1. 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

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
July 1, 2008
NuFact08-WG3: Zisman

3. 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

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
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5. MICE Cooling Channel Eight 201-MHz RF cavities LH2 absorbers
Courtesy of S. Q. Yang, Oxford Univ.
July 1, 2008
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6. MICE Stages
Present staging plan
July 1, 2008
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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)
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NuFact08-WG3: Zisman

8. Estimated Performance (2)
ICOOL simulation shows transverse emittance reduction of ≈10%
July 1, 2008
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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
July 1, 2008
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10. MICE Hall Webcam is available for up-to-date views
see
Many photos taken as well
July 1, 2008
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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
July 1, 2008
NuFact08-WG3: Zisman

12. 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
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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
July 1, 2008
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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
July 1, 2008
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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
July 1, 2008
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)
July 1, 2008
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?
July 1, 2008
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)
July 1, 2008
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19. Muon Collider Scheme Fits on Fermilab site
Based on Project X at Fermilab
July 1, 2008
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20. 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
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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
July 1, 2008
NuFact08-WG3: Zisman

22. 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

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
July 1, 2008
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!
July 1, 2008
NuFact08-WG3: Zisman