MICE Ionization Cooling Channel and Phase II Construction Michael S. Zisman Center for Beam Physics Accelerator & Fusion Research Division Lawrence Berkeley

MICE Ionization Cooling Channeland

Phase II Construction

Michael S. ZismanCenter for Beam Physics

Accelerator & Fusion Research DivisionLawrence Berkeley National Laboratory

MICE Funding Agency Committee Meeting—RALApril 18, 2008

April 18, 2008 MICE-FAC: Zisman 2

Outline•Introduction•Muon beam challenges•Ionization cooling•System description•Stages•Estimated performance•Module design and fabrication status•R&D issues•Future activities•International perspective•Summary


Introduction (1)•Motivation for MICE

— muon-based Neutrino Factory is most effective tool to probe neutrino sector and, hopefully, observe CP violation in leptons

o 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

o 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

•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


Introduction (2)•Another key aim:

— show that design tools (simulation codes) agree with experimento gives confidence that we can optimize design of an actual facility– we are testing a section of “a” cooling channel, not “the”

cooling channel simulations are the means to connect these two concepts

•Both simulations and apparatus to be tested should be as realistic as possible— must incorporate full engineering details of all components into

the simulation

•Here I will cover the cooling channel concept, component design, fabrication status, and supporting R&D


Muon Beam Challenges•Muons created as tertiary beam (p )

— low production rateo need target that can tolerate multi-MW beam

— large energy spread and transverse phase spaceo need solenoidal focusing for the low energy portions of the facility– solenoids focus in both planes simultaneously

o need emittance coolingo high-acceptance acceleration system and decay ring

•Muons have short lifetime (2.2 s at rest)— puts premium on rapid beam manipulations

o high-gradient RF cavities (in magnetic field) for coolingo presently untested ionization cooling techniqueo fast acceleration systemIf intense muon beams were easy

to produce, we’d already have them!


Ionization Cooling (1)•Ionization cooling analogous to familiar SR damping process in electron storage rings— energy loss (SR or dE/ds) reduces px, py, pz

— energy gain (RF cavities) restores only pz

— repeating this reduces px,y/pz ( 4D cooling)

— presence of LH2 near RF cavities is an engineering challengeo we get lots of “design help” from Lab safety committees!


Ionization Cooling (2)•There is also a heating term

— for SR it is quantum excitation— for ionization cooling it is multiple scattering

•Balance between heating and cooling gives equilibrium emittance

— prefer low (strong focusing), large X0 and dE/ds (H2 is best)

XmEEds

dE

dsd NN

03

2

2 2

)GeV 014.0(1

ds

dEXm

equilNx

0

2

.,,

2

GeV 014.0

Cooling Heating


Ionization Cooling (3)•Merit factors for candidate MICE absorbers

— scaled as equilibrium emittanceo requirements for Al windows and extended absorber for H2 and He degrade these ideal values by about 30%

– H2 remains best, even with windows included

Material (dE/dx)min

(MeV g-1 cm2)

X0

(g cm-2)

Relative merit

Gaseous H2 4.103 61.28 1.03

Liquid H2 4.034 61.28 1

He 1.937 94.32 0.55

LiH 1.94 86.9 0.47

Li 1.639 82.76 0.30

CH4 2.417 46.22 0.20

Be 1.594 65.19 0.18


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)

o TOF, Cherenkov, Calorimeter


MICE Cooling Channel

Courtesy of S. Q. Yang, Oxford Univ.Courtesy of S. Q. Yang, Oxford Univ.

LHLH22 absorbers absorbers

EightEight 201-MHz RF cavities

201-MHz RF cavities


MICE Stages•Present staging plan


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

o momentum: 200 MeV/c (variable)o momentum spread: 20 MeV/c x,y ≈ 5 cm; x’,y’ ≈ 150 mrad

— channelo solenoid field: ≈ 3 T : 0.42 mo cavity phase: 90° (on crest)


Estimated Performance (2)•ICOOL simulation shows transverse emittance reduction of ≈10%


Estimated Performance (3)•Virtual scan over emittance used to determine equilibrium emittance— transmission is 100% for input emittance below 6 mm-rad

o high emittance behavior reflects “scraping” as well as cooling


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, Chinao initial conductor order delivered

— RF cavities will be similar to existing MuCool prototypeo fabrication to get under way shortly


ICST Coil Winding Facility

De-spooling and Tensioning Apparatus Coil Winding Apparatus

Winding a Copper Test Coil


Winding banding Cooling ChargingWinding coil

Von Mises Stress in CC

Stress and deflection calculations include the winding pre-stress in the coiland banding, which keeps the coil from lifting off the mandrel when it is fullycharged to a current of 210 A. The minimum winding Pre-stress is 70 MPa. The aluminum banding pre-stress is 30 MPa.


ICST Team•Strong team available to work on CC


MuCool Test Cavity•Test cavity similar to MICE design has been fabricated— in place at Fermilab MTA— Be window design also successfully tested

42-cm


Technology for MICE Cavity

Local annealing of ports

Extruded port

Development of the techniqueDevelopment of the technique

Cavity ports being extruded (pulled)

Power coupler and RF windowPower coupler and RF window


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

o 20-L LH2 absorber (plus safety windows) fits inside


LH2 System•LH2 system design is based on using metal hydride bed as storage tank— R&D system being set up at RAL to test operation

•Design has passed two international safety reviews and is presently being fabricated in industry


MuCool R&D (1)•NFMCC’s MuCool program does R&D on cooling channel components in support of MICE— RF cavities, absorbers

•Carried out in MuCool Test Area (MTA) at Fermilab — located at end of 400 MeV linac and shielded for eventual beam

tests


MuCool R&D (2)•Motivation for cavity test program: observed degradation in cavity performance when strong magnetic field present— 201 MHz cavity easily reached 19 MV/m without magnetic field— initial tests in fringe field of Lab G solenoid now under way

201 MHz cavity

5-T solenoid + 805-MHz cavity

805 MHz results


Test Setup at MTA • The 805-MHz and 201-MHz cavities at MTA, FNAL for RF The 805-MHz and 201-MHz cavities at MTA, FNAL for RF

breakdown studies with external magnetic fields.breakdown studies with external magnetic fields.

805 MHz pillbox cavity805 MHz pillbox cavity

201 MHz cavity201 MHz cavity


Tests with Magnetic Fields

Separation of the nearest Separation of the nearest curved Be window from curved Be window from the face of Lab-G magnet the face of Lab-G magnet reduced from 110 to 10 reduced from 110 to 10 cmcm

Maximum possible Maximum possible magnetic field near the magnetic field near the Be window ~1.5 T ( with Be window ~1.5 T ( with 5 T in magnet)5 T in magnet)

The 201-MHz cavityThe 201-MHz cavity

Lab-G magnetLab-G magnet


Initial Results•First results indicate evidence for multipactor in presence of magnetic field— but, increase in dark current rate slower than expected

o data still preliminary


LH2 System R&D at RAL•Test system at RAL is presently under construction — intent is to validate the system and make it the “first article”

(of 3)o both components and computer controls must be vetted


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)


Future Activities•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”


International Perspective•International community holds annual “NuFact” workshops— provides opportunity for physics, detector, and accelerator

groups to plan and coordinate R&D efforts at “grass roots” level— venue rotates among geographical regions (Europe, Japan, U.S.)Year Venue

1999 Lyon, France

2000 Monterey, CA

2001 Tsukuba, Japan

2002 London, England

2003 New York, NY

2004 Osaka, Japan

2005 Frascati, Italy

2006 Irvine, CA

2007 Okayama, Japan

2008 Valencia, Spain


Summary•MICE is making excellent progress towards Phase II

— design of coupling coils complete (ICST Harbin)o MOU between LBNL and HIT for fabrication in place

— RF cavity design being finalized— focus coil module contract placed

— LH2 R&D system being prepared at RAL

•Fabrication of CC and FC getting under way— fabrication of RF cavities will begin shortly

•Strong R&D program under way to develop and test key components— RF, LH2 absorbers

•We are looking forward to first ionization cooling measurements!


Final Thought•Challenges of a muon accelerator complex go well beyond those of standard beams— developing solutions requires substantial R&D effort to specify

o expected performance, technical feasibility/risk, cost (matters!)

Critical to do experiments and build components. Paper studies are not enough!

Documents

MICE Ionization Cooling Channel and Phase II Construction Michael S. Zisman Center for Beam Physics Accelerator & Fusion Research Division Lawrence Berkeley