck Ankenbrandt Fermilab

  14. target Proton beam BR=1 Tm Start of match to HCC wedge Target + Wedge @ Edge of Dipole Followed by low-Z absorber in HCC to cool the beam and reduce its energy. Chuck Ankenbrandt Fermilab

  15. Advantages of Wedge@edge • Hard momentum cutoff at ~ 150 MeV/c • Eliminates wrong-sign particles • Full width of target magnet is used: magnetic field volume is not wasted • Particles heavier than muons stop in degrader, not in stopping target; thus much better hadron background rejection than in MECO design • Electrons get eaten by high-Z wedge, thus probably not a problem. • Better background suppression means might live with higher intensity • Little dispersion in muon arrival times • May have better mu/proton ratio: • Uses pions at peak of momentum distribution • Uses pions produced near zero degrees • May be less expensive than MECO (maybe even fly under P5 radar?) • Probably can operate with shorter deadtime after proton arrival =>More usable muons per proton =>Could use titanium or other material having Z greater than Aluminum • Proton beam points away from experiment and is easily dumped. • Produces polarized stopping muon beam • Polarization can be varied by changing the thickness of the degrader Chuck Ankenbrandt Fermilab

  16. Iron Toroid for Pion Collection Cartoon of target toroid (thanks to M. Popovic) Chuck Ankenbrandt Fermilab

  17. Iron Toroid Muon Beam • One Lint (16.7 cm) of iron alloy magnetized to 2.5 T: • Attenuates by 1/e (but interactions in it produce more pions) • Bends 400 MeV/c particle by 312 mr • Degrades minimum ionizing particles by about 200 MeV/c • So an iron toroid in the forward direction can: • Make a parallel pion beam for a selected momentum p* • Shift the momentum spectra at each prod. angle to peak at p* • Pick p* to maximize muon flux after HCC at stopping target • Works much like a DC horn • Perhaps follow with Dipole+Wedge for muons, then HCC Chuck Ankenbrandt Fermilab

  18. Summary • Project X can supply protons for mu2e • At Booster intensities, and • Up to 150-200 kW • Muons, Inc. and Fermilab are exploring alternatives to MECO for pion production, muon collection and delivery. • Muon cooling via HCC looks promising. • Effective use of cooling requires different production concepts. • The mu2e collaboration is considering detector upgrade possibilities. Chuck Ankenbrandt Fermilab

  19. Backup slides Chuck Ankenbrandt Fermilab

  20. Additional Capabilities/Other Compelling Physics • (The MI-based neutrino program) • A m->e conversion experiment: mu2e • wants to momentum-stack in the Accumulator, • then rebunch and slow-extract from Debuncher. • It would benefit from cooling of stopping muons. • A muon cooling experimental program: • A prototype front end • Target station with low beam power • Muon collection, cooling, and re-acceleration • A muon test beam (including slow-spill beam) • Test concepts and components • Etc. Chuck Ankenbrandt Fermilab

  21. AP-4 Line The original SNuMI connections AP-5 Line Euclid: “The shortest distance between two points is a straight line.” Chuck Ankenbrandt Fermilab

  22. The proposed path The cheapest route between two rings is via existing beam lines. Chuck Ankenbrandt Fermilab

  23. MI and RR time lines for NOnA <-20 Booster ticks-> The Recycler is empty for as many as 8 Booster ticks. Chuck Ankenbrandt Fermilab

  24. RECYCLER Q522B Q522A MAIN INJECTOR Bending the beam out of the Recycler (The path into the Recyler will be implemented forNOnA) Chuck Ankenbrandt Fermilab

  25. Bending the beam into the P150 Line P150LINE ~20 mr vertical bend out of Recycler and into P150 Chuck Ankenbrandt Fermilab

  26. Matching Recycler to P150 Line The MAD output for the P150 line. The red arrows indicate the approximate separation between the two dipole magnets, with the first being in the Recycler and the second in the P150 line. Chuck Ankenbrandt Fermilab

  27. Matched Transfer Line from Recycler to P150 Chuck Ankenbrandt Fermilab

  28. Synergies with SNuMI • B->R->AS will: • eliminate the need for the AP-4 line, • provide opportunity for early commissioning of momentum-stacking in the Accumulator, and • motivate mitigation of radiation issues in the enclosure. • Modifications for SNuMI era: • AP-5 line or equivalent will still be needed. • There will still be a slot in the Recycler to transport the beam. • We’ll need a fast extraction system for Recycler to P150 line. • Only two “free” Booster batches will remain for other programs. Chuck Ankenbrandt Fermilab

  29. B->R->ASRequirements • Two dipole magnets (Cooling Ring Dipoles) • Two Transrex Power supplies (available) • Two quads such as existing Recycler quads • Two trim dipoles and two trim quads • All these components are available Chuck Ankenbrandt Fermilab

  30. Recent documentation (note contributors) Chuck Ankenbrandt Fermilab

  31. Abstract=Summary • “A way to deliver 8-GeV protons from the Booster to the Antiproton Source via existing enclosures and beam lines is described. By using the existing 8-GeV line and most of the Recycler as parts of the beam path, the scheme avoids the need for new civil construction and new beam transport lines. In this way, as soon as the Tevatron Collider era is over, the Antiproton Source can be rapidly transformed into a very useful pair of proton storage rings for various applications.” Chuck Ankenbrandt Fermilab

  32. Momentum-stacking in the Accumulator “Self-Bunching of a Coasting Beam in the Accumulator” by Dave McGinnis • Conclusion of that paper: • “For the projected SNUMI intensity of 14.1x1012 particles in the Accumulator at a 95% momentum spread of 15.9MeV, and an RF feedback gain of 14dB, the beam should be stable with a factor of two margin. This result can be tested by cooling 100mA of antiproton beam on the stacking lattice (h=0.10) to a frequency width of 7.9 Hz.” • B->R->AS would enable commissioning of momentum stacking in the Accumulator • http://beamdocs.fnal.gov/SNuMI-public/DocDB/ShowDocument?docid=198 Chuck Ankenbrandt Fermilab

  33. 8 GeV Linac (Project X) and mu2e Chuck Ankenbrandt Fermilab Mu2e Collaboration Meeting August 1, 2007 My Preferred title: Linac & Recycler & Accumulator & Debuncher: Consider the Possibilities (Like 1969 movie) Chuck Ankenbrandt Fermilab

  34. Considering the possibilities Chuck Ankenbrandt Fermilab

  35. Outline • 1) Introduction/Overview • 2) Linac & Recycler & Accumulator & Debuncher: • Consider the Possibilities • a) Review/discuss Fermilab BEAMS-DOC-2812-V: • Using an ILC-Style 8 GeV H- Linac for a Muon to Electron Conversion Experiment by Ankenbrandt, Geer, and Prebys • b) Update of that note • 3) Summary/Conclusions Chuck Ankenbrandt Fermilab

  36. 8 GeV Proton sources Proton Linac (H-) 8 GeV? H- t Chuck Ankenbrandt Fermilab

  37. 1) Introduction/Overview • The question that is addressed is: • How will mu2e get proton beam in the Project X era? • In a note to Young-Kee Kim’s Steering Group, • we (Geer, Prebys, and I) discussed that question. • In this talk, I will briefly review and update that note. • For completeness, a copy of that note is included in this document. • Assumptions that went into that note: • 1) By the time that Project X is commissioned, mu2e will already be running (concurrent with NOnA or SNuMI) using beam from Booster to Recycler to Accumulator to Debuncher. • 2) Lab management will want to decommission the present Linac and Booster once Project X is commissioned. • What’s new since the note was written: • 1) Rumor has it that experts are pessimistic about the feasibility of slow extraction from the Recycler. If verified, that would preclude running directly off the Recycler. • 2) Ways have been conceived for using more beam from Project X; variations of option 3a. (Thanks to interesting conversations with Tom Roberts and Dave Johnson) • 3) Hence I’ve been thinking more recently in terms of an intensity upgrade rather than a mere continuation of mu2e at similar intensities. Chuck Ankenbrandt Fermilab

  38. Title page of the note • Using an ILC-Style 8 GeV H- Linac for a Muon to Electron Conversion Experiment • C. Ankenbrandt, S. Geer, and E. Prebys • Fermi National Accelerator Laboratory, PO Box 500, Batavia, IL 60510 • Abstract • We describe how the H- beam from an ILC-Style 8 GeV H- Linac can be collected, rebunched, and slowly extracted to provide a beam suitable for a muon to electron conversion experiment (mu2e). The scheme would permit simultaneous operation of the muon program with the future NuMI program, delivering O(1020) protons per year at 8 GeV for the mu2e experiment. Chuck Ankenbrandt Fermilab

  39. INTRODUCTION • In a communication to the Fermilab long-range steering committee, D. McGinnis [1] has proposed to upgrade the Fermilab proton source by replacing the existing Linac/Booster with an ILC-Style 8 GeV H- Linac delivering 9 mA in 1 ms long pulses at 5Hz. There would be 7 Linac pulses per 1.4 sec Main Injector cycle, each pulse containing 5.7  1013 H-. The first 3 pulses would be injected via H- injection into the Recycler. The circulating 1.7  1014 protons would then be extracted in a single turn and transferred to the Main Injector to be used for the NuMI program. This would leave up to 4 Linac pulses, which could also be injected into the Recycler, available for an 8 GeV physics program. Previous notes have described how 8 GeV protons from the Booster can be transferred to the Fermilab Antiproton source [2], then rebunched and slow extracted [3] to produce a primary beam suitable for a muon to electron conversion experiment [4]. In this note we describe how protons from the McGinnis scheme [1] can be used for a muon to electron conversion experiment. We assume that the scheme described in References [2] and [3] to deliver protons from the Booster to the Accumulator for the experiment will have already been implemented by the time the new Linac is commissioned. It is also assumed that the present Linac and Booster will be decommissioned shortly after the new Linac is commissioned, so beam for the experiment would have to come from the Recycler. One way to accomplish this would be to run the experiment directly off the Recycler; the other way would be to transfer beam to the Accumulator. The two alternatives are discussed in the following paragraphs. Chuck Ankenbrandt Fermilab

  40. Directly off the Recycler (probably not feasible) • Once per Main Injector cycle, one Recycler fill (5.7  1013 protons) would be used for the muon to electron conversion experiment. The protons would be rebunched into about 7 equally-spaced bunches, then slowly extracted for about 0.7 seconds from the Recycler near MI52 and transferred to the Antiproton Source enclosure via the P150 line. The beam would then be transported directly to the experiment, bypassing the Accumulator. That would require a new beamline in the Antiproton Source enclosure connecting the P150 line to the transfer line to the experiment. The other three available Linac cycles would not be used. This scenario would provide about 50 kW of beam power at 8 GeV with a duty cycle of about 50% for the muon conversion experiment. It would preclude other uses of 8 GeV beam which require the Recycler. Chuck Ankenbrandt Fermilab

  41. Recycler to Accumulator • Various ways to take beam from the Recycler to the Accumulator for the experiment can be conceived. Subsequent beam processing in the Accumulator and Debuncher would then be similar to the plan that uses beam from the Booster. a) In one scheme, one complete Recycler fill is extracted in a single turn at MI52 and transmitted via P150 to the Accumulator. The beam is injected into the Accumulator using multi-turn (7-turn) transverse stacking in both transverse planes. That should be feasible because the transverse acceptances in the Accumulator are each about an order of magnitude larger than those of the Recycler. That scheme would provide about 50 kW of beam power to the experiment with a duty cycle of about 90%. The three other available Linac cycles could be used for other 8-GeV physics. b) Another method would “steal” about 1/7th of the beam destined for the Main Injector. The beam occupying one seventh of the circumference of the Recycler would be kicked out and transmitted to the Accumulator via the path described previously. No stacking would then be required in the Accumulator. That would provide about 21 kW of beam power for the experiment with a duty cycle of about 90%. It would also create a useful abort gap in the Main Injector beam. The four other cycles available from the Linac could all be used for other 8-GeV physics. c) The third method would “steal” Accumulator-length batches from each of the four Recycler fills not destined for the Main Injector. Each of those could then be separately rebunched in the Accumulator, transferred to the Debuncher, and slowly extracted over 200 msec. That would provide about 28 kW of beam power for the experiment with a duty cycle of about 50%. The rest of these four cycles could be used for other 8-GeV physics. Chuck Ankenbrandt Fermilab

  42. Update: intriguing options for more proton beam power. • 1) Full 200-kW capability using transverse stacking into the Accumulator: • a) Take two linac squirts at a time into the Recycler; • b) Single-turn extract the whole circumference at once ; • c) Transverse stack into the Accumulator; • d) Form a single bunch in the Accumulator; • e) Transfer to the Debuncher; • f) Slow spill from the Debuncher; • g) Repeat this process twice per Main Injector cycle. • 2) As above, but using momentum stacking: • a) Take two linac squirts at a time into the Recycler; • b) Extract Accumulator-length batches at 33-ms intervals; • c) Momentum stack into the Accumulator; • d) Form a single bunch in the Accumulator; • e) Transfer to the Debuncher; • f) Slow spill from the Debuncher; • g) Repeat this process twice per Main Injector cycle. Chuck Ankenbrandt Fermilab

  43. Email from Nagaslaev • From vnagasl <vnagasl@fnal.gov> • Sent Monday, July 30, 2007 8:40 pm • To ankenbra@fnal.gov • Subject Accumulator apertures • Chuck, • I think principal limitation of the Accumulator acceptance after • necessary rearrangements would be • around 20 pimm unnormalized. However, one of the horizontal limitations • currently is Extraction • Lambertson (15 pi), and one would need to increase substantially the • EKIK power in order to bring it • to 20 pi. • These numbers are not official. • Vladimir Chuck Ankenbrandt Fermilab

  44. Summary from beam note • If the proton source is upgraded with an ILC-style 8 GeV Linac, it appears there are several options that would enable an intense beam of 8 GeV protons to be provided, with the appropriate bunch structure, for a muon to electron conversion experiment. Chuck Ankenbrandt Fermilab

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