Front EndCapture/Phase Rotation& Cooling Studies David NeufferCary Yoshikawa

December 2008

0utlineIntroduction -Factory Front endCapture and -E rotation High Frequency buncher/rotation Study 2B -FactoryShorter version -Factory+-- Collider

Discussion

Variations tried Study 2A ISS baselineShorter bunch train examplenB= 10Better for Collider; as good for -Factory ICOOL/G4Beamline simulations Study of accepted particlesRf cavities in solenoids? Use magnetic insulation ASOL latticeNot too bad Variations Higher energy capture ??

Study2B June 2004 scenario (ISS)Drift 110.7mBunch -51m(1/) =0.00812 rf freq., 110MV330 MHz 230MHz-E Rotate 54m (416MV total)15 rf freq. 230 202 MHzP1=280 , P2=154 NV = 18.032Match and cool (80m)0.75 m cells, 0.02m LiHCaptures both + and -~0.2 /(24 GeV p)

Study 2B ICOOL simulation (NB=18)s = 1ms=109m s=166ms= 216m-4060500MeV/c0DriftBunchRotate500MeV/c0

Features/Flaws of Study 2B Front EndFairly long system ~300m long (217 in B/R) Produces long trains of ~200 MHz bunches~80m long (~50 bunches)Transverse cooling is ~2 in x and y, no longitudinal coolingInitial Cooling is relatively weak ? -Requires rf within magnetic fields in current lattice, rf design; 12 MV/m at B = ~2T, 200MHzMTA/MICE experiments to determine if practical

For Collider (Palmer)Select peak 21 bunchesRecombine after cooling~1/2 lost

-4060m500 MeV/c

Shorter Bunch train example Reduce drift, buncher, rotator to get shorter bunch train:217m 125m 57m drift, 31m buncher, 36m rotatorRf voltages up to 15MV/m (2/3)Obtains ~0.26 /p24 in ref. acceptanceSlightly better ? ~0.24 /p for Study 2B baseline80+ m bunchtrain reduced to < 50mn: 18 -> 10 -3040m500MeV/c

Further iteration/optimizationMatch to 201.25 MHz cooling channelReoptimize phase, frequencyf = 201.25 MHz, = 30, Obtain shorter bunch train

Choose ~best 12 bunches ~ 21 bunch train for Collider at NB= 18 case~12 bunches (~18m)~0.2 /pref in best 12 bunchesDensest bunches are ~twice as dense as NB = 18 case

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Details of ICOOL model (NB=10)Drift 56.4mB=2TBunch- 31.5mPref,1=280MeV/c, Pref,2 =154 MeV/c, nrf = 10 Vrf 0 to 15MV/m (0.5m rf, 0.25m drift) cells 360 MHz 240MHz-E Rotate 36m Vrf = 15MV/m (0.5m rf, 0.25m drift) cellsNV = 10.07 (240 -> 201.5 MHz)Match and cool (80m)Old ICOOL transverse match to ASOL (should redo)Pref= 220MeV/c, frf = 201.25 MHz 0.75 m cells, 0.02m LiH, 0.5m rf, 16.00MV/m, rf =30Better cooling possible (H2, stronger focussing)

Simulations (NB=10)-30m30m500 MeV/c0Drift andBunchs = 89ms = 1mRotates = 125ms = 219mCool

Front end simulationsInitial beam is 8GeV protons, 1ns bunch length

Comparisons of ICOOL and G4BLSimulations of front end and cooling agreeICOOL and G4Beamline results can be matched

Buncher rotator cooler sequence can be developed in both codes

Method Captures both + and -

But some differencesdE/dx is larger in ICOOL Phasing of rf cavities uses different model

12.9 m43.5 m31.5 m36 mdriftbuncherrotatorcaptureMC Front End Layout in G4beamline

G4BeamlineICOOLPi+/Mu+Pi-/Mu-Rotator End

G4BeamlineICOOLPi+/Mu+Pi-/Mu-Cool End

Reduce number of independent frequenciesInitial example had different rf frequency for each cavityBuncher- 42 cavities -31.5m 360to 240 MHzRotator- 48 cavities -36m240 to 202 MHz

Reduce # by 1/3 14 in buncher; 16 in rotatorNearly as good capture (

Accepted particlesAccepted particles fit final beam cuts:AX + Ay < 0.03mAL < 0.2m

Initial beam has momenta from ~75 to ~600 MeV/cFinal beam is ~200 to 300 MeV/c

Transverse emittance is cooled from ~0.014 to ~0.0036 600 MeV/c600MeV/c0 MeV/c0 MeV/c

Accepted Longitudinal distros1m135m135m196m196m-30m40m600 MeV/c600 MeV/c0 MeV/c0 MeV/c

Accepted Beam propertiesFor study 2A acceptance means several cuts:AX + Ay < 0.03mAL < 0.2mFor beam within acceptances, t, N,rms = 0.0036m (from ~0.007)L, N,rms = ~0.04m (from ~0.09)

Emittances are much smaller than the full-beam emittances xrms = 6cm (all-beam)xrms = 3.6cm (accepted-beam)

-30cm+30cm-30cm+30cm

Variations - focusing Buncher and Rotator have rf within 2T fieldsField too strong for rf field ??Axial field within pill-box cavities

Solutions ??Open-cell cavities ??magnetically insulated cavitiesAlternating Solenoid lattice is approximately magnetically insulatedUse ASOL throughout buncher/rotator/cooler

Use gas-filled rf cavitiesASOL lattice

Use ASOL lattice rather than 2TStudy 2A ASOLBmax= 2.8T, *=0.7m,Pmin= 81MeV/c2T for initial driftLow energy beam is lost (P < 100MeV/c)Bunch train is truncatedOK for collider

Also tried weaker focusing ASOLBmax= 1.83T, *=1.1m,Pmax = 54 MeV/c1.33 T for initial driftMatch scaled from 2A match

+ -B(z)

2T -> ASOL

ASOL-1.33T 56m62m133m193m

First ASOL results Simulation results2.8T ASOL0.18 /24 GeV p0.059 /8 GeV p Cools to 0.0075m1.8T ASOL0.198 /24 GeV p0.064 /8 GeV p~10% more than stronger focussingCools to 0.0085m

Baseline (2T -> ASOL) had~0.25 /24 GeV p~0.08 /8 GeV p

Weaker-focusing ASOL has ~10% better acceptance than 2.8T latticeLonger bunch train

Variant-capture at 0.28 GeV/c0.01.0GeV/c1.0GeV/c0.02T 2.8T ASOL-30m+40m-30m+40m1.0GeV/cs=59ms=66ms=126ms=200m

Capture at 280 MeV/cCaptures more muons than 220 MeV/c For 2.T -> 2.8T latticeBut in larger phase space areaLess cooling for given dE/ds sBetter for colliderShorter, more dense bunch trainIf followed by longitudinal cooling

220 MeV/c280 MeV/c

Higher-Energy Simulation resultsHigher energy capture improves capture for high-field latticeCooling is slower

Not as good for low-field latticeWeaker focusing reduces coolingFor High field lattice:2.8T ASOL8GeV beam 0.065 /p in t

DiscussionHigh frequency phase-energy rotation + cooling has been explored

Shorter system better for Collider Shorter bunch train; denser bunches

magnetic insulated lattice could be used rather than B = 2 or 1.75 T latticeSlightly worse performance (?)~10 to 20% worse for neutrino factory Ok for Collider Particles lost are at end of bunch train

Any Questions?

Project X Status

High-frequency Buncher and -E RotatorForm bunches first

-E rotate bunches