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

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 July 1, 2008 NuFact08-WG3: Zisman

Aims of MICE MICE cooling demonstration aims to: Another key aim: 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 July 1, 2008 NuFact08-WG3: Zisman

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 July 1, 2008 NuFact08-WG3: Zisman

MICE Cooling Channel Eight 201-MHz RF cavities LH2 absorbers Courtesy of S. Q. Yang, Oxford Univ. July 1, 2008 NuFact08-WG3: Zisman

MICE Stages Present staging plan July 1, 2008 NuFact08-WG3: Zisman

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) July 1, 2008 NuFact08-WG3: Zisman

Estimated Performance (2) ICOOL simulation shows transverse emittance reduction of ≈10% July 1, 2008 NuFact08-WG3: Zisman

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 July 1, 2008 NuFact08-WG3: Zisman

MICE Hall Webcam is available for up-to-date views see http://mice.iit.edu/mico/webcams/ Many photos taken as well July 1, 2008 NuFact08-WG3: Zisman

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 July 1, 2008 NuFact08-WG3: Zisman

MuCool Test Cavity Test cavity similar to MICE design has been fabricated in place at Fermilab MTA Be window design also successfully tested D. Li talk 42-cm July 1, 2008 NuFact08-WG3: Zisman

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 July 1, 2008 NuFact08-WG3: Zisman

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 July 1, 2008 NuFact08-WG3: Zisman

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 July 1, 2008 NuFact08-WG3: Zisman

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) July 1, 2008 NuFact08-WG3: Zisman

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? July 1, 2008 NuFact08-WG3: Zisman

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) July 1, 2008 NuFact08-WG3: Zisman

Muon Collider Scheme Fits on Fermilab site Based on Project X at Fermilab July 1, 2008 NuFact08-WG3: Zisman

6D Cooling at RAL (1) 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 “HCC” July 1, 2008 NuFact08-WG3: Zisman

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 July 1, 2008 NuFact08-WG3: Zisman

Comments Based on putative collider timeline we see My view 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 July 1, 2008 NuFact08-WG3: Zisman

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 July 1, 2008 NuFact08-WG3: Zisman

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! July 1, 2008 NuFact08-WG3: Zisman