Experimental Tests of Cooling: Expectations and Additional Needs

1. Experimental Tests of Cooling:Expectations andAdditional Needs Michael S. Zisman Center for Beam Physics Accelerator & Fusion Research Division Lawrence Berkeley National Laboratory NuFact08 WG3—Valencia July 1, 2008

2. Why Do a Cooling Experiment? • Motivation for cooling experiment • muon-based Neutrino Factory is most effective tool to probe neutrino sector and, hopefully, observe CP violation in leptons • results will test theories of neutrino masses and oscillation parameters, of importance for both particle physics and cosmology • a high-performance Neutrino Factory (≈1021e aimed at far detector per 107 s year) depends on ionization cooling • straightforward physics but not experimentally demonstrated • facility will be expensive (O(1B€)), so prudence dictates a demonstration of the key principle • a Muon Collider depends even more heavily on ionization cooling NuFact08-WG3: Zisman

3. Aims of MICE • MICE cooling demonstration aims to: • design, engineer, and build a section of cooling channel capable of giving the desired performance for a Neutrino Factory • place this apparatus in a muon beam and measure its performance in a variety of modes of operation and beam conditions • Another key aim: • show that design tools (simulation codes) agree with experiment • gives confidence that we can optimize design of an actual facility • we test a section of “a” cooling channel, not “the” cooling channel • simulations are the means to connect these two concepts • Make simulations + test apparatus as realistic as possible • Thought-provoking question: is the cooling demo for “us” or for “them”? • the latter audience is tougher to convince NuFact08-WG3: Zisman

4. System Description • MICE includes one cell of the FS2 cooling channel • three Focus Coil (FC) modules with absorbers (LH2 or solid) • two RF-Coupling Coil (RFCC) modules (4 cavities per module) • Along with two Spectrometer Solenoids with scintillating fiber tracking detectors • plus other detectors for confirming particle ID and timing (determining phase wrt RF and measuring longitudinal emittance) • TOF, Cherenkov, Calorimeter NuFact08-WG3: Zisman

5. MICE Cooling Channel Eight 201-MHz RF cavities LH2 absorbers Courtesy of S. Q. Yang, Oxford Univ. NuFact08-WG3: Zisman

6. MICE Stages • Present staging plan NuFact08-WG3: Zisman

7. Estimated Performance (1) • Simulations of MICE performance carried out with several codes • nominal cooling performance estimated with ICOOL • full detailed simulations done with G4MICE • Typical parameters • beam • momentum: 200 MeV/c (variable) • will cover range of roughly 140–240 MeV/c • momentum spread: 20 MeV/c • x,y ≈ 5 cm; x’,y’ ≈ 150 mrad • channel • solenoid field: ≈ 3 T • : 0.42 m • cavity phase: 90° (on crest) NuFact08-WG3: Zisman

8. Estimated Performance (2) • ICOOL simulation shows transverse emittance reduction of ≈10% NuFact08-WG3: Zisman

9. Estimated Performance (3) • Virtual scan over emittance used to determine equilibrium emittance • transmission is 100% for input emittance below 6  mm-rad • high emittance behavior reflects “scraping” as well as cooling NuFact08-WG3: Zisman

10. MICE Hall • Webcam is available for up-to-date views • see http://mice.iit.edu/mico/webcams/ • Many photos taken as well NuFact08-WG3: Zisman

11. RFCC Module • Module comprises one coupling coil and 4 RF cavities • in advanced design stage • CC design and fabrication done in collaboration with ICST in Harbin, China • initial conductor order delivered • RF cavities will be similar to existing MuCool prototype • fabrication to get under way shortly NuFact08-WG3: Zisman

12. MuCool Test Cavity 42-cm • Test cavity similar to MICE design has been fabricated • in place at Fermilab MTA • Be window design also successfully tested D. Li talk NuFact08-WG3: Zisman

13. FC Module • Focus coil module vendor has been selected • contract award delayed until recently due to STFC funding woes • comprises two coils that can run with same or opposite polarity • 20-L LH2 absorber (plus safety windows) fits inside NuFact08-WG3: Zisman

14. LH2 System • LH2 system design is based on using metal hydride bed as storage tank • Design has passed two international safety reviews • R&D system presently being fabricated in industry NuFact08-WG3: Zisman

15. LH2 R&D System • LH2 R&D system will be assembled and tested at RAL • intent is to validate the system and make it the “first article” (of 3) • both components and computer controls must be vetted NuFact08-WG3: Zisman

16. Absorber Windows • Required windows must be large (300 mm diameter), thin (~125 m) and strong (4x safety factor) • Aluminum windows designed by Oxford and built at U.-Miss. • 125 m; machined from single piece of Al • burst at 140 psi (nearly 10 atm) NuFact08-WG3: Zisman

17. Future Activities • Assuming MICE is successful, it will demonstrate • an understanding of 4D cooling process • an understanding of the technical challenges that must be met • component design • system-level operational issues • This should suffice for developing a Reference Design Report for a Neutrino Factory (an IDS-NF task) • demonstration of magnetically insulated cavity performance beneficial • What else is missing? • an equivalent demonstration of 6D cooling (for a collider) • a demonstration of “final” transverse cooling (for a collider) • Are these necessary for designing a Muon Collider? • for getting funding approval? • or only for building one? NuFact08-WG3: Zisman

18. Magnetic Insulation • Before proceeding to a realistic 6D cooling demonstration, substantial component R&D must be done • means to avoid, or at least mitigate, degradation of RF gradient in strong B field is most critical • e.g., magnetically insulated open cell (Palmer’s concept) • suitable wedge-shaped absorbers (LH2 or otherwise) • practical and affordable high-field solenoids for collider final cooling 201 MHz (subsequent test) 805 MHz (initial test) NuFact08-WG3: Zisman

19. Muon Collider Scheme Fits on Fermilab site Based on Project X at Fermilab NuFact08-WG3: Zisman

20. 6D Cooling at RAL (1) “HCC” • RAL muon beam facility will continue to be valuable after MICE is completed • continuing to a 6D cooling demonstration is attractive option • “Poor man’s” test of 6D cooling in MICE • “Rich man’s” test of 6D cooling, e.g., FOFO snake, Guggenheim, HCC NuFact08-WG3: Zisman

21. 6D Cooling at RAL (2) • Several issues to consider • timetable for doing such experiments • cost • available effort for planning and execution • Possible (fast-track) Muon Collider timetable and cost estimate presented to P5 by Palmer NuFact08-WG3: Zisman

22. Comments • Based on putative collider timeline we see • feasibility study complete in 2012 (same as RDR for Neutrino Factory) • RDR complete in 2015 • CDR complete in 2018 • My view • impractical to complete convincing 6D cooling demo(s) by 2012 • completing MICE will be a pacing item (if continuing at RAL) • component R&D is also a pacing item (even if not continuing at RAL) • demo experiment(s) may be too late for RDR as well • with adequate budget + staffing, might get one done • in any case, progress on component design will be useful for RDR • aim for completing all demo experiment(s) no later than the CDR phase • in time for input to (expected) international design and cost review NuFact08-WG3: Zisman

23. Summary • MICE making excellent progress • design of coupling coils complete; fabrication started (ICST Harbin) • RF cavity design finalized; procurements initiated • focus coil module contract placed • LH2 R&D system being prepared at RAL • MICE should answer most questions of 4D cooling • we are looking forward to first ionization cooling measurements! • remaining issue is final cooling for collider • same physics but very challenging components (~50 T solenoids) • 6D cooling will likely require a substantial experiment • adopting “Guggenheim” or “FOFO snake” scheme would reduce the cost (almost same components as MICE) • Strong R&D program to develop and test key components must continue and expand NuFact08-WG3: Zisman

24. Final Thought • Challenges of a muon accelerator complex go well beyond those of standard beams • developing solutions requires substantial R&D effort to specify • expected performance, technical feasibility/risk, cost (matters!) Critical to do experiments and build components. Paper studies are not enough! NuFact08-WG3: Zisman